irrigatedagriculture and wildlife conservation: …jthompso/pdf_files/env_mgt_paper.pdfconservation...

Irrigated Agriculture and Wildlife Conservation:Conflict on a Global ScaleA. DENNIS LEMLY *

United States Forest ServiceSouthern Research StationColdwater Fisheries Research UnitDepartment of Fisheries and Wildlife SciencesVirginia Tech University, Blacksburg, Virginia 24061-0321,

USA

RICHARD T. KINGSFORDNew South Wales National Parks and Wildlife ServiceP.O. Box 1967Hurstville, New South Wales 2220, Australia

JULIAN R. THOMPSONWetland Research UnitDepartment of GeographyUniversity College LondonLondon WC1H OAP, United Kingdom

ABSTRACT / The demand for water to support irrigated agri-culture has led to the demise of wetlands and their associ-ated wildlife for decades. This thirst for water is so pervasivethat many wetlands considered to be hemispheric reservesfor waterbirds have been heavily affected; for example, theCalifornia and Nevada wetlands in North America, the Mac-

quarie Marshes in Australia, and the Aral Sea in central Asia.These and other major wetlands have lost most of their his-toric supplies of water and some have also experienced seri-ous impacts from contaminated subsurface irrigation drain-age. Now mere shadows of what they once were in terms ofbiodiversity and wildlife production, many of the so-called‘‘wetlands of international importance’’ are no longer the keyconservation strongholds they were in the past. The conflictbetween irrigated agriculture and wildlife conservation hasreached a critical point on a global scale. Not only has localwildlife suffered, including the extinction of highly insularspecies, but a ripple effect has impacted migratory birdsworldwide. Human societies reliant on wetlands for their live-lihoods are also bearing the cost. Ironically, most of the deg-radation of these key wetlands occurred during a period oftime when public environmental awareness and scientificassertion of the need for wildlife conservation was at an all-time high. However, designation of certain wetlands as ‘‘re-serves for wildlife’’ by international review boards has notslowed their continued degradation. To reverse this trend,land and water managers and policy makers must assessthe true economic costs of wetland loss and, depending onthe outcome of the assessment, use the information as a ba-sis for establishing legally enforceable water rights that pro-tect wetlands from agricultural development.

Irrigation is essential to support agricultural produc-tion in many arid and semiarid regions of the world.However, there is often an important trade-off. Thebenefits from irrigation are offset by environmentalcosts, particularly to wetlands and wildlife. The inten-sive cultivation practices typically used in modern agri-culture—as well as the underlying profit motive—placehigh demands on water supplies and put a premium onarable land. As a consequence, native wetlands can beeliminated in a short period of time (Frayer and others1989, Moore and others 1990). Wetlands can be lost dueto draining and direct conversion to agricultural land orbecause water removal from rivers and streams for use

in irrigation robs wetlands of their source of water, andthey simply dry up. In the western United States, forexample, wetland losses due to agriculture are severe,exceeding 90% in many locations, and have beenoccurring virtually unimpeded for the past 100 years(Preston 1981, Reisner 1986, Thompson and Merritt1988).

In addition to direct loss of wetland acreage, wet-lands can be functionally lost due to contamination ofthe water supplies from agricultural pesticides andherbicides in surface runoff from irrigated fields (Roeand others 1980, Nell 1987, Moore and others 1990).Another important source of contamination was identi-fied in the United States in the early 1980s—subsurfaceirrigation drainage. Irrigation water trapped by shallowclay lenses must be removed or drained or else itwaterlogs the root zone and kills crops. The resultantdrainage contains elevated concentrations of soil traceelements, salts, and other constituents and ultimately

KEY WORDS: Agricultural irrigation; Wetlands; Wildlife conservation;Water policy; Environmental economics; Ecosystemmanagement

*Author to whom correspondence should be addressed.

DOI: 10.1007/s002679910039

Environmental Management Vol. 25, No. 5, pp. 485–512 r 2000 Springer-Verlag New York Inc.

reaches major wetlands, streams, and rivers (Moore andothers 1990). Fish and wildlife populations have beenpoisoned by drainwater contaminants at several loca-tions (Lemly and others 1993, Lemly 1994a, Presser1994, Presser and others 1994). Thus, although agricul-tural-related reductions in water supplies have causedthe demise of wetlands for centuries, there are morerecent threats that are just now being identified andinvestigated. The implication of these threats on aglobal basis is serious (Lemly 1994b, 1996) and under-scores the severity of the irrigation/wildlife dilemma.One thing is certain—finding an environmentally accept-able balance for irrigated agriculture is more compli-cated, yet more necessary, than ever before.

Because such a small portion of historic wetlandsnow remain in most arid and semiarid regions, they areespecially valuable as wildlife habitat, both as refuges forresident wildlife populations and as stopovers andwintering/breeding grounds for migrating waterfowland shorebirds (Frayer and others 1989). These wet-lands constitute the last stronghold for remnant popula-tions of endangered and threatened wildlife, plants,and fishes, whose survival as species hangs by a precari-ous hydrological thread that is all too easily cut byirrigated agriculture (Schroeder and others 1988, Ste-phens and others 1988, Hoffman and others 1990). Insome locations the wetlands are valuable archaeologicalsites and have been used to identify and trace humanoccupancy and culture dating back several thousandyears (Raven and Elston 1988, 1989, 1990). Wetlandscontinue to play key roles in supporting many humanpopulations through their varied functions, products,and attributes (e.g., Dugan 1990).

Many of the world’s key wetlands have been recog-nized for the wildlife conservation benefits they pro-vide. For example, international scientific review boardsand political leaders have espoused these benefits andcalled for protection of wetlands through such promi-nent efforts as the Ramsar Convention and the RioConference (Denny 1994). These and other meetingshave resulted in certain sites being designated as ‘‘wet-lands of international importance,’’ ‘‘hemispheric re-serves for shorebirds,’’ or ‘‘conservation wetlands’’(Thompson and Merritt 1988, Dugan 1990, Whighamand others 1993). Much of this effort has coincidedwith, and perhaps to some extent been fueled by, theenvironmental movement that began in the 1960s.Although this societal movement produced a ground-swell of public, private, and scientific interest andinvolvement in environmental issues dealing with wet-lands and wildlife, which persists even today, mostefforts have turned out to be nothing more than‘‘eco-speak’’—words that convey good intentions, rally

support from certain facets of society and polarizeothers, but have little or no mechanism for implement-ing real changes in environmental management policy.In point of fact, a virtual mountain of good intentions,scientific meetings, and proclamations pointing out theneed to protect wetlands for wildlife conservation andother beneficial uses has done little to prevent theircontinued degradation. This has been particularly truewhen the opposing force was irrigated agriculture.

In this paper we illustrate the magnitude of the issueby presenting case examples that span four continents.In addition to focusing attention on the issue in a broadsense, it is critical to provide constructive guidance tothose that seek to correct problems at a local level. Tothat end, we also discuss an economic-based approachfor developing site-specific water policies that will ad-dress the needs of wetlands and wildlife.

Case Examples

North America

Background. Limited availability of water was one ofthe major obstacles to early settlement of many arid andsemiarid regions in western North America (Reisner1986). In the United States, the shortage of water andperceived need to homestead on desert lands led to theestablishment of the US Bureau of Reclamation in 1902(then named the Reclamation Service). The primarymission of this agency was to ‘‘reclaim’’ unproductivelands by bringing water to arid regions and turningdesert into farmland. This reclamation began in earnestwith the completion of the Newlands Water Project inNevada in 1915 and reached a peak with the building ofsuch massive water storage/diversion projects as HooverDam on the Colorado River, the California Aqueductacross the Mojave Desert, and the Central Valley Irriga-tion Project in California (Reisner 1986, Hoffman andothers 1986). However, the price for this reclamationand the associated increase in agricultural productionwas a sharp decline in the amount of water available tonative wetlands. For example, most of the historic flowsof the upper and middle reaches of the San JoaquinRiver, California, are impounded and diverted foragricultural irrigation (Clifton and Gilliom 1989, Stateof California 1990). Native fishes and aquatic communi-ties have disappeared and the once important runs ofchinook salmon (Oncorhynchus tshawytscha) no longertake place (Moyle 1976, Moore and others 1990). About90% of the historic wetlands in California’s CentralValley are gone, due primarily to irrigated agriculture,and over 60% of the entire Pacific flyway waterfowlpopulation is now channeled into the remaining wet-

A. D. Lemly and others486

lands during migration (Frayer and others 1989). Cata-strophic mortality has resulted because large numbersof birds are forced into small areas, where they are moresusceptible to disease outbreaks brought on by crowd-ing and contaminant-related stress (Gilmer and others1982).

A combination of reduced freshwater inflows andcontaminated subsurface irrigation drainage has seri-ously degraded wetlands throughout western NorthAmerica (Figure 1, Table 1). Impacts to wildlife havebeen severe, and the conservation benefits provided bythese wetlands have dropped precipitously (Lemly andothers 1993, Lemly 1994a). Battles for water rightsbetween settlers, agriculture, urban developers, andwater authorities have raged for well over a century(Reisner 1986), but only in the last few years have thewater needs of remnant native wetlands gained atten-tion and become the focus of water management policy.A notable example is the wetlands located in theLahontan Valley of northwestern Nevada (Figure 1).Consisting of Stillwater Marsh, Carson Lake Marsh, andthe Carson Sink, these wetlands form the terminus of

the Carson River. Their story provides an excellentillustration of the irrigation–wildlife dilemma in NorthAmerica.

Conservation values of the Lahontan wetlands. The La-hontan Valley wetlands are of paramount importance inmaintaining breeding populations of shorebirds, marsh-birds, and waterfowl that are managed and protectedunder the North American Migratory Bird Treaty Act(Margolin 1979). These western Nevada wetlands havelong been recognized as a critical area for migratorybirds in the Pacific flyway. Lahontan Valley supportsabout half the Pacific flyway’s entire population ofcanvasback ducks (Aythya valisineria), and up to 90% ofthe flyway’s snow geese (Chen hyperborea) stop to useStillwater and Carson Lake marshes in the fall. Over65% of the tundra swans (Olar columbianus, a federallyprotected species) nest at these wetlands and over 7000redhead ducklings (Aythya americana, a species givenpriority conservation status by the US Fish and WildlifeService) are produced annually. Although crowded intoless and less habitat (see the section below on effects onwildlife), large numbers of birds utilize these wetlands.Peak populations of 12,000 tundra swans, 25,000 canvas-back ducks, 20,000 redhead ducks, 150 bald eagles(Haliaeetus leucocephalus, a federally listed endangeredspecies), 30,000 American white pelicans (Pelecanuserythrorhynchos), and over 250,000 other waterfowl havebeen recorded in recent years. The numbers of shore-birds and marshbirds include thousands of black-necked stilts (Himantopus mexicanus), American avocets(Recurvirostra americana), long-billed dowichers (Limno-dromus scolopaceus), white-faced ibis (Plegadis chihi), andegrets (Casmerodius albus, Leucophoyx thula). The Lahon-tan wetlands have been classified as a HemisphericReserve within the Western Hemisphere ShorebirdReserve Network by an international panel of scientists(Thompson and Merritt 1988).

Benefits to community. Archaeological research indi-cates that humans have occupied the Lahontan wet-lands for at least 5000 years (Raven and Elston 1988,1989, 1990). The wetlands provided Native Americanswith abundant food resources such as seeds and tubersfrom cattail, alkali, and hardstem bulrush; fish; water-fowl and their eggs; and marsh mammals. Simpson(1876) wrote about the abundance of fish in themarshes: ‘‘the lake is filled with fish . . . the Indians havepiles of fish lying about drying, principally chubs andmullet.’’ Fish bones are commonly found in archaeologi-cal sites at the wetlands, suggesting that fish were asignificant source of food for the local people(Greenspan 1988). Fish have provided community ben-efits more recently as well. The Lahontan cutthroattrout (Onchorhynchus clarki henshawi) were much sought

Figure 1. A sample of significant wetlands in North Americaaffected by irrigated agriculture. L marks the location of theLahontan Valley wetlands, which include Stillwater Marsh, andthe numbers identify the following wetlands: 1, KestersonMarsh; 2, Grasslands Marshes; 3, Rasmus Lee Lake and GooseLake wetlands; 4, Ouray wetlands; 5, Benton Lake wetlands; 6,Mexican riverine wetlands; 7, South Saskatchewan River Basinwetlands.

Irrigation and Wildlife Conservation 487

Table 1. Sample of wetlands in North America where wildlife conservation efforts have been affectedby irrigated agriculturea

Wetland StatusbAgricultural

cause of impactPeriod of

impactEffects on wetlands

and wildlife References

Stillwater Marsh NWR, Ramsar site,hemisphericreserve forshorebirds

Water diversions for cropirrigation resulted in.90% reduction ofinflows and producedcontaminatedsubsurface drainage.

1915–present Loss of 71% of wetlands;production ofshorebirds cut by.60%; death anddeformity of birds andfish due tocontaminants inirrigation drainage;mortality ofendangered species.

Hoffman andothers (1990),Hallock andHallock (1993),Lemly (1994a)

Kesterson Marsh NWR Contaminated subsurfaceirrigation drainage.

1978–1985 Death and deformity ofthousands of waterfowland shorebirds; allmarshland (2,388 ha)drained and sedimentsexcavated. No wetlandsremain.

Zahm (1986),Hoffman andothers (1986),Marshall (1985)

GrasslandsMarshes

NWR, SWMA,70% privateownership

Freshwater inflowsreplaced bycontaminatedirrigation drainage.

1950–present Accumulation ofdrainwatercontaminants inshorebirds to toxiclevels for reproduction.

Ohlendorf andothers (1987),Hothem andWelsh (1994)

Rasmus Lee Lake,Goose LakeWetlands

SWMA Contaminated subsurfaceirrigation drainage.

1986–present Bioaccumulation ofselenium to toxiclevels; death anddeformity of waterfowland shorebirds.

Peterson andothers (1988),See and others(1992a,b)

Ouray Wetlands NWRSWMA

Contaminated subsurfaceirrigation drainage.

1960–present Bioaccumulation ofselenium to toxiclevels; death anddeformity of waterfowl,shorebirds, and fish;mortality ofendangered species.

Stephens andothers (1988,1992), Waddelland Stanger(1992),Hamilton andothers (1996)

Benton LakeWetlands

NWR Freshwater inflowsreplaced bycontaminatedirrigation drainage.

1970–present Bioaccumulation of traceelements to toxic levelsin waterfowl,shorebirds, and fish;reproductiveimpairment in birds.

Knapton andothers (1987),Lambing andothers (1987)

Mexican RiverineWetlands

WPSWMA

Diversion of freshwaterinflows for irrigation;salinization of surfaceand ground watersupplies.

1963–present Loss of .50% of wetlandsand shallow waterhabitat; local loss of upto 68% of native fishspecies; total extinctionof 15 rare orendangered fishspecies.

Contreras-Balderas andLozano-Vilano(1994)

SouthSaskatchewanRiver BasinWetlands

NPPPPWMA

Diversion of freshwaterinflows for irrigation;salinization of surfaceand ground watersupplies.

1940–present Loss of .40% of wetlandsand shallow waterhabitat; declines inbird usage andproduction.

Livingstone andCampbell(1992), Gilbertand Ramey(1995)

aRefer to Figure 1 for location of wetlands.bNWR: national wildlife refuge; SWMA: state wildlife management area; WP: wildlife preserve; NP: national park; PP: provincial park; PWMA:provincial wildlife management area.


after by fishermen in the early 1900s. The sport fisherypotential of the wetlands led to the introduction ofseveral species of nonnative fishes between 1920 and1940. Some adapted well and provided substantialrecreational opportunities for local anglers. Large-mouth bass (Micropterus salmoides), for example, sup-ported a highly popular fishery until the 1970s, whenthe population virtually disappeared (see the sectionbelow on impacts of irrigation). Other current uses ofthe wetlands by local people include hunting, trapping,fishing, birdwatching, swimming, hiking, camping, andconservation education classes.

In addition to direct benefits to the local community,there are considerable benefits that extend far beyondthe Lahontan Valley. For example, the Lahontan wet-lands are an essential link in the support system forwaterfowl that are sought by hunters throughout thePacific flyway, which includes a huge area of the westernUnited States, Canada, and Mexico. The economicrevenues associated with waterfowl hunting can besubstantial. In California, for example, these revenuesexceeded US$85 million in 1990 and formed thelivelihood of people ranging from hunting guides toindustry workers that manufacture hunting equipment(Moore and others 1990). In addition to migratorywaterfowl, many species of shorebirds (pelicans, cur-lews, stilts, avocets, etc.) that nest in Stillwater andCarson Lake marshes are enjoyed for nonconsumptiveuses at locations far distant from the Lahontan Valley. InArizona and New Mexico, for example, environmentaleducation and conservation classes, nature trail toursand hikes, and birdwatching all involve wildlife that canbe traced to western Nevada wetlands. The distantvalues and benefits associated with these wetlands werea key factor leading to the decision for their designationas a Hemispheric Reserve in the late 1970s (Thompsonand Merritt 1988).

Impacts of irrigation and effects on wildlife. An extensivewetland ecosystem comprising some 70,000 ha existedin low areas of the Carson Desert of northwesternNevada prior to completion of the Newlands IrrigationProject in 1915 (see Figure 1 for location). Of thisamount, 14,000 ha in Stillwater Marsh, 11,000 ha inCarson Lake Marsh, and about 11,000 ha at the mouthof the Carson River in the Carson Sink (Fallon NationalWildlife Refuge) were terminal drainage areas for theCarson River and were directly impacted by the New-lands Project. Since initiation of the project in 1905, thequantity and quality of the water reaching the terminalwetlands has declined precipitously. Water quantity hasbeen reduced due to diversion of water from the CarsonRiver for use in irrigating cropland, primarily to growalfalfa that is harvested and sold as livestock feed in

Nevada and neighboring states. Water quality has de-clined because of saline, contaminated subsurface drain-age formed as a by-product of irrigation. The net effecthas been elimination of 59,000 ha of wetlands inexchange for the water used to irrigate 22,000 ha ofland. A summary of the changes that have occurred inwater supplies, and associated wetland losses, is given inTables 2 and 3. A total of 84% of the native wetlands aregone, and the remaining marshland receives water thatcontains up to 100 times the historic concentrations ofdissolved solids, including toxic trace elements such asmercury, arsenic, and selenium (Hoffman and others1990, Hallock and Hallock 1993). The changes in waterquality have led to extensive declines in marsh vegeta-tion in the remaining wetlands (Hoffman and others1990, Lemly 1994a).

Irrigation-induced effects on wildlife have been se-vere. Fish populations are greatly reduced, and thespecies composition has changed since historical times.For example, Lahontan cutthroat trout, a federallylisted endangered species, have been totally eliminated.

Table 2. Characteristics of water supplya

for wetlands in northwestern Nevada, USA

Parameter andtime period

CarsonRiver

CarsonLake

StillwaterMarsh

Water quantity (ha-ft)Historical (1845–1960) 166,000 166,000 110,000Recent (1970–1988) 121,000 10,000 22,000

Dissolved-solidsconcentration(mg/liter)

Historical (1845–1960) 160 170 270Recent (1970–1988) 220 1,170 1,170

aData from Hallock and Hallock (1993).

Table 3. Wetland lossesa in northwesternNevada, USA

Location

Area (ha)Loss(%)Pre-1905 1987

Stillwater WildlifeManagement Area 13,350 3,885 71

Carson Lake 10,925 2,265 79Fallon National

Wildlife Refuge 10,525 0 100Winnemucca Lake

National WildlifeRefuge 11,330 0 100

Humboldt WildlifeManagement Area 23,475 5,260 78

Total 69,605 11,410 84

aData from Hoffman and others (1990).


Largemouth bass, an introduced species that oncesupported an extensive recreational fishery, have alsoentirely disappeared. Most of the native species are nowabsent from the wetlands, and those that remain arepollution-tolerant fishes such as common carp (Cypri-nus carpio) and mosquitofish (Gambusia affinis). Theonce diverse fish forage base supporting Americanwhite pelicans has been greatly reduced. River otter(Lutra canadensis), mink (Mustela vison), frogs, andturtles—characteristic marsh species that were oncenumerous—are all gone. Other species, such as theAmerican curlew (Numenius americanus), have experi-enced precipitous declines in numbers, to the pointthat they are now uncommon. Muskrats (Ondatra zibethi-cus), freshwater clams, and aquatic snails were onceabundant throughout the wetlands but only small,remnant populations remain. Freshwater clams, forexample, are only present in Stillwater Point Reservoir,which is the area with the lowest concentration ofdissolved solids (Hallock and Hallock 1993).

Waterfowl production is now much reduced com-pared to historical conditions. The numbers of nestingbirds as well as the percentage of successful waterfowland shorebird nests have steadily declined due to loss ofwetland acreage and emergent vegetation coupled withexposure to contaminants in irrigation drainage water.Only about 25% of nests succeed in hatching even onechick, and the birds that do fledge contain elevatedconcentrations of mercury and selenium. Moreover, thewater in many marsh areas is toxic to aquatic lifebecause of the accumulated salts and trace elementsthat are leached out of crop land during irrigation andcarried to the wetlands in drainwater (e.g., selenium,boron, molybdenum, lithium, arsenic). There are alsopublic health concerns. Selenium, for example, accumu-lates in biota to concentrations that are 10,000 timesthose present in water, resulting in tissue residues inwaterfowl that are four times the safe levels for humanconsumption (Hallock and Hallock 1993).

Water policy and outlook for the future. The trend ofdwindling water supplies for Lahontan Valley wetlands,which began in 1905, continued unchecked until 1992.Degradation of Stillwater Marshes occurred throughoutthis period despite legislation (Migratory Bird TreatyAct in 1918), which supposedly provided for protectionof aquatic bird habitat on national wildlife refuges(Vencil 1986). Diligent efforts were made by the US Fishand Wildlife Service (the principal agency responsiblefor managing the wetlands) to identify and characterizeproblems and propose solutions to the water issuesaffecting the Lahontan Valley wetlands beginning in thelate 1970s (Thompson and Merritt 1988). These effortsachieved very limited success. Prior to 1987, the federal

management agreements between the US Fish andWildlife Service (FWS) and the US Bureau of Reclama-tion (USBR, the agency responsible for the NewlandsIrrigation Project) did not protect water supplies to thewetlands, i.e., there were no specific water rights thatwould ensure the size or integrity of remaining wet-lands. In principle, virtually all of the water flow of theCarson River was available for irrigation or other uses.The marshes obtained water after the needs of agricul-ture were met—through controlled releases from irriga-tion canals or as a result of surface and subsurfacereturn flows from flood-irrigated land—and from pre-cautionary flood-control releases (spills) from nearbyLahontan Reservoir. Thus, the wetlands were forced toexist entirely on leftovers, most of which were degradedin quality and not predictable, protected, or guaran-teed. Recognizing the uncertainty of even these meagerleavings, the FWS reached an agreement with the USBRin 1987 that established a limited water right to securethe available agricultural drainage and precautionaryspill water for use in wetland management at StillwaterNational Wildlife Refuge (Hoffman and others 1990).

Research studies conducted by the FWS in 1988–1990 further delineated the link between agriculturalirrigation in the USBR’s Newlands Project and toxicthreats to wildlife on Stillwater Refuge (Hallock andHallock 1993). Because the FWS has federal and interna-tional legal responsibilities for wildlife on the refuge,i.e., it is obligated to provide suitable (uncontaminated)habitat for birds that are managed and protected underthe US–Canada–Mexico Migratory Bird Treaty Act, itbrought a legal challenge against the USBR to obtainclean water supplies for maintaining permanent wet-lands. A ruling and subsequent order issued by USFederal Court led to the establishment of operatingcriteria and procedures (OCAP) for the NewlandsProject in 1992. Recent (1967–1986) average wetlandsizes for Carson Lake and Stillwater Marsh were 4000 haand 5600 ha, respectively. Under OCAP, the USBR isrequired to deliver sufficient water to maintain about2000 ha of wetlands at Carson Lake and about 2800 haat Stillwater, which reduces them to less than 10% oftheir historical size. Thus, although a yearly supply ofwater was mandated by law, the net effect was a loss ofwetlands. Moreover, a mixture of irrigation drainageand freshwater can be supplied, which results in dis-solved-solids concentrations four to seven times greaterthan historical conditions (Hallock and Hallock 1993).

Stillwater National Wildlife Refuge and the otherremnant Lahontan Valley wetlands do not have a brightfuture. The legal challenge brought by the FWS hadlittle effect on water policy. The court action amountedto settlement of an interagency argument without


remedying the situation on the refuge. This case ex-ample illustrates the fact that agricultural interests cansucceed in controlling water policy even if there arelegal factors that would seem to favor wetlands andwildlife. OCAP will be the rule of law throughout theforeseeable future unless a substantial new challenge ismounted. It is possible that such a challenge could besuccessful if it combines the forces of wetland managersarmed with a strong economic-based case for changingwater policy, with well educated and involved localcommunities (see the section below on reversing thetrend).

Australia

Background. Agricultural development is concen-trated in the southeast and southwest and along the eastcoast of Australia (Newman and others 1996, Saundersand others 1996), where most of the population livesand rainfall is relatively high and reliable. Most of thecontinent is arid (about 70%) with highly variablerainfall (Stafford Smith and Morton 1990). Pastoralism(grazing) is the principal land use in arid regions, withlivestock (sheep and cattle) dominating agriculturalproduction. The tropical belt across northern Australiais also predominantly grazed by livestock and threats tomany wetlands reflect this grazing (Blackman andothers 1996, Whitehead and Chatto 1996).

The impact of agriculture on wetlands of Australia issignificant (Goodrick 1970, Lane and McComb 1988,Lothian and Williams 1988, Norman and Corrick 1988,Pressey and Harris 1988). The most serious causes aredraining of wetlands, diverting water from wetlands,and drowning of wetlands (Figure 2, Table 4). Genera-tion of electricity (Kirkpatrick and Tyler 1988, Kings-ford 1995) and urban development (Lane and Mc-Comb 1988, Adam 1995) have destroyed wetlands, butagriculture has caused most wetland loss. Coastal swampswere drained to graze livestock or plant sugar cane(Table 4). In the southeast corner of Western Australia,clearing and irrigation of land to grow cereals raised thewater table and caused the salinity of wetlands to rise.The 1960s was the beginning of the great developmentof water resources within Australia. In New South Wales,for example, a 25-year plan was initiated in 1971 tospend A$723 million (about US$60 million, in 1997dollars), primarily on building dams (WRIC 1971).Australia now boasts the largest per capita water storagein the world (Wasson and others 1996). In New SouthWales there are 144 large storage reservoirs, each with acapacity of greater than 1000 Ml (106 liters) (Kingsford1995). These have had a significant impact on wetlandsand water resources in the country. Management ofwater for irrigation, mainly with large dams, has severely

affected river flows (Walker 1985, Barmuta and others1992, Maheshwari and others 1995) and wetlands (Pres-sey and Middleton 1982) (Table 4). With the changedwater regime, many wetlands now store water perma-nently, which has killed aquatic vegetation adapted towet and dry cycles (Table 4). A more insidious problemis the impact of upstream diversion of water on theextent and duration of flooding (Table 4). A notableexample is the Macquarie Marshes (Figure 2).

Conservation values of the Macquarie Marshes. TheMacquarie Marshes form the extensive terminal wet-land of the Macquarie River (Figure 2), which beginsabout 460 km to the southeast with a catchment of73,000 km2. A small amount of water can flow throughto the Darling River. The marshes are one of sixwetlands listed under the Ramsar Convention in thestate of New South Wales (790,000 km2) and were oneof the first wetlands in Australia to be recognized fortheir conservation importance. Part was declared a birdand animal sanctuary at the beginning of this century(Paijmans 1981), culminating in the protection in 1971of 18,000 ha under legislation as a nature reserve.

The Macquarie Marshes are best known as one of the

Figure 2. A sample of significant wetlands in Australia af-fected by irrigated agriculture. Lines mark the major drainagedivisions in Australia. M marks the location of the MacquarieMarshes and the numbers refer to the following wetlands: 1,Swan Coastal Plain; 2, Lake Toolibin; 3, Ord and Parry Riverfloodplains; 4, Bool Lagoon; 5, Carrum wetlands; 6, Koo-wee-rup Swamp; 7, Macleay River floodplain; 8, Murray Riverwetlands; 9, Lake Albacutya; 10, Menindee Lakes; 11, Hattah-Kulkyne Lakes; 12, Kerang wetlands; 13, Barmah-MillewaForest; 14, Murrumbidgee wetlands; 15, Narran Lake; 16,Gwydir wetlands; 17, Wetlands of the Border Rivers; 18,Herbert River floodplain; 19, Bowling Green Bay wetlands.


Table 4. Sample of 20 key wetlands in Australia affected by irrigated agriculturea

Wetland StatusAgricultural




Barmah/MillewaForest

Ramsar site Diversion and regulation ofwater for irrigation.Timber harvesting. Flowsin the wetland regulated.

1936–present About 50% of wetland lost.Decreased floodfrequency and changesin season of flooding.Wetland vegetation lessreliant on floodingreplaced more aquaticvegetation.

Buckmaster andothers(1979), Bren(1988, 1992)

Wetlands of theBorder Rivers

No reservestatus

Diversion and regulation ofwater for irrigation.

1980–present Decreased wetlandflooding.

Kingsford(unpublished)

Bowling GreenBay

National park,Ramsar site

Water augmentation toinflowing rivers fromirrigation.

1970–present Altered hydro-perioddrowns vegetation.

Blackman andothers (1996)

Carrumswamplands

No reservestatus

Swamps drained foragriculture.

1870–1950 Wetland area declinedfrom 10,000 acres to 200acres.

Norman andCorrick(1988)

East coastwetlands ofNew SouthWales

IncludesKooragangIsland naturereserve

Drainage schemes to limitflooding damage toagricultural and urbanland.

1900–1980s Drainage affected 96% ofwetland area on MacleayRiver floodplain.

Goodrick(1970),Pressey(1989)

Gwydirwetlands

No reservestatus

Diversion and regulation ofwater for irrigation. 70%reduction in floods of 100Gl/month. Floodingfrequency halved, fromone in two years to one infour years. Drains andchannelization. Elevatedlevels of herbicides andinsectides (endosulfan)detected.

1960s–present Reduction in areas ofaquatic vegetation, reedbeds from 4,000 ha to250 ha. Abundance anddiversity of waterbirdsdeclined: 58 species to45 species.

Debus (1989),Keyte (1992),Bennett andGreen (1993)

Hattah-KulkyneLakes

National park,Ramsar site,biospherereserve

River regulation has reducedinflows to the lakes fromthe Murray River.

1900–present Increased blooms ofcyanobacteria. Reducedflood frequency.

Hull (1996)

Herbert Riverfloodplain

National park(part),wetlandreserves, fishhabitatreserve

Decline in water qualitycaused by sugar caneproduction. Drainsreplaced naturalwatercourses.

1960s–present Most of wooded swampsand many other wetlandsdestroyed.

Blackman andothers (1996)

Kerangwetlands

Ramsar sitewildlifereserves

Water levels heldpermanently high inwetlands. Increasedsalinity. Levees to controlflooding, channelling ofwater courses. Saline waterdisposed in somewetlands.

1936–present Prolonged inundationcaused loss of aquaticvegetation adapted towet and dry cycles.Increased salinityaffected fauna and flora.

Hull (1996)

Koo-wee-rupSwamp

No reservestatus

Drainage for agriculture. 1960–1980 No wetland remains,declined from 40,000 ha.No aquatic plants oranimals.

Norman andCorrick(1988)

Lake Albacutya National park,Ramsar site,NationalHeritage

Historical records indicatereduced flooding becauseof upstream diversion ofwater for irrigation. Risingsaline groundwater.

1920s–present Degradation of vegetationcommunities.

Hull (1996)


Table 4. (Continued)





MacquarieMarshes

Nature reserve,Register ofNationalEstate,Ramsar site

Diversion of water upstreammainly for irrigation.

1969–present Reduced wetland size by atleast 40%–50%. Numberof waterbirds and speciesin decline. Wetlandvegetation in decline.

Kingsford andThomas(1995)

MenindeeLakes

Included inKinchegaNational Park

Water levels kept artificiallyhigh for irrigation andpublic water supply.Tandou Lake no longer awetland.

1950s–present Aquatic vegetation killedby too much flooding.Reduced numbers ofwaterbirds. Waterbirdcommunity dominatedby piscivores. Erosion oflakeshores.

Kingsford(1995)

Murray Riverwetlands

No reservestatus

Water levels kept artificiallyhigh for irrigation on 35%of wetlands.

1900–present Death and deterioration offloodplain vegetation.

Bren (1990),Pressey(1990), Smithand Smith(1990)

MurrumbidgeeRiverwetlands

No reservestatus

Water levels kept artificiallyhigh; 62% of wetland areawith water levelscontrolled locally.

1950s–present 570 ha of floodplaineucalypt trees killed;ducks did not breedwhere water levels werehighly controlled.Breeding of herons,egrets, and cormorantsdependent on floodingof red gum. Loss of somebreeding habitat foregrets.

Briggs andothers(1994),Thorntonand Briggs(1994),Briggs andothers (1997)

Narran Lake Nature reserve Water diversion forirrigation.

1985–present Reductions of flow by 31%. DPI (1996)

Ord and ParryRiverfloodplains

Nature reserveand Ramsarsite

Building of reservoir (LakesArgyle and Kununurra).Reduced flooding. Ordirrigation scheme divertswater.

1972–present Prevented migration offish; impact ondownstream wetlands.Submerged seasonalwetlands (e.g.Packsaddle Swamp).

Lane andMcComb(1988)

Swan CoastalPlain

No reservestatus

Drainage of wetlands foragriculture, roads, urbandevelopment. Increasedwater levels.

up to 1964 70% of wetlands lost orsignificantly altered byclearing of vegetation.

Halse (1989)

SouthwestWesternAustralia

Affected naturereservesinclude LakesToolibin(Ramsarsite);Dumbleyung,Coyrecup,Pinjarrega,Nonalling,Beverley lakes

Clearing of drylandvegetation for agriculture.

1900–1960s Salinization of wetlands iscommon.

Halse (1987),Lane andMcComb(1988),Froend andothers(1987), Halseand others(1993)

Lower southeast wetlandsof SouthAustralia(include BoolLagoon)

Bool and HacksLagoon(Ramsar site;conservationpark)

Drainage to increaseavailability of lands forgrazing livestock.

1863–1981 Loss of wetlands; affected53% of flood proneareas; more than 93%loss of permanent lakesand swamps.

NRC (1993),Jensen andothers (1983)

aRefer to Figure 2 for location of wetlands.


more important sites in Australia for colonially breed-ing waterbirds (Marchant and Higgins 1990). Duringthe 1990 flood, more than 80,000 nests were estimatedin the Macquarie Marshes (Johnson personal communi-cation); before extraction of water, colonies were num-bered at more than 100,000 (Cooper 1954). In 1990,ciconiiformes were the most common colonially breed-ing waterbirds. Most were straw-necked ibis (Threskiornisspinicollis; 55,000) with glossy ibis (Plegadis falcinellus;1000), Australian white ibis (Threskiornis aethiopica; 6700),intermediate egrets (Ardea intermedia; 17,000), and ru-fous night herons (Nycticorax caledonicus; 1500). Seventy-two species of waterbirds are recorded from the Macqua-rie Marshes, including 43 breeding species (see list inKingsford and Thomas 1995). Seven of these are listedas threatened under legislation in New South Wales(e.g., magpie geese, Anseranas semipalmata) and 15 arecovered by bilateral migratory bird agreements betweenAustralia and Japan. The Macquarie Marshes have thelargest stand of river red gums (Eucalyptus camaldulensis)in northern New South Wales, the largest reed beds ofany wetland in New South Wales, and the most southerlyoccurrence of collibah woodland (E. coolibah) (EPA1995).

The Macquarie Marshes also act as a filtering system.Water quality is generally improved as it flows throughthe Macquarie Marshes. The marshes filter total phos-phorus, total nitrogen, and suspended solids whenflows are sufficiently high (DWR 1994, DLWC 1995).There is also some evidence that the Macquarie Marshesare reducing rising salt loads in the Macquarie River byremoving the salt and behaving as a groundwaterrecharge system (Williamson and others 1997).

Benefits to community. About 14% of the MacquarieMarshes is reserved under legislation (Kingsford andThomas 1995), with the rest managed by private land-holders under freehold or lease to the government ofNew South Wales. Most of these landholders graze cattleand have lived in the area since the beginning of the20th century. The value of their holdings is dependenton flooding, which provides forage for cattle. Based onNovember 1996 estimates (regional gross margin), thevalue of grazing in the Macquarie Marshes is estimatedto be A$5.2–7.5 million (about US$430,000–620,000)(Cunningham 1997). Of 27 landholders interviewedthroughout the Maquarie Marshes, all believed thatriver regulation and extraction of water had disastrouslyaffected the area (Cunningham 1997). As the wetlandhas contracted, so have their livelihoods. According toone landholder, whose family settled in the Marshes inthe 1880s, his capacity to raise cattle has declinedconsiderably because of water extraction upstream

(McHugh 1996). Grazing may also have significanteffects on wetlands (Robertson 1997).

Management of the Macquarie Marshes cannot besolely local. The reliance of other parts of Australia onthe successful breeding of waterbirds in the MacquarieMarshes, the size of the wetland, and its internationalrecognition mean that the wider Australian communityhas an input into its management. Tourism in the area isgrowing, despite the difficulty in accessing parts of theMacquarie Marshes. At least one landholder offersaccommodation for visitors. The reserve does not havethe status of a national park, so tourism is not encour-aged. No facilities are available within the MacquarieMarshes Nature Reserve but open days once a yearattract at least 100 people.

The Macquarie Marshes are an important part of theculture of Australian society. For the local rural commu-nities, the wilderness of the Macquarie Marshes wasregarded as a challenge for young men charged withrounding up cattle (McHugh 1996). On 9 April 1993,about 1000 people traveled to the Macquarie Marshesfor a concert (McHugh 1996). The band Siroccolaunched their tribute to the Macquarie Marshes (Wet-land Suite: A Celebration of the Macquarie Marshes) bystaging a concert that was broadcast by satellite by RadioAustralia (Australian Broadcasting Corporation) to anestimated 50 million people.

Impacts of irrigation and effects on wildlife. In 1896, thefirst weir was built on the Macquarie River to managewater. Nine large dams, five major weirs and severalminor weirs, a water transfer scheme, and numerousother regulatory structures (Kingsford and Thomas1995) store water for later release to a large irrigationindustry. About 89% of the water diverted from theMacquarie River is used for irrigation (DWR 1991).Irrigation increased after Burrendong Dam was built in1967. Burrendong Dam has a storage capacity 70%larger than any other regulatory storage in the Macqua-rie Valley. Irrigated cotton was first grown in the Valleyin 1967 (McHugh 1996) and now accounts for morethan half of the water use for irrigation (DLWC unpub-lished data). It peaked in 1993–1994 when 543,000 Ml(106 liters) were diverted for irrigation. Originallyflooding up to 1,280,000 ha (SKPPL 1984), the Macqua-rie Marshes now inundates about 130,000 ha duringlarge floods (Kingsford and Thomas 1995).

The impact of irrigated agriculture on the wetlandand its waterbirds is profound. The total amount ofwater reaching the Macquarie Marshes is a highlysignificant predictor of wetland size (Kingsford andThomas 1995). Due to reduction in flows as a result ofdiversion of water upstream mainly for irrigated agricul-ture, the wetland is now conservatively 40%–50% smaller


than it was before water was diverted (Kingsford andThomas 1995). Before the Burrendong Dam was built,about 50% of the water that passed the upstream gaugeat Dubbo reached the Macquarie Marshes. Now onlyabout 21% of this water reaches the marshes, despite nochanges in catchment rainfall in the period 1944–1993(Kingsford and Thomas 1995). Areas of river red gumsin the main area of the Macquarie Marshes havedeclined by about 14% (Brereton 1994) but may havedeclined by significantly more on the margins of themarshes. Red gums in one area declined by over 50%between 1934 and 1981; reed beds experienced similardeclines between 1963 and 1972 (Brander 1987). Watercouch (Paspalum paspaloides) has declined by 40% insome areas during the period 1949–1991, with exoticdryland vegetation replacing it (Brereton 1994). Num-bers of waterbirds and the numbers of species declinedin the period 1983–1995 (Kingsford and Thomas 1995,Kingsford unpublished data). Reduced flows have alsoimpacted the size of breeding colonies of ciconiiformes(Kingsford and Johnson unpublished data). Conserva-tively, this has probably meant that there are now about100,000 fewer nests over a period of 11 years as result ofwater that was diverted from the Macquarie River(Kingsford and Johnson unpublished data). Fish sur-veys also indicate a decline (WRC 1979).

A smaller scale impact is that of water levels that aremaintained higher than normal in some stream chan-nels to supply irrigation and livestock needs. Theseartificial levels have killed aquatic vegetation adapted toseasonal drying in parts of the marshes. Some channelshave eroded, limiting the potential for flows to go overtheir banks and inundate the floodplain (EPA 1995).

As well as impacts of irrigation upstream of theMacquarie Marshes, about 11,000 ha of the MacquarieMarshes were landscaped for irrigation, with aboutanother 4400 ha potentially irrigated during floods orhigh flows (McHugh 1996). In 1991 cotton was grownon the floodplain of the Macquarie Marshes, adjacentto the nature reserve (McHugh 1996).

Irrigation upstream of the Macquarie Marshes is alsoraising water tables, which has caused salinity problemsthat are contributing to long-term increases in thesalinity of water reaching the Macquarie Marshes (Wil-liamson and others 1997). Four pesticide productsoccur in the river: endosulfan, atrazine, prometryn, andparathion (O’Brien 1995). Most sampling during thesummer of 1994–1995 at two sites at the beginning ofthe Macquarie Marshes detected levels of endosulfangreater than 0.01 µg/l, which is the agreed thresholdfor protection of aquatic ecosystems (O’Brien 1995).

Water management plan and outlook for the future.Revision of the 1986 Water Management Plan for theMacquarie Marshes (DWR and NPWS 1986) began inMarch 1994. The name of this policy instrument beliesits importance; it deals with water management in theentire Macquarie Valley. The 1986 plan did not preventa rapid increase in diversions of water upstream of theMacquarie Marshes. There were 200 submissions to anissues paper and 1600 submissions to a draft revisedplan in 1995. The Macquarie Marshes Water Manage-ment Plan was published in August 1996 (DLWC andNPWS 1996) and aimed ‘‘. . . to identify and secureflows, from a finite water resource shared with others, toensure the ecological sustainability of the MacquarieMarshes’’ (DLWC and NPWS 1996). There were elevenrules about access to water. The main ones were anincreased allocation of water to the Macquarie Marshesof 75,000 Ml—in addition to 50,000 Ml that was alreadyprovided—and a limit on access to uncontrolled tribu-tary flows or dam spills of 50,000 Ml. For this process,uncontrolled flows from downstream tributaries or damspills are declared surplus and are accessible for theirrigation industry, which can pump water into largeoff-river impoundments. During one year in the early1990s about 200,000 Ml of this uncontrolled flow wasdiverted.

The effect of the rules for managing flows to theMacquarie Marshes is estimated to reduce by 14%average diversions to irrigation, resulting in a long-termaverage impact of 6% on gross economic margins in theMacquarie Valley (DLWC and NPWS 1996). However,the prediction of a 6% economic loss did not includethe positive economic benefits such as livestock grazing.Importantly, the plan established management prin-ciples for the sustainability of the Macquarie Marshes inclear recognition of the long-term impact of diversionsupstream. Although criticized by the irrigation commu-nity, the plan received some local support. Of 112riparian landholders between the southern end of themarshes and the Barwon River, mainly graziers, 109(97%) supported the initiative to restore flows to theMacquarie Marshes through the policy changes putforward in the Macquarie Marshes Water ManagementPlan. In contrast, the reception by the irrigation indus-try upstream of the marshes was hostile. The rural townof Trangie was closed down as 1200 of the ruralcommunity demonstrated against the policy. A groupset up to advise on water management in the MacquarieRiver, the Macquarie River Advisory Council, preparedan alternate plan after engaging a wetland ecologist. Inlate 1995, nine of the 12 members on the councilrepresented irrigators or had irrigation interests, andthere were no environmental representatives (Media


Associates 1997). Some of the proposals put forward bythe council were incorporated in the final MacquarieMarshes Water Management Plan, but insufficient scien-tific evidence was given to support their full alternateplan. Its focus was management of water within theMacquarie Marshes, ostensibly avoiding the issue ofincreasing diversions upstream. The 1996 plan estab-lished a much broader advisory group of 12 communitymembers, only one of whom directly represented irriga-tion interests.

The policy as set out in the Macquarie Marshes WaterManagement Plan (DLWC and NPWS 1996) representsa landmark in the sustainable management of waterresources in Australia. Nowhere else has the difficultproblem of ecological sustainability of wetlands and theimpact of irrigated agriculture and its diversion of waterupstream been seriously grappled with at a catchmentlevel. Moreover, of all the examples given in this paper,the Macquarie Marshes are the only wetlands wheredegradation has been effectively halted. Conditionshave stabilized primarily because of very strict controlson access to irrigation water. Importantly, there is a

commitment to evaluate the availability and allocationof water within the catchment as a whole rather thanfocusing on isolated or segmented areas. The key tosuccessful protection of these wetlands depended onclosing the loopholes that so often exist in watermanagement—loopholes that give agriculture first pri-ority for water. At Macquarie Marshes, the loopholeswere effectively closed by developing a plan for inte-grated management of the entire watershed, includingthe water needs for sustaining wildlife resources.

Africa

Background. The most extensive wetlands in theAfrican continent are the large seasonally inundatedfloodplains (Figure 3). These wetlands, which includenotable examples such as the Inner Delta of the Nigerin Mali, the Sudd of the Sudanian Upper Nile andZambia’s Kafue Flats, provide valuable habitats forwildlife. They support a huge variety of birdlife and arevital for many migratory species that winter within them(Hollis 1986, Treca and Ndiaye 1996). The presence ofwater in many floodplains during the dry season pro-

Figure 3. Major African floodplain wetlands.


vides important grazing areas for wild ungulates duringperiods when the surrounding drylands are desiccated.

In addition to their importance for wildlife, Africa’sfloodplains play a vital life-support role for a significantproportion of the continent’s population (e.g., Drijverand Marchand 1985). Human populations have forcenturies utilized the agricultural, fisheries, hunting,grazing, and water resources provided by floodplains(e.g., Adams 1996). These wetlands have rightly beentermed ‘‘the heart of Sahelian life systems’’ (Drijver andRodenburg 1988, Drijver and Van Wetten 1992).

Historically, the different uses of floodplain re-sources were integrated economically and ecologically(Adams 1992, Hollis and Acreman 1994). Floodplains

have been able to support wildlife and people. However,the last 40 years have witnessed the development ofmany large-scale water management schemes, fre-quently associated with dams and irrigated agriculture(Thompson 1996). In 1987, Van Ketel and othersidentified 114 dams that were likely to impact wetlandsin West Africa alone. Drijver and Van Wetten (1992)stated that by the year 2020 all Sahelian wetlands will besubject to the impacts associated with upstream dams.These impacts will have profound consequences for thewildlife and human populations that depend on thesewetlands. Table 5 provides examples of African flood-plain wetlands that, despite some degree of conserva-tion status, have been detrimentally affected by agricul-

Table 5. Examples of impact of agriculture on Africa’s floodplain wetlandsa



impactEffects on wetland


Logonefloodplain,Cameroon

Includes theWazaNational Park

Upstream barrage forirrigation and riversideembankment toprotect irrigationscheme.

1970–present Reduced wet seasoninundation and loss ofgrazing for wildlifeincluding ungulates andelephant.

Drijver andMarchand(1985),Wesselingand others(1996)

Floodplain ofthe BenueRiver,Cameroon

Close proximityto threenationalparks

Large dam and reservoirfor 29,000 ha ofirrigation.

1982–present Loss of important wildlifehabitat beneath thereservoir, reduction indownstream inundation,disruption of migrationroutes of large mammalsincluding buffalo,antelope and elephant.

Drijver andMarchand(1985)

Hadejia-NguruWetlands,northeastNigeria

Partly nationalpark andnaturereserves

Two large dams, onebarrage and twolarge-scale irrigationschemes upstream.Expansion of small-scale irrigation withinthe wetlands.

1971–present Reduced wet seasoninundation leading todeclines in wildlife habitat.Removal of naturalvegetation cover. Reportsof river pollution withagricultural chemicals.

Hollis andothers(1993a),Thompsonand Hollis(1995),Thompson(1995), thispaper

Phongolofloodplain,South Africa

Includes theNdmu gamereserve

Dam constructedupstream for 40,000 haof irrigated land.

1970–early1990s

Changes to hydrologicalregime of the floodplainincluding reduced floodflows and inundationextent. Recently anartificial flood regime hasbeen established.

Acreman(1994),Bruwer andothers (1996)

Senegal Delta,Senegal

Includes theDjoudjNationalPark, aRamsar site,WorldHeritage siteand nationalpark

Upstream dam forirrigation and hydro-power, downstreambarrage to preventsaline intrusion, riverembankments toprevent flooding,expansion of irrigatedagriculture.

1985–present Loss of wetland habitat tonumerous rice schemes.Reduced water supplies tosome wetland areas,reduced fish populations,Encroachment offreshwater vegetation intoareas of open water.

Drijver andMarchand(1985),N’diaye(1997), Vinke(1996)

aRefer to Figure 3 for location of wetlands.


tural activities. The floodplain wetlands of the Hadejia-Jama’are River Basin are a good example, with all theelements that characterize the conflict between agricul-ture, conservation, and sustainable wetland manage-ment in Africa.

Conservation values of the floodplain wetlands of theHadejia-Jama’are Basin. The largest floodplain wetlandswithin the semiarid Hadejia-Jama’are Basin are locatedaround the confluence of the Hadejia and Jama’arerivers (Figure 4). This area is commonly referred to asthe Hadejia-Nguru Wetlands (e.g., Hollis and others1993a). The wetlands are dependent upon wet seasondischarges originating in the wetter headwaters of thesetwo rivers. For much of the year the basin’s rivers arelargely dry, and it is not until the beginning of the wetseason in April or May that water begins to flow withintheir channels. Approximately 80% of the annual run-off upstream of the wetlands occurs during August andSeptember (Hollis and others 1993b). As dischargesincrease, floodwaters begin to inundate the wetland’sfadamas (the Hausa term for seasonally flooded areas).Peak flood extents, which historically often exceeded2000 km2, are attained during September–October(Thompson 1995). Subsequently, a gradual decline inflooding occurs so that by April only a few core areasremain inundated. These cover less than 10% of the

peak wet season flood extent (Polet and Thompson1996).

Vegetation communities within the wetlands reflectthe governing influence of the wet season floods. Thesurrounding areas that are not inundated are character-istically scrub and bushland dominated by Ziziphisjujuba, Acacia seyal, and A. arabica. Grassland dominatedby Andropogon gayanus and Oryza bathii borders theflooded zone, while semipermanent lakes and swampsare dominated by mats of floating Echinochloa stagnina(Adams and others 1993a).

The floodplains of the Hadejia-Jama’are Basin areexceptional for the support they provide to wildlife andhuman communities. Although Shelton (1984) reportsthat parts of the wetlands provide habitat for reedbuck(Redunca arundium), grey duiker (Sylvicapra grimmia),red-fronted gazelle (Gazella rufifrons), warthog (Phaco-choerus aethiopicus), and bush pig (Potamochoerus porcus),it is for their waterfowl populations that they arefamous. Annual bird surveys have identified over 70different waterbird species from 15 families (Garba Boyiand Polet 1996a, Polet and others 1997). In 1997 thewetlands hosted over 320,000 water-related birds, manyof which were Palearctic migrants. The importance ofthe wetlands for migratory birds has been emphasized

Figure 4. The Hadejia-Jama’are River Basin and the Hadejia-Nguru Wetlands.


by a number of workers. Perennou (1991) stated thatthey qualified as internationally important using Ram-sar criteria. More than 1% of the western Palearcticpopulations of ferruginous duck (Aythya nyoca) havebeen counted in the wetlands, while they play host toover 2% of the total West African populations ofwhite-faced tree duck (Dendrocygna viduata), spur-winged geese (Plectropterus gambensis), and knob-billedgeese (Sarkidiornis melanotos) (Garba Boyi and Polet1996b). Garba Boyi and others (1992) concluded thatthe Hadejia-Nguru Wetlands are the fifth most impor-tant site for Palearctic migrants in West Africa. Scott andRose (1996) identified the wetlands as a key site forAnatidae (swans, geese, and ducks) in Africa andwestern Eurasia.

The wetlands’ importance for wildlife is recognizedthrough a number of conservation oriented designa-tions. A central area of 938 km2 forms one of three sitesthat constitute the Chad Basin National Park (Mamza1995). Within the park hunting, fishing, grazing, agricul-ture, and other forms of disturbance are prohibited(Adams 1993). A number of smaller designated reservesalso exist within the wetlands, most notably the DagonnaWaterfowl Sanctuary in the northeast and the BaturiaWetlands Reserve in the west-central part of the wet-lands. Nigeria is at present not a signatory to the RamsarConvention. However, the Hadejia-Nguru Wetlandswould be a likely candidate for one of the country’s firstRamsar sites if Nigeria embraces the convention in thefuture (Akinsola and others 1996).

Benefits to community. The Hadejia-Nguru Wetlandsprovide multiple benefits for human communities. Theagricultural sector includes the cultivation of flood rice,recession and rainfed cropping, and small-scale irriga-tion based on surface and groundwater extraction(Polet and Thompson 1996). The wetlands are also animportant center of fish production, while the flood-plain forests provide fuelwood and timber. Barbier andothers (1991) showed that these three sectors have acombined value of US$51/ha or, when related to thewater required to inundate the floodplain, US$14,548/ha. The floodplain also provides important dry seasonpastures and numerous uses are made of wetlandvegetation for both livestock and humans. The annualfloods recharge the wetlands’ shallow alluvial aquifers,which are the principal sources of potable water for over1.5 million people.

Impacts of irrigation and effects on wildlife. Over the lastfew decades significant changes have taken place withinthe Hadejia-Jama’are Basin that have impacted both thewildlife and human populations within its floodplainwetlands. Drought has been a recurring influence thathas reduced river flows and consequently the extent of

inundation within the wetlands. A hydrological modelof the basin (Hollis and Thompson 1993a, Thompsonand Hollis 1995) shows that while flood extents ex-ceeded 2000 km2 in the 1960s, during the followingdecade the area inundated was commonly 1000–2000km2. Throughout the 1980s flood extents were evensmaller; in 1984 only 300 km2 flooded. Some relativelywet years have recently enabled flood extents to approxi-mate those experienced in the 1970s. Superimposed onthese natural variations are a number of human influ-ences that have impacted the wetlands. The drivingforce behind these changes has been irrigated agricul-ture.

Within the wetlands the expansion of small-scaleirrigation has led to the replacement of natural vegeta-tion or rainfed agricultural land with small (typically1- to 4-ha) plots in which relatively high-value cropssuch as wheat, peppers, onions, sweet potato, andtomatoes are grown. The expansion of this form ofagriculture was aided by a sharp rise in wheat prices inthe 1970s and 1980s resulting from a ban on wheatimports (Kimmage 1991). This coincided with thedissemination of approximately 70,000 portable irriga-tion pumps by the Kano State Agricultural and RuralDevelopment Programme (KNARDA). This change inagricultural practices has enabled the cropping of areaspreviously considered marginal for cultivation (Akin-sola and others 1996). It has led to the removal ofhabitat for wildlife, although at present no detailedestimates of the magnitude of this loss have beenattempted. Muslim and Umar (1995) suggested thatagricultural intensification has also resulted in increas-ing concentrations of chemical pollutants, largely fromfertilizers, within the wetland’s rivers.

A far more widespread impact on the wetlands hasresulted from the construction of large-scale irrigationschemes and associated dams. There are currently over20 dams within the river basin, all upstream of theHadejia-Nguru Wetlands. The largest are associatedwith two major irrigation schemes located on theHadejia River or its tributaries (Figure 4). The KanoRiver Irrigation Project (KRIP) is the biggest scheme atpresent. Irrigation water is provided by Tiga Dam, thelargest dam in the basin, which was constructed duringthe period 1971–1974. The plan for KRIP envisaged itsdevelopment in two distinct phases. A total irrigatedarea of 27,000 ha was planned for phase I (KRIP-I),while phase II (KRIP-II) would add a further 40,000 ha.Construction of phase I began in 1977, and to datearound 14,000 ha have been completed. The maincrops grown during the wet season are rice, maize,cowpeas, and millet, while in the dry season tomatoesand wheat predominate (Adams and others 1993b).


Plans to expand the scheme do exist, although FAO(1993) has highlighted the prerequisite for improvedmaintenance and rehabilitation of existing sections ofthe scheme.

The first phase of the Hadejia Valley Project (HVP),the second major irrigation scheme, is under construc-tion. The scheme involves a barrage across the HadejiaRiver just upstream of the Hadejia-Nguru Wetlands anda planned 12,500 ha of formal irrigation. At presentaround 7000–8000 ha have been completed. ChallawaGorge Dam on the Challawa River, upstream of Kano, islinked to the HVP. The dam, which was completed in1992, is designed to store water during the wet seasonand subsequently release it downstream for use on theHVP.

The development of these large-scale schemes hashad a tremendous impact on the hydrology of the riverbasin. These impacts have been concentrated in down-stream areas. By retaining and utilizing water upstream,the schemes have reduced the magnitudes of down-stream flood discharges and thereby the area inundatedwithin the floodplain. The first impacts were felt soonafter the closure and filling of Tiga Dam in 1976.Reduced flood extents resulted in crop failures anddeclining fisheries within the wetlands. Stock (1978)suggested that the impacts of Tiga Dam were moresevere than those associated with the droughts of theearly 1970s. The declining flood extents are confirmedby the reported loss of recession farms along theHadejia River (Wallace 1980). In 1977 local people werecomplaining that ‘‘the land is dying’’ (Kulatunga andothers 1977, cited in Olofin 1996). Hydrological model-ing undertaken by Hollis and Thompson (1993b) andThompson (1995) shows that Tiga Dam and the KRIPhave reduced peak flood extents by an average of 11%.These reductions are much more pronounced in dryyears when ecosystems are already stressed. In 1984, forexample, only 55% of the area that would have beenflooded without the dam and irrigation scheme wasactually inundated (Thompson 1995).

Declining flood extents have recently been com-pounded by the completion of the Challawa Gorge Damand work on the Hadejia Valley Project. For example,dramatic declines in the inundated area were reportedin 1992, the year in which the Challawa Gorge Damcame into operation. The hydrological model showsthat flood extents are, on average, over 17% lower withthe current extent of irrigation on the KRIP and HVPthan those that could be anticipated if the schemes werenot in place (Thompson 1995).

The negative impacts of declining flood extentsupon human activities within the wetlands have beenwidely reported (e.g., Hollis and others 1993a). Wildlife

can be expected to have been similarly affected. Forexample, the Baturia Wetland Reserve lies along theKeffin Hausa River, a major tributary of the HadejiaRiver. Historically the reserve was extensively inundatedin the wet season. However, in recent years the area hasbeen largely dry as flows within the Keffin Hausa havebeen reduced by drought, upstream irrigation schemes,and sedimentation within its channel. Groundwaterlevels in the area appear to have declined because therecharge provided by the floods has been lost. Conse-quentially the reserve’s groundwater woodland is becom-ing degraded (Adams 1993). This process has beenexacerbated by the illegal large-scale cutting of fuel-wood in the area. The future of the reserve is uncertain.

Thomas and others (1993) predicted that sincefloodplain fisheries are closely related to flood extent(e.g. Welcomme 1985), the upstream irrigation schemeswill have serious impacts on fish communities. This, inturn, has significant implications for the fauna depen-dent upon fish. It is a second blow to the waterfowl ofthe wetlands whose available habitat has been reducedby the declining inundation. Polet and others (1997)identified a close relationship between flood extent andnumbers of water-related birds. Garba Boyi and Polet(1996a) found that both the number and speciesdiversity of waterbirds were diminished in recent yearsof poor flooding. In particular, Akinsola and others(1996) highlighted the declining populations of largebirds such as cranes, storks, and pelicans, which theyattributed to declining flood extents. The remainingbirds are congregating in the few remnant core areasthat are flooded on a regular basis (Olofin 1996). Thecompetition between wildlife and human activities suchas agriculture and fishing is increasing in these areas.This conflict is exacerbated by a growing human popu-lation within the wetlands and the expansion of small-scale irrigation. Additionally, the concentration of birdsin a few areas favors illegal hunting, which is a seriousproblem within the wetlands (Akinsola 1996). Anyfurther expansion in the area of large-scale irrigationwithin the basin will clearly have tremendous implica-tions for wildlife and human communities within thewetlands. In particular, plans for 84,000 ha of irrigationand a massive dam at Kafin Zaki on the as yet un-dammed Jama’are River will reduce flood extents by anaverage of over 50% (Thompson 1995).

Water policy and outlook for the future. The clear conclu-sion from this case study is that any form of conserva-tion initiative for the wetlands must encompass activitiestaking place within the whole river basin. The majorimpacts on the floodplains of the Hadejia-Jama’areBasin have come from irrigation schemes several 100


km upstream. The example of the Baturia WetlandReserve indicates that bestowing a protected status onan area does not prevent damage resulting from activi-ties beyond the boundaries of the protected area.Within the Hadejia-Jama’are Basin considerable progresshas been made towards the development of an inte-grated system for the allocation of water among thedifferent parts of the basin (Polet and Thompson1996). A water management plan is currently beingprepared that will incorporate the water requirementsof the wetlands as well as those associated with agricul-ture, domestic supplies, and industry. The plan willinclude the release of artificial floods from upstreamdams in order to maintain inundation within thefloodplain (Thompson and Hollis 1995). Much of thecredit for these promising developments lies with theHadejia-Nguru Wetlands Conservation Project, an IUCNfield project based within the wetlands.

Central Asia

Synopsis of the Aral Sea episode. Spanning the bordersof three former Soviet republics (Kazakhstan, Uzbe-kistan, and Turkmenistan), the Aral Sea was once theworld’s fourth largest terminal lake (area 68,000 km2,volume 1090 km3). It is being desiccated due to waterdiversions for agricultural irrigation. During the 1950sand 1960s, plans were developed for major expansion ofirrigation in the Aral Sea Basin. At that time, it waspredicted that the increased water demands wouldreduce inflow to the Aral Sea and reduce its size.However, using a typical agricultural cost–benefit sce-nario, most state authorities, and some scientists, viewedthis as a worthwhile trade-off—river water would be farmore valuable if used for irrigation than if allowed toreach the sea. This ecologically short-sighted, oversimpli-fied scenario compared anticipated economic gainsfrom irrigated agriculture with tangible (existing) ben-efits from the sea. Not surprisingly, the expected ben-efits from agriculture won out. Given the positiveeconomic projections, many viewed the inevitable shrink-age of the Aral Sea to a brine lake as being desirable.The possibility of significant adverse environmentalimpacts was largely dismissed—the saving graces ofirrigation were supposed to far outweigh any minoreffects that might occur.

Large-scale irrigation quickly changed the Aral Seaecosystem. Between 1960 and 1987, the surface eleva-tion of the Aral dropped by almost 13 m, and its areadecreased by 40% (Micklin 1988). If current waterdemands for irrigation continue unchecked, the AralSea will shrink to a salt-brine remnant that is unfit forhuman, agricultural, or wildlife use early in the nextcentury. Although relatively unpublicized and unknown

in the Western Hemisphere compared to the previouscase examples from North American and Australia, thescale of impacts to the Aral Sea—on such a large body ofwater in such a short period of time—is unprecedented.The result ranks as arguably one of the world’s mostnotorious environmental catastrophes, surpassing thenuclear contamination at Chernobyl and the petroleumspill of the Exxon Valdez. Russian commentators havereferred to the situation as an impending disaster andone of the greatest ecological problems of the 20thcentury.

Some of the severe environmental problems thathave occurred in the Aral Sea episode include: (1)Exposure of salt crusts—when the sea shrank, saltsaccumulated on the bottom and exposed some 27,000km2 of salt-encrusted beaches. Once dried, this crum-bling salt is blown for distances up to 1000 km inmassive salt-dust storms. Twenty-nine of these stormsoccurred between 1975 and 1981 alone. An estimated43 million metric tons of salt are deposited annually asaerosols by rain and dew over a 200,000 km2 area.Numerous wetlands and plant communities far distantfrom the Aral Sea have been heavily impacted becauseof this airborne salinization. (2) Loss of fish species—biological productivity has steeply declined due tosalinization of the water. By the early 1980s, 20 of 24native fish species had disappeared, and the commer-cial catch (48,000 metric tons in 1957) fell to near zero.Some fish canneries on the shores of the Aral Sea haveclosed (some fishing villages now lie 80 km from theshoreline); others slashed their work forces and persistonly because of fish imported at high-cost from theAtlantic, Pacific, and Arctic oceans. Contaminated irri-gation drainage (pesticides and herbicides) has pol-luted the water and fishery in several locations, prompt-ing a halt to commercial fishing. Employment related tothe Aral fishery, reported at 60,000 in the 1950s, hasdisappeared, leading to abandonment of many fishingvillages. (3) Impacts on human health (UNEP 1992,Perera 1993, Pearce 1995)—in Karakalpakstan, a semiin-dependent republic of Uzbekistan: (a) 97% of 700,000women are anemic (more than five times the number adecade ago); (b) there is a rising incidence of kidneyand thyroid disease and of esophageal, stomach, andliver cancer in women; (c) the incidence of viralhepatitis has risen by 50% over last 10 years; (d) one infive men is rejected as medically unfit for militaryservice; (e) life expectancy is 20 years less than averagefor rest of the former Soviet Union; (f) infant mortalityis 50% above average for Uzbekistan and highest in theformer Soviet Union (similar data are emerging forother areas close to Aral Sea); (g) the Uzbekistangovernment reports that 90% of irrigated fields in


Karakalpakstan are salinated, one in five has beenabandoned, and 80% of fields in Kzyl Orda are affectedby salt; and (h) the United Nations estimates that 75million tonnes of salt, chemicals, and dust enter theatmosphere from the seabed during dust storms eachwinter. (4) Loss of wetlands and wildlife—the extensivedelta wetlands that once existed at the mouth of the SyrDar’ya and Amu Dar’ya rivers disappeared, along withthe important ecological functions and societal benefitsthey provided, i.e., vast marsh grass acreage that formeda natural feed base for livestock, spawning grounds thatsupported commercial fishing, commercial huntingand trapping, abundant reeds that were harvested forindustry, and irreplaceable habitat for wildlife conserva-tion. Native plant communities in the remnant wetlandshave degraded and, in some locations, completelydisappeared. Much of the animal fauna that utilized thepreirrigation wetlands is gone, for example, muskrat(Ondatra zibethica), wild boar (Sus scrofa), deer (Cervussp.), golden jackal (Canis aureus); numerous birds, forexample, ibis (Platalea leucorodia), pelican (Pelecanuscrispus), swan (Cygnus olor), and flamingo (Phoenicopterusruber); and several endangered species such as the Asiantiger (Panthera tigris). By the 1980s only 38 (20%) of the173 animal species that once lived in the Aral wetlandssurvived (Micklin 1988).

The future of the Aral Sea and its remnant wildlifepopulations is uncertain at best. Reversing the sea’srecession and many of the associated environmentalproblems could be achieved if more freshwater reachedit. However, the water supplies are now ingrained into anew agricultural economic base—created and justifiedon false assumptions—that makes this possibility re-mote.

There may be ways to partially restore the sea withexisting water supplies. By 1990 the sea’s progressive fallin surface level divided it into two sections; a smallnorthern part (Small Aral) and a much larger anddeeper southern part (Large Aral). In 1992 an earthendam was built to contain flows in the Small Aral as anattempt to stabilize the ecosystem within this smallportion of the sea (Aladin and others 1995). Resultswere dramatic. Within nine months, the surface levelrose by more than a meter and salinity began todecrease. Containing the inflow of freshwater signifi-cantly enlarged the brackish water zone of the Syrdar’yaRiver estuary and enabled freshwater fish to leave theSmall Aral and feed in areas not occupied for 10–15years. Invertebrates (amphipods and mysids), reeds,wading birds, and ducks returned to the estuary andrestoration of some of the former biological diversitywas evident. However, the dam broke in only ninemonths and these ecological improvements were quickly

lost. In light of the 1992 experiment there has beenconsiderable support for rebuilding the dam to make ita permanent part of the Aral Sea’s long-term manage-ment strategy (Aladin and others 1995). Althoughconditions in the Large Aral would continue largelyunchanged, the positive ecological benefits, combinedwith the fact that most of the human population andeconomic base resides along the coast of the Small Aral,makes this a favored option.

Preservation of the entire Aral Sea ecosystem wouldlikely require implementation of a controversial projectto divert water from western Siberia into the Aral SeaBasin. However, this proposal is meeting with strongopposition from those that would have to give up claimto their water. Having seen the disaster caused by watershortages at the Aral, sharing is difficult even amongnations with close cultural and economic ties. The onlypositive action taken thus far has been construction of acollector canal to transport contaminated irrigationdrainage from the Amu Dar’ya basin to the sea. It maybe too late for the magnitude of changes necessary tosignificantly improve the condition of the entire AralSea; it may already be beyond rescue (Micklin 1988).

How to Reverse the Trend: Recommendationsfor Water and Wetland Management Policy

The preceding examples illustrate how irrigatedagriculture has shaped water utilization and allocationpolicies at the expense of some of the world’s mostecologically valuable wetlands. Even the recommenda-tions of prominent scientists and review boards, throughsuch highly visible and global efforts as the RamsarConvention, have done little to slow their continueddegradation. This longstanding trend must be reversedif wetlands are to provide the critical habitat necessaryfor effective wildlife conservation and associated ben-efits to society. Two principal conditions must be met:(1) further degradation from existing irrigation activi-ties must be prevented and adverse impacts mitigated,and (2) adequate planning and assessment for pro-posed irrigation projects must take place. Althoughthese conditions are conceptually simple and straightfor-ward, they are virtually impossible to achieve withoutfirst understanding a basic truth: irrigation policiestypically revolve around perceived economic and soci-etal benefits, many of which probably can not bejustified environmentally or economically if examinedclosely. For example, the anticipated economic benefitsof agricultural irrigation projects may be more thanoffset by environmental degradation and artificial watershortages (Livingstone and Campbell 1992, Contreras-Balderas and Lozano-Vilano 1994, Psychoudakis and


others 1995). In some cases, large-scale irrigated agribusi-ness can actually contribute to high poverty ratesamong local communities (e.g., Grondin 1986). Ifwetland managers wish to achieve meaningful changesin water policy, then they should exploit these inherentweaknesses.

The question of how best to resolve water issues maybe answered by examining two of the key perceptionsthat have guided policy decisions: (1) water is wasted ifit goes out to sea or into a wetland (many farmersbelieve that water that passes them by is not beingproperly utilized), and (2) agriculture provides manyeconomic benefits to many people—locally and faraway—but wetlands provide few economic benefits andthey are restricted to local people. These perceptionsare clearly not true. One of the key wetland principles isthat they often provide functions and values beyondtheir boundaries and far from adjacent ecosystems(Richardson 1994). Moreover, wetlands provide manybenefits (not necessarily obvious to water policy mak-ers) that may far exceed the value of agricultural crops,if carefully enumerated. For example, African flood-plain wetlands provide agricultural, fishing, and fuel-wood benefits that are over five times the value offormal irrigated agriculture (Thompson and Hollis1995, Barbier and Thompson 1998). The relative eco-nomic value of wetlands becomes even greater if theapparent benefits provided by agriculture contain hid-den costs. For example, irrigation production is oftensubsidized by public revenues (usually unknown to mosttaxpayers) through government supply of low-cost wa-ter, encouraging surplus production year after year, andgovernment (artificial) markets for buying surpluses(Lemly 1994a). Other hidden costs include the tax-payer expense of building and maintaining infrastruc-ture (dams, weirs, canals) and the expense of rehabilitat-ing degraded rivers and wetlands, which in Australiaamounted to A$3.32 billion (about US$280 million, in1997 dollars) in 1994 alone (DEST 1996), not countingenvironmental subsidies (i.e., impacts on fauna andflora). Wetland managers and wildlife conservationistsshould develop an approach that illustrates the eco-nomic costs (liabilities) of agriculture and highlightsthe values (benefits) of wetlands. This can give wetlandsand wildlife an equal or greater priority than agricul-ture in water policy decisions.

The goal is to fairly weigh up the benefits and costs ofagriculture and conservation. A strong, perhaps indisput-able case for conservation can be made based uponeconomic benefits, i.e., the monetary values derivingfrom consumptive (e.g., hunting, fishing, trapping,timber, grazing, subsistence) and nonconsumptive (e.g.,ecological, aesthetical, heritage, cultural, biodiversity,

conservation) uses of wetlands and wildlife. A compel-ling case is necessary because of a simple truth—political actions shaped by economic forces drive waterpolicy. Agricultural interests typically have the ear (andoften the wallet) of water policy makers. It is not enoughfor wetland managers and conservationists to be vocaland assertive about water needs for wildlife—this ap-proach has failed time after time. A compelling eco-nomic case must be presented, supported by cleardocumentation, before recommendations for conserva-tion are seriously considered or adopted. Regardless ofwhether the issue is wetlands, irrigation, or some otherwater use, the greater the associated economic values,the more attention it will receive by policy makers.

Some of the key elements in an economic-basedapproach to wetland management include: (1) provid-ing policy makers with empirical data on the values(existing and potential revenues) of consumptive andnonconsumptive use of wildlife (e.g., recreation, hunt-ing, fishing, birdwatching, maintenance of threatenedor endangered species); (2) providing policy makerswith data on the monetary benefits of preserving orexpanding wetlands or restoring degraded wetlands toimprove flood control, erosion/sediment/nutrient con-trol, timber production, food production for humans(e.g., fish, shrimp, ducks), quantity and quality of watersupplies for off-wetland uses (e.g., human consumptionand domestic use); and (3) providing policy makerswith data on the monetary value (losses) resulting fromexisting or potential degradation (economic benefitsnot being realized due to impacts from agriculturalirrigation, subsidies, rising groundwater, salinity, ero-sion, etc).

Recognition of the importance of demonstrating theeconomic value of wetlands has led to a number ofpublications that outline the approaches that can beadopted (e.g., Barbier and others 1996, Costanza andothers 1997). An excellent example of how to estimatewetland values for regional watershed planning is givenby Hruby and others (1995). Wetland preservationproduces two types of economic value: use value (con-sumptive or nonconsumptive) and nonuse (existence)value. Determining use values is fairly straightforwardsince the product or benefit carries an established,known cost. However, it is seldom done. It seems to bemuch easier to measure farm inputs/outputs in supportof irrigation than to document wetland values. In theMacquarie Marshes, for example, no attempt was madeto tabulate the economic benefit provided by floodplaingrazing as a way to counter the economic analysis thatshowed how changes in water management could affectirrigation.

Estimating nonuse values is somewhat more elusive


and depends upon societal perceptions of wetlandfunctions, the culture and needs of the people whoexploit them, and, to some extent, their location.However, it is critical that nonuse values be includedbecause wetlands provide benefits to both the local andglobal economy that are not easily recognized and areoften given too little weight in policy decisions (Cos-tanza and others 1997). A survey of public attitudes andwillingness to pay for wetland preservation/expansionis one method for ascribing values to nonuse attributesof wetlands (Loomis 1990, Whitehead and Blomquist1991, Stevens and others 1995). Nonuse values canoften exceed use values by a substantial margin. It ispossible for these values to be considered in the sameway we might believe in artistic values or heritage valuesor quality-of-life values. Including nonuse values in aneconomic approach to wetland management can makea key difference when agricultural interests are pittedagainst wetlands and wildlife. For example, the NewSouth Wales government in Australia reached decisionsfor managing the Macquarie Marshes based in largepart on ecological grounds (wildlife preservation) de-spite considerable lobbying by the irrigation industrywith arguments that about A$35 million (about $US3million) and about 500 jobs would be lost (MDBMC1996, Morrison and Kingsford 1997).

To produce the data necessary for an economic-based approach, wetland managers may need to enlistthe assistance of other professionals, particularly ingathering information for items 2 and 3. For example,comprehensive environmental assessments that incorpo-rate geological, hydrological, and biological compo-nents should be made of existing irrigation projects todetermine if the quantity or quality of water suppliesreaching wetlands is unacceptably affected (e.g., throughwater diversions, pesticide contamination, salinization,subsurface irrigation drainage, etc.). Wildlife biologistsand wetland scientists may determine if ecologicalviability of the wetland is threatened. Knowledgeableauthorities in hydrology, aquatic toxicology, and ecologi-cal risk assessment could also broaden the evaluationand assessment (Lemly 1997, Lemly and Richardson1997). The economic impact of detrimental ecologicaleffects should be conveyed to management authoritiesand policy makers and also to the local communitiesthat will be affected (educating the public can create apowerful force in support of conservation). This willillustrate the extent to which perceived benefits fromagriculture are offset by the actual economic andsocietal benefits from wetlands. For example, Barbierand Thompson (1997) show that the economic benefitsof developing all the irrigated agricultural schemesplanned for the Hadejia-Jama’are Basin account for less

than 14% of the economic losses that would result fromreduced inundation of the floodplain.

Proposed agricultural irrigation projects should un-dergo a rigorous technical review (by experts in thevarious disciplines discussed above) to assess waterdemand and supply relationships and to determine thepotential for water deficits, salinization, contamination,subsurface irrigation drainage, and impact on wetlands.Preventing wildlife problems through a preirrigationscreening process will result in less adverse impacts toagriculture than correcting, at very high cost (usuallyborne by the taxpayers), environmental damage once ithas occurred (Lemly 1993, 1994a). Identifying andevaluating potential problems is the key. For example,information on local geology can be used to determinethe location of impermeable subsurface soils and iden-tify areas that would become waterlogged and produceirrigation drainage that could contain potentially harm-ful levels of soil trace elements (e.g., selenium, arsenic,boron). These areas should probably not be irrigated.

Projects that involve water diversions impose a highdegree of environmental risk because they can greatlymodify the quality of water reaching or residing inwetlands even though water quantity issues may be themost obvious concern and may seemingly be accountedfor. As the previous case examples illustrate, terminalwetlands are some of the most valuable and highlyrecognized for wildlife conservation, and they are alsoespecially vulnerable to progressive declines in waterquality because of evaporative concentration of saltsand contaminants as freshwater inflows are reduced. Inthe Lahontan Valley wetlands of Nevada, for example,gradual changes in aquatic vegetation and declines inwildlife food plants and fish due to increased salinityand buildup of contaminants took place over a 40-yearperiod, even in the best marshes where water levels weremaintained similar to historic conditions (Hoffman andothers 1990, Hallock and Hallock 1993, Lemly 1994a).A cascade of subtle, but important, biological effectscan occur if water quality is changed. Thus, evenprojects that will apparently not cause water quantityproblems must be evaluated very cautiously becausethere are many hidden dangers associated with divert-ing freshwater supplies away from wetlands.

Proper analysis of wetland functions at an ecosystemscale can determine the necessary hydrologic regimeand also identify risks from various amounts of waterreduction (Lemly 1997, Lemly and Richardson 1997).Simply maintaining flooded conditions may not sufficebecause some wetland flora and fauna require a sea-sonal dry period. Moreover the timing of water inputsor reductions in flow (hydroperiod) may conflict withthe normal seasonal occupancy and utilization by wild-


life. Both the biological system of a wetland and itshydrological underpinnings must be understood beforeadequate plans can be made to preserve it. An environ-mental assessment that integrates wetland ecology, hy-drology, geomorphology, and soils can greatly improvethe evaluation of proposed water development projectsand identify likely impacts to wildlife. Importantly, thisapproach can be used to determine whether a watermanagement scenario poses an unreasonable risk (bio-logically defined) to the sustainability of a particularwetland (Lemly and others 1998).

Conclusions

The conflict between irrigated agriculture and wild-life conservation has reached a critical point on a globalscale. Many key wetlands are now a mere shadow of whatthey once were in terms of biodiversity and wildlifeproduction. Not only does local wildlife suffer, includ-ing extinction of highly insular species, but a rippleeffect impacts migratory birds literally around theworld. Pleas and declarations made by scientists andenvironmentalists calling for wetland preservation havegone largely unheeded. Recent developments such asthe Biodiversity Convention of the United NationsConference in Rio de Janeiro (Denny 1994) showwillingness to resolve environmental issues related towetlands. Agenda 21, a global partnership for sustain-able development in the next century, was established.Although the goals are noble, conferences such as thismay merely establish political correctness rather thaninstitute meaningful changes in environmental manage-ment policy. ‘‘Care must be taken that the euphoriaborn at the Rio Conference is not allowed to degenerateinto a series of platitudes in which words like biodiver-sity and sustainable development become political wordsof convenience rather than words of true meaning’’(Denny 1994). This quote highlights the key failing ofpast efforts: much is said and written, but it is business asusual on Monday morning. Moreover, the track recordestablished over the past 40 years suggests that sustain-able development is a political code name for perpetualgrowth, used strategically to make development morepalatable to those who would oppose it (Willers 1994).

Agricultural threats to wetlands and wildlife conserva-tion are often disguised within a sustainable develop-ment scenario, i.e., that continued growth and develop-ment are compatible with environmental constraints. Asnoted by Pearce and others (1989), ‘‘sustainable devel-opment has come to mean whatever suits the advocacyof the individual or group concerned.’’ Advocacy forsustainable agriculture under a false pretense of environ-mental compatibility has been a principal factor guid-

ing water policy decisions for decades. Environmentalmanagement has been intense and largely in onedirection—toward agricultural development. Yet, therecurring result has been that so-called sustainabledevelopment guaranteed the deterioration of wetlandecosystems and loss of biodiversity.

Recent surveys reveal that steady growth of irrigatedagriculture is continuing to occur (e.g., Anonymous1997). Water demands for domestic and industrial usewill no doubt expand substantially over the next 30years (Postel and others 1996). However, overcomingthe water policy inertia exerted by agriculture in orderto achieve wetland preservation goals is not a futileproposition. In many cases, informing and educatinglocal communities can be a pivotal factor in watermanagement decisions. Perhaps the most importantmessage we wish to convey in this paper is that ecologi-cal disasters caused by agricultural irrigation are notinevitable. Rural communities whose rivers and wet-lands have not yet been exploited can mobilize and dosomething before it is too late. Changes can be broughtabout to improve the management and ecologicalcondition of those that have been exploited. Withcooperation and strategic planning, local citizens andwetland managers can have a significant effect on howwater policies are developed and implemented. Effortsat the local level, on a case-by-case basis, are what willcause the changes necessary for wildlife conservation.Detailed economic valuation of wetland resources andapplication of the resultant ecosystem capital in waternegotiations should be the major focus of these efforts.

A clear conclusion from this paper is that any form ofconservation initiative for wetlands must encompassactivities taking place within whole watersheds. Achiev-ing success will depend on how well an integratedsystem for the allocation of water among the differentparts of the basin can be developed and implemented.Water management plans that acknowledge and explic-itly incorporate the water requirements of wetlands aswell as those associated with agriculture, domesticsupplies, and industry are necessary. Negotiating agree-ments that satisfy all parties will be difficult at best.However, the reversal of degradation in Australia’sMacquarie Marshes and the progress evident in restor-ing Nigerian floodplain wetlands demonstrate thatecologically sound water management policies are attain-able for wetlands on a large scale despite widely diver-gent interests and priorities. We hope that this paperwill help in on-going efforts to develop water policiesthat will conserve wetlands and wildlife around theworld.


Acknowledgments

We thank the following individuals for providingreview comments that improved this paper: Drs. S. V.Briggs, C. A. Dolloff, M. T. Maher, Mr. B. Johnson, andMr. G. Polet. Information on impacts of agriculture onAustralian wetlands was provided by A. Corrick, A.Jensen, S. A. Halse, and J. G. Blackman. We alsoacknowledge the support and encouragement of theHadejia-Nguru Wetlands Conservation Project andIUCN during the course of research in northeastNigeria.

Literature Cited

Acreman, M. C. 1994. The role of artificial flooding in theintegrated development of river basins in Africa. Pages35–44 in C. Kirby and W. R. White (eds.), Integrated riverbasin development. Wiley, Chichester, UK.

Adam, P. 1995. Urbanization and transport. Pages 55–75 in R.Bradstock, T. D. Auld, D. A. Keith, R. T. Kingsford, D.Lunney, and D. Sivertsen (eds.), Conserving biodiversity:Threats and solutions. Surrey Beatty & Sons, Sydney, NewSouth Wales, Australia.

Adams, W. M. 1992. Wasting the rain: Rivers, people andplanning in Africa. Earthscan, London.

Adams, W. M. 1993. The wetlands and conservations. Pages211–214 in G. E. Hollis, W. M. Adams, and M. Aminu-Kano(eds.), The Hadejia-Nguru Wetlands: Environment, economyand sustainable development of a Sahelian floodplain wet-land. IUCN, Gland, Switzerland.

Adams, W. M. 1996. Economics and hydrological managementof African floodplains. Pages 21–33 in M. C. Acreman, andG. E. Hollis (eds.), Water management and wetlands inSub-Saharan Africa. IUCN, Gland, Switzerland.

Adams, W. M., M. Garba Boyi, and G. E. Hollis. 1993a. Naturalresources of the Hadejia-Jama’are floodplain. Pages 11–18in G. E. Hollis, W. M. Adams, and M. Aminu-Kano (eds.),The Hadejia-Nguru Wetlands: Environment, economy andsustainable development of a Sahelian floodplain wetland.IUCN, Gland, Switzerland.

Adams, W. M., G. E. Hollis, and I. A. Hadejia. 1993b.Management of the river basin and irrigation. Pages 119–148 in G. E. Hollis, W. M. Adams, and M. Aminu-Kano(eds.), The Hadejia-Nguru Wetlands: Environment, economyand sustainable development of a Sahelian floodplain wet-land. IUCN, Gland, Switzerland.

Akinsola, O. A., A. U. Ezealor, and G. Polet. 1996. Conserva-tion of waterbirds in the Hadejia-Nguru Wetlands, Nigeria:Current efforts and problems. Paper presented at the 9thPan African ornithological congress, Accra, Ghana, 1–8December 1996.

Aladin, N. V., I. S. Plotnikov, and W. T. W. Potts. 1995. The AralSea dessication and possible ways of rehabilitating andconserving its northern part. Environmetrics 6:17–29.

Anonymous. 1997. 1996 irrigation survey reflects steady growth.Irrigation Journal Jan/Feb.

Barbier, E. B., and J. R. Thompson. 1998. The value of water:Floodplain versus large-scale irrigation benefits in northernNigeria. Ambio 27:434–440.

Barbier, E. B., W. M. Adams, and K. Kimmage. 1991. Economicevaluation of wetland benefits: The Hadejia-Jama’are flood-plain, Nigeria. London Environmental Economics Centrediscussion paper DP 91-02. International Institute for Envi-ronment and Development, London.

Barbier, E. B., D. Knowler, and M. C. Acreman. 1996. Eco-nomic valuation of wetlands: A guide for policy makers andplanners. IUCN Publications Unit, Cambridge, UK.

Barmuta, L. A., R. Marchant, and P. S. Lake. 1992. Degrada-tion of Australian streams and progress towards conserva-tion and management in Victoria. Pages 65–79 in P. J. Boon,P. Calow, and G. E. Petts (eds.), River Conservation andManagement. John Wiley & Sons, New York.

Bennett, M. J. A., and J. Green. 1993. Estimating the waterrequirements of the lower Gwydir wetlands. New SouthWales Department of Water Resources, Sydney, New SouthWales, Australia.

Blackman, J. G., T. W. Perry, G. I. Ford, S. A. Craven, S. J.Gardiner, and R. J. De Lai. 1996. Queensland. A directory ofimportant wetlands in Australia, 2nd ed. Australian NatureConservation Agency, Canberra, Australia.

Brander, D. 1987. Environmental changes in the southernMacquarie Marshes: 1934 to 1987. Honours thesis, Univer-sity of New South Wales, New South Wales, Australia.

Bren, L. 1988. Effects of river regulation on flooding of ariparian red gum forest on the river Murray, Australia.Regulated Rivers 2:65–77.

Bren, L. 1990. Red gum forests. Pages 231–242 in N. Mackayand D. Eastburn (eds.), The Murray. Murray Darling BasinCommission, Canberra, Australia.

Bren, L. 1992. Tree invasion of an intermittent wetland inrelation to changes in the flooding frequency of the RiverMurray, Australia. Australian Journal of Ecology 17:395–408.

Brereton, G. 1994. Summary report. Macquarie Marshesmanagement strategy—stage 1, biophysical investigations,natural resources management strategy. New South WalesDepartment of Water Resources, Dubbo, New South Wales,Australia.

Bruwer, C., C. Poultney, and Z. Nyathi. 1996. Communitybased hydrological management of the Phongolo flood-plain. Pages 199–211 in M. C. Acreman, and G. E. Hollis(eds.), Water management and wetlands in sub-SaharanAfrica. IUCN, Gland, Switzerland.

Briggs, S. V., P. F. Hodgson, and P. Ewin. 1994. Changes inpopulations of waterbirds on a wetland following waterstorage. Wetlands (Australia) 13:36–48.

Briggs, S. V., S. A. Thornton, and W. G. Lawler. 1997.Relationship between hydrological control of river red gumwetlands and waterbird breeding. Emu 97:31–42.

Buckmaster, D. E., I. Hastings, and P. L. Rogan. 1979. Inquiryinto water allocations in northern Victoria. Fish and WildlifeVictoria, Paper number 21. Melbourne, Victoria, Australia.

Clifton, D. G., and R. J. Gilliom. 1989. Sources and concentra-tions of dissolved salts and selenium in the San JoaquinRiver and its tributaries, California, October 1985 to March


1987. Water-resources investigations report 88-4217. USGeological Survey, Sacramento, California.

Contreras-Balderas, S., and M. L. Lozano-Vilano. 1994. Water,endangered fishes, and development perspectives in aridlands of Mexico. Conservation Biology 8:379–387.

Cooper, R. P. 1954. Birds of the Macquarie Marshes, NewSouth Wales. Memoirs of the National Museum of Victoria19:137–163.

Costanza, R., R. d’Arge, R. de Groot, S. Farber, M. Grasso, B.Hannon, K. Limburg, S. Naeem, R. V. O’Neill, J. Paruelo,R. G. Raskin, P. Sutton, and M. van den Belt. 1997. The valueof the world’s ecosystem services and natural capital. Nature387:253–260.

Cunningham, G. 1997. Macquarie Marshes grazing study—1996. Unpublished final report to the Macquarie MarshesCatchment Committee. Sydney, New South Wales, Australia.

Debus, S. J. 1989. Moree Watercourse. RAOU Newsletter 81:5.

Denny, P. 1994. Biodiversity and wetlands. Wetlands Ecology andManagement 3:55–61.

DEST (Department of Sport and Territories). 1996. Subsidiesto the use of natural resources. Department of Sport andTerritories, Commonwealth of Australia, Canberra, Austra-lia.

DLWC (Department of Land and Water Conservation). 1995.Central and north west regions water quality program1994/95 report on nutrients and general water quality.Report No. TS95.088. Water Quality Services Unit, Techni-cal Services Division, Department of Land and WaterConservation, Orange, New South Wales, Australia.

DLWC and NPWS (Department of Land and Water Conserva-tion and National Parks and Wildlife Service). 1996. Macqua-rie Marshes water management plan 1996. National Parksand Wildlife Service and Department of Land and WaterConservation, Hurstville, New South Wales, Australia.

DPI (Department of Primary Industries). 1996. Unregulatedflow studies for the Condamine/Balonne/Culgoa Riversystem. Report for the Dumaresq-Barwon Border RiversCommission. Department of Primary Industries, Brisbane,Queensland, Australia.

Drijver, C. A., and M. Marchand. 1985. Taming the floods:Environmental aspects of floodplain development in Africa.Centre for Environmental Studies, University of Leiden,Leiden, The Netherlands.

Drijver, C. A., and W. F. Rodenburg. 1988. Water managementat the cross roads: The case of the Sahelian Wetlands. Paperpresented at the international symposium of hydrology ofwetlands in semi-arid and arid regions, Seville, Spain, May1988.

Drijver, C. A., and C. J. Van Wetten. 1992. Sahel Wetlands 2020:Changing development policies or losing Sahel’s best re-sources. Centre of Environmental Science, University ofLeiden, Leiden, The Netherlands.

Dugan, P. 1990. Wetland conservation: A review of currentissues and required action. IUCN, Gland, Switzerland.

DWR (Department of Water Resources). 1991. Water re-sources of the Macquarie Valley. Department of WaterResources, Sydney, New South Wales, Australia.

DWR (Department of Water Resources). 1994. Central andnorth west regions water quality program 1993/94 report on

nutrients and general water quality. Report No. TS94.088.Water Quality Unit, Technical Services Division, Depart-ment Water Resources, Sydney, New South Wales, Australia.

DWR and NPWS (Department of Water Resources and Na-tional Parks and Wildlife Service). 1986. Water managementplan for the Macquarie Marshes. Department of WaterResources and National Parks and Wildlife Service, Hurst-ville, New South Wales, Australia.

EPA (New South Wales Environment Protection Authority).1995. New South Wales state of the environment 1995. NewSouth Wales Environment Protection Authority, Sydney,New South Wales, Australia.

FAO (Food and Agriculture Organization). 1993. Nigeria:Irrigation project: Identification report. Report No. 30/93CP NIR 56. Food and Agriculture Organization, UnitedNations, Rome, Italy.

Frayer, W. E., D. D. Peters, and H. R. Pywell. 1989. Wetlands ofthe California Central Valley: Status and trends—1939 tomid-1980’s. US Fish and Wildlife Service, Portland, Oregon.

Froend, R. H., E. M. Heddle, D. T. Bell, and A. J. McComb.1987. Effects of salinity and waterlogging on the vegetationof Lake Toolibin, Western Australia. Australian Journal ofEcology 12:281–298.

Garba Boyi, M., and G. Polet. 1996a. Birdlife under waterstress: The case of the Hadejia-Nguru Wetlands, northernNigeria. Pages 147–152 in R. D. Belilfuss, W. R. Tarboton,and N. N. Gichuki (eds.). Proceedings of the African craneand wetland training workshop, Maun, Botswana, 8–15August 1993. International Crane Foundation, Baraboo,Wisconsin.

Garba Boyi, M. and G. Polet. 1996b. Afrotropical Anatidaepopulation trends in the Hadejia-Nguru Wetlands, northernNigeria (1988–1994). Gibier Faune Sauvage, Game and Wildlife13:587–598.

Garba Boyi, M., N. D. Burgess, and K. G. Smith. 1992.Ornithological significance of the Hadejia-Nguru Wetlands,northern Nigeria. Paper presented at the 8th Pan Africanornithological congress, Burundi.

Gilbert, C. L., and J. B. Ramey. 1995. Riverine wetlands of theAlberta prairie. Alberta Parks and Wildlife, Edmonton,Alberta.

Gilmer, D. S., M. R. Miller, R. D. Bauer, and J. R. LeDonne.1982. California’s Central Valley wintering waterfowl: Con-cerns and challenges. Transactions of the North AmericanWildlife and Natural Resources Conference 47:441–452.

Goodrick, G. 1970. A survey of wetlands of coastal New SouthWales. C.S.I.R.O. Division of Wildlife Research TechnicalMemorandum Number 5. C.S.I.R.O., Canberra, Australia.

Greenspan, R. L. 1988. Fish remains. Pages 312–326 in C.Raven and R. G. Elston (eds.), Preliminary investigations inStillwater Marsh—human prehistory and geoarchaeology.US Fish and Wildlife Service, Portland, Oregon.

Grondin, B. 1986. Does big agribusiness spell communitydoom? California Farmer May.

Hallock, R. J., and L. L. Hallock. 1993. Detailed study ofirrigation drainage in and near wildlife management areas,west-central Nevada, 1987-90. Part B. Effect on biota inStillwater and Fernley Wildlife Management Areas and


other nearby wetlands. Water-Resources Investigations Re-port 92-4024B. US Geological Survey, Carson City, Nevada.

Halse, S. A. 1987. Probable effect of increased salinity on thewaterbirds of Lake Toolibin. Technical report number 15.Department of Conservation and Land Management, Perth,Western Australia.

Halse, S. A. 1989. Wetlands of the Swan Coastal Plain past andpresent. Pages 105–108 in G. Lowe (ed.), Swan coastalgroundwater management conference—proceedings. West-ern Australian Water Resources Council publication No.1/89. Perth, Western Australia.

Halse, S. A., G. B. Pearson, and S. Patrick. 1993. Vegetation ofdepth-gauged wetlands in nature reserves of south-westWestern Australia. Technical report number 30. Depart-ment of Conservation and Land Management, Perth, West-ern Australia.

Hamilton, S. J., K. J. Buhl, F. A. Bullard, and S. F. McDonald.1996. Evaluation of toxicity to larval razorback sucker ofselenium-laden food organisms from Ouray National Wild-life Refuge on the Green River, Utah. US Fish and WildlifeService, Denver, Colorado.

Hoffman, R. J., R. J. Hallock, T. G. Rowe, M. S. Lico, H. L.Burge, and S. P. Thompson. 1990. Reconnaissance investiga-tion of water quality, bottom sediment, and biota associatedwith irrigation drainage in and near Stillwater WildlifeManagement Area, Churchill County, Nevada, 1986-87.Water-resources investigations report 89-4105. US Geologi-cal Survey, Carson City, Nevada.

Hoffman, S. E., N. J. Williams, and A. I. Herson. 1986. TheKesterson story. Proceedings of the first biennial confer-ence, pp. 1–9. National Water Supply Improvement Associa-tion, Springfield, Virginia.

Hollis, G. E. 1986. The modeling and management of theinternationally important wetland at Garaet El Ichkeul,Tunisia. IWRB special publication number 4. InternationalWaterfowl Research Bureau, Slimbridge, UK.

Hollis, G. E., and M. C. Acreman. 1994. The functions ofwetlands within integrated river basin development: Interna-tional perspectives. Pages 351–365 in C. Kirby and W. R.White (eds.), Integrated river basin development. Wiley,Chichester, UK.

Hollis, G. E., and J. R. Thompson. 1993a. Hydrological modelof the floodplain. Pages 69–79 in G. E. Hollis, W. M. Adams,and M. Aminu-Kano (eds.), The Hadejia-Nguru Wetlands:Environment, economy and sustainable development of aSahelian floodplain wetland. IUCN, Gland, Switzerland.

Hollis, G. E., and J. R. Thompson. 1993b. Water resourcedevelopments and their hydrological impacts. Pages 149–190 in G. E. Hollis, W. M. Adams, and M. Aminu-Kano(eds.), The Hadejia-Nguru Wetlands: Environment, economyand sustainable development of a Sahelian floodplain wet-land. IUCN, Gland, Switzerland.

Hollis, G. E., W. M. Adams, and M. Aminu-Kano (eds.). 1993a.The Hadejia-Nguru Wetlands: Environment, economy andsustainable development of a Sahelian floodplain wetland.IUCN, Gland, Switzerland.

Hollis, G. E., S. J. Penson, J. R. Thompson, and A. R. Sule.1993b. Hydrology of the river basin. Pages 19–67 in G. E.Hollis, W. M. Adams, and M. Aminu-Kano (eds.), TheHadejia-Nguru Wetlands: Environment, economy and sus-

tainable development of a Sahelian floodplain wetland.IUCN, Gland, Switzerland).

Hothem, R. L., and D. Welsh. 1994. Contaminants in eggs ofaquatic birds from the Grasslands of central California.Archives of Environmental Contamination and Toxicology 27:180–185.

Hruby, T., W. E. Cesanek, and K. E. Miller. 1995. Estimatingrelative wetland values for regional planning. Wetlands15:93–107.

Hull, G. 1996. Victoria. Pages 605–757 in R. Blackley, S.Usback, and K. Langford (eds.), A directory of importantwetlands in Australia, 2nd ed. Australian Nature Conserva-tion Agency, Canberra, Australia.

Jensen, A., P. Hoey, P. Kopli, R. Shepherd, M. Till, and M.Weinert. 1983. The effects of drainage on groundwaterbehaviour in counties Cardwell and Buckingham and theeffect on the Coorong. Unpublished report to Minister ofWater Resources, 1981–1983. Adelaide, South Australia.

Keyte, P. 1992. Lower Gwydir wetland—preliminary identifica-tion of resource management issues—discussion paper.Lower Gwydir wetland management plan steering commit-tee. New South Wales Department of Water Resources,Sydney, New South Wales, Australia.

Kimmage, K. 1991. The evolution of the ‘wheat trap’: TheNigerian wheat boom. Africa 60:471–500.

Kingsford, R. T. 1995. Ecological effects of river managementin New South Wales. Pages 144–161 in R. Bradstock, T. D.Auld, D. A. Keith, R. T. Kingsford, D. Lunney, and D.Sivertsen (eds.), Conserving biodiversity: Threats and solu-tions. Surrey Beatty and Sons, Sydney, New South Wales,Australia.

Kingsford, R. T., and R. F. Thomas. 1995. The MacquarieMarshes in arid Australia and their waterbirds: A 50 yearhistory of decline. Environmental Management 19:867–878.

Kirkpatrick, J. B., and P. A. Tyler. 1988. Wetlands and theirconservation. Pages 1–16 in A. J. McComb and P. S. Lake(eds.), The conservation of Australian wetlands. SurreyBeatty and Sons, Sydney, New South Wales, Australia.

Knapton, J. R., W. E. Jones, and J. W. Sutphin. 1987. Reconnais-sance investigation of the quality of water, bottom sediment,and biota in the Sun River Project, West Central Montana.Water-resources investigations report 87-4244. US Geologi-cal Survey, Missoula, Montana.

Lambing, J. H., W. E. Jones, and J. W. Sutphin. 1987.Reconnaissance investigation of the quality of water, bottomsediment, and biota in the Bowdoin National WildlifeRefuge and ajacent areas of the Milk River IrrigationProject, Northeastern Montata. Water-resources investiga-tions report 878-4243. US Geological Survey, Missoula,Montana.

Lane, J. A. K., and A. J. McComb. 1988. Western Australianwetlands. Pages 127–146 in A. J. McComb and P. S. Lake(eds.), Conservation of Australian wetlands. Surrey Beattyand Sons, Sydney, New South Wales, Australia.

Lemly, A. D. 1993. Subsurface agricultural irrigation drainage:The need for regulation. Regulatory Toxicology and Pharmacol-ogy 17:157–180.


Lemly, A. D. 1994a. Irrigated agriculture and freshwaterwetlands: A struggle for coexistence in the western UnitedStates. Wetlands Ecology and Management 3:3–15.

Lemly, A. D. 1994b. Agriculture and wildlife: Ecologicalimplications of subsurface irrigation drainage. Journal ofArid Environments 28:85–94.

Lemly, A. D. 1996. Identifying and reducing environmentalrisks from agricultural irrigation drainage in developingcountries. Proceedings of the Congress of Toxicology in DevelopingCountries 3:177–190.

Lemly, A. D. 1997. Risk assessment as an environmentalmanagement tool: Considerations for freshwater wetlands.Environmental Management 21:343–358.

Lemly, A. D., and C. J. Richardson. 1997. Guidelines for riskassessment in wetlands. Environmental Monitoring and Assess-ment 47:117–134.

Lemly, A. D., S. E. Finger, and M. K. Nelson. 1993. Sources andimpacts of irrigation drainwater contaminants in arid wet-lands. Environmental Toxicology and Chemistry 12:2265–2279.

Lemly, A. D., R. Best, W. Crumpton, M. Henry, D. Hook, G.Linder, P. Masscheleyn, H. Peterson, T. Salt, and R. Stahl.1999. An ecosystem approach to risk assessment in freshwa-ter wetlands. Chapter 4 in M. A. Lewis and others (eds.),Ecotoxicology and risk assessment for wetlands. SETACPress, Pensacola, Florida.

Livingstone, A. J., and I. A. Campbell. 1992. Water supply andurban growth in southern Alberta: Constraint or catalyst?Journal of Arid Environments 23:335–349.

Loomis, J. B. 1990. The economic value of water to wildlife andfisheries in the San Joaquin Valley. Transactions of the NorthAmerican Wildlife and Natural Resources Conference 55:202–213.

Lothian, J. A., and W. D. Williams. 1988. Wetland conservationin South Australia. Pages 147–166 in A. J. McComb and P. S.Lake (eds.), The Conservation of Australian wetlands.Surrey Beatty and Sons, Sydney, New South Wales, Australia.

Maheshwari, B. L., K. F. Walker, and T. A. McMahon. 1995.Effects of regulation on the flow regime of the River Murray,Australia. Regulated Rivers—Research & Management 10:15–38.

Mamza, J. U. 1995. Nature conservation in the Komadugu-Yobe Basin. Pages 39–48 in M. Aminu-Kano (ed.), Thecritical water resources of the Komadugu-Yobe Basin. Pro-ceedings of a workshop on the management of the waterresources of the Komadugu-Yobe Basin. National Institutefor Policy and Strategic Studies, Kuru, Jos, Nigeria, andHadejia-Nguru Wetlands Conservation Project, Nguru, Nige-ria.

Marchant, S., and P. J. Higgins. 1990. Handbook of Australian,New Zealand and Antarctic birds, Volume 1. Ratites toducks. Oxford University Press, Melbourne, Victoria, Austra-lia.

Margolin, S. 1979. Liability under the Migratory Bird TreatyAct. Ecological Law Quarterly 7:989–1010.

Marshall, E. 1985. Selenium poisons refuge, California poli-tics. Science 229:144–146.

McHugh, S. 1996. Cottoning on. Stories of Australian cotton-growing. Hale & Iremonger, Sydney, New South Wales,Australia.

MDBMC (Murray-Darling Basin Ministerial Council). 1996.Setting the cap. Report of the independent audit group.Murray-Darling Basin Ministerial Council, Canberra, Austra-lia.

Media Associates. 1997. Where the river runs dry—featuringthe Macquarie Marshes. Video (42 minutes). Media Associ-ates, Canberra, Australia.

Micklin, P. P. 1988. Desiccation of the Aral Sea: A watermanagement disaster in the Soviet Union. Science 241:1170–1176.

Moore, S. B., J. Winckel, S. J. Detwiler, S. A. Klasing, P. A. Gaul,A. R. Kanim, B. E. Kesser, A. B. Debevac, A. Beardsley, andL. A. Puckett. 1990. Fish and wildlife resources and agricul-tural irrigation drainage in the San Joaquin Valley, Califor-nia. San Joaquin Valley Drainage Program, Sacramento,California.

Morrison, M., and R. T. Kingsford. 1997. The management ofinland wetlands and river flows and the importance ofeconomic valuation in New South Wales. Wetlands (Australia)16:83–98.

Moyle, P. B. 1976. Inland fishes of California. University ofCalifornia Press, Berkeley, California.

Muslim, I., and A. I. Umar. 1995. Water resources andagricultural development in Jigawa State. Pages 49–62 in M.Aminu-Kano (ed.), The critical water resources of theKomadugu-Yobe Basin. Proceedings of a workshop on themanagement of the water resources of the Komadugu-YobeBasin. National Institute for Policy and Strategic Studies,Kuru, Jos, Nigeria, and Hadejia-Nguru Wetlands Conserva-tion Project, Nguru, Nigeria.

N’diaye, A. 1997. Ecological problems caused by dams in WestAfrica: Case study of Djoudj National Park, Senegal. Pages142–145 in R. C. Prentice and R. P. Jaensch (eds.), Develop-ment policies, plans and wetlands. Proceedings of workshop1 of the international conference on wetlands and develop-ment, Kuala Lumpur, Malaysia, 9–13 October 1995. Wet-lands International, Kuala Lumpur, Malaysia.

Nell, J. M. 1987. Data for selected pesticides and volatileorganic compounds for wells in the western San JoaquinValley, California, February to July 1985. Open-file report87-48. US Geological Survey, Sacramento, California.

Newman, P., B. Birrell, D. Holmes, C. Mathers, P., Newton, G.,Oakley, A., O’Connor, B., Walker, A., Spessa, and D. Tait.1996. Human settlements. Pages 1–57 in N. Alexander andR. Taylor (eds.), Australia: State of environment 1996. Anindependent report presented to the Commonwealth Minis-ter for the Environment by the State of the Environment,Advisory Council. CSIRO Publishing, Melbourne, Victoria,Australia.

Norman, F. I., and A. H. Corrick. 1988. Wetlands in Victoria: Abrief review. Pages 17–34 in A. J. McComb and P. S. Lake(eds.), The conservation of Australian wetlands. SurreyBeatty & Sons, Sydney, New South Wales, Australia.

NRC (Natural Resources Council of South Australia). 1993.Upper south east dryland salinity and flood managementplan—draft environmental impact statement—for publiccomment. Published by Upper South East Dryland Salinityand Flood Management Plan Steering Committee, Ad-elaide, South Australia.


O’Brien, J. M. 1995. Central and north west regions waterquality program: 1994/95 Macquarie cotton industry bench-marking. Technical services division report TS95.029. Depart-ment of Land & Water Conservation, Orange, New SouthWales, Australia.

Ohlendorf, H. M., R. L. Hothem, T. W. Aldrich, and A. J.Krynitsky. 1987. Selenium contamination of the Grasslands,a major California waterfowl area. The Science of the TotalEnvironment 66:169–183.

Olofin, E. A. 1996. Dam-induced drying-out of the Hadejia-Nguru Wetlands, northern Nigeria and its implications forthe fauna. Pages 141–145 in R. D. Belilfuss, W. R. Tarboton,and N. N. Gichuki (eds.), Proceedings of the African craneand wetland training workshop, Maun, Botswana, 8–15August 1993. International Crane Foundation, Baraboo,Wisconsin.

Paijmans, K. 1981. The Macquarie Marshes of inland northernNew South Wales. CSIRO Division of Land Use ResearchTechnical Paper No. 41, Canberra, Australia.

Pearce, D., A. Markandja, and E. B. Barbier. 1989. Blueprintfor a green economy. Earthscan, London.

Pearce, F. 1995. Poisoned waters. New Scientist October 21:29–33.

Perennou, C. 1991. Les Recensement Internationaux d’Oiseaxd’Eau en Afrique Tropicale. IWRB Special Publication No.15. International Waterfowl and Wetlands Research Bureau,Slimbridge, UK.

Perera, J. 1993. A sea turns to dust. New Scientist October21:24–27.

Peterson, D. A., W. E. Jones, and A. G. Morton. 1988.Reconnaissance investigation of water quality, bottom sedi-ment, and biota associated with irrigation drainage in theKendrick Reclamation Project area, Wyoming, 1986–87.Water-resources investigations report 87-4255. US Geologi-cal Survey, Cheyenne, Wyoming.

Polet, G., and J. R. Thompson. 1996. Maintaining the floods:Hydrological and institutional aspects of managing theKomadugu-Yobe River Basin and its floodplain wetlands.Pages 73–100 in M. C. Acreman and G. E. Hollis (eds.),Water management and wetlands in sub-Saharan Africa.IUCN, Gland, Switzerland.

Polet, G., I. S. Dutse, O. A. Akinsola, and M. Garba Boyi. 1997.The 1997 survey of waterfowl and water related birds of theHadejia-Nguru Wetlands, Nigeria. Hadejia-Nguru WetlandsConservation Project, Nguru, Nigeria.

Postel, S. L., G. C. Daily, and P. R. Ehrlich. 1996. Humanappropriation of renewable fresh water. Science 271:785–788.

Presser, T. S. 1994. The Kesterson effect. Environmental Manage-ment 18:437–454.

Presser, T. S., M. A. Sylvester, and W. H. Low. 1994. Bioaccumu-lation of selenium from natural geologic sources in westernstates and its potential consequences. Environmental Manage-ment 18:423–436.

Pressey, R. L. 1989. Wetlands of the Lower Clarence Flood-plain, northern coastal New South Wales. Proceedings of theLinnaean Society of New South Wales 111:143–155.

Pressey, R. L. 1990. Wetlands. Pages 167–181 in N. Mackay andD. Eastburn (eds.), The Murray. Murray Darling BasinCommission, Canberra, Australia.

Pressey, R. L., and J. H. Harris. 1988. Wetlands of New SouthWales. Pages 35–57 in A. J. McComb and P. S. Lake (eds.),Conservation of Australian wetlands. Surrey Beatty & Sons,Sydney, New South Wales, Australia.

Pressey, R. L., and M. J. Middleton. 1982. Impacts of floodmitigation works on coastal wetlands in New South Wales.Wetlands 2:27–44.

Preston, W. L. 1981. Vanishing landscapes: Land and life in theTulare Lake Basin. University of California Press, Berkeley.

Psychoudakis, A., S. Papoutsi-Psychoudaki, and A. M. M.McFarquhar. 1995. An economic assessment of an irrigationproject affecting a Greek wetland. Wetlands Ecology andManagement 3:225–232.

Raven, C., and R. G. Elston. 1988. Preliminary investigations inStillwater Marsh—human prehistory and geoarchaeology,Volumes 1 and 2. US Fish and Wildlife Service, Portland,Oregon.

Raven, C., and R. G. Elston. 1989. Preliminary investigations inStillwater Marsh—human prehistory and geoarchaeology,Volume 3. US Fish and Wildlife Service, Portland Oregon.

Raven, C., and R. G. Elston. 1990. Preliminary investigations inStillwater Marsh—human prehistory and geoarchaeology,Volume 4. US Fish and Wildlife Service, Portland Oregon.

Reisner, M. 1986. Cadillac Desert: The American West and itsdisappearing water. Viking-Penguin Press, New York.

Richardson, C. J. 1994. Ecological functions and human valuesin wetlands: A framework for assessing forestry impacts.Wetlands 14:1–9.

Robertson, A. I. 1997. Land-water linkages in floodplain riversystems: The influence of domestic stock. Pages 207–218 inN. Klomp and I. Lunt (eds.), Frontiers in ecology. ElsevierScience, Oxford, UK.

Roe, G. P., J. E. Nitshke, S. H. Nosworthy, and L. R. Speher.1980. Environmental impact study on the effect of drainagein the south east of South Australia. South Eastern DrainageBoard, Adelaide, South Australia.

Saunders, D., A. Beattie, S. Eliot, M. Fox, B. Hill, B. Pressey, D.Veal, J. Venning, M. Maliel, and C. Zammit. 1996. Biodiver-sity. Pages 1–68 in N. Alexander and R. Taylor (eds.),Australia: State of environment 1996. An independentreport presented to the Commonwealth Minister for theEnvironment by the State of the Environment, AdvisoryCouncil. CSIRO Publishing, Melbourne, Victoria, Australia.

Schroeder, R. A., D. U. Palawski, and J. P. Skorupa. 1988.Reconnaissance investigation of water quality, bottom sedi-ment, and biota associated with irrigation drainage in theTulare Lake Bed area, southern San Joaquin Valley, Califor-nia, 1986–87. Water-resources investigations report 88-4001.US Geological Survey, Sacramento, California.

Scott, D. A. and P. M. Rose. 1996. Atlas of Anatidae populationsin Africa and western Eurasia. Wetlands International,Wageningen, The Netherlands.

See, R. B., D. A. Peterson, and P. Ramirez, Jr. 1992a. Physical,chemical, and biological data for detailed study of irrigationdrainage in the Kendrick Reclamation Project area, Wyo-ming, 1988–90. Open-file report 91-533. US GeologicalSurvey, Cheyenne, Wyoming.


See, R. B., D. L. Naftz, D. A. Peterson, J. G. Crock, J. A.Erdman, R. C. Severson, P. Ramirez, Jr., and J. A. Armstrong.1992b. Detailed study of selenium in soil, representativeplants, water, bottom sediment, and biota in the KendrickReclamation Project area, Wyoming, 1988–90. Water-resources investigations report 91-4131. US Geological Sur-vey, Cheyenne, Wyoming.

Shelton, N. 1984. Wetlands of the north: A conservationchallenge. Nigerian Conservation Foundation Newsletter Decem-ber:13–17.

Simpson, J. H. 1876. Report of explorations across the GreatBasin of the Territory of Utah for a direct wagon-route fromCamp Floyd to Genoa, in Carson Valley, in 1859. Reprint ofUS Army Engineer Department Document. University ofNevada Press, Reno, Nevada.

SKPPL (Sinclair Knight Partners Pty., Ltd.). 1984. New SouthWales Inland Rivers Flood Plain Management Studies—Macquarie Valley. Sinclair Knight and Partners Pty., Ltd.,Sydney, New South Wales, Australia.

Smith, P., and J. Smith. 1990. Floodplain vegetation. Pages215–228 in N. Mackay and D. Eastburn (eds.), The Murray.Murray Darling Basin Commission, Canberra, Australia.

Stafford Smith, D. M., and S. R. Morton. 1990. A framework forthe ecology of arid Australia. Journal of Arid Environments18:255–278.

State of California. 1990. Irrigation water use in the CentralValley of California. California Department of Water Re-sources, Sacramento, California.

Stephens, D. W., B. Waddell, and J. B. Miller. 1988. Reconnais-sance investigation of water quality, bottom sediment, andbiota associated with irrigation drainage in the MiddleGreen River Basin, Utah, 1986–87. Water-resources investiga-tions report 88-4011. US Geological Survey, Salt Lake City,Utah.

Stephens, D. W., B. Waddell, L. A. Peltz, and J. B. Miller. 1992.Detailed study of selenium and selected elements in water,bottom sediment, and biota associated with irrigation drain-age in the Middle Green River Basin, Utah, 1988–90.Water-resources investigations report 92-4084. US Geologi-cal Survey, Salt Lake City, Utah.

Stevens, T. H., S. Benin, and J. S. Larson. 1995. Public attitudesand economic values for wetland preservation in NewEngland. Wetlands 15:226–231.

Stock, R. E. 1978. The impact of the decline of the HadejiaRiver in Hadejia Emirate. Pages 141–146 in G. J. vanApeldoorn (ed.), The aftermath of the 1972–74 drought inNigeria. Centre for Social and Economic Research, AhmaduBello University, Zaria, Nigeria.

Thomas, D. H. L., M. A. Jimoh, and H. Matthes. 1993. Fishing.Pages 97–115 in G. E. Hollis, W. M. Adams, and M.Aminu-Kano (eds.), The Hadejia-Nguru Wetlands: Environ-ment, economy and sustainable development of a SahelianFloodplain wetland. IUCN, Gland, Switzerland.

Thompson, J. R. 1995. Hydrology, water management andwetlands of the Hadejia-Jama’are Basin, northern Nigeria.PhD thesis. University of London, London.

Thompson, J. R. 1996. Africa’s floodplains: A hydrologicaloverview. Pages 5–20 in M. C. Acreman, and G. E. Hollis

(eds.), Water management and wetlands in sub-SaharanAfrica. IUCN, Gland, Switzerland.

Thompson, J. R., and G. E. Hollis. 1995. Hydrological model-ing and the sustainable development of the Hadejia-NguruWetlands, Nigeria. Hydrological Sciences Journal 40:97–116.

Thompson, S. P., and K. L. Merritt. 1988. Western Nevadawetlands—history and current status. Nevada Public AffairsReview 1:40–45.

Thornton, S. A., and S. V. Briggs. 1994. A survey of hydrologi-cal changes to wetlands of the Murrumbidgee River. Wet-lands (Australia) 13:1–13.

Treca, B., and S. Ndiaye. 1996. The black crowned cranes inthe Senegal Delta. Pages 103–105 in R. D. Belilfuss, W. R.Tarboton, and N. N. Gichuki (eds.), Proceedings of theAfrican crane and wetland training workshop, Maun,Botswana, 8–15 August 1993. International Crane Founda-tion, Baraboo, Wisconsin.

UNEP (United Nations Environmental Program). 1992. Diag-nostic study for the development of an action plan for theconservation of the Aral Sea. Unpublished report. UnitedNations Environmental Program, Nairobi, Kenya, Africa.

Van Ketel, A., M. Marchand, and W. F. Rodenburg. 1987. WestAfrica review: A comprehensive listing of water manage-ment projects and an outline of their effects on wetlands.Edwin Report No. 1. Centre for Environmental Studies,University of Leiden, Leiden, The Netherlands.

Vencil, B. 1986. The Migratory Bird Treaty Act—protectingwildlife on our national refuges—California’s KestersonReservoir, a case in point. Natural Resources Journal 26:609–627.

Vinke, P. P. 1996. The integrated development programme forthe left bank of the Senegal River Valley. Pages 145–153 inM. C. Acreman, and G. E. Hollis (eds.), Water managementand wetlands in sub-Saharan Africa. IUCN, Gland, Switzer-land.

Waddell, B. H., and M. C. Stanger. 1992. The influence ofselenium on incubation patterns and nesting success ofwaterbirds at Ouray National Wildlife Refuge, Utah. Contami-nant Report R6/400S/92. US Fish and Wildlife Service, SaltLake City, Utah.

Walker, K. F. 1985. A review of the ecological effects of riverregulation in Australia. Hydrobiologia 125:111–129.

Wallace, T. 1980. Agricultural projects and land in northernNigeria. Review of African Political Economy 17:59–70.

Wasson, B., B. Banens, P. Davies, W. Maher, S. Robinson, D.Tait, and S. Watson-Browne. 1996. Inland waters. Pages 1–68in N. Alexander and R. Taylor (eds.), Australia: State ofenvironment 1996. An independent report presented to theCommonwealth Minister for the Environment by the Stateof the Environment Advisory Council. CSIRO Publishing,Melbourne, Victoria, Australia.

WCIC (Water Resources and Irrigation Commission). 1971.Water resources of New South Wales. Government Printer,Sydney, New South Wales, Australia.

Welcomme, R. L. 1985. River fisheries. FAO fisheries technicalpaper 262. Food and Agriculture Organization, UnitedNations, Rome, Italy.


Wesseling, J. W., C. A. Naah, C. A., Drijver, and D. Ngantou.1996. Rehabilitation of the Logone floodplain, Cameroon,through hydrological management. Pages 185–198 in M. C.Acreman, and G. E. Hollis (eds.), Water management andwetlands in sub-Saharan Africa. IUCN, Gland, Switzerland.

Whigham, D., D. Dykyjova, and S. Hejny. 1993. Wetlands of theworld. I. Inventory, ecology and management. Kluwer Aca-demic Publishers, Dordrecht, The Netherlands.

Whitehead, J. C., and G. O. Blomquist. 1991. Measuringcontingent values for wetlands: Effects of information aboutrelated environmental goods. Water Resources Research 27:2523–2531.

Whitehead, P. J., and R. Chatto. 1996. Northern Territory.Pages 119–175 in A directory of important wetlands inAustralia, 2nd ed. Australian Nature Conservation Agency,Canberra, Australia.

Willers, B. 1994. Sustainable development: A new worlddeception. Conservation Biology 8:1146–1148.

Williamson, D. R., G. W. B. Gates, G. Robinson, G. K., Linke,M. P. Seker, and W. R. Evans. 1997. Salt trends. Historictrend in salt concentration and saltload of stream flow inthe Murray-Darling Drainage Division. Dryland technicalreport No. 1. Murray-Darling Basin Commission, Canberra,Australia.

WRC (Water Resources Commission). 1979. Southern Macqua-rie Marshes water management works: Environmental im-pact assessment. Rankine and Hill Pty., Ltd., Water Re-sources Commission, New South Wales, Australia.

WRIC (Water Resources and Irrigation Commission). 1971.Water resources of New South Wales. Government Printer,Sydney, New South Wales, Australia.

Zahm, G. R. 1986. Kesterson Reservoir and Kesterson NationalWildlife Refuge: History, current problems, and manage-ment alternatives. Transactions of the North American Wildlifeand Natural Resources Conference 51:324–329.


irrigatedagriculture and wildlife conservation: …jthompso/pdf_files/env_mgt_paper.pdfconservation...

Documents