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Mid Murrumbidgee Alluvium

Groundwater Management Area 013 Gundagai to Narrandera

Groundwater Resources Status Report – 2007

Publisher

NSW Department of Water and Energy Level 17, 227 Elizabeth Street GPO Box 3889 Sydney NSW 2001T 02 8281 7777 F 02 8281 [email protected]

Mid Murrumbidgee Alluvium. Groundwater Management Area 013: Gundagai to Narrandera. Groundwater Resources Status Report – 2007

( Previously published in July 2008 under the title Mid Murrumbidgee Groundwater Management Area 013: Status Report – 2007)

February 2009

ISBN 978 0 7347 5904 7

Acknowledgements

Written by Mark Mitchell. Location and contour diagrams by Georgina Spencer.

This publication may be cited as:

Mitchell, M., 2009, Mid Murrumbidgee Alluvium. Groundwater Management Area 013: Gundagai to Narrandera. Groundwater Resources Status Report – 2007, NSW Department of Water and Energy, Sydney

© State of New South Wales through the Department of Water and Energy, 2009

This work may be freely reproduced and distributed for most purposes, however some restrictions apply. Contact the Department of Water and Energy for copyright information.

Disclaimer: While every reasonable effort has been made to ensure that this document is correct at the time of publication, the State of New South Wales, its agents and employees, disclaim any and all liability to any person in respect of anything or the consequences of anything done or omitted to be done in reliance upon the whole or any part of this document.

DWE 09_025

Mid Murrumbidgee Alluvium: Groundwater Management Area 013: Gundagai to Narrandera Groundwater Resources Status Report 2007

Contents

Abstract .................................................................................................................................. v

1.0 ................................................................................................................. 1 Introduction

2.0 ....................................................................................................................... 2 Location

3.0 ....................................................................................................................... 4 Geology

4.0 .............................................................................................................. 4 Hydrogeology4.1 ........................................................................................... 8 Lachlan Formation4.2 .............................................................................................. 8 Cowra Formation4.3 ........................................................................................ 8 Groundwater Quality

5.0 ............................................................................................. 10 Rainfall and River Flow5.1 ........................................................................................................... 10 Rainfall5.2 .................................................. 12 Groundwater and Surface water Interaction5.3 ................................................................................. 16 River Aquifer interaction

6.0 ....................................................................... 20 History of Groundwater Management6.1 ............................................................................. 20 Annual Average Recharge6.2 ................................................................................ 20 Groundwater Allocations6.3 ................................................................................... 23 High Yielding Licences

7.0 .............................................................................. 25 Overview of Groundwater Levels7.1 ................................................................................... 25 Standing Water Levels7.2 ............................................. 27 Lachlan Aquifer Piezometric Surface Contours7.3 ......................................................................... 28 Groundwater Level Contours7.4 ................................................................ 32 Head Difference Between Aquifers

8.0 .............................................................. 34 Sustainable Yield and Recharge Estimates

9.0 ...................................................................................................... 35 Groundwater Use

10.0 ............................................................................ 36 Groundwater Management Zones10.1 ............................................................................................................ 36 Zone 1

10.1.1 Overview ............................................................................................ 36 10.1.2 Water levels ....................................................................................... 36 10.1.3 Allocation and Licensed Usage.......................................................... 36

10.2 ............................................................................................................ 38 Zone 210.2.1 Overview ............................................................................................ 38 10.2.2 Water levels ....................................................................................... 38 10.2.3 Allocation and Usage ......................................................................... 39

i | NSW Department of Water and Energy, January 2009


10.3 Zone 3 ............................................................................................................ 40 10.3.1 Overview ............................................................................................ 40 10.3.2 Water levels ....................................................................................... 40 10.3.3 Allocation and Usage ......................................................................... 42



11.0 ................................................................................................................ 47 Conclusion

12.0 ................................................................................................................ 48 References

Figures

Figure 1. Mid Murrumbidgee Groundwater Management Area.............................................. 3

Figure 2. Zone 2 basement contours in metres to Australian Height Datum.......................... 5

Figure 3. Zone 3 basement contours in metres to Australian Height Datum.......................... 6

Figure 4. Location of Department of Water and Energy groundwater level monitoring sites . 7

Figure 5. Average monthly rainfall for Gundagai, Wagga Wagga and Narrandera.............. 10

Figure 6. Mid Murrumbidgee Cumulative Residual Mass..................................................... 11

Figure 7. Mid Murrumbidgee Cumulative Residual Mass and Groundwater Levels near Collingullie............................................................................................................ 12

Figure 8. Groundwater level in the Cowra Aquifer and River Height Hydrographs measured to the Australian Height Datum at Narrandera. ................................... 13

Figure 9. Groundwater Hydrographs and Stream Height at Tarcutta................................... 14

Figure 10. Cumulative Residual Mass Curves for Rainfall and Tarcutta Creek Stream Height ...................................................................................................... 14

Figure 11. Groundwater Hydrographs and Monthly Cumulative Deviation Stream Height at Wagga Wagga ................................................................................................. 15

Figure 12. Relationship between the groundwater level in the Cowra aquifer and the Murrumbidgee River Level March 1995 ............................................................... 17


ii | NSW Department of Water and Energy, January 2009






Figure 18. Distribution of Licensed Purposes in the Mid Murrumbidgee GWMA 013 .......... 22

Figure 19. Distribution of Licensed Entitlement in the Mid Murrumbidgee GWMA 013 ....... 22

Figure 20. Location of high yield bores throughout the Mid Murrumbidgee GWMA 013...... 23

Figure 21. Distribution of entitlement throughout GWMA 013.............................................. 24

Figure 22. Standing groundwater levels in 1973, 1996 and 2007 ........................................ 26

Figure 23. Groundwater level contours in AHD for 1973, 1996 and 2007............................ 30

Figure 24. Change in groundwater levels between 1973 and 1996, 1996 and 2007, 1973 and 2007 ..................................................................................................... 31

Figure 25. 2007 Head difference between the Cowra and Lachlan Aquifers and 1973 to 2007 change in head difference between Cowra and Lachlan aquifers . 33

Figure 26. Groundwater and Murrumbidgee River hydrograph of GW030160 and the Gauging Station at Wagga Wagga....................................................................... 36

Figure 27. Proportion of groundwater licenses in Zone 1..................................................... 37




Figure 31. Groundwater hydrograph of GW030125 ............................................................. 40

Figure 32. Standing water level metres below ground level hydrograph of GW030094 ...... 41

Figure 33. Time Series Hydrograph of GW403571 located in the western area of zone 3 .. 41






iii | NSW Department of Water and Energy, January 2009


Tables

Table 1. Monthly Average Rainfall in Millimetres ................................................................. 10 Table 2. High Yield Licenses Entitlement for GWMA 013 .................................................... 21 Table 3. High Yielding Groundwater Licenses in GWMA013 by purpose ............................ 21 Table 4. Lachlan aquifer change in piezometric pressure elevation between Oura and

Narrandera ............................................................................................................. 27 Table 5. Cowra aquifer change in elevation of the groundwater between Oura and

Narrandera ............................................................................................................. 28 Table 6. Sustainable Yield and Entitlements in GWMA 013 ................................................ 34 Table 7. Usage in megalitres by purpose and year.............................................................. 35

iv | NSW Department of Water and Energy, January 2009


v | NSW Department of Water and Energy, January 2009

Abstract This is the fourth report on the Mid Murrumbidgee Groundwater Management Area (GWMA) 013. The report outlines the level of entitlement, the sustainable yield, the pressures, and the condition of the groundwater resource as of 2007.

The GWMA is an alluvial aquifer system which is associated with the floodplain of the Murrumbidgee between Gundagai and Narrandera in south western NSW. The system consists of two aquifers, the lower being the Lachlan formation and the upper the Cowra formation. The Lachlan aquifer is high yielding, contains low salinity water and consists of quartz sands and gravel. This aquifer is used as a town water supply for Wagga Wagga and many towns and villages in the riverina. The overlying Cowra formation contains mostly clays and silts with minor sand and gravel lenses. It is a low yielding formation suitable for mostly stock and domestic purposes.

The Mid Murrumbidgee GMMA has a long term average extraction limit of 89,000ML/yr (Ross 1999), with the current level of entitlement of 82,497ML/yr. The current level of usage is approximately 32,000ML/yr. Close to half of all groundwater extraction is for town water supply from bore fields located in close proximity to Wagga Wagga. A growth of about thirty percent in irrigation usage has occurred during the previous 10 years, due to a combination of factors including the cap on surface water entitlements and lower surface water allocations as a result of drought conditions.

Monitoring of groundwater levels in the GWMA has been occurring since the late 1960s and early 1970s. The monitoring has shown that there was a significant rise in groundwater levels associated with the 1974 floods. Groundwater levels generally declined following 1974. Groundwater level monitoring shows the influence that large scale extraction in the Wagga Wagga area, associated with town water supplies and from irrigation between Wagga Wagga and Narrandera since 2000.

The influence of the current dry conditions, lower river levels and development of the groundwater resource has also seen a noticeable change in the relationship between the Murrumbidgee River and the groundwater system. There are indications that groundwater levels in the Cowra aquifer were previously above the river height are now below the base of the river, suggesting a change in the relationship between the two systems.

This report provides an indication of the current condition of the groundwater resource and the changes that have occurred over time and since the previous Status Report prepared in 2000.


1.0 Introduction This report is for the Mid Murrumbidgee alluvial aquifer, which consists of unconsolidated sediments associated with the Murrumbidgee Valley from Gundagai to Narrandera, and the lower sections of the tributaries; Tarcutta and Kyeamba Creeks, as shown in Figure 1. The area is defined as the Mid Murrumbidgee Groundwater Management Area (GWMA) 013.

The groundwater is used for irrigation of winter and summer crops, fodder crops, dairy, rice, viticulture, horticulture and aquaculture. The resource is also a vital source of water for a number of communities throughout the mid and upper Murrumbidgee catchment. Town water supply is the largest use of the resource presently. However, irrigation development in the area since the late 1990s has resulted in a significant increase in groundwater usage.

The allocation of volumetric entitlements for the area was suspended in September 2002 with an embargo being placed on the area. The embargo was established because of concerns of the level of entitlement exceeding the estimated sustainable yield. The embargo also excludes the construction of addition production bores, with exclusions for replacement works or where a test bore licence has been issued prior to August 2007.

This is the fourth groundwater status report that has been prepared for the Mid Murrumbidgee Alluvial aquifer. Previous reports were prepared in 1986, 1995, and 2000. The embargo on further water entitlements in 2002 and the current development of a water sharing plan has prompted reporting on this area.

The report outlines the area, the geological setting and the history of groundwater management in the groundwater management unit. It then provides an overview of licensed entitlements and the change in groundwater levels since the commencement of monitoring, the current sustainable yield estimates and usage throughout the GWMA. The distribution of entitlement, works and groundwater levels by zone is also provided.

1 | NSW Department of Water and Energy, January 2009



2.0 Location The Mid Murrumbidgee GWMA covers an area of approximately 1236 km2 and is situated within the Murrumbidgee River valley between Gundagai and Narrandera, and includes the lower sections of the tributaries of Kyeamba and Tarcutta Creeks. The management area is broken into the following five zones, shown in Figure 1:

Zone 1 – Gundagai to Oura

Zone 2 – Oura to Pomingalarna

Zone 3 – Pomingalarna to Narrandera

Zone 4 – Tarcutta Creek

Zone 5 – Kyeamba Creek The boundary for GWMA 013 was initially defined in the late 1960s and since that time drilling has provided additional information as to the extent of the aquifer system. Prior to the implementation of the embargo on further entitlements within the management area the boundary for the GWMA was amended. The management area is shown in Figure 1.

The regulated Murrumbidgee River has its highest flows occurring during the irrigation season from October to March and low flows during April to September. The climate in the area has a winter dominant rainfall with the mean annual rainfall ranging from 493 at Narrandera to 713 mm at Gundagai. The median average annual temperature is between 22 and 23°.


Figure 1. Mid Murrumbidgee Groundwater Management Area



3.0 Geology The investigation area consists of Cainozoic alluvial sediments. There are two distinct formations which are locally known as the Tertiary Lachlan Formation (from 2 to 12 million years old) and the Quaternary Cowra Formation (1 to 2 million years old). These formations are equivalent to the Calivil Formation and Shepparton Formation respectively in the Murray Geological Basin. A similar lithology to this area occurs in the upper Lachlan catchment of NSW.

4.0 Hydrogeology The Murrumbidgee alluvial aquifer ranges in width from about 1 kilometre at Gundagai, to about 20 kilometres upstream of Narrandera. At Narrandera the bedrock boundary is very close to the river, and the aquifer narrows down to about 4 kilometres. GWMA 013 covers an area of 1236 square kilometres, and comprises the main body of the Murrumbidgee alluvial sediments and the lower sections of Kyeamba and Tarcutta Creeks.

The Mid Murrumbidgee alluvial aquifer overlies Ordovician and Devonian metamorphosed sediments and granites. The depth of the unconsolidated sediments of the GWMA generally increases to the west, although there are some isolated bedrock highs beneath the management area. The depth of the alluvial sediments for the main sections of the alluvial valley in zones 2 and 3 are respectively shown in Figures 2 and 3.

As discussed above, there are two alluvial formations.. The lower formation (Lachlan ) is a confined aquifer system while the overlying formation (Cowra) is a semi confined to unconfined aquifer system. These two formations are typical of alluvial sediments that exist in the south eastern Murray Darling Basin.

Groundwater exploration bores have been drilled in the GWMA 013 since the late 1960s and early 1970s. The majority of development occurred during this period. The initial exploration bores were established to define the aquifer extent, productivity, and quality. These bores where incorporated into the Departments observation network and have since been monitored regularly. A location of monitoring sites in GWMA 013 is shown in Figure 4. There are 98 sites that are monitored either monthly, three monthly, or with time series data loggers. Many of the sites have multiple pipes extending to different depths within the aquifer.

Groundwater hydrographs for selected observation bores have are presented in this report. The hydrographs clearly reveal that the 1974 flood was a major recharge influence throughout the GWMA. Other influences include groundwater usage for irrigation from the late 1990s and declines associated with the drier period in the early 1980s and the present dry period since about 1998.


Mid Murrumbidgee Alluvium: Groundwater Management Area 013: Gundagai to Narrandera. Groundwater Resources Status Report 2007

Figure 2. Zone 2 basement contours in metres to Australian Height Datum

0 km 5 km

Pomingalrna Oura

Wagga Wagga



Figure 3. Zone 3 basement contours in metres to Australian Height Datum

0 km 5 km

Narrandera

Pomingalarna

Collingullie



Figure 4. Location of Department of Water and Energy groundwater level monitoring sites



4.1 LACHLAN FORMATION

Lachlan Formation sediments are commonly clean grey quartz sands and gravels, with intermittent layers of grey clay. The clay lenses are remnants of floodplain and/or wetland environments and were deposited in an environment of high rainfall and humidity. There are also records of the occurrence of wood fragments documented in drill logs and a palynological study of the sediments dated them as Pliocene in age (Wooley 1972).

The formation commences from near Oura east of Wagga Wagga and increase in thickness to about 120m at Narrandera (37 to 160m below ground surface). Yields from the aquifer vary depending upon the thickness and quality of sand and gravel layers intercepted. Yields range from about 10L/s at Oura to about 150L/s near Narrandera. Yields from individual bores depend on the bore construction.

4.2 COWRA FORMATION

The Cowra Formation consists of brown to yellow polymictic sediments of sands, gravel, silts, and clay. The polymictic nature of the formation suggests that mechanical weathering was dominant. The climate during the Quaternary was much drier than during the Tertiary, and the sediments in this layer reflect the typical flood/drought cycle of streams from a semi arid environment (Wooley 1972).

The formation extends from ground surface down to varying depths. The formation increases in thickness from Gundagai in the east, where it extends to a depth of about 25 metres, to about 40m around Narrandera. The main poorly sorted gravel zones of the formation typically extend from about 2 to 24 metres below ground surface. The gravel layers are interlayered with clay and silt.

Yields from the gravel layers are much lower than from the Lachlan Formation, with a maximum yield of about 15 L/s. Groundwater from the formation is generally used for stock and domestic supplies due to the poorer water quality, lower yields, and limited aquifer drawdown.

4.3 GROUNDWATER QUALITY

The groundwater in the Lachlan formation typically has low salinity, with recorded measurements of less than 500µS/cm, which is classified as good quality drinking water. Therefore the groundwater in this aquifer is commonly used for town water supplies. The salinity of the groundwater in the formation generally ranges from 150µS/cm to 950µS/cm, increasing with distance from the Murrumbidgee River. Groundwater salinities have been recorded above 1500µS/cm at depths of greater than 90m in the western area of the GWMA. However, there is no significant stratigraphic change corresponding to the increase in water salinity. The iron and manganese levels in this formation are variable, with iron concentrations range from less than 0.1 up to 1.5mg/L (the desirable limit for human consumption is 0.3mg/L). Manganese levels range from less than 0.02 up to 24mg/L (Manganese concentrations above 0.5 mg/L may have health implications). High levels of dissolved iron can often lead to clogging of bore screens, pumps, and other equipment.




Aeration of this water once it is pumped from the bore should cause some of this iron to drop out of solution, and reduce further clogging of pipes and fittings.

The groundwater quality of the upper Cowra Formation is generally of a higher salinity than the Lachlan Formation. Groundwater salinity concentrations in the formation increase with distance from the Murrumbidgee River. The groundwater salinity level between Wagga Wagga and Gundagai is typically less than 1000mg/L. The groundwater salinity downstream of Wagga Wagga can be much higher than 1000mg/L, especially where the aquifer is isolated from the river. The concentration of iron in the aquifer is also much higher than the Lachlan Formation, and levels of up to 70mg/L have been reported (Wooley 1972).

Total dissolved solids levels greater than 1000mg/L will cause scaling, and will most likely be unacceptable based on taste (National Health and Medical Research Council 1996). Groundwater salinity greater than 1000mg/L is also unsuitable for most irrigation, but may be used for stock water supply. Iron levels in the Cowra Formation are generally quite high, and can range up to 70mg/L.


5.0 Rainfall and River Flow

5.1 RAINFALL

The average rainfall in the Mid Murrumbidgee GWMA has a decreasing trend from east to west. Rainfall is highest in the eastern areas around Gundagai, and lowest around Narrandera in the west. Monthly rainfall figures for the three stations are presented below in Table 1.

Table 1. Monthly Average Rainfall in Millimetres Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Total

Gundagai 65.8 41.1 43.6 54.9 67 60.3 78.6 63.2 68.4 69.2 49.5 52.3 713.9

Wagga Wagga 40 39.2 43.1 44 49.4 58.9 50 52.9 48.5 56.7 42.2 37.5 562.2

Narrandera 35 34 29.5 35.9 41.5 36.6 37.3 40.3 36.5 42.8 33.2 35.8 438.4

Rainfall in the area reflects a mediterranean climate of high rainfall during winter and early spring. The seasonal and yearly variation in the average monthly rainfall throughout the GWMA is shown in Figure 5.

Figure 5. Average monthly rainfall for Gundagai, Wagga Wagga and Narrandera

0

10

20

30

40

50

60

70

80

Janu

ary

Februa

ryMarc

hApri

lMay

June Ju

ly

Augus

t

Septem

ber

Octobe

r

Novem

ber

Decem

ber

Month

Mea

n R

ainf

all (

mm

)

NarranderaWagga WaggaGundagai



The monthly rainfall cumulative residual mass curve for Gundagai, Wagga Wagga, and Narrandera is shown in Figure 6. The cumulative residual mass curve differentiates between the effect of rainfall and the underlying trend. It highlights periods of below average rainfall as a downward trending slope, and periods of above average rainfall as an upward trending slope (Boehmer 1998). Yearly figures would normally be used if long term trends (50 to 100 years) were to be assessed. Alternatively, monthly figures can be used to look at shorter periods of time (5 to 30 years) and can demonstrate seasonal trends.

The cumulative residual mass curves for Wagga Wagga and Narrandera show similar variations from the mean. The curve for Gundagai shows that there has been a significantly larger variation from the mean in the amount of above and below average rainfall in comparison to Wagga Wagga and Narrandera.

The consistent trend in the three curves is that, between 1974 and 1989 there was a period of below average rainfall. This was followed by a period of above average rainfall until 2001. Since 2001, there has been a noticeable downward trend in the charts associated with the current below average rainfall and drought conditions These trends are also reflected in the groundwater hydrographs for the area, as discussed in Section 11.

Figure 6. Mid Murrumbidgee Cumulative Residual Mass

Mid Murrumbidgee Cumulative Residual Mass Curve

-500

0

500

1000

1500

2000

1958 1961 1964 1967 1970 1973 1976 1979 1982 1985 1988 1991 1994 1997 2000 2003 2006

Year

Cum

ulat

ive

Res

idua

l Mas

s

NarranderaWagga WaggaGundagai



Figure 7. Mid Murrumbidgee Cumulative Residual Mass and Groundwater Levels near Collingullie

-500

0

500

1000

1500

2000

1958 1961 1964 1967 1970 1973 1976 1979 1982 1985 1988 1991 1994 1997 2000 2003 2006

Year

Cum

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Res

idua

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s

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163

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165

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167

168

Gro

undw

ater

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el (m

AH

Dl)

NarranderaWagga WaggaGundagaiGW30057 Pipe 1

Representing rainfall as a cumulative residual mass enables it to be compared to groundwater level trends. There are obvious correlations between rainfall trends and groundwater levels at many locations throughout the GWMA, however these trends are most apparent in the Cowra aquifer at locations not strongly influenced by recharge from the Murrumbidgee River. Groundwater levels for the Cowra aquifer near Collingullie, and the monthly cumulative residual mass rainfall curve for the management area is presented in Figure 7. This graph indicates that trends in groundwater levels have a reasonable degree of correlation with the cumulative residual mass curve for monthly rainfall.

5.2 GROUNDWATER AND SURFACE WATER INTERACTION

The groundwater levels in the shallow Cowra aquifer indicate various degrees of connection with the Murrumbidgee River and Tarcutta Creek water levels. The 1974 flood had a major impact on groundwater levels throughout the system. The elevated groundwater levels associated with the flood event resulted in reversal of groundwater flows associated with the elevated groundwater levels for the following three to four years. This is apparent in a majority of the bore hydrographs. The rise in groundwater levels caused by the 1974 flood indicate that the Murrumbidgee River is closely linked to the groundwater system, and that large flood events are a major recharge source for the Mid Murrumbidgee alluvial aquifers.

The close relationship between the stream height and the groundwater levels are shown in Figure 8 for an area in close proximity to Narrandera at the western end of the GWMA. At this location the river level is higher than the groundwater level in the Cowra aquifer. The groundwater levels have a similar long term trend to the river height between 1973 and 1997, with noticeable responses to river heights greater than 143m AHD.



Figure 8. Groundwater level in the Cowra Aquifer and River Height Hydrographs measured to the Australian Height Datum at Narrandera.

Murrumbidgee River @ Narrandera and GW025395

135

136

137

138

139

140

141

142

143

144

145

146

1972 1975 1978 1981 1984 1987 1990 1993 1996 1999 2002 2005 2008

Date

Wat

er L

evel

(mA

HD

)

Murrumbidgee River @ NarranderaGW025395 Pipe 2

Post 1997, groundwater and river levels have experienced a constant declining trend and there is a reduced response in the groundwater levels to river height variations. During this period there has been a period of lower river level heights and a measurable influence of groundwater extraction from the Lachlan aquifer. It is likely the relationship is moving towards the behaviour of a disconnected system, where there is a constant rate of loss from the river system.

The relationship between Tarcutta Creek and the groundwater system is shown in Figure 9. Stream height is presented as actual stream height above sea level, and as a monthly residual mass curve. The cumulative residual mass curve of the mean river height enables trends over successive months and years to be established. This in turn allows improved recognition of the relationship between stream height and groundwater levels due to the time lag in groundwater level response. In this example, there is a good relationship. Post 1996 groundwater pumping commenced in the area and there is a noticeable decline in the groundwater level between 1996 and 1998. Post 1998 the groundwater level has possibly established a new equilibrium and there is a close relationship between the groundwater level and the stream cumulative mass residual curve. Tarcutta Creek is an unregulated stream and therefore there is a strong correlation between cumulative residual mass curves for stream height and rainfall, as shown in Figure 10.



Figure 9. Groundwater Hydrographs and Stream Height at Tarcutta

Tarcutta Creek @ Borambola and GW030385

190.5

191

191.5

192

192.5

193

193.5

194

1979 1982 1985 1988 1991 1994 1997 2000 2003 2006 2009

Year

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evel

(mA

HD

)

-25

-20

-15

-10

-5

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5

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15

20

25

Cum

ulat

ive

Res

idua

l Mas

s

Tarcutta @ Borambola 410047GW030385 Pipe 1Tarcutta Ck Cumulative Residual Mass

Figure 10. Cumulative Residual Mass Curves for Rainfall and Tarcutta Creek Stream Height

Cumualtive Residual Mass Curves for Rainfall and Tarcutta Creek

-200

-100

0

100

200

300

400

500

600

700

800

1978 1981 1984 1987 1990 1993 1996 1999 2002 2005 2008

Year

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-5

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ream

Hei

ght

Wagga Wagga RainfallTarcutta Ck Stream Height



Figure 11. Groundwater Hydrographs and Monthly Cumulative Deviation Stream Height at Wagga Wagga

Murrumbidgee River @ Wagga Wagga and GW030639

169

170

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172

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1971 1974 1977 1980 1983 1986 1989 1992 1995 1998 2001 2004 2007 2010

Year

Wat

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(mA

HD

)

Murrumbidgee River @ Wagga Wagga

30639 (9.1 - 21.2 - Screen interval metres below ground level)

The relationship between the Murrumbidgee River and the Cowra aquifer in the vicinity of Wagga Wagga is shown in Figure11. Located in the vicinity of Wagga Wagga are the town water supply bore fields of Riverina Water County Council and Goldenfields Water County Council, which strongly influence groundwater levels in the area.

The groundwater levels in the aquifer are similar to the river height. The influence of the river on the groundwater level is not as pronounced since 2003. This is possibly caused by the lower river levels and groundwater extraction from the Lachlan aquifer by Riverina Water County Council and Goldenfields Water County Council.

The Murrumbidgee River, Tarcutta Creek and Kyeamba Creek and the alluvial aquifer system are connected systems throughout the majority of the GWMA. It is only in the western extent of the GWMA that the groundwater level is greater than 1 to 2 metres below the base of the river signifying a losing reach of the river.



5.3 RIVER AQUIFER INTERACTION

As illustrated in section 5.2 there is a close relationship between the Murrumbidgee River and the aquifer system in the GWMA. The relationship between the water sources has altered with the development of the groundwater system for irrigation and town water supplies.

Assuming a linear gradient between the river gauging stations between Wagga Wagga and Narrandera, the difference in the elevation of the river and the water level in Cowra aquifer have been mapped for the month of March in 1995, 2000, 2001, 2003, 2005, and 2006. This would be a period of maximum difference between the two water sources, with higher river flows associated with irrigation and declines in groundwater levels associated with groundwater usage.

The mapping of difference between the two water sources, shows that the river has altered from being a gaining to a losing stream in the central area of zone 3 with minimal changes in the other areas of the zone. The most significant change in behaviour has occurred during the past 5 years.

The diagrams in Figures 12 to 17 illustrate the change between the river height and the groundwater level. The relationship between the river and the groundwater system has altered, from the groundwater level in the Cowra aquifer being mainly above the river height to being similar or below the river height, with the most significant change occurring in the central area of zone 3 of the GWMA since 2005.

Since 2005, the difference between the river level and the groundwater level in the Cowra aquifer has changed from being either being approximately equal to or higher than the river level to being up to 2 metres below the river height. This indicates that the river in this reach has altered from being either in equilibrium or being a gaining stream to a losing stream. The influence of the change on the river system is uncertain, but is likely to influence the aquifer recharge characteristics of the area.



Figure 12. Relationship between the groundwater level in the Cowra aquifer and the Murrumbidgee River Level March 1995




6.0 History of Groundwater Management The NSW Water Reforms highlighted the need to assess aquifers, and determine if they were in a ‘high risk’ category (Ross 1999). The Water Management Act 2000 has objectives of managing water resources within sustainable limits.

The Mid Murrumbidgee GWMA 013 was designated as a high risk aquifer in Ross (1999). This was based on the high yielding and low salinity nature of the aquifer, vulnerability to pollution, and also to the fact that Wagga Wagga and other towns depend on the system for water supply.

The GWMA 013 is administered under the Water Act 1912 and is proposed to be included as a water source of the inland alluvial Macro Water Sharing Plan, under the Water Management Act 2000, which is currently under development.

An embargo on the issuing of additional groundwater allocations in the management area was implemented in September 2002. A small amount of growth in allocation has occurred since its implementation through the conversion of non volumetric licenses, an exemption for industrial/commercial uses for less than 10ML, and an exemption for quarries that existed prior to the implementation of the embargo that extracted groundwater for dewatering.

6.1 ANNUAL AVERAGE RECHARGE

Recharge of the Cowra aquifer in the management area is from river leakage, rainfall, flood events, and to a less extent irrigation. Recharge of the Lachlan aquifer is from vertical leakage from the Cowra aquifer and leakage from the surrounding fractured rock. Flood events are a significant source of aquifer recharge. This is demonstrated by the significant rise in groundwater levels associated with the 1974 floods, as shown in Figure 7.

The report Recharge Assessment for Priority Groundwater Systems within NSW (Ross 1999) estimated annual average recharge to the management area is 127,000ML/yr. The long term average extraction limit for the management area is 89,000ML/yr. The long term average extraction limit, is the volume available for extraction from the management area. The difference between the estimated annual average recharge and the long term average extraction limit is water that is reserved for the environment.

6.2 GROUNDWATER ALLOCATIONS

The policy for allocated groundwater in the Mid Murrumbidgee GWMA 013 prior to the embargo was based on the total property area overlying the aquifer. The allocation policy within each zone was based upon aquifer volume and groundwater availability. The zones are shown in Figure 1 and are as described below:

Zone 1 – Upstream of Oura Zone 2 – Oura to Pomingalarna Zone 3 – Pomingalarna to Narrandera Zone 4 – Tarcutta Alluvium Zone 5 – Kyeamba Alluvium

The majority of the entitlement within the GWMA is within zone 3. The distribution of high yield licenses within the GWMA is shown in Table 2.



Table 2. High Yield Licenses Entitlement for GWMA 013

Zone No. of Licenses

Total Entitlement (ML)

No. Property Accounts

Average Entitlement per

property account(ML)

No. of Constructed

Bores

1 16 1684 12 140 16

2 97 27491.5 64 121* 87

3 128 48667 89 552 104

4 23 2453 14 183 16

5 22 2202 16 140 22

Total 282 82497.5 195 439 241

* The majority of the entitlement in the zone is held by Riverina Water County Council and Goldenfields Water County Council. These entitlements and licenses have been excluded from the average entitlement for zone 2

Groundwater is mainly used for irrigation and town water supply. The distribution of entitlements, purposes, and licenses with the GWMA are shown in Table 3. The majority of the entitlement and licenses are within zones 2 and 3. Figure 18 presents the distribution of the number of licenses in each zone by purpose.

Table 3. High Yielding Groundwater Licenses in GWMA013 by purpose

Purpose Irrigation/ Aquaculture Industrial Town Water Supply Recreation Total

Zone No. of Licenses

Volume (ML)

No. of Licenses

Volume (ML)

No. of Licenses

Volume (ML)

No. of Licenses

Volume (ML)

No. of Licenses

Volume (ML)

1 14 1484 0 0 2 200 0 0 16 1684

2 68 6864.5 6 200 16 20000 7 427 97 27491.5

3 106 43102 10 643 11 4912 1 10 128 48667

4 15 2353 0 0 3 100 1 4 23 2453

5 21 2119 1 83 0 0 0 0 22 2202

Total 224 56504.5 17 926 32 25212 9 437 286 82497.5



Figure 18. Distribution of Licensed Purposes in the Mid Murrumbidgee GWMA 013

0

20

40

60

80

100

120

No.

of L

icen

ses

1 2 3 4 5Zone

Licensed Purposes

Irrigation/AquacultureIndustrialTown Water SupplyRecreation

Irrigation accounts for 67% of groundwater entitlement, Town Water 31%, and Industrial and Recreation entitlement make up a very small percentage of the overall entitlement. The overall entitlement volumes for the various licensed purposes are shown in Figure 19.

Figure 19. Distribution of Licensed Entitlement in the Mid Murrumbidgee GWMA 013

0

5000

10000

15000

20000

25000

30000

35000

40000

45000

Meg

alitr

es

1 2 3 4 5Zone

Entitlement Distribution

Irrigation/AquacultureIndustrialTown Water SupplyRecreation



6.3 HIGH YIELDING LICENCES

The groundwater works are generally concentrated close to the Murrumbidgee River and the major tributaries. The distribution of high yield groundwater licenses throughout the GWMA is shown in Figure 20. Entitlements are most concentrated around Wagga Wagga, and associated with the town water supply bore fields. The distribution of groundwater entitlements is shown in Figure 21.

Figure 20. Location of high yield bores throughout the Mid Murrumbidgee GWMA 013



Figure 21. Distribution of entitlement throughout GWMA 013



7.0 Overview of Groundwater Levels Contour maps of the groundwater level have been prepared for the shallow Cowra aquifer and the deeper Lachlan Aquifer. Bores used to create the contour maps were selected based upon the lithological logs and the depth of the screened interval. Bores were not included if they were screened in both the Cowra and Lachlan formations.

The time periods selected were March 1973, March 1996, March 2007. March 1973 was selected as an early benchmark as, in the following years, groundwater levels were heavily influenced by the 1974 flood, town water supply pumping, and the 1982-83 drought. March 1996, represents the period prior to the commencement of development and usage of the groundwater resource for irrigation, and March 2007 represents current conditions.

The groundwater data from these periods has been contoured for the Cowra and Lachlan aquifers to demonstrate the groundwater flow direction and the change over time. Data for the deep and shallow formations is presented as metres above sea level, as this allows groundwater flow paths to be identified.

7.1 STANDING WATER LEVELS

The standing water levels (SWL) is the depth of the groundwater level beneath ground surface. SWL in the Cowra and Lachlan aquifers in March 1973, March 1996, and March 2007 are shown in Figure 22. In 1973 the standing water levels were generally less than 8 metres and 14 metres below ground level in the Cowra and Lachlan aquifers, with the deepest water levels being in the southern and central areas of zone 3. The groundwater levels in 1996 were generally higher than those in 1973, with the exception of in the vicinity of Wagga Wagga where they are influenced by town water supply extraction. By March 2007 there has been a significant change in the standing water levels, as a result of the development of the system for irrigation and town water supplies and drought. The groundwater levels were generally less than 14 metres and 18 metres below ground level in the Cowra and Lachlan aquifers, with areas at greater depths in the vicinity of Wagga Wagga, and the central southern and northern areas of zone 3. These areas are influenced by groundwater pumping for irrigation and town water supplies.

Figure 22 illustrates the change in the water level in the Cowra and Lachlan aquifers for the period from March 1973 to March 1996, March 1996 to March 2007, March 1973 to March 2007. Rising water levels are represented by positive values, while falling water levels are indicated by negative values.



Figure 22. Standing groundwater levels in 1973, 1996 and 2007



7.2 LACHLAN AQUIFER PIEZOMETRIC SURFACE CONTOURS

The piezometric pressure level for the Lachlan aquifer currently ranges from about 132 metres above sea level at Narrandera to 193 metres above sea level in the Oura area (Figure 23). This represents a groundwater level difference of approximately 60 metres. The steepest section occurs in the vicinity of Wagga Wagga, where groundwater levels fall about 20 metres over a distance of about 25 kilometres, associated with change in surface elevation in the area.

The change in gradient between Oura and Narrandera has remained relatively constant over the period from 1973 to 2007. In 1973 it was 56m, 1996 58m, and 2007 54m. However, the difference in elevation between the periods have changed, see Table 4, with the most significant change occurring between 1996 and 2007. This is likely to be associated with the drought conditions experienced during this period and the development of groundwater irrigation in the area during this period.

Table 4. Lachlan aquifer change in piezometric pressure elevation between Oura and Narrandera

Area 1973 SWL AHD 1996 SWL AHD 2007 SWL AHD

Oura region 193m 193m 186m

Narrandera region 137m 135m 132m

The groundwater flow direction in 1973 and 1996 was from east to west from Oura to Narrandera, with no obvious signs of groundwater usage except in the Wagga Wagga area associated with town water supply usage. In 1973, the only obvious sign of usage was in the west Wagga Wagga area. In 1996, the influence of groundwater usage from town water supplies had significantly increased with noticeable drawdown in the groundwater level in the western, and central areas of Wagga Wagga and in the Gumly Gumly area.

The 2007, groundwater flow contours show the influence of groundwater usage in zone 3 from irrigation and in zone 2 from the town water supply usage. In Zone 3, the groundwater flow contours have changed from flowing from east to west in the 1973 and 1996 to showing the influence of extraction in the central area of the zone. In the central area the contours have increased in gradient from the east to the central area to the west and show the influence of extraction in the central area of the zone. In zone 2, there is a noticeable influence of groundwater usage around the major town water supply bore fields.

The groundwater levels in the Lachlan aquifer have altered during the period between 1973 and 2007. The most significant changes have occurred between 1996 and 2007 when development of the resource for irrigation has occurred.

In the period between 1973 and 1996 there was approximately a 1 metre increase in the groundwater level in the central and western areas of zone 3 and a 14 metre decline in zone 2 associated with town water supply usage. The influence of irrigation and town water supply extraction is most evident in the period from1996 to 2007, with declines of about 16 metres in zone 2 and between 11 and 12 metres in the central and western areas of zone 3. The most



significant change in groundwater levels in the period from 1973 to 2007 was about 11 to 12 metres in the central to western areas of zone 3 and up to 25 metres in zone 2.

This would be the maximum drawdown to be expected as it is the end of the irrigation period and groundwater levels would recover during the winter period as shown in the hydrographs in Section 12.

7.3 GROUNDWATER LEVEL CONTOURS

The groundwater level in the Cowra aquifer ranges from about 135 metres above sea level at Narrandera to 191 metres above sea level in the Oura area, as shown in Figure 23. This represents a groundwater level difference of approximately 56 metres. The steepest section occurs in the vicinity of Wagga Wagga, where groundwater levels fall about 20 metres over a distance of about 25 kilometres, associated with change in surface elevation in the area.

The change in gradient between Oura and Narrandera has remained relatively constant over the period from 1973 to 2007. In 1973 it was 55m, 1996 56m, and 2007 56m. However, the difference in elevation between the periods have changed, see Table 5, with the most significant change occurring between 1996 and 2007. This is likely to be associated with the drought conditions experienced during this period and the development of groundwater irrigation in the area during this period.

Table 5. Cowra aquifer change in elevation of the groundwater between Oura and Narrandera Area 1973 SWL AHD 1996 SWL AHD 2007 SWL AHD

Oura region 193m 193m 191m

Narrandera region 138m 137m 135m

The groundwater flow direction in 1973 and 1996 was from east to west from Oura to Narrandera, with no obvious signs of groundwater usage except in the Wagga Wagga area associated with town water supply usage. In 1973, the only recorded usage was in the west Wagga Wagga area. In 1996, the influence of groundwater usage from town water supplies has significantly increased with noticeable drawdown in the groundwater level in the western, and central areas of Wagga Wagga and in the Gumly Gumly area.

In the Lachlan aquifer, the 2007 groundwater flow contours show the influence of irrigation usage in zone 3 and town water supply usage in zone 2. In Zone 3, the direction of groundwater flow has changed from a general westerly trend to convergence to the central area where the water level gradient has also increased.

In zone 2, there are depressions in the groundwater level associated with groundwater usage by the major town water supply bore fields.

The alteration in the 2007 groundwater flow direction and gradient show the connection between the Cowra and Lachlan aquifers, and that extraction from the Lachlan aquifers causes vertical leakage from the overlying Cowra aquifer.

The groundwater levels in the Cowra aquifer have altered during the period between 1973 and 2007. The most significant changes have occurred between 1996 and 2007 when




development of the resource for irrigation had occurred. This is illustrated in Figure 24, which show the change over time between 1973 to 1996, 1996 to 2007, and 1973 to 2007.

In the period between 1973 and 1996 there was approximately a 3 metre increase in the central and western areas of zone 3 and a 4 metre decline in zone 2 associated with town water supply usage. The influence of irrigation and town water supply extraction is most evident in the period from 1996 to 2007, with declines of about 12 metres in zone 2 and between 3 to 3.5 metres in the central and western areas of zone 3. The overall change in the period from 1973 to 2007 was about 4 to 4.5 metres in the central to western areas of zone 3 and up to 10 metres in zone 2.

The decline in the Cowra aquifer reflects the usage from the Lachlan aquifer. The smaller response from the Cowra aquifer indicates that usage from the Lachlan aquifer is from storage, however the decline in pressure due to usage is causing vertical leakage from the Cowra to the Lachlan aquifer. The drawdown shown is likely to be the maximum drawdown to be expected as it is the end of the irrigation period and groundwater levels would recover during the winter period as shown in the hydrographs in Section 12.


Figure 23. Groundwater level contours in AHD for 1973, 1996 and 2007



Figure 24. Change in groundwater levels between 1973 and 1996, 1996 and 2007, 1973 and 2007



7.4 HEAD DIFFERENCE BETWEEN AQUIFERS

The head difference between the shallow and deep aquifers can give an indication of stressed areas of the aquifer, and reveal the vertical direction of groundwater flow. Areas in the Mid Murrumbidgee unaffected by pumping will have minimal head difference between the shallow and deep systems. Increased extraction from the deep aquifer result in an increase in the variation between the piezometric head of the Lachlan aquifer and the groundwater level in the Cowra aquifer, hence a greater head difference is experienced.

Figure 25 illustrates the head difference between the Cowra and Lachlan aquifers in 2007. On average the piezometric head in the Lachlan aquifer is 3.6m below the groundwater level in the Cowra aquifer. The head differences are largest at Gumly Gumly and Wagga Wagga. This is due to the large volumes of groundwater extraction occurring around these areas for town water supply. In zone 3, there are noticeable differences in the southern central area and in the north western area. The increased difference between the piezometric head of the Lachlan aquifer and the water table level in the Cowra aquifer is associated with groundwater usage for irrigation.

A comparison of the head difference between 1973 and 2007 illustrated in Figure 25 shows that the most significant changes have occurred in zone 2 associated with town water usage and in the southern central and north western areas of zone 3 associated with the development of irrigation usage. The increase in the difference between the piezometric head of the Lachlan aquifer and the groundwater level in the Cowra aquifer between 1973 and 2007, indicates an increase in vertical leakage from the Cowra aquifer and possibly the Murrumbidgee River. In addition, there are currently no locations where there is a positive head gradient from the Lachlan to the Cowra aquifer.




Figure 25. 2007 Head difference between the Cowra and Lachlan Aquifers and 1973 to 2007 change in head difference between Cowra and Lachlan aquifers


8.0 Sustainable Yield and Recharge Estimates Sustainable yield calculations are established as a percentage of average annual recharge. The annual recharge to the Mid Murrumbidgee alluvial aquifer system is estimated to be about 127,000ML/yr. This is based on leakage from the Murrumbidgee River and rainfall recharge over the GWMA. The long term average extraction limit of the groundwater system is taken to be 70 percent of the average annual recharge, and is therefore estimated to be about 89,000ML/yr. This correlates to an average entitlement of about 0.7ML/ha over the main body of the GWMA 013 (Ross 1999). Table 6 shows a break-up of current entitlement volumes compared to estimated sustainable yield limits by zone. With entitlements totalling 82,497.5ML the system as a whole is just under 87 percent allocated, excluding zones 4 and 5 which were not included in the estimated annual average recharge by Ross (1999). In isolation Zone 2 is over allocated, with groundwater use in the zone causing water level declines.

Table 6. Sustainable Yield and Entitlements in GWMA 013 Zone Area

(Ha) Sustainable Yield Limit

(ML)

Total Entitlement

(ML)

No. of Licenses

No. of Constructed

Bores

2006/07 Usage (ML)

% Allocated

Intensity of Entitlement

(ML/Ha)

1 22,767 19,038 1,684 16 16 51 8.6 0.07

2 11,507 9,623 27,491.5 97 88 16,587 283 2.37

3 72,156 60,339 48,667 128 106 14,432 81 0.67

4 3,856 * 2,453 23 23 285 0.64

5 2,388 * 2,202 22 21 53 0.92

Total 112,674 82,497.5 282 254 31,408 0.74

* The annual average recharge estimates for Tarcutta and Kyeamba Creeks were not calculated in the report prepared by Ross 1999

The recharge figure of 127,000ML was calculated for the main body of the Mid Murrumbidgee GMA 013, and did not consider the Tarcutta and Kyeamba alluvial areas. Information about the recharge to these tributaries is uncertain, and the methodology used in a report by Ross (1999) may not be applicable. For this reason these areas have been left out of the long term average extraction limit calculations until further information is obtained.

A numeric model for the Mid Murrumbidgee GWMA is currently under development for zone 2 and 3, which extends from upstream from Narrandera to about 4 kilometres downstream of Oura. The modelling will assist in improving the current knowledge of the relationship between the Murrumbidgee River, groundwater extraction and the behaviour of the Cowra and Lachlan aquifers.




9.0 Groundwater Use Groundwater is used for the irrigation of winter and summer crops, fodder crops, dairy, rice, viticulture, horticulture and aquaculture. The resource is also a vital source of water for a number of communities throughout the mid and upper Murrumbidgee catchment. Town water supply is the largest use of the resource presently. However, irrigation development in the area since the late 1990s has resulted in a significant increase in groundwater usage.

There is limited recorded usage for the area prior to the 2001/02 year. Prior to the 2001/02 the available usage data was mainly from the water supply authorities. Since 2001/02 water use has been recorded by meters and licence holder return cards.

Usage since 2001/02 has ranged between 24,000ML/yr and 34,000 ML/yr. A significant proportion is for town water supplies, however there has been measurable growth in irrigation usage mainly in Zone 3. Table 7 and Figure 24 show the recorded usage for the GWMA.

Table 7. Usage in megalitres by purpose and year 2001/02 2002/03 2003/04 2004/05 2005/06 2006/07

Town Water Supply (ML) 19,693 20,783 17,735 N/A 15,841 15,269

Irrigation (ML) 4,953 15,043 16,065 6,680 12,689 16,678

Commercial (ML) 0 0 0 35 164 281

Total (ML) 24,646 35,826 33,800 6,715 28,693 32,228

The majority of usage is in zones 2 and 3 of the GWMA. The major use in zone 2 is for town water supply, while in zone 3 it is irrigation.


10.0 Groundwater Management Zones This section discusses groundwater occurrence in greater detail for each zone and examines changes in water levels over time.

10.1 ZONE 1

10.1.1 Overview The zone consists of the main Murrumbidgee alluvial aquifer upstream of Oura. This section of the main aquifer is quite shallow, and groundwater yields are minimal compared to areas downstream. The thickness of alluvial material ranges from about 24 metres at Gundagai to about 65 metres at Oura. The aquifer is reasonably narrow throughout this section at about 1.5 to 2.5 kilometres wide.

10.1.2 Water levels As throughout the GWMA groundwater levels in the zone show the influence of river level fluctuations and since 2000 have declined with the drought conditions. The groundwater levels in the Cowra and Lachlan aquifers are highly connected with minimal differentiation between the aquifer, as shown in observation bore GW030160 in Figure 26.

10.1.3 Allocation and Licensed Usage The total entitlement for this section of the aquifer is 1684ML, with an average entitlement of 140ML per property account. Figure 27 shows the proportion of licensed works in zone 1.

Figure 26. Groundwater and Murrumbidgee River hydrograph of GW030160 and the Gauging Station at Wagga Wagga

2

3

4

5

6

7

8

9 Jan-70Jan-71Jan-72Jan-73Jan-74Jan-75Jan-76Jan-77Jan-78Jan-79Jan-80Jan-81Jan-82Jan-83Jan-84Jan-85Jan-86Jan-87Jan-88Jan-89Jan-90Jan-91Jan-92Jan-93Jan-94Jan-95Jan-96Jan-97Jan-98Jan-99Jan-00Jan-01Jan-02Jan-03Jan-04Jan-05Jan-06Jan-07Jan-08Jan-09

Date

Met

res B

elow

Gro

und

Lev

el

30160-1 (17.0 - 23.0m - Screen Interval Metres Below Ground Level)



GW030160



Figure 27. Proportion of groundwater licenses in Zone 1

Zone 1 Licensed Works

17%

0%

0%

2%

81%

0%

0%

irrigationcommercialmonitoringtown water supplys&daquaculturerecreation



10.2 ZONE 2

10.2.1 Overview

The zone consists of the main Murrumbidgee alluvial aquifer between Oura and the Malebo Range west of Wagga Wagga. This section of the aquifer has a narrow deep valley of alluvial sediments. The Lachlan aquifer is high yielding, supplying water for Wagga Wagga and regional centres in the eastern Riverina. Annual usage from the aquifer for town water supply is approximately 15 gigalitres. The thickness of alluvial material ranges from about 65 metres to about 85 metres at in the central area of the zone. The aquifer is narrow throughout this section at about 5 to 6 kilometres wide.

10.2.2 Water levels

The observation bores GW025393 and GW030114 in figures 28 and 29 illustrate the connection between the Murrumbidgee River and the aquifer systems in the zone. The groundwater levels in the mid 1970s reflected the level of the Murrumbidgee River. Increased extraction from the aquifer system for town water supply has resulted in significant declines in groundwater levels in both of the aquifers. The response of the Cowra aquifer to extraction from the Lachlan aquifer is evident. However, it does not respond directly to the periods of high extraction as shown in the Lachlan aquifer.


Bore No.: GW025393Natural Surface Elevation: 179.52m AHD

0

5

10

15

20

Jan-

67Ja

n-68

Jan-

69Ja

n-70

Jan-

71Ja

n-72

Jan-

73Ja

n-74

Jan-

75Ja

n-76

Jan-

77Ja

n-78

Jan-

79Ja

n-80

Jan-

81Ja

n-82

Jan-

83Ja

n-84

Jan-

85Ja

n-86

Jan-

87Ja

n-88

Jan-

89Ja

n-90

Jan-

91Ja

n-92

Jan-

93Ja

n-94

Jan-

95Ja

n-96

Jan-

97Ja

n-98

Jan-

99Ja

n-00

Jan-

01Ja

n-02

Jan-

03Ja

n-04

Jan-

05Ja

n-06

Jan-

07Ja

n-08

Jan-

09

Date

Wat

er L

evel

Bel

ow G

roun

d L

evel

(m)

156.52

161.52

166.52

171.52

176.52W

ater

Lev

el m

AH

D

25393-1 (12.1 - 18.1m - Screen Interval Metres Below Ground Level)25393-2 (48.7 - 60.8m - Screen Interval Metres Below Ground Level)25393-3 (79.8 - 81.6m - Screen Interval Metres Below Ground Level)Murrumbidgee River @ Wagga Wagga





2

7

12

17

22

Jan-70Jan-71Jan-72Jan-73Jan-74Jan-75Jan-76Jan-77Jan-78Jan-79Jan-80Jan-81Jan-82Jan-83Jan-84Jan-85Jan-86Jan-87Jan-88Jan-89Jan-90Jan-91Jan-92Jan-93Jan-94Jan-95Jan-96Jan-97Jan-98Jan-99Jan-00Jan-01Jan-02Jan-03Jan-04Jan-05Jan-06Jan-07Jan-08Jan-09

Date

Wat

er L

evel

Bel

ow G

roun

d (m

)

158.04

163.04

168.04

173.04

178.04

Wat

er L

evel

mA

HD

30114-1 (16.7 - 19.7m - Screen Interval Metres Below Ground Level)30114-2 (42.6 - 48.6m - Screen Interval Metres Below Ground Level)30114-3 (54.8 - 79.1m - Screen Interval Metres Below Ground Level)Murrumbidgee River @ Wagga Wagga

10.2.3 Allocation and Usage

The total entitlement for this section of the aquifer is 27491.5ML, with an average entitlement per property account of 121ML. This excludes the two town water supple entitlements of 16000 and 4000 ML. Figure 30 shows the proportion of licensed works in zone 2.



23%

2%

25%

6%

41%

1% 2%




10.3 ZONE 3

10.3.1 Overview The zone consists of the main Murrumbidgee alluvial aquifer between the Malebo Range and Narrandera. The thickness of the aquifer ranges from 65 metres to a maximum of 160 metres at Narrandera. The aquifer system maximum depth through the majority of the zone is approximately 100 metres. The width of the aquifer system varies from being narrow at the eastern extent being about 4 kilometres to a maximum width of about 25 kilometres in the central to western extent of the zone.

10.3.2 Water levels The observation bores GW030125 (Figure 31) and GW030094 (Figures 32) illustrate the groundwater level trends in the zone. GW030125 in located in the central area of the zone, while GW030094 is located in the western area. The groundwater levels in the mid 1970s show the influence of the 1974 flood and show no influence of groundwater extraction. Increased extraction from the aquifer system for irrigation has influenced groundwater levels with noticeable declines associated with pumping. Groundwater levels have also declined throughout the 2000s partly due to groundwater usage and the dry climatic conditions. The influence of these contributing factors is difficult to isolate. The influence of groundwater extraction is noticeable in the chart of GW403571 in Figure 33 which has a time series logger installed. The chart clearly illustrates the Cowra and Lachlan aquifers response to pumping in the area and its recovery to pumping events and the recovery associated with the reduced usage during the winter months.

Figure 31. Groundwater hydrograph of GW030125


0

2

4

6

8

10

12

14

16

18

Jan-70Jan-71Jan-72Jan-73Jan-74Jan-75Jan-76Jan-77Jan-78Jan-79Jan-80Jan-81Jan-82Jan-83Jan-84Jan-85Jan-86Jan-87Jan-88Jan-89Jan-90Jan-91Jan-92Jan-93Jan-94Jan-95Jan-96Jan-97Jan-98Jan-99Jan-00Jan-01Jan-02Jan-03Jan-04Jan-05Jan-06Jan-07Jan-08Jan-09

Date

Wat

er L

evel

Bel

ow G

roun

d (m

)

147.84

149.84

151.84

153.84

155.84

157.84

159.84

161.84

163.84

165.84W

ater

Lev

el m

AH

D





Figure 32. Standing water level metres below ground level hydrograph of GW030094

Bore No.: GW030094Pipe 1 Natural Surface Elevation: 153.45m AHDPipe 2 Natural Surface Elevation: 153.67m AHDPipe 3 Natural Surface Elevation: 153.47m AHD

2

4

6

8

10

12

14


Date

Wat

er L

evel

Bel

ow G

roun

d (m

)

137.47

139.47

141.47

143.47

145.47

147.47

149.47

151.47

Wat

er L

evel

mA

HD

30094-1 (50.2 - 62.3m - Screen Interval Metres Below Ground Surface)



Figure 33. Time Series Hydrograph of GW403571 located in the western area of zone 3

Bore No.: GW403571

7

8

9

10

11

12

13

1429/11/2006 18/01/2007 9/03/2007 28/04/2007 17/06/2007 6/08/2007 25/09/2007 14/11/2007 3/01/2008

Date

Wat

er L

evel

Met

res

Bel

ow G

roun

d

Pipe 2 74 - 77m - Screen Interval Metres Below Ground Level

Pipe 1 34 -37m - Screen Interval Metres Below Ground Level




The total entitlement for this section of the aquifer is 48667ML, with an average entitlement per property account of 552ML.

Growth in usage in the area has occurred since the late 1990s. The influence of the usage is illustrated in the groundwater flow contours in Figures 22 to 25, with there being slight change in flow direction from east to west to showing the influence of groundwater usage in the central area of the zone. Figure 34 shows the proportion of licensed works in zone 1.



32%

3%

5%

3%

56%

1%

0%




10.4 ZONE 4

10.4.1 Overview

The zone consists of the Cowra and Lachlan aquifers underlying the Tarcutta Creek floodplain. The aquifer system thins out from approximately 50m thickness at the confluence with the Murrumbidgee River to approximately 30 metres at Tarcutta. The Lachlan aquifer thins out upstream in the zone but is still present at Tarcutta. Irrigation bores in the zone are concentrated in the northern area of the zone.

10.4.2 Water levels

The observation bore GW030385, in Figure 35 illustrates the connection between the Tarcutta Creek and aquifer systems in the zone. The groundwater levels reflect the levels of Tarcutta Creek. Increased extraction from the aquifer system for irrigation has influenced groundwater levels with noticeable declines associated with groundwater usage. Groundwater levels have also declined throughout the 2000s partly due to groundwater usage and the dry climatic conditions.


Bore No.: GW030385

0

1

2

3

4

5

6

7

8

9


Date

Wat

er L

evel

Bel

ow G

roun

d L

evel

(m)

185.55

186.55

187.55

188.55

189.55

190.55

191.55

192.55

193.55

194.55

195.55

Wat

er L

evel

mA

HD

30385-1 (8.0 - 11.0m - Screen Interval Metres Below Ground Level)30385-2 (32.0 - 37.0m - Screen Interval Metres Below Ground Level)30385-3 (45.0 - 48.0m - Screen Interval Metres Below Ground Level)Tarcutta @ Borambola 410047

Natural Surface Elevation 195.6m


The total entitlement for this section of the aquifer is 2453ML, with an average entitlement per property account of 183ML. Figure 36 shows the proportion of licensed works in zone 1.





29%

0%

30%

5%

34%

0%

2%




10.5 ZONE 5

10.5.1 Overview

The zone consists of the Cowra and Lachlan aquifers underlying the Kyeamba Creek floodplain. The aquifer systems thin out from approximately 50m thickness at the confluence with the Murrumbidgee River to approximately 30 metres 20 kilometres south of the zone boundary with zone 2. The Lachlan aquifer thins out in mid point of the management zone, with irrigation bores in the zone concentrated within this aquifer.

10.5.2 Water levels

Monitoring in the zone is limited to the northern area, where there is minimal groundwater usage. The groundwater levels in the zone have declined by about 5 metres between 2001 and 2007. This is illustrated by observation bore GW030286, in Figure 37.


0

2

4

6

8

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14

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70

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71

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74

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77

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78

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79

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83

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85

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86

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Date

Wat

er L

evel

Bel

ow G

roun

d L

evel

(m)

179.5

181.5

183.5

185.5

187.5

189.5

191.5

193.5

Wat

er L

evel

mA

HD




Bore No.:GW030286Natural Surface Elevation: 193.5 mAHD


The total entitlement for this section of the aquifer is 2119ML, with an average entitlement per property account of 140ML. Figure 38 shows the proportion of licensed works in zone 1.





33%

0%

9%

0%

58%

0%

0%




11.0 Conclusion The mid Murrumbidgee GWMA 013 consists of the main alluvial aquifers between Gundagai and Narrandera including the tributaries of Tarcutta and Kyeamba Creeks. This system can be divided into two main formations based on time periods and depositional environments. The deeper Lachlan Formation is typically a very high yielding aquifer with good quality groundwater. The shallower Cowra Formation is generally lower yielding, and of poorer quality groundwater.

Groundwater allocations in the GWMA have increased since the last Status report prepared in 2000. The total entitlement has risen from about 61000ML to 82497.5ML an increase of about 35%. This increase is associated with the issuing of entitlements prior to the embargo in 2002 and the issuing of entitlements for quarries that intersected the aquifer system prior to the embargo.

The main water users in the GWMA have altered since the previous status report. In zone 2 the major usage is still for town water supply at Wagga Wagga and Gumly Gumly. Since 2000, irrigation use of groundwater has significantly increased and now represents 60% of water usage, with majority of irrigation development being in zone 3.

The development of groundwater resource for irrigation in zone 3 has caused a measurable change in the behaviour of groundwater system. Prior to 1996 the Cowra aquifer system alternated between being a gaining or losing system. Presently the Cowra aquifer groundwater levels are below the base of the river system. The difference between the piezometric head of the Lachlan aquifer and the groundwater level in the Cowra aquifer has also increased since 1996, which correlates with the development of the resource for irrigation.

Groundwater monitoring is of major importance for optimal management of this system, and it is essential that the current level of groundwater level monitoring be maintained. Short and long term fluctuations in groundwater levels over time need to continue to be monitored and reported. Monitoring of the groundwater quality also needs to occur, as there a strong reliance of town water supplies on the Lachlan aquifer.

Groundwater levels throughout the system were strongly influence by the 1974 flood, which served as a major recharge source for the entire system. Since that time water levels have experienced minor declines and rises that generally correspond with rainfall trends. Since the late 1990s, groundwater levels throughout the system have continually declined, and this is most likely due to the lower rainfall, levels in the river being lower, and therefore recharge to the groundwater system is also most likely to be lower than average. Also the development of groundwater usage for irrigation has influenced groundwater levels.

The GWMA 013 is divided into 5 zones, which are based upon the characteristics of the aquifer system. Recharge estimates for the aquifer system are used to estimate sustainable yield of the GWMA to be about 89,000ML. This volume is for the main alluvium of the GWMA and does not include tributary aquifers. Additional work is required to establish recharge values for the tributaries. Management at a zone level is appropriate, in particular to ensue that over extraction in any particular area does not become a problem.




12.0 References Boehmer W.K. (1998) Re-Assessment of Sustainable Extraction From Groundwater Basins

of Different Size in Semi-Arid and Arid Area. Proceedings 1998 International Groundwater Conference, Groundwater Sustainable Solutions p 13-18.

NSW Department of Water Resources (1995) Mid Murrumbidgee: GWMA 013.DWR. Sydney

NSW Department of Water Resources (1995) Review of groundwater use and water level behaviour in the mid Murrumbidgee alluvial sediments: Status Report No.2. DWR. Sydney

National Health and Medical Research Council (1996) National Water Quality Management Strategy Australian Drinking Water Guidelines – Summary. Agricultural and Resource Management Council of Australia and New Zealand.

Ross J (1999) Sustainable Yield Estimates for High Risk Aquifers in NSW. DLWC, Sydney Unpublished.

Webb L (2000) Groundwater status report for the mid Murrumbidgee alluvial aquifers. NSW Department of Land and Water Conservation. Sydney

Wooley D.R. (1972) Groundwater Geology of the Alluvial Aquifers of the Murrumbidgee Valley Between Narrandera and Gundagai. UNSW MSc Thesis.

Water Resources Commission (1986) Groundwater resources of the upper Murrumbidgee River valley alluvium: Status report No.1. WRC. Sydney

groundwater management area 013 gundagai to narrandera · mid murrumbidgee alluvium: groundwater...

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