report - department of water...report lake quitjup hydrology study prepared for water corporation...

$: REPORT - Department of Water...REPORT Lake Quitjup Hydrology Study Prepared for Water Corporation Infrastructure Planning Branch 629 Newcastle Street LEEDERVILLE WA 6007 20 April 2005J:\JOBS\42905401\REPORTS\507-F7002.1.DOC\21-APR-05$
R E P O R T

Lake Quitjup Hydrology Study

Prepared for

Water Corporation Infrastructure Planning Branch 629 Newcastle Street LEEDERVILLE WA 6007

20 April 2005

42905401.06001 / 507-F7002.0

J:\JOBS\42905401\REPORTS\507-F7002.1.DOC\21-APR-05

Project Manager: ………………………………….. John Barnett Principal Hydrogeologist

Project Director: ………………………………….. John Barnett Principal Hydrogeologist

URS Australia Pty Ltd Level 3, The Hyatt Centre 20 Terrace Road East Perth, WA 6004 Australia Tel: 61 8 9221 1630 Fax: 61 8 9221 1639

Author:

………………………………….. John Barnett Principal Hydrogeologist

………………………………….. Robin Connolly Associate Hydrologist

Date: Reference: Status:

20 April 2005 42905401.06001/507-F7002.1 Revision 1

URS Australia Pty Ltd (ABN 46 000 691 690) Level 3, The Hyatt Centre 20 Terrace Road East Perth, WA 6004 Australia Tel: 61 8 9221 1630 Fax: 61 8 9221 1639

21 April 2005 Water Corporation Infrastructure Planning Branch 629 Newcastle Street LEEDERVILLE WA 6007 Attention: Mr Len Baddock Senior Hydrogeologist Dear Sir, Subject: LAKE QUITJUP HYDROLOGY STUDY – FINAL REPORT Attached are ten copies of the final report for the Lake Quitjup Hydrology Study. We have incorporated or addressed your comments on the draft report and trust that this project is now complete. Thank you for the opportunity to work with you on this project and we look forward to working with you in the future. Yours faithfully URS AUSTRALIA PTY LTD John Barnett Principal Hydrogeologist

Contents


i

1 Introduction------------------------------------------------------------------------------------------------- 1-1

2 Field Investigations -------------------------------------------------------------------------------------- 2-1

3 Topography, Vegetation and Land Use ----------------------------------------------------------- 3-1

4 Geology ------------------------------------------------------------------------------------------------------ 4-1

5 Hydrogeology ---------------------------------------------------------------------------------------------- 5-1

5.1 General 5-1 5.2 Groundwater Quality 5-1 5.3 Hydrographs 5-1

6 Surface Hydrology---------------------------------------------------------------------------------------- 6-1

6.1 Drainage and Catchment Characteristics 6-1 6.2 Distribution and Classification of Wetlands 6-1 6.3 Lake Quitjup 6-2 6.4 Conceptual Water Balance Model 6-2

6.4.1 Lake Quitjup 6-3 6.4.2 Wetlands Area 6-3

7 Miscellaneous Site Investigations ------------------------------------------------------------------ 7-1

7.1 Access for Drilling 7-1 7.2 Access to Lake Quitjup 7-1 7.3 Coffee Rock – Magnetic Susceptibility 7-1 7.4 Potential Use of Geophysical Methods for Further Investigation of Superficial

Formations 7-2

8 Conclusions ------------------------------------------------------------------------------------------------ 8-1

9 Recommendations --------------------------------------------------------------------------------------- 9-1

9.1 Monitor Bore Construction 9-1 9.2 Monitoring Programme 9-1

9.2.1 Surface Water 9-1 9.3 Bathymetric Surveys 9-2 9.4 Groundwater 9-3

10 References -------------------------------------------------------------------------------------------------10-1

11 Limitations -------------------------------------------------------------------------------------------------11-1

List of Tables, Figures, Plates & Appendices


ii

Tables

Table 1 Field Measurements................................................................................................... 5-3 Table 2 Predicted Water Balance – Lake Quitjup .................................................................. 6-5 Table 3 Predicted Water Balance – Wetlands ........................................................................ 6-7 Table 4 Surface Water Monitoring Plan................................................................................. 9-2

Figures

Figure 1 Location Plan, with Census Data, February 1995

Figure 2 Digital Terrain Model

Figure 3 Catchments

Figure 4 Distribution and Classification of Wetlands

Figure 5 Provisional Drilling Sites

Figure 6 Air Photographs 1951-1996, Lake Quitjup

Plates

Plate 1 Cleared Farmland, Near Jangardup Mine

Plate 2 Blue Gum Plantation on Boundary of National Park

Plate 3 Watercourse Near URS 01, Exposed Coffee Rock

Plate 4 Excavated Coffee Rock, Farm Dam

Plate 5 Hand Auger Hole, SW2 Site, Groundwater at 0.9 m Depth

Plate 6 Claypan, Underlain by Salty Groundwater at 1.3 m

Plate 7 Wetland Area, 371800E; 6196200N

Plate 8 Beaufortia Lowland, Vegetated Dune in Background

Plate 9 Seasonal Wetland, SW2 Area, Looking East

Plate 10 Looking North over Gingilup Swamp from Coastal Dunes

List of Tables, Figures, Plates & Appendices


iii

Plate 11 Telephoto North across Gingilup Swamps, Blue Gum Plantation in Background

Plate 12 Looking South across Lake Quitjup

Plate 13 Monitoring Site SW1, Lake Quitjup, Looking West

Plate 14 Melaleuca Woodland, North Margin of Lake Quitjup

Plate 15 Upper Catchment, North of Fouracres Road

Plate 16 Black Point Road, National Park Entrance

Plate 17 Black Point Road, Typical Section

Plate 18 Black Point Road, Deep Sand Section

Plate 19 Seasonal Wetland, Black Point Road

Plate 20 Entrance to White Point Track, from Black Point Road

Plate 21 Deep Sand, White Point Track

Plate 22 White Point Track, Typical Section

Plate 23 Jangardup Boundary Track



Plate 26 Gingilup Swamps Track

Plate 27 Entrance to Walking Track to Lake Quitjup

Appendices

Appendix A Chemical Analyses

Appendix B Hydrographs

Appendix C Rainfall Data

SECTION 1 Introduction


1-1

1 Introduction

The Water Corporation is investigating the feasibility of abstracting groundwater for public water supply from the Yarragadee Formation in the Southern Perth Basin. A hydrogeological evaluation of the eastern part of the Scott Coastal Plain has indicated that such abstraction might cause drawdown at the water-table in the vicinity of Lake Quitjup, in the D’Entrecasteaux National Park.

Access to the area is limited, because of wetlands and dunes, and there are few tracks through the area. Consequently much of the area has not as yet been investigated by drilling.

A hydrology study of the area has therefore been undertaken to:

• collate any existing hydrological data for the area;

• infer the likely hydrological and hydrogeological properties of the area;

• design a monitoring program;

• scope an appropriate investigation drilling programme; and

• assess the feasibility of using geophysics to investigate the hydrogeology.

The area of study is the coastal plain between Gingilup Swamp and Lake Jasper E358000 to E377000, 50H UTM Coordinates (Figure 1).

The investigations and results of the study are described in the report.

SECTION 2 Field Investigations


2-1

2 Fie ld Investigations

The field investigations comprised:

• Hydrological reconnaissance of Lake Quitjup and seasonal wetlands.

• Establishment of two surface water monitoring sites.

• Hand-augering to water-table at 4 sites.

• Measurement of water-levels, EC, temperature and pH in piezometers, farm dams and farm bores encountered during reconnaissance.

• Sampling of water from Lake Quitjup and from one hand-auger hole for chemical analysis.

• Sampling of coffee rock for determination of magnetic susceptibility.

• Investigation of access for drilling rigs, and of access to Lake Quitjup.

SECTION 3 Topography, Vegetation and Land Use


3-1

3 Topography, Vegetation and Land Use

The area of study is an area of poorly-drained low-lying coastal plain between the Scott River catchment to the west, and the Donnelly River catchment to the east.

The elevation of the plain ranges from about 44 m AHD in the east to 22 m AHD in the west, with a gentle slope to the south, where it is bounded by vegetated coastal dunes up to 195 m AHD in elevation. To the north the plain passes into undulating terrain at the southern margin of the Blackwood Plateau (Figure 2).

The coastal plain is covered by heath vegetation, with rushes and sedges covering seasonally-inundated wetlands and the margins of Lake Quitjup. There are some irregular low linear sand dunes with Banksia and Jarrah.

The coastal dunes are generally covered by Bull Oak and Karri woodland, with low heath on the coastal side.

The Blackwood Plateau margin, originally Jarrah forest, is now largely cleared for irrigated pasture and agriculture (Plate 1), with extensive plantation areas of Tasmanian Bluegum (Plate 2).

SECTION 4 Geology


4-1

4 Geology

The study area is within the Bunbury Trough, in the Southern Perth Basin. The geology of the Scott Coastal Plain is described in Baddock (1995) and Rockwater (2004), and is summarised briefly below.

The plain is underlain by superficial formations unconformably overlying the Leederville Formation in the western part of the area, and the Yarragadee Formation elsewhere. The Bunbury Basalt overlies the Yarragadee Formation at Black Point, and as a discontinuous linear flow to the east of Lake Quitjup.

The superficial deposits on the plain range from about 5-20 m in thickness, and consist mainly of sand with minor silt and clay, of estuarine, lagoonal and lacustrine origin. Some peat and coal layers are present, and a discontinuous layer of ferruginous-cemented sand (‘coffee rock’) is common within a few metres of ground surface (Plates 3 and 4).

The unconformity surface at the base of the superficial formations slopes gently southwards towards the coast, so that the superficial formations increase in thickness in that direction.

The superficial formations beneath the plain are assigned to the Guildford Formation, with irregular low sand dunes at the surface probably corresponding to the Bassendean Sand. Deposits of peat and reworked peaty sand are continuing to form in seasonally inundated wetland areas.

The hand-auger borings made during the site visit encountered superficial sands which are fine to medium grained, well sorted, and well rounded with some frosted grains, indicating an aeolian origin. The coffee rock was shown to be discontinuous by probing with a driven metal spike; probings nearby to coffee rock outcrops commonly encountered no hard layers to 1.8 m depth.

The Tamala Limestone forms the bulk of the coastal dunes, and overlaps the seaward margin of the Guildford Formation. The Tamala Limestone consists of limestone, calcareous sandstone and sand. It forms heavily vegetated dunes which are unconformably overlain by younger dunes of Safety Bay Sand adjacent to the shoreline. These younger dunes are partially covered by low heath with some unvegetated and mobile areas. The Tamala Limestone and Safety Bay Sand range up to 200 m in combined thickness.

The eastern limit of the Leederville Formation beneath the superficial formations is undefined in the centre of the study area, due to lack of borehole information. It is absent in the east and northeast of the area, where the superficial formations are directly underlain by the Yarragadee Formation, apart from small local occurrences of the Bunbury Basalt.

SECTION 5 Hydrogeology


5-1

5 Hydrogeology

5.1 General

The direction of flow in the superficial formations is towards the coast, and water-table contours are generally parallel to the coast (Rockwater, 2004). Seasonal fluctuations are in the range of 1-3 m. Much of the coastal plain is flooded during winter, and the water-table was recorded at 0.9-1.4 m in hand-auger holes below the lower ground during the site reconnaissance in February 2005 (Plate 5).

There are generally upward heads from the Leederville Formation to the superficial formations in the western part of the area, and downward heads to the Yarragadee Formation in the east (Rockwater, 2004). Varma (2003) reports water-levels in the Yarragadee Formation in the Lake Jasper area of 2-4 m lower than levels in the superficial formations.

5.2 Groundwater Quality

Rockwater (2004) report that the salinity of groundwater in the superficial formations in this area generally ranges from 100-530 mg/L TDS.

Measurements of Electrical Conductivity (EC) in farm drains or soaks in the vicinity of the Jangardup mine site ranged from 463-1127 µS/cm (Table 1, Figure 1). These EC values correspond to TDS of about 225-550 mg/L, using the EC:TDS ratio of 0.49 from the analysis of Lake Quitjup (Appendix A). The salinity of the dams may have been affected by evaporation but is in the same general range as reported by Rockwater. The pH ranged from 7.3-10, being elevated by the addition of lime, which is a general agricultural practice in the area.

EC values from dams and soaks in the coastal dunes ranged from 475-1895 µS/cm, equivalent to 230-930 mg/L TDS. The pH ranged from 7.4-9.2, the water being derived from limestone. Two bores in the dunes gave EC values of 327 and 792 µS/cm (equivalent to TDS of 160 mg/L and 390 mg/L).

Measurements of EC were also obtained from three hand-auger holes in the eastern part of the area. Two adjacent holes 25 m apart, on the White Point Track, gave contrasting values of 1680 µS/cm and 40,000 µS/cm. Both struck a hard layer, probably coffee rock, at 1.2-1.3 m depth. The more saline groundwater underlies a small claypan (Plate 6), and indicates build-up of salt in a layer perched on coffee rock. The pH of the saline water was measured at 4.5. A full analysis of the saline perched water is appended; it is of sodium chloride type (Appendix A).

5.3 Hydrographs

The Water and Rivers Commission (Department of Environment) have monitored water-levels in the Scott Coastal Bores approximately twice-yearly since 1989-1992.



5-2

Monitored bores in the vicinity of the study area are as follows:

Superficial Formations: SC13C, SC14B, SC16B, SC17B and SC21B

Leederville Formation: SC13B, SC14A, SC17A

Yarragadee Formation: SC13A, SC16A, SC18A, SC18B, SC19A and SC21A

Hydrographs for all these bores are included as Appendix B.

The superficial formation bores show a general seasonal fluctuation in the range 1-2 m. Water-levels have generally remained steady from year to year, except for SC14B and SC16B. Bore SC14B has shown a very slight decline of 0.2 m since year 2000, but it is understood that adjacent piezometer SC14A (screened in the Leederville Formation) is now equipped with a windmill pump. In Bore SC16B, the seasonal minimum shows a decline of 0.4 m since 2001, although levels recover fully each year to their previous level. The slight decline in Bore SC16B may be due to proximity to blue gum plantations; pumping from the Yarragadee Formation for irrigation may also be partly responsible. Annual rainfall totals since 1950, generated for the location of Lake Quitjup, from the Bureau of Meteorology SILO Data Drill, are included as Appendix C.

The consistent seasonal maxima in Bores SC13C, SC17B and SC21B indicate that recharge has not declined in response to recent lower-than-average rainfall. Water levels in the superficial formations at these sites have remained unaffected by slight declines in the underlying Leederville Formation (SC13B and SC17B) or Yarragadee Formation (SC21B).

Of the three Leederville monitoring bores, SC13B shows a seasonal fluctuation of 2-2.5 m, and SC17A of 0.2-0.4 m. SC14A is now equipped with a windmill pump and has only been monitored occasionally. Water-levels in SC13B remained steady until 1999, and the seasonal maxima show an apparent decline of about 1 m since then, although minima have remained about the same. Bore SC17A shows a slight rise in water-levels of about 0.3 m to the Year 2000, and a very slight decline, of about 0.2 m, in seasonal minima since that year.

The Yarragadee monitoring bores generally show seasonal fluctuations in the range of 1-2 m. Most of the bores show very slight declines in water-level, up to 0.5 m, over recent years, except for Bore 18B. Bore 18B, screened from 15-21 m, has shown a decline in water-level of about 1.5 m since 1998, which may be related to local abstraction for agriculture. The adjacent SC18A, screened from 97-100 m, shows a lesser decline of about 0.5 m.



5-3

Table 1 Field Measurements

Coordinates

Source East North

Elevation (m AHD)

Casing Top

EC (µS/cm @ 25°C)

Temp (°C)

pH Water Level

(m below ground)

Total Depth (m)

from Casing Top

Comments

Farm Dam 372745 6196237 - 1127 25.9 8.4 - - -

Farm Dam 372418 6196230 - 463 24.3 9.1 - - Hard Coffee Rock

Piezo G 372458 6196174 35.4 - - - Dry 1.57 Casing stick-up 0.5 m

Farm Dam 371636 6198689 - 1157 24.5 10.0 ~1.5 – 2.0 - Iron-cemented sand

Farm Dam 371643 6199734 - 480 24.8 7.3 ~2.5 - Iron-cemented sand

Farm Dam 371778 6196980 - 606 21.2 7.7 - - Coffee Rock

Piezometer 369112 6198234 - - - - 2.32 3.77 Casing stick-up 0.45 m

Wobbled Well 365010 6194921 - - - - - - Inaccessible to probe

Farm Dam 365072 6194882 - 912 23.9 9.2 - - Water level marker 0.66 m above current level

Farm Dam 365186 6194813 - 985 21.6 7.4 ~3.0 - Water tea-coloured

Farm Dam 365171 6194831 - 475 21.2 7.9 - - Algae in water

Piezometer 370035 6199378 - - - - 1.8 2.96 Casing stick-up 0.57 m

Hand-auger Bore

365137 6199285 - - - - 0.92 1.8 No hard layer

Pond 368627 6203912 - 1255 26.7 4.3 - - Alongside Fouracres Road



5-4

Table 1 (continued)

Coordinates

Source East North

Elevation (m AHD)

Casing Top

EC (µS/cm @ 25°C)

Temp (°C)

pH Water Level

(m below ground)

Total Depth (m)

from Casing Top

Comments

Hand-auger Bore

363460 6197625 - 1680 21.3 - 1.07 1.2 Hard layer at 1.2 m

Hand-auger Bore

363460 6197651 - 40000 - 4.5 1.28 1.3 Hard layer at 1.3 m

Dam No. 3 361439 6196760 - 1895 21.9 8.5 ~2.0 - -

Bore 361167 6195858 - 792 18.9 7.6 ~27 40 Reported depths

Bore 363974 6195037 - - - - 12.18 22.5 Windmill. Casing stick-up 0.38 m

Bore 363470 6195151 - 327 (Tank)

20.7 - - 12 Reported depth

Hand-auger Bore

359448 6200730 - 1341 22.2 6.4 1.05 1.42 -

Piezo SJ 19A 376065 6192109 - - - - 5.10 - Casing stick up 1.5 m

Piezo SJ 19B 376065 6192109 - - - - 2.22 - Casing stick up 1.5 m

Piezo SJ 19C 376065 6192109 - - - - 1.43 - Casing stick up 1.5 m

SECTION 6 Surface Hydrology


6-1

6 Surface Hydrology

6.1 Drainage and Catchment Characteristics

A catchment map for Lake Quitjup and the surrounding wetlands is shown in Figure 3. The area has two main landforms: wetlands in the low-lying areas (termed wetlands) and uplands on the Blackwood Plateau (termed forested uplands). There is a transitional landscape between the two which has largely been cleared for agriculture. The plateau generates runoff that makes its way down to the low-lying areas and ponds. The low-lying areas also pond as a result of direct rainfall. Lake Quitjup, and possibly one lake to the west also retain ponded water due to a groundwater connection.

The wetlands are seasonally inundated, during the wetter months of winter, May to September. Depths of inundation throughout the area, as indicated by debris marks on vegetation and posts, varies from about 0.3 m up to 1 m. There was little sign of flowing water through the bulk of the wetland area, indicating that much of the ponding occurs as a result of direct rainfall, with steady flows from the forested upland and farmland areas in the north towards the south and west. The wetlands to the north of the Jangardup mine site appear to drain towards the southwest. It is not clear how connected the wetlands are, nor how far runoff from the forested uplands reaches into the wetlands. The runoff could contribute to surface ponding, at least along the northern margin of the wetlands.

Surface water movement in undisturbed areas is likely to be slow as flow paths are likely to be heavily vegetated and tortuous. Some erosion was observed on the Black Point Road as a result of vegetation removal, concentration and diversion of flows. This indicates that flows from the north reach this area and move toward the west; the magnitude of flows varies depending on the amount of rainfall during winter.

It is likely that water in the wetlands infiltrates and evaporates during early summer. At the time of the URS site visit, in February 2005, the wetlands were dry. This indicates that the wetlands are typically dry during much of summer but may wet up quickly with the onset of reasonable rainfall in winter.

6.2 Distribution and Classification of Wetlands

The wetlands of the D’Entrecasteaux National Park have been mapped and classified by Semenuik (1997, Water and Rivers Commission, Report WRT 12), as reproduced on Figure 4.

The main part of the Scott Coastal Plain is classified as extensive palusplain (AD9), made up of irregular and sometimes coalescing sumplands and damplands with irregular dunes, and underlain by estuarine sediments. Palusplain is defined as a seasonally waterlogged flat, sumplands as seasonally inundated basins, and damplands as seasonally waterlogged basins. Representative photographs of the Scott Coastal Plain are shown on Plates 7-11.

The inland part of the coastal dunes to the southwest and west of Lake Quitjup is described as sumplands and damplands in blowout dune areas (AD3). The wetlands are underlain by quartz sand, with a surface layer of peat in wetter basins.



6-2

Lake Quitjup itself is classified, with Lake Jasper to the east, as a permanently inundated basin, containing fresh and acidic water (AD7).

The area of Blackwood Plateau abutting the Scott Coastal Plain to the north is characterised as a complex association of laterite, pisolite gravel, sand and colluvial and alluvial flats, containing irregular sumplands and damplands (AD13). Plate 15 shows a typical view of this area.

6.3 Lake Quitjup

Lake Quitjup is located at the down gradient boundary of the coastal plain, against the edge of the coastal dunes.

It is a permanent lake, located in a depression at the seaward margin of the Scott Coastal Plain, where the plain is bounded by coastal dunes. The lake has maintained its current size and shape since original air photography in 1951 (Figure 6).

The salinity of the lake corresponds to the groundwater in the superficial formations. The approximate elevation of the lake, 35 m AHD from the Digital Terrain Model, corresponds with regional water-table contours. Lake Quitjup is therefore apparently in hydraulic connection with groundwater in the superficial formations, and is effectively a window into the water-table formed in a local depression. Local farmers report that the level remains constant within 0.2 – 0.3 m. Accumulated reed debris, observed at about 0.5 m above lake level in February 2005, appears to support this contention, allowing for the effects of wave action.

A wading traverse was made into the eastern part of the lake. The maximum water depth encountered in this area was 0.79 m. The substrate was sand to about 150 m due south of the shoreline, with an increasing thickness of soft black organic mud to the southwest, causing the traverse to be terminated at 371275E 6194653N, where the mud was 0.42 m thick, below 0.7 m of water.

The EC of Lake Quitjup was 677 µS/cm (TDS (sum) of 369 mg/L), and pH of 6.2. A full analysis of Lake Quitjup is appended (Appendix A). The water is of sodium chloride type.

6.4 Conceptual Water Balance Model

Conceptual water balances for Lake Quitjup and the wetlands area are given in Tables 2 and 3. The wetlands area is delineated in Figure 3. The water balances are based on the limited available data and are intended to characterise broad water balance trends only. There are no data on groundwater inflows and outflows, at this time, to verify the water balance components.

There is also insufficient information to allow comment on the characteristics of aquifers under the wetland and how they control seepage rates from the wetland.



6-3

6.4.1 Lake Quitjup

The predicted Lake Quitjup water balance (Table 2) indicates that about half the water inflow is from rainfall and half from groundwater seepage into the lake. The site observations suggest that there is no surface water inflow to (or outflow from) the lake, and this is reflected in the water balance model. About one-third of outflow is loss to evaporation and two-thirds is loss to groundwater seepage, probably to the south. Transpiration from fringing reed beds is included in the evaporation component.

Salt is brought into the lake in rainfall and seepage and leaves the lake in seepage. It was assumed that no salt leaves the lake in evaporated water. A basic assumption of the modelling was that the salt load in the lake is not increasing over time. As there is no surface water inflow or outflow, salt concentrated by evaporation must be leaving the lake in seepage, and being replaced by relatively fresh seepage inflow water. The seepage inflow volume was estimated to be relatively large, as a result. The lake’s volume (about 360 ML at 0.75 m deep) is removed in seepage at least every 2 months during the peak outflow period (August-December). This large amount of seepage outflow ensures that the lake does not accumulate salt and remains fresh.

The optimised salt load of inflow seepage was about 350 mg/L, slightly less than the average concentration of water in the lake.

Salinity of the lake water varies from a low of about 206 mg/L in August to a peak of about 600 mg/L in late summer, in response to variations in water depth and salt loads in the various inflow and outflow water pathways.

Depth of water in the lake varies during the year over a range of about 0.3 m, in response to rainfall and seepage inputs and seepage and evaporation outflows.

6.4.2 Wetlands Area

The predicted water balance of the wetlands (Table 3) is characterised by high rainfall input and relatively high seepage outflows to groundwater. The area receives surface water inflows and seepage from the forested uplands and farm land areas to the north and direct rainfall.

Runoff and seepage from the contributing catchments formed a small component of the wetland water balance. This is because runoff and seepage rates from the contributing catchment are small and the contributing catchment is only about 40% of the total area. Runoff from the contributing area varies from 1.5 to 2.5% of rainfall and seepage from 3-10%. It was assumed that the non-ponded areas within the wetlands themselves did not runoff and rain falling directly onto ponded areas was counted as rainfall, not runoff. All rainfall over the wetland area was considered an input, making rainfall the largest inflow.

Field observations indicate that the area is not saline, so salt imported in runoff and seepage and concentrated by evaporation must be largely lost to seepage outflows. The water balance model reflects this, predicting that about three-quarters of inflows are lost to seepage out of the wetland area. The evaporation component of the water balance includes a component of transpiration by vegetation. As a



6-4

proportion of rainfall over the total wetland area and contributing catchment excluding the dunes (154 km2), seepage outflow corresponds to about 36% of average annual rainfall.

Salt levels vary during the time the wetlands hold water, but salinity levels are low. There is a peak in salinity during early winter, as salt left over from the previous winter redissolves. The salt level falls during winter with dilution from rainfall then rises again as the lake dries out. Average salinity is low, about 100 mg/L, because the water balance is dominated by low-salt rain inflow. Individual local areas, such poorly drained claypans or areas with perched groundwater, though, are likely to concentrate salts and be saline.

Water depths reach up to 0.3 m on average. In individual wet years, water depths may be greater than that. High seepage outflows mean that the wetland areas are accordingly dry for part of summer. The duration of this dry period is likely to be variable depending on rainfall.



6-5

Table 2 Predicted Water Balance – Lake Quitjup

Weather/Stream Flows Water Balance Water/Depth/Area/Quality Month Average rainfall

(mm/mth)

Average pan evaporation (mm/mth)

Actual evaporation(mm/month)

Stream Flow In

(mm/mth)

Rainfall In(ML)

Stream Flow In

(ML)

Groundwater Seepage In

(ML)

Evaporation Out (ML)

Groundwater Seepage Out

(ML)

Overflow (ML)

Volume Of Water In

Lake (ML)

Depth Of Water In Lake (m)

Area Of Inundation

(km2)

Salt In Lake (T)

Salinity In Lake

(T/ML)

Dec 590 1.01 0.82 219 0.37 Jan 19 184 147 0 15 0 88 121 113 0 459 0.90 0.75 208 0.45 Feb 18 155 124 0 14 0 33 93 48 0 365 0.78 0.66 197 0.54 Mar 34 131 105 0 27 0 11 69 1 0 333 0.73 0.62 201 0.60 Apr 73 81 65 0 58 0 0 40 0 0 352 0.76 0.64 201 0.57 May 157 59 48 0 126 0 0 31 0 0 447 0.88 0.74 203 0.45 Jun 206 47 38 0 166 0 18 28 42 0 562 0.99 0.81 192 0.34 Jul 211 50 40 0 170 0 65 33 99 0 665 1.04 0.83 182 0.27 Aug 163 60 48 0 131 0 167 40 150 0 773 1.06 0.82 201 0.26 Sep 120 72 58 0 97 0 227 47 203 0 846 1.04 0.78 228 0.27 Oct 91 99 80 0 74 0 232 62 240 0 850 1.04 0.78 245 0.29 Nov 46 126 101 0 37 0 174 78 241 0 740 1.06 0.83 236 0.32 Dec 27 164 131 0 22 0 122 108 187 0 590 1.01 0.82 219 0.37

Sum 1,163 1,230 0 937 0 1,136 750 1,324 0 Inflows (% of total) 45 0 55 Outflows (% of total) 36 64 0



6-6

Table 2 (continued)

Assumptions Climate station * Data Drill for Lat, Long: -34.40 115.60 (DECIMAL DEGREES), 34 24'S 115 36'E Your Ref: LQuitjup Rainfall Stream Flow Groundwater Evaporation

Water TDS (T/ML) 0.01 0.20 0.35 0.00 Salt density (kg/m3) 1,360 (URS 1999, Gorenc et al. 1984) Evaporation factor (fraction) 0.8

Assumptions Starting salt based on observations in lake. Dry season (Feb-Mar) water depth is ~0.75 m. Salinity and lake water levels stable from year-to-year. Seepage in related to rainfall, lagged 3 months. Seepage out related to lake depth.



6-7

Table 3 Predicted Water Balance – Wetlands

Weather/Stream Flows Water Balance Water/Depth/Area/Quality Month Average rainfall

(mm/mth)

Average pan evaporation (mm/mth)

Actual evaporation(mm/month)

Stream Flow In

(mm/mth)

Rainfall In(ML)

Stream Flow In

(ML)

Groundwater Seepage In

(ML)

Evaporation Out (ML)

Groundwater Seepage Out

(ML)

Overflow (ML)

Volume Of Water In Wetland

(ML)

Depth Of Water In Wetland

(m)

Area Of Inundation

(km2)

Salt In Wetland

(T)

Salinity In Wetland (T/ML)

Dec 6,308 0.16 33 523 0.08 Jan 19 184 147 0.0 1,506 0 0 4,889 2,271 0 654 0.02 30 350 0.53 Feb 18 155 124 0.0 1,408 0 0 3,767 236 0 0 0.00 30 238 Mar 34 131 105 0.2 2,697 44 122 3,138 0 0 0 0.00 30 335 Apr 73 81 65 0.5 5,806 95 263 1,939 0 0 4,225 0.11 32 543 0.13 May 157 59 48 1.1 12,534 205 567 1,526 1,521 0 14,485 0.36 37 798 0.06 Jun 206 47 38 1.5 16,519 270 747 1,415 5,215 0 25,392 0.63 43 1,104 0.04 Jul 211 50 40 1.5 16,855 276 763 1,717 9,141 0 32,427 0.81 46 1,311 0.04 Aug 163 60 48 1.2 13,002 213 588 2,231 11,674 0 32,325 0.81 46 1,306 0.04 Sep 120 72 58 0.9 9,597 157 434 2,670 11,637 0 28,207 0.71 44 1,180 0.04 Oct 91 99 80 0.7 7,304 120 330 3,507 10,154 0 22,299 0.56 41 1,018 0.05 Nov 46 126 101 0.3 3,651 60 165 4,152 8,028 0 13,995 0.35 37 782 0.06 Dec 27 164 131 0.0 2,190 0 0 4,839 5,038 0 6,308 0.16 33 523 0.08

Sum 1,163 1,230 8.0 93,068 1,440 3,980 35,791 64,914 0 Inflows (% of total) 94 1 4 Outflows (% of total) 36 64 0



6-8

Table 3 (continued)

Assumptions Climate station * Data Drill for Lat, Long: -34.40 115.60 (DECIMAL DEGREES), 34 24'S 115 36'E Your Ref: LQuitjup

Rainfall Stream Flow Groundwater Evaporation

Water TDS (T/ML) 0.01 0.20 0.50 0.00

Forested uplands

Farm Land Wetlands - total

Wetlands - Ponded Extent

Dunes

Catchment (km2) 54.00 20.00 80.00 40.00 26.00

Forested uplands


Wetlands - Ponded

Dunes

Runoff (per cent rain) 1.50% 2.50% 0.00% 0.00% 0.00%

Forested uplands


Wetlands - Ponded

Dunes

Seepage (per cent rain) 3.00% 10.00% 0.00% 0.00% 0.00% Salt density (kg/m3) 1,360 (URS 1999, Gorenc et al. 1984) Evaporation factor (fraction) 0.8

Assumptions Starting salt based on observations in the wetlands. Dry season (Feb-Mar) water depth is ~0.75 m. Salinity and lake water levels stable from year-to-year. Seepage in related to rainfall, lagged 3 months. Seepage out related to lake depth. Runoff threshold = 28 mm rain Shallow seepage in threshold = 28 mm rain

SECTION 7 Miscellaneous Site Investigations


7-1

7 Misce llaneous Site Investigations

7.1 Access for Drilling

There are several vehicle tracks along the boundary of the national park, and across the national park, which would provide access for drilling rigs. All these are accessible only from the north, access from the south being prevented by steep gradients through the coastal dunes.

Five sites have been provisionally selected with the aim of delineating the eastern boundary of the Leederville Formation beneath the superficial formations, and the nature of the superficial formations themselves in the national park (Figure 5).

These sites are:

URS01, URS02 : on Black Point Road, both sites pegged and flagged

URS03 : on White Point Track, pegged and flagged

URS04 : Southeast corner of track bordering farmland surrounding Jangardup mine site. Not pegged.

URS05 : Boundary track around Blue Gum Plantation, accessible from Fouracres Road. Not pegged.

The various tracks are depicted on the following plates:

Black Point Road : Plates 16-19

White Point Road : Plates 20-22

Jangardup Boundary Track : Plates 23-25

Gingilup Swamps Track : Plate 26

7.2 Access to Lake Quitjup

Lake Quitjup can be accessed via a rehabilitated vehicle track, now accessible only on foot, which originates from the Jangardup boundary track, 0.9 km from the southwest corner of the cleared farmland. The origin of the track is shown on Plate 27.

Walking time to Lake Quitjup is about 30 minutes.

7.3 Coffee Rock – Magnetic Susceptibility

Two representative samples of coffee rock were measured for magnetic susceptibility, using a JH-8 Magnetic Susceptibility Meter provided by the Department of Exploration Geophysics at Curtin University of Technology.

SECTION 7 Miscellaneous Site Investigations


7-2

The results were as follows:

SAMPLE 1 (E 367705; N 6200030) : (0.2 – 0.4) x 10-3 SI units

SAMPLE 2 (E 372418; N 6196230) : (0.1 – 0.2) x 10-3 SI units

The magnetic susceptibility of the rock is low, and similar to average values for clays and sandstones. The coffee rock could therefore not be detected by magnetometer, whether by airborne or ground survey.

7.4 Potential Use of Geophysical Methods for Further Investigation of Superficial Formations

The results from any drilling program could be further extrapolated by geophysical survey, to determine the relative clay content of the superficial formations, and hence the degree of hydraulic connection between the Yarragadee Formation and the water-table.

The nature of the superficial formations, in terms of relative clay content, could be investigated by ground electromagnetic survey, using an EM34 instrument, to extend interpretation from the drilling sites.

The survey would be done as a series of soundings, at 10 m, 20 m and 40 m dipole separation. The soundings would be taken with hoops in both vertical and horizontal configurations, giving horizontal and vertical dipoles. This would give nominal penetration depths of 7.5 m, 15 m, 30 m and 60 m.

Assuming a total aggregate survey length of 40 km, along the northern boundary of the national park, and along Black Point Road, White Point Track and Gingilup Swamp Track, and soundings every 100 m, the cost of such a survey would be about $20,000.

SECTION 8 Conclusions


8-1

8 Conclusions

1. Lake Quitjup is a permanent lake, and is apparently in hydraulic connection with groundwater in the superficial formations.

A conceptual water balance for the lake indicates that about half the inflow to the lake is derived from groundwater, and half from direct rainfall. About two-thirds of the outflow is accounted for by groundwater, and one-third by evaporation.

The salinity of the lake, measured at about 370 mg/L in February 2005, is predicted by the conceptual water-balance to range between about 200 mg/L in August to 600 mg/L in late summer.

Lake Quitjup is accessible from the boundary track around the cleared farmland which surrounds the Jangardup mine site. The walking track originates 0.9 km east of the southwest corner of the cleared farmland.

2. Much of the Scott Coastal Plain becomes inundated in an average winter wet season. The annual rainfall is high: 1,200 to 1,300 mm.

At Lake Quitjup the long-term average rainfall is estimated at 1,163 mm, having been slightly less since 1983 at an average of 1,044 mm (Bureau of Meteorology, SILO Data Drill). Most of the rain (almost 90 percent) falls during May to October.

The inundation is derived from direct rainfall on the plain, together with runoff from the Blackwood Plateau to the north. During the dry season, November to April, the ponded surface water dissipates by evaporation and by infiltration to the shallow water-table. The water-table below the lower-lying parts of the plain was 0.9 – 1.0 m below ground in February 2005. The only remaining surface water was in Lake Quitjup.

A conceptual water-balance for the wetlands indicates that water-depths generally range up to 0.3 m in winter, and that salinities of the surface water are generally low, of the order of 100 mg/L, except very locally in isolated or perched claypans.

3. The extensive ponding of surface water on the Scott Coastal Plain provides a source of potential additional recharge to groundwater which is currently lost to evaporation. This would provide a buffer against lowering of the water-table which might be caused by future abstraction from the underlying Yarragadee Formation. Any reduction in the period of ponding as a result of such induced recharge might, however, affect the wetland vegetation to some degree.

Hydrographs of the Scott Coastal series of monitor bores do not show any decline in water-table as a result of slightly declining water-levels in the underlying Yarragadee or Leederville Formations. Additional monitor bores are required in the D’Entrecasteaux National Park to investigate the degree of hydraulic connection between the water-table and the underlying Yarragadee Formation in that area.

4. The presence of coffee rock cannot be readily detected by geophysical methods, as it has very low magnetic susceptibility, similar to clay or sandstone.

SECTION 8 Conclusions


8-2

The nature of the superficial formations, in terms of relative clay content, could be investigated by ground electromagnetic survey, using an EM34 instrument, to extend interpretation from the drilling sites.

5. Shallow bores to monitor water-table levels can be readily constructed by hand-auger, providing there is no shallow coffee rock at a particular site. Coffee rock is discontinuous, so potential monitor bore sites can be located by metal depth probe.

SECTION 9 Recommendations


9-1

9 Recommendations

9.1 Monitor Bore Construction

The provisional drilling sites should be accessible in the dry season, to either a track-mounted rig or 4WD-mounted rig. A Gemco rig would be suitable, but might require towing across the sandy section on White Point track.

Monitor bores could be constructed by either hollow-auger, reverse-circulation or by rotary mud-circulation. The maximum depth of bores would be 40 m, with three piezometers installed at each site – one at the water table (maximum depth 4 m), one in the lower part of the superficial formations (maximum depth 20 m), and one in the underlying Leederville or Yarragadee Formation (maximum depth 40 m).

Construction would be with 50 mm Nominal Diameter Class 9 PVC tubing, slotted against the selected aquifer interval. The annulus between tubing and borehole wall would be packed with 1.6-3.2 m graded gravel against the slotted section, and sealed with bentonite or bentonite-cement. A lockable steel protector cap would be set in a cement block at the surface.

Completed bores would be developed by flushing with air or water, and gamma-logged down hole to aid in stratigraphic interpretation.

All piezometers would be surveyed for position (accuracy + 5m) and elevation (accuracy + 0.01 m).

9.2 Monitoring Programme

9.2.1 Surface Water

Current Status and Issues

There is little information describing the hydrology and water balance of Lake Quitjup and the surrounding wetlands. Accordingly, a monitoring program is needed to help characterise the area’s hydrology.

A characteristic of the area is its inaccessibility during winter. Much of the wetland area becomes wet and untraffickable, either on foot or in a vehicle during winter. Accordingly, access to Lake Quitjup or other areas of the wetlands during winter for sampling is probably not practical, indicating an increased reliance on automatic-logging equipment.

Objectives

The objectives of the monitoring program are to:

• help characterise variation in water levels in Lake Quitjup and other significant wetlands.



9-2

Implementation

Details for implementation of the monitoring plan are given in Table 4.

Table 4 Surface Water Monitoring Plan

Monitoring Location Sampling Methods Analysis

SW1 - Lake Quitjup

371,553 m E 6,194,783 m N

Continuous logging (daily or weekly, depending on rates of change) of water level and electrical conductivity. Convert water level to volume using a depth-volume relationship. Tie water levels to AHD.

Identify seasonal changes in water level and quality; update the lake water balance and refine estimates of groundwater flows into and out of the lake.

SW2 – Claypan near monitoring bore URS3

365,137 m E 6,199,285 m N

Continuous logging (daily or weekly, depending on rates of change) of water level and electrical conductivity. Convert water level to volume using a depth-volume relationship. Tie water levels to AHD.

Identify seasonal changes in water level and quality, help characterise the claypans water balance, help identify flow- through patterns for the area.

Weather Source or record, as a minimum: daily rainfall close to Lake Quitjup. Source daily pan evaporation for the area. Pan evaporation estimates can be sourced from the Bureau of Meteorology. Rainfall may need to be measured on-site.

Use as input to the water balance and for general interpretation of the data.

The two monitoring points have been staked with steel pegs. These points are indicative, and may be moved as required to facilitate access. Datum at the two sites should be surveyed and water depth measurements tied to Australian Height Datum (AHD). This is needed to allow correlation with bore water levels through the area.

Bathymetric surveys of Lake Quitjup and the claypan at SW2 may be useful to improve water-balance estimates, and the necessity for such a survey can be assessed after data has been collected on water-levels and salinity for a minimum period of 12 months. See Section 9.3 for discussion of possible survey techniques.

Data should be collated in an appropriate database, reviewed regularly and error checked. Water balances for the two lakes should be updated as new data becomes available.

9.3 Bathymetric Surveys

On advice from a local surveying firm (Nigel Paul, Spectrum Surveys), the most efficient bathymetric survey method for Lake Quitjup is likely to be by boat using a calibrated depth sounder linked to a differentially corrected GPS for horizontal positioning. Areas inaccessible by boat, banks, etc can be surveyed on foot using conventional, differentially corrected GPS. It is recommended that the survey in the lake characterises the top of the silt layer, the water depth, and the banks up to the local top of bank.



9-3

The claypan at monitoring point SW2 can probably be surveyed when dry, on foot or using a small vehicle with a conventional, differentially corrected GPS.

9.4 Groundwater

Monitoring Bore SC19A, the nearest existing Water and Rivers Commission monitoring bore to Lake Quitjup, should be equipped with a water-level data-logger.

This will enable detailed water-level trends to be compared with Lake Quitjup water-levels, to determine whether groundwater levels in the superficial formations are in-phase with the lake, to confirm the hydraulic connection between groundwater and lake levels.

SECTION 10 References


10-1

10 References

Baddock, L.J. (1995). Geology and Hydrogeology of the Scott Coastal Plain, Perth Basin.

Cable Sands (WA) Pty Ltd. Annual Hydrological Review – 2001/2002.

Mohsenzadeh, H.A. and Diamond, R.E. (2000). Modelling Nutrient Management on Scott Coastal Plain, Bore Completion Report and Pumping Test Results, Stage 2. Hydrogeology Report No. HR166, Water and Rivers Commission.

Rockwater (2004). South-West Yarragadee, Eastern Scott Coastal Plain, Assessment of Hydrogeology, Drainage and Potential Effect on the Water Table of Drawdown in the Yarragadee Aquifer. Report for Water Corporation.

Varma, S. (2003). An Analytical Technique for Determining Hydraulic Conductance and Water Balance of Lake Jasper Western Australia. DoE Internal Report (unpublished).

Vic Semenuik Research Group (1997). Mapping and Classification of Wetlands from Augusta to Walpole in the South West of Western Australia. Water and Rivers Commission Report WRT 12.

SECTION 11 Limitations


11-1

11 Limitations

URS Australia Pty Ltd (URS) has prepared this report in accordance with the usual care and thoroughness of the consulting profession for the use of Water Corporation and only those third parties who have been authorised in writing by URS to rely on the report. It is based on generally accepted practices and standards at the time it was prepared. No other warranty, expressed or implied, is made as to the professional advice included in this report. It is prepared in accordance with the scope of work and for the purpose outlined in the Proposal dated 24 February 2005.

The methodology adopted and sources of information used by URS are outlined in this report. URS has made no independent verification of this information beyond the agreed scope of works and URS assumes no responsibility for any inaccuracies or omissions. No indications were found during our investigations that information contained in this report as provided to URS was false.

This report was prepared between February – April 2005 and is based on the conditions encountered and information reviewed at the time of preparation. URS disclaims responsibility for any changes that may have occurred after this time.

This report should be read in full. No responsibility is accepted for use of any part of this report in any other context or for any other purpose or by third parties. This report does not purport to give legal advice. Legal advice can only be given by qualified legal practitioners.

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Water Level (m), Below Ground

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Plates

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Plates


1

Plate 1 – Cleared Farmland, Near Jangardup Mine

Plate 2 – Blue Gum Plantation on Boundary of National Park

Plates


2

Plate 3 – Watercourse Near URS 01, Exposed Coffee Rock

Plate 4 – Excavated Coffee Rock, Farm Dam

Plates


3

Plate 5 – Hand Auger Hole, SW2 Site, Groundwater at 0.9 m Depth

Plate 6 – Claypan, Underlain by Salty Groundwater at 1.3 m

Plates


4

Plate 7 – Wetland Area, 371800E; 6196200N

Plate 8 – Beaufortia Lowland, Vegetated Dune in Background

Plates


5

Plate 9 – Seasonal Wetland, SW2 Area, Looking East

Plate 10 – Looking North over Gingilup Swamp from Coastal Dunes

Plates


6

Plate 11 – Telephoto North across Gingilup Swamps, Blue Gum Plantation in Background

Plate 12 – Looking South across Lake Quitjup

Plates


7

Plate 13 – Monitoring Site SW1, Lake Quitjup, Looking West

Plate 14 – Melaleuca Woodland, North Margin of Lake Quitjup

Plates


8

Plate 15 – Upper Catchment, North of Fouracres Road

Plate 16 – Black Point Road, National Park Entrance

Plates


9

Plate 17 – Black Point Road, Typical Section

Plates


10

Plate 18 – Black Point Road, Deep Sand Section

Plate 19 – Seasonal Wetland, Black Point Road

Plates


11

Plate 20 – Entrance to White Point Track, from Black Point Road

Plate 21 – Deep Sand, White Point Track

Plates


12

Plate 22 – White Point Track, Typical Section

Plate 23 – Jangardup Boundary Track

Plates


13



Plates


14

Plate 26 – Gingilup Swamps Track

Plate 27 – Entrance to Walking Track to Lake Quitjup

Appendix A Chemical Analyses


Appendix B Hydrographs


Appendix C Rainfall Data


report - department of water...report lake quitjup hydrology study prepared for water corporation...

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