Dealing with salinity in Wheatbelt Valleys - Department of Water

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Morrell, Hatton and Curry 6320000 6300000 6280000 6260000 6240000 600000 600000 ( 330 325 NYABING 620000 320 310 FLOWNET WEST 305 620000 315 PINGRUP ( 290 300 ONGERUP ( 295 640000 295 300 305 290 640000 A simplified flownet (Salama et al. 1996a) (Figure 3) was constructed from the generated water level map. The flow net indicates that all the groundwater from the shallow and deep aquifers is discharging into the lake system. It also shows that the groundwater flow in the upper parts of the catchment discharges into the surface streams in confluent areas of the catchment. In the reserve sub-catchment, groundwater discharge is also taking place at the lower parts of the catchment due to the shallow basement in these areas. The map also showed that the general groundwater flow in the catchment is from the west and east towards the central parts of the lakes. The congested flow channels indicate major groundwater accumulation and discharge zones that highlight the hot spots in the catchment. The other important point to be taken into consideration is that most of these lakes, swamps and streams receive subsurface lateral flow from the interface between the shallow sandy topsoil layer and the low permeability clays characteristic of the duplex soils. Numerical groundwater modelling (FLOWTUBE, Dawes et al. 2000) explored the catchment’s groundwater behaviour during present and future conditions and its responses to land use changes. This modelling included sensitivity tests of the model 295 300 305 310 325 660000 FLOWNET EAST 320 FLOWNET SOUTH 660000 Figure 3: Groundwater Flownet – 8 – 310 680000 LEGEND 315 JERRAMUNGUP ( 680000 Towns Roads Headline Streamline parameters, for they were estimated with significant uncertainty. Predictive scenario modelling was performed from present conditions out 100 years for recharge rates of 10 mm, 20 mm, 40 mm and 60 mm for three flow tubes from three major subcatchments and one flow tube representing 9 minor sub-catchments (Figure 4). The sensitive analysis was conducted using a recharge value of 40 mm that was assumed to represent the average recharge taking place at the present time in this area. Recharge scenarios were performed with recharge equal to 10 mm, 20 mm, 40 mm and 60 mm per year. For these simulations, the values for hydraulic conductivity (0.5) and specific yield (0.1) were used. Calibrations indicated that the present day recharge is within the range of 30–40 mm. This was determined by comparing the model results with water level trends in other catchments in the area and water level patterns in drilled wells in the catchment. By increasing recharge to 60 mm the aquifer fills up more quickly and the final groundwater head is closer to the surface in most areas and above the surface in discharge areas. When recharge is reduced to less than 10 mm the groundwater head falls in most areas to levels reported and considered as a pre-clearing situation. 6320000 6300000 6280000 6260000 6240000
6320000 6300000 6280000 6260000 6240000 600000 600000 ( LEGEND NYABING 620000 Towns Roads Subcatchments Lakes Drainage Line Flowtube #1 Flowtube #2 Flowtube #3 Flowtube #4 620000 640000 ( ONGERUP ( 640000 FLOWTUBE modelling was used to model the effects of four recharge scenarios: 10, 20, 40 and 60 mm on water levels and groundwater discharge to 2100. Four sub-catchments were modelled. Flowtube#1 represented the flow patterns and rates of rise in a single stream catchment. Flowtube#2 simulated the flow in the presence of the reserve and showed the effect of vegetating more than 50% of the catchment on groundwater levels and groundwater discharge. Flowtube#3 represented multiple flows from a large sub-catchment. Flowtube#4 represented nine minor subcatchments. The results of FLOWTUBE modelling for Flowtube#1 (Figure 5) showed that at the present rates of recharge (40 mm), water levels will continue rising at a rate varying between 0.1–0.35 m year. The rate of rise varied depending upon the position in the landscape, with the highest rise being in the upper parts of the catchment that receives the highest recharge. Reducing the recharge to 20 mm, the rate of rise would range between 0.05–0.18 m per year, while reducing the recharge to 10 mm the rate of rise would be only 0.01–0.06 m per year. Although reducing the recharge rate does not reduce water levels except when the recharge rates are PINGRUP 660000 660000 Figure 4: Modelled sub-catchments – 9 – 680000 JERRAMUNGUP ( 680000 Morrell, Hatton and Curry reduced by 90%, the results of the FLOWTUBE modelling showed that the surface water discharge (overflow from the aquifers and subsurface lateral flow) is greatly reduced from 12,000 m 3 d –1 for 40 mm of recharge to less than 300 m 3 d –1 for 10 mm of recharge. On the other hand groundwater discharge through the aquifer system would be reduced from 300 m 3 d –1 for 40 mm recharge to about 150 m 3 d –1 . This is not greatly reduced as it is controlled by the aquifer thickness and its capacity of transmitting water. The results of modelling for Flowtube#2 (Figure 6) showed that at the present rates of recharge (40 mm) water levels will continue rising in the cleared part of the catchment at a similar rate to Flowtube#1. The results also showed that the only effect the reserve had is that it shifts the boundary of the groundwater catchment to the edge of the reserve. Due to the rising water levels in the areas adjacent to the reserve, water level gradients will be reversed and groundwater will start flowing back to the reserve at a rate depending on the hydraulic properties of the aquifer. It is expected that if this trend continues, the marginal areas of the reserves would be progressively degenerated. It is also shown that if the reserve is cleared or lost, more than 57% of the area of the catchment will be waterlogged. 6320000 6300000 6280000 6260000 6240000
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Foreword Dealing with Salinity in W
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1Day one: Monday 30th July. Field t
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Papers Dealing with Salinity in Whe
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Ali and Coles biggest challenges fa
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Ali and Coles erosion, maintenance
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Ali and Coles expected under these
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Ali and Coles Coles, N.A. & Ali, M.
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Commander, Schoknecht, Verboom and
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APPRECIATING AND CREATING OUR HISTO
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services. The Government responded
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WHEATBELT VALLEYS IN DIFFICULTIES T
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argue that they were really abnorma
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1990s, the wheatbelt valleys in par
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REFERENCES Agstats (1997). Agricult
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George and Coleman two to four fold
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George and Coleman surface, the vas
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George and Coleman for example in t
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George and Coleman current trends c
Page 61 and 62: George and Coleman While not as div
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Page 65 and 66: George and Coleman advantages of so
Page 67 and 68: George and Coleman this volume). In
Page 69 and 70: George and Coleman Venture Economy
Page 71 and 72: George and Coleman Lawrence, C. (19
Page 73 and 74: Hatton and Ruprecht WATCHING THE RI
Page 75 and 76: Since the mid 1970s annual rainfall
Page 77 and 78: Effect of clearing on runoff The ot
Page 79 and 80: Salinity Monthly streamflow (ML) 10
Page 81 and 82: The ratio of the salt outputs to in
Page 83 and 84: - 11 - Hatton and Ruprecht Table 4:
Page 85 and 86: THE FUTURE In looking at the future
Page 87 and 88: McFarlane, D.J., George, R.J. & Far
Page 89 and 90: Keighery, Halse and McKenzie Terres
Page 91 and 92: Keighery, Halse and McKenzie Wetlan
Page 93 and 94: Keighery, Halse and McKenzie specie
Page 95 and 96: Keighery, Halse and McKenzie enviro
Page 97 and 98: Lloyd number of legal cases pending
Page 99 and 100: Lloyd 0 -500 -1000 -1500 -2000 -250
Page 101 and 102: Lloyd Table 3. Sheep grazing days i
Page 103 and 104: Lloyd Hectares project to provide w
Page 105 and 106: INTRODUCTION The Lake Chinocup Catc
Page 107 and 108: agriculture) in various stages, the
Page 109 and 110: - 3,477 ha of remnant vegetation or
Page 111: Scientists talk of up to 30% of the
Page 115 and 116: Although the waterlogged area under
Page 117 and 118: eliminates drainage through the nex
Page 119 and 120: REFERENCES Dawes, W.R., Stauffacher
Page 121 and 122: Pannell ECONOMICS, SOCIETY AND ENVI
Page 123 and 124: Pannell • the area of land protec
Page 125 and 126: Pannell Proposals to construct majo
Page 127 and 128: Pannell been conducted for the Cent
Page 129 and 130: Pannell investments in long-term la
Page 131 and 132: Pannell Pannell, D.J. (2001). Dryla
Page 133 and 134: Porter, Bartle and Cooper Table 1:
Page 139 and 140: Porter, Bartle and Cooper operation
Page 141 and 142: Porter, Bartle and Cooper Increase
Page 145 and 146: Porter, Bartle and Cooper support i
Page 147 and 148: Porter, Bartle and Cooper that is a
Page 149 and 150: CASE STUDY - TOOLIBIN LAKE AND CATC
Page 151 and 152: • The distribution, storage and m
Page 153 and 154: Secondly, there is a set of practic
Page 155 and 156: within three categories: relationsh
Page 157 and 158: CONCLUSIONS Actions to protect and
Page 159 and 160: FIELD TOUR LOCATIONS FIELD TOUR NOT
Page 161 and 162: COLES FARM “Avon River Basin Over
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Conference Outcomes Dealing with Sa
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with Salinity in Wheatbelt Valleys:
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with Salinity in Wheatbelt Valleys
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Photo Gallery 2 Dealing with Salini
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APPENDIX 1 BACKGROUND HYDROLOGY AND
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WHEATBELT HYDROLOGY Flow in the Yil
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Flow (ML) STREAM SALINITY Salt Rive
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APPENDIX 2 WATER MANAGEMENT OPTIONS
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APPENDIX 3 MANAGING WATER AND SALIN
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SUMMARY- TIMELINE OF RECENT SIGNIFI
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RECENT HISTORY OF WATER AND SALINIT
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Figure 1. Hydrological cross-sectio
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Depth (m) 316 315 314 313 312 311 M
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FURTHER INVESTIGATIONS AND MANAGEME
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