Dealing with salinity in Wheatbelt Valleys - Department of Water

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The Land Monitor data (Table 2) shows an increase in all shires, although the magnitude is highly variable (0.05 to 15%). The increase over the period 1987--1991 to 1995–1996 is about 0.5%. This equates to an annual increase of less than 0.1% (1% per decade). A comparison of the ABS statistics George and Coleman and Land Monitor data is not possible as methods differ too greatly. However it is worth noting that for the Kellerberrin Scene chosen for comparison (Table 3), salinity has both reduced and increased, depending on the shire and timeframe chosen. Table 3: Comparison of saline area (1979, 1989, 1995) for five shires in the Kellerberrin Scene. Shires ABS (1979) ABS (1989)* Land Monitor 1989** Land Monitor 1995** Tammin 5692 9507 (9.26) 7492 (6.8) 8417 (7.6) Trayning 1584 3155 (2.62) 6750 (4.1) 7577 (4.6) Kellerberrin 4057 5568 (3.45) 11580 (6.0) 11964 (6.2) Bruce Rock 5066 6960 (2.92) 11517 (4.2) 12609 (4.6) Merredin 3443 5450 (1.98) 7537 (2.3) 9138 (2.8) * Shire areas as reported by George (1990) ** Figures in brackets are percent change since 1979 census. Table 4: Draft estimates of the area of land within the Kellerberrin 'Land Monitor' satellite image that have a high probability of having a shallow watertable at equilibrium if no salinity management is undertaken and current trends in groundwater levels continue. Data is reported in four classes (0.5–2.0 m) as height above the lowest point in the valley. Shire Upland Areas* Shallow watertable with Height Above (ha) % Upland Height Above (ha) Height Above (ha) Height Above (ha) Total (ha) % Total 0.5 m % 0.5 1.0 m 1.5 m 2 m All **(< 2m) All Merredin 232961 63359 19 14151 10491 8430 96431 29.3 Nungarin 63226 37023 32 7148 5035 3872 53078 45.6 Bruce Rock 180057 60193 22 14612 9952 7702 92459 33.9 Trayning 108191 39227 24 7709 5574 4493 57003 34.5 Kellerberrin 126368 43474 23 9637 6707 5366 65184 34.0 Corrigin 205923 35618 13 10923 8404 6943 61888 23.1 Tammin 72481 24384 22 6299 4060 3057 37800 34.3 Wyalkatchem 100608 44383 28 6347 4581 3623 58934 36.9 Quairading 136405 44878 22 10410 5859 4093 65240 32.4 Dowerin 124477 42869 23 8091 5951 4913 61824 33.2 1350696 435408 22.8 95327 66614 52492 649841 34 * Includes areas with low probability of a shallow watertable ** Includes all areas with a higher probability of a shallow watertable; includes all currently saline land. Based on local government boundaries provide by DOLA. What proportion is at risk of salinisation? Several methods have been used to estimate the likely future extent of salinity. Anon (1988) projected trends from the ABS data and also estimated the area of the valleys in the Wheatbelt to suggest a range of between 10 and 20%. Ferdowsian et al. (1996) used a range of methods, principally surveys, rate of watertable rise and landform type, and concluded – 7 – that approximately 33% of the Wheatbelt landscape were at risk. In 2001, Short & McConnell used regional soils maps and groundwater trends to estimate the likely area of shallow watertables at equilibrium (~8 M ha). In 2001, as part of the Land Monitor project, estimates by regional hydrologists once again formed the basis of developing a means to predict areas that at equilibrium exhibit a high probability of having a shallow watertable if hydrologic
George and Coleman current trends continue. The technique relies on derivatives from the high-resolution digital elevation models (called height above which is essentially topographically low areas in valleys) which have been compared with hydrologists' estimates. Four zones (< 0.5 m, 1.0 m, 1.5 m, 2.0 m) have been classified on the basis of height above areas of low elevation. While not salinity risk maps, the products allow a first approximation of the areas which are low in the landscape and which are likely to develop shallow watertables at equilibrium. A preliminary estimate of the area with a high probability of having a shallow watertable at equilibrium was derived for the Kellerberrin satellite image (Table 4). The total area analysed is 2 M ha, covering 10 Shires. An area of 435,408 ha (22.8%) has been classified as at risk of future shallow watertables (< 0.5 m) and approximately 34% of the area is within 2.0 m. Shires with the greatest area predicted to have a shallow watertable are Wyalkatchem and Nungarin, while Corrigin and Merredin have the least. These estimates, which include all land that currently has a shallow watertable (primary salinity and dryland salinity), are similar to that derived by Ferdowsian et al. (1996). However by contrast, the new data allows a better estimate of areas at higher (0.5 m) and lower risk, within areas of a shallow watertable. More information at the paddock scale is required to further refine these indications of risk. Given the nature of the groundwater systems and resultant dryland salinity, it is necessary to consider the natural landscape and what functions groundwater discharge landforms played in establishing a prior water balance and saline ecology before reviewing options for its management. PLAYAS (SALT LAKES) Palaeohydrology and changing hydrodynamics in wheatbelt valleys Groundwater discharge and salinity are not new to Western Australia. For at least 0.7 M years, calcareous and saline soils have occurred in southeastern and south-western Australia (Bowler et al. 1976). Reconstruction of the palaeohydrology of playas in north-western Victoria by Bowler et al. (1976) and Bowler & Teller (1986) over the past 80,000 years suggest that there have been at least four watertable maxima (36,000, 24,000, 6,000 and 1,000 yr BP) during this period. The pollen record also shows that during these climate phases the – 8 – distribution of vegetation changed (Bowler et al. 1976). Combined pollen and geomorphic evidence shows that during periods of elevated watertable levels, salinity developed across land previously covered by perennial woody vegetation (Macumber 1978). In Western Australia, where the situation is less clear as few detailed studies have been conducted, radiocarbon dating by Bowler (1976) postulated a short-lived dune-building phase (15,000 to 20,000 BP) associated with major landscape aridity and potentially saline conditions. Climate induced hydrologic change, particularly watertable and salinity fluctuations are also likely to have been responsible for the unique suite of landforms still recognisable in the wheatbelt valleys. Valley landforms such as playas, lunettes and widespread parnas are related to the redistribution of sediment, salt and water during arid periods (De Dekker 1988). Similarly, vegetation has adapted to and perhaps modified these patterns. At one extreme, playas are a very obvious form of discharge and may represent a window into the groundwater systems (e.g. salt lakes). At the other, they may be a marker reflecting the groundwater and salinity status of a previous climate and associated hydrological period. At least five types of discharge landforms can be seen in the landscape: dry claypans, vegetated claypans, large salt lakes, isolated playas and salt lake 'fields' (called 'Boinkas' by Macumber 1991). Dry claypans and vegetated claypans are common in mid to upper catchment positions, particularly in the Eastern and Southern Wheatbelt, where they occur tens of kilometers from existing saline areas. They have been demonstrated to have a relatively deep and rising watertable (George et al. 1991) and in many but not all cases, represent markers of a previous climatic phase when watertables were higher. Larger salt lakes and isolated playas are common and may have several forms. Large lakes such as Lake Brown and Lake Moore have extremely flat floors that evaporate surface and groundwater, depending on antecedent conditions. These lakes often give the appearance of being 'full' after light rain and soon after may be partially covered in halite efflorescence. Similarly, individual playas can also appear to have large volumes of storage in periods of high discharge and low evaporation, with some lakes appearing to empty and fill on a daily basis. In these playas, groundwater is strongly connected via the edge of the lake and respond to barometric and related affects.
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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
Page 7 and 8: Ali and Coles biggest challenges fa
Page 9 and 10: Ali and Coles erosion, maintenance
Page 11 and 12: Ali and Coles expected under these
Page 13 and 14: Ali and Coles Coles, N.A. & Ali, M.
Page 15 and 16: Commander, Schoknecht, Verboom and
Page 41 and 42: APPRECIATING AND CREATING OUR HISTO
Page 43 and 44: services. The Government responded
Page 45 and 46: WHEATBELT VALLEYS IN DIFFICULTIES T
Page 47 and 48: argue that they were really abnorma
Page 49 and 50: 1990s, the wheatbelt valleys in par
Page 51 and 52: REFERENCES Agstats (1997). Agricult
Page 53 and 54: George and Coleman two to four fold
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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
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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
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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
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- 3,477 ha of remnant vegetation or
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Scientists talk of up to 30% of the
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6320000 6300000 6280000 6260000 624
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Although the waterlogged area under
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eliminates drainage through the nex
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REFERENCES Dawes, W.R., Stauffacher
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Pannell ECONOMICS, SOCIETY AND ENVI
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Pannell • the area of land protec
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Pannell Proposals to construct majo
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Pannell been conducted for the Cent
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Pannell investments in long-term la
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Pannell Pannell, D.J. (2001). Dryla
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Porter, Bartle and Cooper Table 1:
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Porter, Bartle and Cooper operation
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Porter, Bartle and Cooper Increase
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Porter, Bartle and Cooper support i
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Porter, Bartle and Cooper that is a
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CASE STUDY - TOOLIBIN LAKE AND CATC
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• The distribution, storage and m
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Secondly, there is a set of practic
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within three categories: relationsh
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CONCLUSIONS Actions to protect and
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FIELD TOUR LOCATIONS FIELD TOUR NOT
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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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Dealing with salinity in Wheatbelt Valleys - Department of Water

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