Soil problems and associated catchment issues
Hill, A. (2004) Soil problems and associated catchment issues. In: Iron & Sulphur Bacteria Workshop, 11 - 14 February, Murdoch University, Perth, Australia.
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Detailed mapping of the extent of wetlands on the Swan and Scott Coastal Plain (Hill et al, 1996, VCSRG, 1997) and the described 50 and 200 m buffer zones of critical and secondary influence when used in tandem with wetland or river environmental protection policies, remain critically useful policy mechanisms, not only for WAʼs bi¬odiversity hot spot protection, but also for Acid Sulphate Soil problem prevention.
Precaution and prevention of soil problems and water pollution in situ is almost always better and orders of magnitude cheaper than paying for distant end-of-pipe pollution treatment solutions. This sensible approach characterized water and drain¬age planning and leading sustainability work in water sensitive design in Western Australia (WA), a decade ago.
If WAʼs wetland and strategic drainage planning work were not currently in a state of neglect, and instead 1990ʼs strategic drainage planning approaches or wetland pro¬tection practices been used in a recent wetland development in Perthʼs City of Stir¬ling, it is probable that the acid sulphate pollution resulting from wetland drainage would not have occurred. Instead, protection of wetland habitat and water regime and the diligent use of Average Annual Maximum Groundwater Levels (AAMGL) as a drain invert design imperative (GB Hill & Partners (1995), Evangelisti (1994), Rockwater (1995)), would have ensured that the wetland habitat or water regimes were protected, that water was kept in peat and underlying soil profiles, and that acid sulphate soils remained benign and as a result, that acid, nutrients and heavy metals are not mobilised.
Unfortunately State interagency focus has been redirected for many years on to the best remaining wetlands in Perth and on the long negotiated major wetland protec¬tion policy described in the Perth Bushplan report (Government of Western Aus¬tralia, 1998), leaving vulnerable even these 20% of the best remaining Swan Coastal Plain wetlands, now being cleared and drained predominantly for low cost housing at a rate of 10-13 % per year.
These valuable wetlands were the focus of much of Perthʼs internationally signifi¬cant biodiversity and their loss reflects a little-discussed ecological catastrophe (Sed¬don, 1972; Bala, 1993; Hill et al, 1996).
Wetlands were described in 1990ʼs water planning as the kidneys of our catchments. The loss of ecological services provided by all wetlands and the subsequent poor design of the drainage schemes that are subsequently placed in many of these areas, lowering groundwater far below AAMGL, compounds the tragedy of recent and past wetland habitat clearing with the likelihood of perpetual seasonal acid sulphate soil pollution. This does not need to happen.
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