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Effect of catchment land use change on the water resources and water quality

Congress: 2008
Author(s): Olga Barron, Michael Donn, Antony Barr, Daniel Pollock, Warrick Dawes
CSIRO Land and Water, Floreat, Western Australia (contact:
AbstractGreenfield urbanisation adversely affects the catchment water balance, including groundwater, wetland and surface water, and may impact on groundwater and stormwater quality. While changes in the water balance are almost immediate, the water quality variation may occur over a considerable period of time. Effect of urbanisation on water quality depends on the degree of the pre-development water balance alteration and adopted water management practices. The decision support system (DSS) for urban development in complex hydrological/hydrogeological conditions and surface/groundwater interaction processes is in a focus of multiagency multidisciplinary research, aiming for reduction in nutrients losses from former agricultural land to surface water and sourcing the local water resources for non-potable use in quickly developing metropolitan catchments. The Swan-Canning Estuary (Perth, Western Australia) is already suffering from ongoing threats due to euthrophication. Urban expansion in one of fastest developing area (Southern River catchment) is challenged by many environmental issues: a high groundwater table (<2mBGL) with extensive water logging during wet seasons associated with the Superficial Aquifer; high nutrient concentrations in shallow groundwater (TPmean=1.75mg/l up to 10mg/l; TNmean=4.85mg/l up to 250mg/l); high export rate arising from current and historical land use (TP losses >0.3kg/ha/year) and the requirements for maintenance of existing environmentally sensitive wetlands. DSS is based on a number of integrated modelling tools, including GIS models, MODHMS model (surface/groundwater interaction model), and water and nutrient fluxes in unsaturated zone, all of which were validated on intensive catchment survey and monitoring program. A number of water management scenarios were evaluated aiming to improved water cycle management within new urban developments. Management variables include groundwater and stormwater control, water reuse and water conservation.
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