The effects of water supply for the city Perth, Western Australia, on other forms of land use

Abstract

Havel, J.J., 1975. The effects of water supply for the city Perth, Western Australia, on other forms of land use. Landscape Plann., 2: 75–132. The city of Perth in Western Australia is characterized by outstanding geographical isolation, and by the concentration of a high proportion of the State's population. Coupled with a strongly-seasonal climate, this results in a heavy demand on the limited local water resources. The water supply is drawn from two sources — the underground water resource of the coastal plain on which the city is situated, and the surface water resource of the adjacent plateau. The underground water resource currently under development consists of both deep artesian aquifers and shallow unconfined aquifers. The latter take the form of large domes of water within the coastal dunes, which are composed of highly porous sands. The swamps and lakes of the coastal plain are simply intersections of the ground surface and regional water table. Lowering of the regional water table by pumping may be expected to affect those forms of land use dependent on the presence of ground water close to or above the surface of the ground, such as conservation of flora and fauna, pine silviculture, intensive agriculture and water-based recreation. The surface water resource of the plateau is governed by strong climatic and topographic gradients, to a large degree related to distance from the escarpment which forms the western margin of the plateau. Eastward progression is associated with a decrease in rainfall and in dissection of the landscape. These in turn result in decreasing run-off and increasing storage of salt within the landscape. Removal of forest cover leads to a decrease in evapotranspiration and an increase in quantity and salinity of the water yield. Marked seasonal fluctuations in water yield and demand necessitate storage of water in valley reservoirs. The effect of water supply is therefore twofold — through the drowning of the river valleys and through the constraints imposed on land use in the catchments. The drowning of the valleys reduces opportunities for water-based recreation and for establishment of highly productive pine plantations, and endangers certain vegetation types confined to this portion of the landscape. The constraints imposed on the various activities within the catchment cause relocation of hardwood logging, displacement of agriculture, increased cost of mining and reduction of land-based recreation, but also facilitate conservation of flora and fauna on the uplands.