The Gnangara Groundwater Area is bounded by the Moore River, Swan River and Gingin Brook. It covers 2,200 km2 and recharges from rainfall. The largest aquifers are the Superficial, Mirrabooka, Leederville and Yarragadee North. Groundwater levels are declining due to a decrease in rainfall in recent years, an increase in abstraction of groundwater and the Gnangara Pine plantation.