The Moore River is located in the Moore-Hill Basin. It is 288km long and has a catchment of 13,450km2. The Moore River’s eastern reaches originate near Dalwallinu and the northern reaches originate east of Coorow. It enters the ocean at the Moore River estuary at Guilderton, in the Shire of Gingin. The estuary only opens to the ocean during higher river flows in winter. Salinity levels in the river catchment vary from brackish to saline with the exception of the tributary, Gingin Brook, which remains fresh throughout the year.