Rainwater harvesting in arid regions of Australia

Water scarcity is a major problem in arid regions. Water in these regions is sourced mainly from groundwater and rainwater. Rainwater harvesting is a technique where surface runoff is collected during rain and retained for subsequent use such as irrigation and toilet flushing. In this chapter, rainwater harvesting potential from the roof catchments in the arid region is investigated based on the rainfall data at 15 different locations in the arid regions of Australia. Ten different rainwater tank sizes and three different combinations of water uses are considered in this study. It is found that a 20 kL tank can provide a reliability of 59%–98% for toilet and laundry use depending on the location within the Australian arid regions. For irrigation and combined use (toilet, laundry, and irrigation), estimated reliability values are smaller than 30%. At the current Australian water price, rainwater harvesting system is not financially viable in the Australian arid regions as the benefit–cost ratio is much smaller than 1.0. The harvested rainwater in the arid regions is four to eight times more expensive than the current water price in Australian cities.