Managed aquifer recharge in integrated water resource management

Abstract

Managed aquifer recharge (MAR) is one tool in integrated water resources management which can restore over-allocated or brackish aquifers, protect groundwater-dependent ecosystems, enhance urban and rural water supplies, reduce evaporation losses and improve water supply security. This chapter describes the ways in which MAR is used around the world and presents two Australian case studies, with a focus on economics. Aquifer storage and recovery of urban stormwater via a confined limestone aquifer is shown to provide a viable alternative to use of existing mains water or desalinated seawater for public open space irrigation. The second case study is a desk-top evaluation of the potential for recharge of harvested floodwater via infiltration basins for irrigation of cotton and faba bean crops. Based on assumptions about scale of operations, component and maintenance costs, and evaporation losses, the net benefits of infiltration basins for a range of infiltration rates were compared with those of surface water storage and of aquifer storage and recovery wells. Infiltration basins with moderate to high rates of infiltration (>0.15 m/d) had the highest net benefits and warrant testing in a pilot program. Water treatment costs make ASR with flood waters unattractive for crop irrigation, in comparison with both basin infiltration and surface storage. Selection of the most economic method of storage depends on availability of an aquifer, soil and subsurface hydraulic characteristics, available quantity and quality of surface water, land value and end use of the water. MAR is shown to offer a range of options thatwarrant investigation in comparison with conventional supply alternatives to enable the most effective water resources management to be implemented.