Banking for the future: Prospects for integrated cyclical water management

Integrated management of surface water and groundwater can provide efficient and flexible use of water by making the best use of the properties of different types of water resources. Integrated cyclical water management can help adaptation to climate variation and uncertainty by varying the proportion of surface water and groundwater allocations over time in response to changing water availability. Water use entitlements and rules specify conditions for the use, storage and exchange of surface water and groundwater. These entitlements and rules provide certainty for water users, investors and managers. Entitlements and rules also need to be flexible to enable users and managers to respond to changing water availability and knowledge. Arrangements to provide certainty and flexibility can conflict. For example guarantees of specific long-term allocations of water, or shares of allocations can conflict with arrangements to bank water underground during wet periods and then to use an increased amount of groundwater in dry periods. Systems of water entitlements and rules need to achieve a balance between certainty and flexibility. This article explores the effect of water entitlements and rules, and arrangements to provide certainty and flexibility for the integration of surface water and groundwater management over time. The analysis draws on case studies from the Namoi River basin in New South Wales and the South Platte River basin in Colorado. Integrated cyclical water management requires a comprehensive, flexible and balanced system of water entitlements and rules that allow extended water carryover, water banking, aquifer storage and recovery over the wet and dry climate cycle. Opportunities for extended carryover and aquifer storage and recovery over the wet and dry climate cycle merit further consideration in New South Wales, Colorado and other jurisdictions.