Assessing urban water use and the role of water conservation measures under climate uncertainty

There has been substantial analysis of the possible impact of climate change on water supply, especially with respect to runoff and river flows. Less attention has been given to urban water use. Little is known of the suitability of various water use forecasting models for predicting climate impacts or of the best procedures for assessing this issue. This paper will: (1) demonstrate the feasibility of a scenario approach to describing possible changes in climate, (2) evaluate the IWR-MAIN model as a source of plausible water use forecasts given uncertain future climate, (3) test the effectiveness of conservation and pricing interventions in reversing the postulated effects of climate change, and (4) assess the significance of climate change for future urban water management. Other possible responses to climate change, such as supply augmentation, are not explicitly considered. Using data for the Washington (DC) metropolitan area, the study reveals problems with IWR-MAIN version 5.1 when used for this purpose, but results in a reasonable assessment of the possible water use consequences of climate change. Variation in future water use due to climate uncertainty was found to be moderate compared to other uncertain influences, and well within reach of feasible policy interventions.