Facing Future Water Scarcity in the Duero-Douro Basin: Comparative Effect of Policy Measures on Irrigation Water Availability

Abstract

This study presents an analysis of possible policy measures to face water scarcity for agriculture in a long-term climate projection (2070–2100). Water availability was computed with the Water Availability and Adaptation Policy Analysis (WAAPA) model. WAAPA simulates water management in a basin at a monthly time scale, accounting for streamflow, reservoir storage, evaporation, and environmental flows. Focus was placed on urban and irrigation demands. Water was first allocated to urban demands (assumed as a priority), and the remaining water resources were allocated to irrigation. First, this availability was compared to an estimated projected evolution of water withdrawals to identify potential conflicts over water supply. If insufficient water was available to satisfy all irrigation demands, policy measures, such as increasing reservoir storage, improving the efficiency of urban water use, and changing the environmental flow allocation, were applied and their effects on irrigation water availability analyzed. The analysis of the Duero-Douro (Spain-Portugal) Basin showed that, although the expected impacts of climate change on water availability for agriculture are high, several policy options can partially compensate for those impacts. Comparatively, a change in environmental flow requirements was the policy measure that most affected Duero-Douro Basin management.