Limiting and timing water supply for agricultural production – The case of the Zayandeh-Rud River Basin, Iran

Abstract

The present study investigates alternative scenarios of timing and reduced water supply in terms of their impacts on agricultural land use, farm revenue and food crop production. It aims to evaluate the implications for the development of different farming systems in one of the most water-scarce irrigation districts in the Zayandeh-Rud River Basin in central Iran, the Roudasht irrigation district. A modified version of Positive Mathematical Programming (PMP) model was used to assess the scenarios. The results from the scenario simulations illustrate that there is substantial potential for improving the management of the limited water supply in the Roudasht irrigation network to reach higher water productivity, agricultural output and gross margins from agricultural activities. A management plan to target a limit in the irrigation water supply only for the month of peak demand, e.g. 60% to 80% of the baseline water supply for May in Roudasht, may have less adverse effects than planning to limit the annual water supply by the same amount but without specifying the monthly timing of the water supply. These results highlight the relevance and impact of the timing of water supply when devising adaptive measures related to the irrigation water supply.