A new framework for evaluating water use reduction strategies using an integrated, holistic, and transparent approach (Urmia Lake basin case study)

Abstract

Agriculture and food security have always faced challenges related to water scarcity, so agricultural water conservation is the most important strategy for overcoming this challenge. In this study, the REWAS tool developed by FAO and Future Water was used to evaluate the effects of technological and management strategies on real water savings (RWS) in the Zarrineh River sub-basin, Iran. Nine farms were investigated (wheat, corn, tomato, sugar beet), including control and treatment farms. According to changes in water consumption and return flows, RWS was calculated for various scenarios of field interventions. To assess the water consumption in Basin scale, REWAS was simplified the accounting framework for water consumption (consumed and unconsumed). In the Zarrineh River sub-basin, the use of the techniques applied in the treatment farm, compared to the control farm (according to farmer customary practices), resulted in a significant reduction of non-beneficial consumption. For example, according to the REWAS evaluation in West s17 farn, the treatment farm consumed the most useful water compared to the control farm (331 mm and 267 mm, respectively), which led to the most useful water consumption at basin scale (to the order of 3920 mm and 3166 mm). According to the results on the scale of the basin , the highest amount of recoverable discharge was also obtained in the control farm with an increase of 3774 MCM over the treatment farm. Using strategies to reduce water consumption resulted in apparent water saving (AWS) at the farm scale, but these AWS were very different from their RWS at the basin scale and the RWS at the basin scale (13%) was much lower than the AWS at the farm scale (38%). According to the results, apparent water savings (AWS) at the farm scale do not reduce water consumption, and may actually increase it when viewed in a basin scale. REWAS concepts indicate that significant amounts of “lost” water are actually recoverable return flows that can be used by downstream users or contribute to wetlands. According to REWAS concepts, real water savings can only be achieved by preventing non-recyclable backflows. Assessing RWS can help decision makers select sustainable interventions that will improve agricultural water productivity by providing information on farm flows, irrigation networks, and basin scales.