Climate change and intensified irrigation as drivers of water imbalance in a large dry basin with two vanishing lakes in Iran

This comprehensive study assesses the profound impact of climate change on water resources and agriculture in the Tashk-Bakhtegan Lake (TBL) basin from 2020 to 2049, shedding light on the urgent need for effective water management strategies. Two Representative Concentration Pathways (RCPs) were used in this study: RCP2.6, a low-emission scenario consistent with strong mitigation efforts, and RCP8.5, a high-emission scenario representing continued intensive fossil fuel use. The hydrological analysis using a modified Eco/agro-hydrological model based on the SWAT model (SWAT-FARS) reveals a significant increase in the annual rate of surface runoff changes under the RCP8.5 scenario, potentially resulting in reduced flows into the TBL and other dams. Performance measures from Water Accounting Plus (WA+) indicate potential 9% and 16% reductions in controllable water supply under RCP2.6 and RCP8.5 scenarios. Despite a notable decrease in controlled water, the study projects a 20% to 42% increase in agricultural water consumption, posing a significant challenge for water management. Compared to the years 2007–2014, outflows decreased by 99% while groundwater storage decreased by 14%. The basin consumption ratio index is almost identical to one, as it was from 2007 to 2014. Given the current level and pattern of agricultural activity and the escalating water crisis due to climate change, it appears that there will be little chance for effective water conservation. The study’s conclusion emphasizes the crucial necessity of implementing TBL basin water management strategies, particularly in response to the projected impacts of climate change. It is essential to consider the availability, consumption, and balance of water resources while developing sustainable farming practices to ensure the long-term sustainability of the water system in the basin.