A holistic assessment of water resources and management in the Zarrineh river sub basin using water accounting plus

The objective of this study is to evaluate water consumption pathways related to land use, productivity, and water productivity in the Zarrineh River sub-basin, Iran, using the Water Accounting Plus (WA+) approach. The WA+ method was chosen due to its comprehensive ability to estimate water consumption across various sectors, including land use and agricultural productivity, and its capacity to account for both inflows and losses, which makes it more suitable for analyzing the water resource situation in the Zarrineh River sub-basin compared to other water accounting approaches. This study examines water inflows and losses in the Zarrineh River sub-basin, where total water availability, including external inputs and rainfall, reaches 3610.53 Million Cubic Meters (MCM) annually. Despite substantial water resources available, 3442.70 MCM is lost through evapotranspiration, with agricultural lands accounting for 1836.13 MCM of this. These findings emphasize the critical need for efficient irrigation systems, as well as complementary techniques like shading and mulching to minimize evaporation losses. With 1747.35 MCM of exploitable water, effective management practices are essential to maximize water productivity, especially in the agriculture sector. Additionally, 185.83 MCM of recoverable outflows present an opportunity for reuse, supporting more efficient water resource management. Managed agricultural areas exhibit higher water productivity (2.54 kg/m³) compared to less efficient sectors within utilized land use (1.74 kg/m³), highlighting areas for potential improvement. Addressing non-beneficial evapotranspiration, totaling 919.4 MCM, through practices such as soil covering and reservoir management, could further enhance water conservation. These findings emphasize the importance of integrating advanced irrigation technologies, efficient water regulation systems, and improving land management to mitigate water loss, enhance productivity, and ensure sustainable water resources in the sub-basin.