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Increases in water demand often result in unsustainable water use, leaving insufficient amounts of water for the environment. Therefore, water-saving strategies have been introduced to the environmental policy agenda in many (semi)-arid regions. As many such interventions failed to reach their objectives, a comprehensive tool is needed to assess them. We introduced a constructive framework to assess the proposed strategies by estimating five key components of the water balance in an area: (1) Demand; (2) Availability; (3) Withdrawal; (4) Depletion and (5) Outflow. The framework was applied to assess the Urmia Lake Restoration Program (ULRP) which aimed to increase the basin outflow to the lake to reach 3.1 × 109 m3 yr−1. Results suggested that ULRP could help to increase the Outflow by up to 57%. However, successful implementation of the ULRP was foreseen to be impeded because of three main reasons: (i) decreasing return flows; (ii) increased Depletion; (iii) the impact of climate change. Decreasing return flows and increasing Depletion were expected due to the introduction of technologies that increase irrigation efficiency, while climate change could decrease future water availability by an estimated 3–15%. We suggest that to reach the intervention target, strategies need to focus on reducing water depletion rather than water withdrawals. The framework can be used to comprehensively assess water-saving strategies, particularly in water-stressed basins.

This paper investigates the hydrologic and water management reasons behind the desiccation of the Hamun Lakes in the Iran-Afghanistan border region. We analysed changes in Hirmand (or Helmand) River flow, the main tributary providing 70% of the lakes’ total inflow, and precipitation during 1960-2016 by calculating standardized indices for precipitation (SPI) and discharge (SDI). Also, we applied Normalized Difference Spectral Indices (NDSIs) using satellite images from 1987 to present to observe monthly areal change of the lakes. The transboundary water body is responding to changes in regional water management, which has severely reduced the lakes’ inflow. Upstream water regulation in Afghanistan coupled with reservoir construction on the Iranian side has caused nearly full desiccation of major parts of the lake system. There is a discernible shift in the relation between the Hirmand River flow at the international border and upstream precipitation over the lakes’ basin before and after 2004. From 1960 to 2003, high river flows were expected to feed the lakes due to high precipitation over the basin. However, the Hirmand River flow at the border declined after 2004 despite large amounts of upstream precipitation, including the largest recorded amounts, especially in the Hindu Kush mountains. Further, environmental water stress caused by anthropocentric water management in Iran by reservoir construction has impacted the area of the lakes. Although a long period of drought from 1998-2004, i.e. climatic driver, decreased the lakes’ area, the lake system is primarily falling victim to anthropogenic flow alterations in the transboundary river basin. The lakes’ shrinkage places socio-economic stress on an already-vulnerable region with important public health implications as the exposed lake beds turn into major sources of sand and dust storms.