Concurrent Reliability and Drought Vulnerability Assessment of Earth Dams in Western Iraq

The western desert of Iraq is one of the most water-stressed environments in the Middle East. Characterized by unpredictable rainfall and long periods of evaporation. Several small earth dams have been constructed in this region, which are the only available surface water source. This makes the reliability of these structures extremely important. Four small dams, Al-Rutbah, Al-Ubiliah, Horan 2, and Horan 3, are evaluated concurrently across five dry seasons (2016, 2018–2021), a design chosen to separate each dam’s own structural characteristics from the shared regional climate. Surface area was extracted from Landsat 8 imagery for 2019 and 2020 and from the JRC Global Surface Water dataset for 2016, 2018, and 2021, then converted to storage volume and used to build a seasonal water balance around evaporation and infiltration losses; a volumetric adequacy index and a composite drought vulnerability index were derived from this balance. Al-Rutbah’s mean adequacy reached the marginal band (0.488), with a mean vulnerability score at the high-risk threshold (0.501). Al-Ubiliah, Horan 2, and Horan 3 remained unreliable by the adequacy index (0.294, 0.154, and 0.256, respectively) and high-risk by the vulnerability index. Al-Rutbah’s greater design capacity provided a partial buffer against the deficits observed at the smaller dams.