The Helmand River is the main source of water for the Sistan Plain and underpins the provision of key ecosystem services, including water supply, agricultural production, forage provision, soil protection, and wildlife habitat. The operation of the Kamal Khan Dam and the diversion of river flow toward Goud-e Zereh have reduced downstream water availability and accelerated land degradation in Sistan. This study aimed to assess land-use and land-cover changes associated with Helmand River water availability before and after the operation of the dam. Land-use/land-cover maps for 2019, 2020, 2024, 2025, and 2026 were produced using Landsat imagery, supervised classification, and the Random Forest algorithm, and their accuracy was evaluated using field-based reference samples. The results showed that, after dam operation, the Hamoun-e Hirmand water body completely dried up, whereas the water-covered area around Kamal Khan Dam and in the Goud-e Zereh region increased from 3,039 ha in 2019 to 62,794 ha in 2026. In the Sistan Plain, agricultural land reached its maximum extent of 69,025 ha in 2020 but declined to 5,776 ha in 2025. In addition, the area of saline lands in the Sistan Plain and Hamoun increased from a minimum of 110,414 ha in 2020 to a maximum of 274,708 ha in 2026. These changes were accompanied by a reduction in rangelands, an expansion of barren lands, increased soil salinity, and greater soil susceptibility to wind erosion. The findings indicate that the diversion of water toward Goud-e Zereh, together with associated declines in agricultural land, rangelands, and soil moisture and the expansion of saline and barren lands, has weakened the ecosystem services provided by the Helmand River.
