Monitoring Water Level Variations of the Urmia Lake by Multi-Altimetry Missions

Urmia Lake (UL) is a super-saline lake in northwestern Iran. Over the past decades, the UL water level has rapidly declined, caused by long periods of drought, reduced inflows, and anthropogenic impacts. Due to the significant impact of UL on agriculture, ecological conditions, and human life, sustainable management of the water resources of the UL basin is a prerequisite for restoring the watershed. One of the most important steps in a restoration program is comprehensive monitoring of the basin's behavior. Satellite radar altimetry missions have become a reliable data source supplementing the in-situ water level, hydrological cycle, and inter-annual variability of the water budget. In this study, we use the level 2 product of Jason-3 and CryoSat-2 and Sentinel-3A datasets acquired in LRM and SAR modes, respectively, from March 2016 to March 2021. The comparison of results with the in-situ water level data shows the RMSE of 0.39, 0.75, and 0.35 meters for the Jason-3, CryoSat-2, and Sentinel-3A, respectively. The higher accuracy of the Sentinel-3 can be due to the higher signal-to-noise compared to the Jason-3 and CryoSat-2. In addition, the results indicate that the UL water level increased by 30, 25, and 68 centimeters in 2016, 2018, and 2019, respectively, while it decreased by 26 and 2 centimeters in 2017 and 2020, respectively. The overall water level has increased from 2016 to 2021.