Groundwater Depletion Over Iran

Abstract

Groundwater depletion, due to both unsustainable water use and a decrease in precipitation, has been reported in many parts of Iran. In order to analyze these changes during the recent decade, in this study, we assimilate Terrestrial Water Storage (TWS) data from the Gravity Recovery And Climate Experiment (GRACE) into the World-Wide Water Resources Assessment (W3RA) model. This assimilation improves model derived water storage simulations by introducing missing trends and correcting the amplitude and phase of seasonal water storage variations. The Ensemble Square-Root Filter (EnSRF) technique is applied, which showed stable performance in propagating errors during the assimilation period (2002–2012). Our focus is on sub-surface water storage changes including groundwater and soil moisture variations within six major drainage divisions covering the whole Iran including its eastern part (East), Caspian Sea, Centre, Sarakhs, Persian Gulf and Oman Sea, and Lake Urmia.

Data assimilation successfully correct for the open-loop simulation variations, e.g., in terms of trends and multi-year variations, especially for groundwater storage. Based on the improved estimates, we find that groundwater trends in a large part of the country’s (Iran) central, western and southern areas are negative representing a significant water availability issue.

—M. Khaki (This chapter is presented following Khaki et al. (2018c), “Determining water storage depletion within Iran by assimilating GRACE data into the W3RA hydrological model”)