How much water did Iran lose over the last two decades?

Study area: Iran. Study focus: Iran, once a pioneer of sustainable water management, is currently facing water bankruptcy. Aggressive exhaustion of non-renewable water has led to a suite of environmental and socio-economic problems across the country. Nevertheless, the understanding of Iran's water loss is still incomplete due to a lack of conclusive data. In this study, we employ satellite gravimetry observations, in-situ and globally precipitation data, and gauged groundwater level to investigate the total water storage (TWS) loss in Iran over the last two decades. New hydrological insights for the region: We quantify Iran's water loss using a data-driven approach supported by a Monte-Carlo simulation. Our analysis indicates TWS loss of 211 +/- 34 km(3) (> twice Iran's annual water consumption) within the 2003-2019 period. The mean groundwater level has dropped significantly at a rate of -28 +/- 1.4 cm/yr. This tremendous water loss happened despite an overall increased relative precipitation rate of + 4.9 +/- 0.02 km3/yr. Thus the TWS loss can only be explained by drastic overexploitation of non-renewable water resources. Two major extreme events occurred during the study period, namely the 2007 drought and early 2019 floods. The former resulted in a total 115 +/- 0.6 km(3) water loss, one-third of the long-term annual precipitation. Approximately the same amount was brought back by a series of extreme precipitation events leading to floods in early 2019. Our results raise critical issues regarding unsustainable water management in Iran and highlight the crucial role of spaceborne measurements for understanding short-term and long-term water availability change in the absence of sufficient ground data.

Automated summary

This study investigates the water loss in Iran over the last two decades using satellite gravimetry observations, in-situ and globally precipitation data, and gauged groundwater level. The results show significant water loss and a drastic overexploitation of non-renewable water resources in Iran. The study also highlights the impacts of extreme events such as droughts and floods on water availability in the region.