Impacts of climate change and water resources development on the declining inflow into Iran's Urmia Lake

Urmia Lake, the world's second largest hypersaline lake, has decreased in size over recent decades primarily because inflow has diminished. This has caused serious socio-environmental consequences similar to those of the Aral Sea disaster. By using the variable infiltration capacity (VIC) model, this study estimates the relative contributions of climate change and water resources development, which includes the construction of reservoirs and expansion of irrigated areas, to changes in Urmia Lake inflow over the period 1960–2010. The model results show that decreases in inflow generally follow observed decreases in precipitation, although the variability in inflow is more pronounced than the variability in precipitation. The results also suggest that water use for irrigation has increased pressure on the basin's water availability and has caused flows to decrease by as much as 40% during dry years. On the other hand, the presence of reservoirs positively contributed to water availability during relatively dry years and did not significantly reduce lake inflow. By accelerating irrigation expansion in the basin, reservoirs have, however indirectly, contributed to inflow reduction. Our results show that annual inflow to Urmia Lake has dropped by 48% over the study period. About three fifths of this change was caused by climate change and about two fifths was caused by water resource development. The results of this study show that, to prevent further desiccation of Urmia Lake, it will be necessary both to develop national plans to reduce irrigation water use and to develop international plans to address climate change.