Water Deficit Estimation Under Climate Change and Irrigation Conditions in the Fergana Valley, Central Asia

Abstract

We evaluated changes in irrigation water deficit in the Fergana Valley, Central Asia under different scenarios of climate change and water management. The Fergana Valley is located within the Syr Darya river basin and is shared between Uzbekistan, Kyrgyzstan, and Tajikistan. The main driver of economic activity in the Valley is cotton farming, which consumes large volumes of water. Growing population drives irrigation water demand with plans to modernize the irrigation system increasing the irrigated areas by 10-15% underway. However, climate change may alter projected water demand increase in the Valley. We estimated the climate-related changes in irrigational water demand in the Fergana Valley in 2020s, 2050s, and 2080s using future weather patterns generated with five global circulation models (GCMs) run under the A1FI, A2, and B1SRES scenarios. Considerably higher temperatures and a moderate change in precipitation lead to increasing potential evapotranspiration (PET), which nearly doubles irrigation water demand by the 2080s. In turn, the area under persistent water deficits increases from current 12% to 18.3% by 2020s, 27% by 2050s, and to 38.2% by 2080s. That is driving demand for a scientifically substantiated scheme of irrigation keeping in mind the quality of soils and groundwater table, correction of water consumption norms for different crops, and change of crop composition in favor of the winter horticulture plantations and cereals. On a long run, a radical modernization of the irrigation system will be needed to cope with climate change in the Fergana Valley.