Observed and projected hydrological changes in the Aral Sea basin

Aral Sea basin has undergone significantly negative environmental alterations over the past 50 years. Water- related stress involves all of key agents of global change: land use/cover change and land degradation, pollution, over-exploitation of surface and groundwater, and climate change/variability. This region is thus emblematic of water cycle changes found throughout the globe. To better understand the regional changes in the hydrological regime due to both global climate change and local anthropogenic influences we explored observed and potential signals of climate variability and change in water use, and assessed their impacts on hydrological systems and water management. Using new hydrometric, land and water use information provided by Uzbekistan Hydrometeorological Service (UZHYDROMET) we analyzed long-term variability of major water balance components along with changes in water use and agricultural structure. Future projections of hydrological regime based on the UNH Water Balance and Water Transport Models (WBM/WTM) which incorporate irrigation and reservoir effects were analyzed along with results from the regional UZHYDROMET water balance model with improved representation of snow and glacier runoff for mountainous regions of Central Asia. Both models demonstrate a general tendency toward decreases in regional river runoff although the changes were neither temporally nor spatially uniform.