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To evaluate potential effects of climate change on the water budget of Bosten Lake, the largest inland freshwater lake in China, we evaluated trends and step change points between 1980 and 2011 in evaporation, air temperature, and precipitation. Significant increases in air temperature accelerated glacier melt, increasing flow in the Kaidu River, which ultimately discharges into Bosten Lake. The increased inflow resulted in increased lake water depth and 10% greater water surface area. Increased surface area along with higher temperatures led to increased lake evapotran-spiration. If glaciers continue to recede and snowpacks continue to decline with projected warmer temperatures under climate change, inflows to Bosten Lake will decrease substantially in the future, with critical implications for long-term water resource management. Our calculations suggest that the water surface area of Bosten Lake should be maintained > 963.14 km(2) to maintain low lake water salinity (total dissolved solids: TDS <= 1.5 g/L), 3-year and 5-year means for annual net inflows to Bosten Lake must be approximately 21.80 x 10(8) m(3) and 23.50 x 10(8) m(3), respectively, and Kaidu River mean runoff must be approximately 35.83 x 10(8) m(3) to maintain that surface area while supplying 14.42 x 10(8) m(3)/yr of water to meet public water demand in the Kongqi Basin. Water should only be diverted from Bosten Lake to the lower Tarim River for ecological restoration in years when Kaidu River annual runoff is > 35.83 x 10(8) m(3). To minimize evaporation loss, water diversions from Bosten Lake should occur between May and September.