Abstract: Lake Bosten， the biggest inland freshwater throughput lake in China， is located in the Yanqi Basin that is a semi-closed basin with rare precipitation surrounding by the Tianshan Ranges， The lake’s water supplies mainly depend on the rivers’ discharges that derived from surrounding mountains. Kaidu River as the largest inflow river to the lake， its east tributary is the unique inflow river that enables the water directly into the lake. Only Kongque River is an outflow river of the lake and its discharges into the river have been controlled by water pump since 1982. In the Central Asia， the lakes’ water resource is very important for the irrigation agriculture and the ecological environment. However， during the past several decades， the lake water level had decreased from 1 044.95 to 1 048.65 m. The water balance method had been used to study the reason of lake water level variation by many researchers， but their estimations about the water budgets were used to be offered as long-term averaged values （i.e. multi-years average） rather than a set of annual data year by year. In this paper， an annual water-budgets model of Lake Bosten is derived for the period 1958-2010. Calculation techniques are used to derive annual main inputs and outputs to the water balance， based on the data of lake rainfall， evaporation pan and rivers’ discharges during the historical period. This approach acknowledges that the water residual is produced here which is representative of the whole uncertainties to the lake， rather than just from individual flows of irrigation drainages and groundwater. The results indicate as follows：（1） During the period 1958-2010， the annual water inputs to lake totally were 14.34×10⁸ m³/a， in which about 95% from river’s inflow； the annual water outputs from lake were 13.96×10⁸ m³/a， about 43% by outflow and 57% consumed with lake evaporation； thus， the lake levels varied 1 047.01±0.94 m corresponding with the lake’s water storages of 71.57±3.92×10⁸ m³/a. The water pump system built in 1982 has played a significant role on the water reconfiguration in the area around Lake Bosten. During the period of 1982-2010， the water outflows by this pump station were 8.07×10⁸ m³/a， and the river’s inflows into the lake were 16.00×10⁸ m³/a， it shows that the pump system has made the proportion of the outflow to the inflow from 31.7% to 50.4% than before. （2） For the extreme hydrological dry year in 1986， the annual inflow only accounted for 60% of the multi-year average； but the outflow from the lake was 155% of the average， it had lowered 0.94 m of the lake level which was the largest decline in historical records； for the wet year， the river’s inflow in 2002 was 2.62 times more than a normal year， which had caused 0.80 m of the lake level increased as being the highest rising records. （3） The alteration of the water residuals from ‘positive values’ to ‘negative values’ indicates that the water exchange between lake and groundwater is existing any time. In a word， when the water residuals of the year with a negative value， the lake water was recharging the groundwater， such as 2000 year and 2002 year； when the water residuals of the year with the positive value beyond of the drainages’ inflow magnitude， the groundwater was recharging the lake， such as 1975 year、1981 year and 1985 year. For the past 53 years， the lake water had recharged the surrounding groundwater with the net inflows about 0.87×108 m3/a totally.

Key words: Lake Bosten, nnual water-budgets, ater residuals, ater balance, ast 50 years