青海湖流域地处东亚季风区、西北干旱区和青藏高原高寒区的交汇地带，流域面积大，地质地貌条件复杂，水文、气象定位观测点稀少，流域水循环过程与水量转换的定量研究较少。本论文采用氢氧稳定同位素技术与传统水化学方法，对青海湖流域的降水来源、河水径流过程、地下水补给、湖水蒸发及青海湖流域水循环进行了系统研究，并分析了青海湖流域的水汽输送特征，探讨了青海湖水位变化的主要影响因素。主要结论如下：1）青海湖流域大气降水多来源于局地蒸发水汽，降水中δ18O呈现较显著的“青海湖”效应和高程效应，流域大气降水线为：δ2H = 7.91 δ18O + 13.94。7~9月份，青海湖流域受控于东亚季风，降水来源于本地蒸发及东亚季风携带的太平洋水汽；10月至翌年6月份，青海湖流域受控于西风环流，降水来源于本地蒸发及西风环流携带的水汽；因唐古拉山的阻挡，西南季风携带的印度洋水汽难以到达青海湖流域。2009年7月至9月，流域输入水量52.32×108m3，输出水量40.83×108m3，净输入水量11.49×108m3；2009年10月至2011年6月，流域输入水量187.32×108m3，输出水量191.02×108m3，净输出水量3.70×108m3。2）青海湖流域内河川径流主要来源于中上游的大气降水，在产汇流过程中经历了不同程度的蒸发和入渗，河水水化学类型为Ca2+-Mg2+-HCO3-型的低矿化度淡水。2009年7月至2010年6月期间，流域平均地表径流深度为77.8mm，径流系数为0.190，地表入湖河水的δ2H 和δ18O年值分别为：-44.73‰和-7.18‰。各子流域因地形及地表类型不同而表现出径流系数差别较大，布哈河流域、沙柳河流域及哈尔盖河流域降水转化为地表径流注入青海湖的比例分别为21.4%、56.2%、47.3%，并相对于降水表现出一定的滞后现象。3）环湖地下水的补给源主要为青海湖流域内大气降水，补给高程多在3400~4000m之间，地下水对青海湖有一定的补给作用。分布在地质断裂带上的地下水的δ2H 和δ18O比其它地下水更贫化，且在季节上波动较大，表明此地下水可能受到裂隙水补给。4）通过对比湖水、降水、河水及地下水的同位素和水化学特征，青海湖湖水来源于外围河水及地下水，经历强烈的蒸发过程后，向着氢氧稳定同位素不断富集，Ca2+、Mg2+、HCO3-、SO42-离子含量减少，Na+、K+、Cl-离子含量增加的方向演化，即形成δ2H和δ18O大于0，水化学类型为Na+-K+-Cl-型的高矿化度咸水。5）基于稳定同位素分馏及湖泊水量平衡模型计算结果表明：在2009年7月~2010年6月间，青海湖流域内总降水为120.52×108m3，蒸发112.72×108m3，净输入水量为7.80×108m3；陆面降水104.32×108m3，转化为河川径流入湖19.89×108m3（占19.07%），地下径流入湖4.41×108m3（占4.23%）；湖面降水16.20×108m3，湖面蒸发33.68×108m3。青海湖水位及流域内水量的变化主要受控于西风环流时段的降水、蒸发及风速等气象因素。

The Qinghai Lake watershed lies in a critical transitional zone, where the East Asian summer monsoon, the Westerly Circulation and the Qinghai-Tibet Plateau monsoon prevail, and it is extremely sensitive to climate changes. Studies on water cycle and water transformation were scarce, because it has a large area, complex geological and geomorphic conditions, and a small number of meteorological and hydrological stations. This paper analyzed the water cycle and the transformation among the precipitation, river water, ground water and lake water in the Qinghai Lake watershed by using isotopic and hydrochemical techniques. And it discussed the major factors controlling the lake level. The main conclusions are as follows:1) Most precipitation derives from local water evaporation. The Qinghai Lake effect and Altitude effect of δ18O are significant. The LMWL (Local Meteoric Water Line) of the Qinghai Lake watershed is δ2H = 7.91 δ18O + 13.94. From July to September 2009, the input, output and net input water are 52.32×108m3, 40.83×108m3 and 11.49×108m3, respectively. The sources of precipitation, controlled by the East Asia summer monsoon, are the local vapor and the Pacific moisture carried by the East Asia summer monsoon. From October 2009 to June 2010, the input, output and net input water are 187.32×108m3, 191.02×108m3 and -3.70×108m3, respectively. The sources of precipitation, controlled by the Westerly Circulation, are the local vapor and the moisture carried by the Westerly Circulation. The moisture carried by the southwest monsoon, blocked by the Tanggula Mountains, is difficult to reach Qinghai Lake watershed.2) The river water derives from the precipitation, which undergoes a process of evaporation, of upper-middle watershed in the same period. The depth of surface runoff is 77.8mm, and the runoff coefficient is 0.190 in the Qinghai Lake watershed. The δ2H and δ18O of river water are -44.73‰ and -7.18‰, respectively, from July 2009 to June 2010. The percentages of transformation from precipitation to river water in the Buha basin, Shaliu basin and Haergai basin are 21.4%, 56.2% and 47.3%, respectively. The river water belongs to low mineralized freshwater and its chemical type is Ca2+-Mg2+-HCO3-. 3) The groundwater around the Qinghai Lake derives from the local precipitation, which undergoes a process of evaporation. The elevation of water supply changes between 3400m and 4000m. Serious depletion and fluctuation of δ18O and δ2H of the groundwater, which lie on fault zone, indicate that the groundwater would be supplied by the fissure water.4) The Qinghai Lake water derives from the peripheral river water, which has undergone a process of severe evaporation. Under the evaporation, the δ18O and δ2H enriched, ion contents of Ca2+, Mg2+, HCO3- and SO42- decreased, ion contents of Na+、K+ and Cl-, TDS and EC increased, gradually. And the lake water became salty water from freshwater, and its chemical type became Na+-K+-Cl- from Ca2+-Mg2+-HCO3- finally.5) From July 2009 to June 2010, the precipitation, evaporation and net input water are 120.52×108m3, 112.72×108m3 and 7.80×108m3, respectively, in the Qinghai Lake watershed. The precipitation on the land is 104.32×108m3. The river water and groundwater transformed from precipitation to the Qinghai Lake are 19.89×108m3 and 5.39×108m3, respectively. The precipitation and evaporation on the lake surface are 16.20×108m3 and 33.68×108m3, respectively. The relationships between lake level and meteorological factors in different periods indicate the changes of Qinghai Lake level is controlled by the meteorological factors, such as precipitation, evaporation and wind speed during the Westerly Circulation.