梯级电站运行下拉萨河干流水文情势变异及归因分析

梯级水电站不同的调度模式对河流水文情势产生的影响存在差异。为了定量分析拉萨河干流梯级水电站不同调度模式对水文情势变化的影响，采用水文变异指标法及变化范围法（IHA-RVA），综合评价了旁多、唐加和拉萨3个水文站32项水文情势指标的改变度及综合改变度。结果表明：常规调度模式下，3站的水文情势发生了轻度改变，综合改变度分别为0.17、0.21和0.20；电力调度模式下，3站的综合改变度分别为0.50、0.54和0.48，属于中度改变。采用多系列贡献率分割法，研究了天然径流量变化、河道外引水退水以及梯级电站调度运行3因素对月均径流改变的贡献率。研究表明：常规调度模式下，3因素对拉萨水文站月均流量改变度的贡献率分别为0.81、0.02和0.17，主导因素为天然径流量变化；电力调度模式下，3因素的贡献率分别为0.56、0.06和0.38，梯级电站调度运行因素的贡献率显著提高，电力调度下梯级电站调度运行对拉萨水文站月均流量改变度的贡献率比常规调度提高了124%。

Influence and attribution of the cascade hydropower station operation on the hydrological regimes in Lhasa River

Different operation modes of cascade hydropower stations may have different effects on the hydrological regimes of a river. In order to quantitatively analyze the influence of different operation modes of the cascade hydropower stations on the hydrological regimes in Lhasa River, the indicators of hydrologic alteration-range of variability approach (IHA-RVA) was applied to analyze the changing degrees of Pangduo,Tangjia and Lhasa station. The results showed that the hydrological regimes of Lhasa River changed slightly under the conventional operation mode (COM), with the comprehensive changing degrees of 0.17, 0.21 and 0.20 respectively. Whereas the comprehensive changing degrees of these three stations reached 0.50, 0.54 and 0.48 respectively under the maximum-hydropower operation mode (MOM), which was classified as moderate changes. Then, the multi-series contribution rate segmentation was used to analyze the contribution rates of the variation of natural runoff, water diversion and cascade reservoir operation with different operation modes to the average monthly runoff. The contribution rates of these three factors to the change of the average monthly runoff of the Lhasa station were 0.81, 0.02 and 0.17 respectively under the COM, indicating that the dominant factor was the variation of natural runoff. The contribution rates of these three factors were 0.56, 0.06 and 0.38 respectively under the MOM, showing a significant increase in contribution rate of cascade reservoir operation. The contribution rate of the cascade reservoir operation of the MOM was 124% higher than that of the COM.