三江源区水源涵养功能评估

为实现三江源区水源涵养功能评估，服务区域生态服务价值估算，从水源涵养的概念出发，解析水源涵养功能的内涵特征和表征指标，提出了三江源区水源涵养功能评估技术框架，并基于SWAT模型建立三江源区水文模型，通过年尺度、月尺度和日尺度的水文模拟，完成三江源区水源涵养功能定量评估.从水文模型校准结果来看，直门达、唐乃亥和香达3个验证站日径流量最大相对误差不超过17.0%，月径流量最大相对误差不超过13.0%；日尺度模型中直门达站模拟效率系数超过了0.6，其他两个站也超过了0.5，月尺度模型中3个验证站模拟效率系数均超过0.6以上；日尺度模型和月尺度模型验证结果均可接受，在一定程度上较好地揭示出了三江源区的水量输出过程、趋势和规律.应用该模型对水源涵养功能进行定量评估，长江流域、黄河流域、澜沧江流域水资源供给量分别可达到158.8×108、326.2×108、72.6×108 m3；考虑土地利用和植被变化对流域径流输出的影响作用，植被破坏可能导致长江流域、黄河流域和澜沧江流域地下径流量分别可能减少98.6×108、200.1×108和44.5×108 m3；在相同降水条件下，低植被覆盖会导致长江流域、黄河流域和澜沧江流域年最大流量的平均值、最大值、最小值分别增加了约80%、60%和30%.研究显示，三江源区在保障下游用水、提升径流调节能力和缓解防洪压力等方面具有突出的作用. 

Assessment of Water Conservation Function in the Three-River Headwaters Region

Based on the concept of water conservation, the connotation and characterization index of water conservation function were analyzed, and the technical framework of water conservation function evaluation in the Three-River Headwaters Region was put forward. Furthermore, a hydrological model in the Three-River Headwaters Region was built based on SWAT model and was used to simulate the runoff of the Three-River Headwaters Region in diffirent time scales. The calibration results of the hydrological model showed that the maximum relative error of the daily runoff was less than 17.0%, and the maximum relative error of the monthly run off was less than 13.0%. In the daily scale simulation, the Nash efficiency coefficient (ENS) of the Zhimenda station was over 0.6, and that of the other two stations were more than 0.5. In the monthly scale simulation, ENS of all three stations was more than 0.6, which showed that the simulation results of the daily and the the monthly scale model were acceptable, and runoff process of the Three-River Headwaters Region was revealed by the developed model. The model was applied to assess the water conservation function of the Three-River Headwaters Region, the Yangtze River, the Yellow River and the Lancang River Basin water supply could be achieved respectively 158.8×10⁸, 326.2×10⁸, 72.6×10⁸ m³. Considering the impact of the land use and the vegetation change in the runoff of the river basin, the vegetation damage could have caused the Yangtze River, the Yellow River, and the Lancang River Basin to reduce the runoff of the underground runoff about 98.6×10⁸, 200.1×10⁸, 44.5×10⁸ m³. Under the condition of same climate, poor vegetation could increase the maximum daily flow of the Yangtze River, the Yellow River and Lancang River Basin about 80%, 60% and 30%. As a result, it was impotant for Three-River Headwaters Region to provide the water supply, improve the regulation capacity of runoff and relieve the flood pressure.