STUDY ON SPATIALAND TEMPORAL DISTRIBUTION OF SNOWMELT

本研究的研究范围为天山地区的乌鲁木齐河流域和长江上游的那齐河流域。本文收集了流域的气象水文资料，描述了流域的一般特征。结果表明，这些盆地覆盖了高海拔地区，气候干冷，高原冰川发育。本研究的主要内容是将分布式水文模型应用于这些流域，获得这些流域的高精度降雨-径流模型。在构建分布式水文模型时，利用了全球地理信息（GLOBE）。模型的输入数据是降水和温度，输出数据是流域径流与观测到的流量进行比较。分布式水文模型将流域地形离散到方形网格点，降水在每个网格点输入。在每个网格点，降水被划分为蒸发、直接径流和基流。然后，直接径流通过网格点的高程数据生成的流量网络流向流域出口。而基流则通过一种水库模型集体转化为流域径流。在应用该分布模型时，根据温度将降水数据视为雨或雪，并考虑雨量计的捕获率和高度依赖性来计算降雪量。如果有地面积雪，则采用度日法计算融雪量。在这些计算中，每个网格点的温度是用数据拟合的温度递减率得到的。通过选取降雪模型相关参数对模型进行最终验证，计算的流域流量与观测数据吻合较好，表明了模型的有效性。少

The study fields of this study are the Urumqi River Basin in the Tianshan mountains and the Naqi River Basin, the upstream reach of the Changjiang River, China. In this study, the meteorological and hydrological data are collected and the general features of these basins are described. The result, in short, is stated that these basins cover the high-altitude region and the climate is dry and cold with development of glaciers at the high altitude.For the major part of this study, the distributed hydrological model is applied to these basins to obtain the high-accuracy rainfall-to-runoff model of these basins. In constructing the distributed hydrological model, the worldwide geographic information(GLOBE) is utilized. Input data to the model are precipitation and temperature and the output data of the basin runoff is compared with the observed discharge there.The distributed hydrological model discretizes the basin topography to the square mesh points and the precipitation is inputted at … More each gid point. At each grid point, the precipitation is divided to the evaporation, direct runoff and the baseflow. The direct runoff, then, is routed through the flow network generated from the elevation data at the grid points to the basin outlet. Wile the baseflow is collectively converted to the basin runoff through a kind of the reservoir model.In applying this distributed model, the precipitation data is treated either as rain or snow depending temperature and the amount of snowfall is calculated taking into account the catch ratio of the rain gage and the altitudinal dependence. If the snow is on the ground, the snowmelt calculation is conducted based of the degree-day method. In these calculations, temperature at each grid point is obtained with the data-fitted temperature lapse rate. The final verification of the model is conducted by selecting the parameters pertaining to the snowfall model, the calculated basin discharge reproduces the observed data satisfactorily, showing the validity of this model. Less