STUDY ON SPATIALAND TEMPORAL DISTRIBUTION OF SNOWMELT

本次研究的研究领域是天山乌鲁木齐河流域和长江上游的那齐河流域，中国。在这项研究中，收集了气象和水文资料，描述了这些流域的总体特征。简而言之，这些流域覆盖高海拔地区，气候干燥寒冷，高海拔冰川发育。本研究的主要内容是将分布式水文模型应用于这些流域，以获得这些流域高精度的降雨径流模型。在建立分布式水文模型时，利用了全球范围的地理信息(GLOBAL)。模型的输入数据为降水和温度，将流域径流输出数据与流域径流实测值进行比较，分布式水文模型将流域地形离散为正方形网格点，降水输入…每一个GID点都更多。在每个网格点上，降水被划分为蒸发、直接径流和基流。然后，直接径流通过从栅格点处的高程数据生成的流量网络输送到流域出水口。同时，通过一种水库模型将基流集中转化为流域径流，将降水资料按降雨量或降雪量随温度变化处理，并考虑雨量计的集水比和海拔高度的影响来计算降雪量。如果雪是在地面上的，则基于度日法进行融雪计算。在这些计算中，每个网格点的温度都是用数据拟合的温度递减率得到的。通过选取降雪模型的相关参数对模型进行了最终验证，计算的流域流量较好地再现了观测数据，表明了该模型的有效性。较少

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