Study on the generalization of stream discharge, water velocity and water temperature by river network analysis

开发了用于流量、温度和水质模型分析的地理信息系统软件，并进行了测试。该模型基于这样的假设，即平均流速和平均水深可能对每个河流顺序具有指定值。在东京附近的山区溪流中，对大约130个站的流速和深度进行了调查。平均流速由流量、平均水深和平均宽度推算。结果表明，这些参数随水流阶数的增加而增大，并取各参数的平均值进行模型分析。该模型覆盖了3~6阶流，因为在一般情况下，2阶流中不存在恒定流，利用地理信息系统软件对线段的连接点和各线段的长度进行分析，然后将数据传输到Excel或Lotus中进行计算。用归一化形式对水的传播时间进行分析，发现在盆地形状系数较大的盆地中，水的传播时间谱呈集中形态。窄盆地和长盆地均为平坦分布。利用简单的热平衡方程和流量的加权平均值估算了流态温度的分布。结论是，大约60%的测试案例是成功的；这些都是分支较多的盆地。BOD稀释度的计算引入了自净和树枝清水的混合。可以说，该模型对水质分析也是有用的。

A GIS software for the model analysis of stream discharge, temperature and water quality has been developed and tested. The model is based on the assumption that mean velocity and mean depth may have specified values for each stream order. Investigations on velocity and depth were carried at about 130 stations in mountain streams near Tokyo. Mean velocity was deduced from amount of discharge, mean depth and mean width. It has been concluded that these parameters increase with the stream order and the mean value of each parameter is taken into the model analysis. The model covers 3^<rd> to 6^<th> order of streams, because permanent flow is not found in 2^<nd> order flow in general case.Conjunction of segments and length of each segment have been analyzed by the GIS software, after then, data are transferred to Excel or Lotus for the calculation. Analysis on travel time of water by normalized form reveals that spectrum of the time shows concentrated shape in basins with large basin shape coefficient. Flat distributions are obtained in narrow and long basins. Distribution of stream temperature has been estimated by simple heat balance equation and weighted mean of the discharge volume. It has been concluded that about 60% of the tested cases are successful ; these are basins with many branches. Dilution of BOD is calculated introducing the self-purification and mixing with clear water from branches. It may be said that the model is also useful for water quality analysis.