A study on the estimation of water-environmental change from urbanization and its preservation method using hydrological and water quality model

本研究评估都市化对水环境（流量与水质）的改变，并提出其保护方法。首先，TOPMODEL（topography-based hydrogenation model）是一个基于物理的分布式径流模型，它不仅能反映河流流量，而且能反映可变源区的分布。该模型被应用到Wajima-Yanagida流域和山田河流域。其次，采用了由森林、稻田、城市子池组成的分布式模型--复合池模型，并结合由实测空间水质数据确定的LQ方程（指数型负荷-流量关系）进行了模拟。结果如下。1. TOPMODEL在长、短期径流量的估算和可变源区分布的模拟方面表现出良好的性能。2. DEM是有效的和有用的计算地形指数用于应用的TOPMODEL.从LQ方程看，城市和水田具有负荷积累和负荷闪发作用，其负荷供给能力比森林小。4.该模型可以根据流域土地利用率来评价水质和流量变化（负荷）。5.在本研究区域内，单位面积的出水负荷由大到小依次为水田、城市、林地。6.该模型可用于评价农季某些养分的浓度上升。

This study evaluates the changes in water environment (in the aspect of discharge and water quality) from urbanization and to propose its preservation method. First, TOPMODEL (topography-based hydrological model) is a physically-based distributed type rainfall-runoff model which can represent not only river flow discharge but also distribution of variable source area. The model is applied to the Wajima-Yanagida catchment and the Yamada river basin. Next, the complex tank model, which is distributed model and includes the forest, paddy field, any city sub-tank model, is used in combination with LQ-equation (loading-discharge relationship of exponential style)determined from observed spatial water quality data. The results are as follows. 1. TOPMODEL shows good performance for estimating long- and short-term runoff and simulating distribution of variable source area. 2. The DEM is effective and useful for calculation of a topographic index used for application of the TOPMODEL.3. From LQ-equation, city and paddy field has a function of accumulation and flash of loading and its ability of supply of loading become smaller as compared as forest. 4. The model can evaluate water quality and discharge changes (loading) from land use ratio of catchment. 5. In current research area, effluent loading from unit area is bigger in order of paddy field, city, forest. 6. The model can evaluate the concentration rise of some nutrient in farming season.