Change of Agricultural Water Management and Its Evaluation of Influence on Hydrological and/or Water Quality Environment in the Area of Lake Shinji and Nakaumi

本研究的基本目的是开发一种技术，提供Hii河农业用水管理所需的水文和水质信息。为该区今后的水环境治理提供了有益的参考。研究结果如下：1. (1)对提出的一种径流模型参数识别方法进行了有效性检验，并对该方法进行了改进。(2)A在UNIX工作站上开发了径流分析系统。（3）但是，为了更好地分析淹没现象和农业用水管理条件，还需要进一步改进径流模型和研究识别方法。2. (1)以实施循环灌溉的稻田小流域为例，研究了污染物的通量。评价了回流污染物通量对剧院环境的贡献。（2）对山区旱地污染物径流进行了评价，并利用实验室蒸渗仪对降雨过程中氮素径流进行了监测。因此，使用树脂包膜肥料可以减少高地氮素外流。3. (1)利用软X射线照相技术对原状水稻土、高地土壤和森林土壤的排水进行了分析。稻田和高地土壤的排水均是先从大孔隙向基质排水。另一方面，对于森林土壤，排水仅发生在基质中。反问题求解得到的非饱和导水率在饱和与近饱和之间存在不连续性，表明流动区域不同。初期考虑大孔隙的导水作用，后期考虑基质的导水作用。

The basic purpose of this study is to develop a technique offering the hydrological and water quality information needed for agricultural water management of Hii River. It also provides an useful information for future way of water environment in this district. The results are as follows : 1. (1) Availability of a proposed method for indentification of runoff model was examined , in which was improved with respect to evaluate a set of runoff model parameter in the any significant digit designated for each parameter. (2)A runoff analysis system was developed by UNIX workstation. (3)But, it was recognized that the further improvement of runoff model and investigation of identification method was necessary for the analysis considered inundation phenomena and condition of agricultural water management. 2. (1) The pollutant fluxes of pollutants were elucidated in a paddy field watershed where a circular irrigation system was implemented. The contribution of pollutant flux in return flow to theater environment was evaluated. (2)The pollutant runoff from upland fields in the mountainous area was evaluated, The nitrogen outflows including the pollutants on rainy days were monitored in experimental lysimeters. It was concluded that saving fertilizer application using resin-coated fertilizer can contribute to the reduction of nitrogen outflows from upland fields. 3. (1) Drainage from undisturbed paddy soils, upland field soils and forest soils were analyzed using soft X-ray radiography. Drainage proceeded from macropore first then to matrix in paddy and upland field soils. On the other hand for forest soils, drainage has occurred in matrix only. Unsaturated hydraulic conductivity obtained from inverse problem showed discontinuity between saturation and near-saturation, which indicated flow region was different. Macropore was considered to channel the drainage at early stage, then matrix conducted the water flow.