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。为该区水环境的未来发展提供了有益的信息。研究结果如下：1。(1)对一种径流模型识别方法的有效性进行了检验，改进了该方法对一组径流模型参数的任意有效数字进行评估。(2)利用UNIX工作站开发径流分析系统。(3)但是，考虑到农业水管理的泛滥现象和状况，需要进一步完善径流模型和研究识别方法。2. (1)研究了水田流域循环灌溉系统中污染物的通量。评价了回流中污染物通量对战区环境的贡献。(2)评价了山区旱田污染物径流，利用实验渗滤仪监测了雨季含污染物的氮流出量。综上所述，采用树脂包膜肥可以减少旱田氮素的外流。3. (1)利用软x射线摄影技术分析了原状水稻土、旱田土和森林土的排水情况。水田和旱田土壤的排水先从大孔排到基质。另一方面，对于森林土壤，排水只发生在基质中。由反问题得到的非饱和导电性在饱和和近饱和之间呈现不连续，表明流动区域不同。前期考虑大孔疏导排水，后期由基质引导水流。

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.