Studies on Utilization of Water Resources and Irrigation Facilities for Sustaining the soundness of Hydrologic System in a river basin with an Urban Sprawl Area

灌溉水不仅是作物的补给水，而且是与当地居民生活和环境息息相关的“区域水”。如今，随着城市化的推进，这种功能恐怕正在丧失。本研究的目的是试图调查的作用，农业基础设施（特别是灌溉池塘）发挥水生环境，包括人工水管理方面，在区域或流域水平的岸和田地区，城市蔓延正在推进。本研究连续进行了河川流量、灌溉池塘的流入流出量、降水量、水质等水文观测，并在此基础上进行了以下几方面的探讨：1.岸和田地区气候和水资源特征调查：利用大坂府内7个测站的AMEDAS数据，通过降水量计算出潜在可用水资源， ...更多信息 以及潜在蒸散量。结果表明，研究区属于日本相对干燥的气候。并在此基础上，对灌溉池塘的地理分布进行了调查，估算了灌溉池塘的水资源存款。2.灌溉池塘的防洪功能评价：以研究区内的灌溉池塘之一的保池池为例，通过实测资料分析和模型模拟两种方法对该池塘的防洪功能进行了评价。结果表明，该灌溉塘的表面积相对于其集水面积而言较小，但其防洪能力较强。3.灌溉塘的营养负荷削减功能评价：在静水条件下，水体经过池塘后，处于水动力状态的河水中的营养盐负荷降低，这一现象是持续的。扩大污水处理基础设施：根据Haruki河流域污水处理连接率的增加，估计河流水污染水平的改善（营养物负荷的减少）。结果表明，在下游人口密度较高的地区增加排污口接入比，比在上游农村地区扩大排污口，对降低河水营养盐负荷水平更有效，综合上述结果，从“蓄水”和“净水”的角度，讨论了维持水文系统健康的灌溉制度。少

Irrigation water has not only a role of feeding water for crops but also a function as "regional water" associated with the local residents' life and environment. Nowadays it is feared that such the function is being lost due to advancing of urbanization. The objective of this study is to try to investigate the role which agricultural infrastructure (especially irrigation pond) plays for aquatic environment, including artificial water management aspect, at a region or basin level in Kishiwada area where urban sprawl is advancing. In this study, hydrological observations such as river flow, inflow and outflow in an irrigation pond, precipitation, water quality, and so on were continuously carried out, and based on these data, the following aspects were discussed.1.Investigation of the characteristic of climate and water resources in Kishiwada area : Using the AMEDAS data at 7 stations within Osaka prefecture, a potentially available water resource, which is calculated by precipitation m … More inus potential evapotranspiration, were estimated at each station. The result indicated that the study area is categorized into relatively dry climate in Japan. And based on the irrigation pond ledger, the geographical distribution of irrigation pond was investigated, and water resources deposit was estimated.2.Evaluation of flood mitigation function of irrigation pond : For Hoji-ike pond which is one of the irrigation ponds, located in the study area, flood mitigation function of the pond was evaluated through both analysis with observed data and model simulation. As a result, it was indicated that this pond mitigated floods enough though its surface area is relatively small for its catchment area.3.Evaluation of nutrient load reduction functions of irrigation pond : It is sustained that nutrient load in river water which was in hydrodynamic state was reduced by going through the pond in which the water was in hydrostatic state.4.Estimation of nutrient load reduction in the river associated with expanding sewerage infrastructure : The improvement of river water pollution level (decrease of nutrient load) according to increasing of the sewerage connecting ratio in the Haruki River watershed was estimated. The results indicated that increasing the sewerage connecting ratio in the down stream area, where the population density is higher, was more effective than expanding the sewerage system to the upper stream area, where is rural area, for decreasing of nutrient load level in river water.Integrated the above results, it was discussed what the irrigation system should be for sustaining the soundness of hydrologic system from the point of view of "storage" and "purification" of water. Less