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

灌溉水不仅具有作物灌溉用水的作用，还具有与当地居民生活和环境相关的“区域水”功能。如今，由于城市化的推进，人们担心这种功能正在丧失。本研究的目的是探讨在城市扩张的岸和田地区，农业基础设施（尤其是灌溉池塘）在区域或流域层面上对水环境（包括人工水管理）的作用。本研究连续开展了河流流量、灌溉池进出水量、降水、水质等水文观测，并在此基础上对以下几个方面进行了探讨。岸和田地区气候和水资源特征的调查：利用大阪府7个站点的AMEDAS数据，估算了每个站点的潜在可利用水资源（以降水量和潜在蒸散量计算）。结果表明，研究区属于日本相对干燥的气候。在此基础上，调查了灌塘的地理分布，估算了灌塘的水资源储量。灌溉塘的防洪功能评价：以研究区内的灌溉塘之一虎箕塘为例，通过实测资料分析和模型模拟，对其防洪功能进行了评价。结果表明，虽然该塘的面积相对于其集水区面积较小，但对洪水的缓解作用是足够的。3 .灌溉塘的养分减载功能评价：通过水静塘，可以减少水动状态下的河水的养分负荷。随着污水基础设施的扩大，河流中养分负荷减少的估算：估算了春树河流域随着污水接驳率的增加，河流水污染水平的改善（养分负荷的减少）。结果表明，在人口密度较高的下游地区，提高污水接驳率比在农村地区的上游地区扩大污水系统更有效地降低了河水中养分负荷水平。结合上述结果，从水的“储存”和“净化”的角度探讨了维持水文系统健康的灌溉系统应该是什么样的。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