The effect of agricultural water management on the water quality environment in low-lying areas

灌溉供水控制系统是近年来农业地区最普遍的水管理项目。但如今，水资源管理要求农村人民将灌溉、排水和水质结合起来，以适应生活方式的变化、土地利用的变化和环境保护的需要。基于这一观点，本文对低洼地区水田的灌溉、排水、水质管理和栽培管理进行了研究。由于青森县津加鲁地区有很大比例被水田覆盖，因此它在历史上利用了几种类型的水。考虑了水利用的三个典型例子：对地区自身灌溉用水的依存率、抽水灌溉用水和排水回用率。这些因素对分析灌排水水质变化、旱地出水量、水质预算和回用肥料具有重要意义。(1)闭式循环灌溉系统区(2)半开式灌溉系统区(3)开式灌溉系统区2。3种类型水田在灌溉期内进出的数据数量和质量结果可以用下图表示：(1)单位面积（ha）的流入和流出负荷均较小，依次为封闭、半开放；和敞开式灌溉系统。在半开式和开式中，在水下耕作和水稻种植期间，输出负荷较大。(2)闭式循环灌溉水田区水质收支属于平衡型，出水量与入水量近似相等。而露天灌溉系统区域属于污染类型。(3)津加鲁水田的流入和流出负荷均小于日本其他水田。特别是闭式循环灌溉系统的负荷较小。(4)从排水到水田的回用肥料在封闭、半开放和开放式灌溉系统中依次较大。特别是闭式循环灌溉系统的氮肥回用量很大。在津加鲁地区和八幡田的低洼地区检查了非耕作和耕作稻田的灌溉用水和耕作管理。需水量为。在水下耕作和水稻种植期间，非耕水田比耕水田面积小。少

The irrigation water supply control system was the most popular of all water management projects in agricultural areas till recently. But now-a-days, water management demands from rural peoples integrated irrigation, drainage and water quality, to correspond with the changing life style, the change in land use and the needs of environmental preservation. Based on this point of view, this paper presents a study of irrigation, drainage, water quality management and cultivation management in paddy fields in low-lying areas.Because a high percentage of the Tsugaru area, Aomori Prefecture is covered by paddy fields, it has historically utilized several types of water utilization.1. Considered are three typical examples of water utilization : the dependence rate on irrigation water from area itself, pumped irrigation water and the ratio of re-used drainage water. These factors are very important for an analysis of the quality change of irrigation-and-drainage water, the outflow load from pad … More dy areas, water quality budget and re-used fertilizer.(1) Closed circulating irrigation system area(2) semi-open irrigation system area(3) open irrigation system area2. The results of the quantity-and-quality data flowing in or out of 3 types of paddy areas during the irrigation periods can be indicated as a fallows :(1) The inflow and outflow load per unit area(ha) is small in the order of closed, semi-open. and open types irrigation system. In semi-open, and open types, the output load is large during the under-water ploughing and rice-planting periods.(2) The water quality budget of paddy area using the closed circulating irrigation system belong to the equilibrium type, where the outflow load is approximately equal to the inflow load. But open irrigation system area belong to the pollution type.(3) The inflow and outflow loads of Tsugaru paddy areas are smaller than those of other paddy areas in Japan. Especially, the loads of closed circulating irrigation system are small.(4) Re-used fertilizer from drainage water to paddy fields is large in the order of closed, semi-open, and open types irrigation system. Particularly, re-used nitrogenous fertilizer of closed circulating irrigation system is very large.3. Irrigation water and cultivation management for non-tilled and tilled paddy fields are examined in low-lying areas of the Tsugaru area and Hachiro-gata polder. Water requirement of. non-tilled paddy fields are smaller than tilled paddy fields during the under-water ploughing and rice-planting periods. Less