Evaluation of Regional Ecosystem for the Patterns of Agricultural Water Balance

本研究的目的是评价稻田水管理对区域生态系统的影响。在不同的农业流域进行了两年的研究和调查。研究结果如下：（1）谷川水系：在低洼水田区，灌溉系统的运行管理具有回流再利用和排水条件的特点。提出了一个复杂的水箱模型来解释水的回用机制，并与实际的水平衡测量进行了评估。提出了评价灌溉系统水分利用效率的退水循环利用概念。中水回用机制对节约灌溉水资源十分有效，但对水质的影响也十分严重。(2)计算水槽模型法可以基本上弄清中川河流域的水量平衡。模式指数的概念 ...更多信息 对于水分利用的诱导，气候和土地利用条件对该指数有较好的解释。径流水质分析表明，灌溉水水质对流域径流水质影响很大。可见，降雨水质对径流水质也有很大影响。(3)信浓川水系;通过对位于新泻平原的两个灌区的水量平衡分析，指出长明渠上游的取水量与下游的需水量不一定相适应，造成排水沟的浪费;从灌溉效率高、管理简单、水质保持等方面考虑，水回用系统是合理的。(4)石狩川水系：该流域灌溉水源为引水坝，稻田用水不受限制。因此，灌溉水回用率相对较小。但近年来这一比例不断上升，预计水质会变得更糟。少

Purpose of this research is the evaluation of influences on the regional ecosystem for water management at paddy fields. Researches and investigations had been carried for two years at the different agricultural watersheds. The results may be summarized as follows :(1) Kasegawa river system ; The operation and management of the irrigation system is characterized by reuse of return flow and drainage condition in low lying paddy area. A complex tank model was proposed to explain the water reuse mechanism and evaluated with actual water balance measurements. The conceptual definition of cyclic use of returning flow was presented for evaluating the water use efficiency in irrigation system. The water reuse mechanism is very effective for conserving irrigation water resources but it has very severe impact on water quality.(2) Nakagawa river system ; The water balance in Nakagawa river basin could be substantially clarified by computing tank model method. And the concept of the pattern index … More for water use being induced, this index was explained clearly by the factors of weather and land use conditions. And the runoff water quality cleared that water quality of irrigation water affected greatly on the water quality of runoff water from the watershed. It cleared that water quality of rainfall also affected very much on water quality of runoff water.(3) Shinanogawa river system ; Some analysis of water budget in two irrigation districts located in Niigata Plain showed that the upstream flow taken into a long open channel is not necessarily fitted to the demand water in down parts of the channel, resulting waste water to drainage canals, and that the water reuse system is a reasonable one from the view of efficient irrigation, simple management and water quality conservation.(4) Ishikarigawa river system ; It is unrestricted of water use at the paddy field that irrigation water source is the diversion dam in this river basin. Therefore, the reuse ratio of irrigation water is small relatively. But that ratio increases for recent years, it is expected that water quality become worse. Less