Evaluation of Regional Ecosystem for the Patterns of Agricultural Water Balance

本研究的目的是评价水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。结果可归纳为：(1)Kasegawa水系；灌溉系统的运行管理特点是利用低洼水田的回流和排水条件。提出了一个复杂的水箱模型来解释水的回用机理，并用实际的水平衡测量进行了评价。为评价灌溉系统用水效率，提出了循环水利用的概念定义。中水回用机制对节约灌溉水资源非常有效，但对水质的影响非常严重。(2)中川水系；中川河流域的水平衡可以通过计算槽模型的方法得到较好的澄清。而模式指数的概念，更多的是由于水资源的诱导，该指数可以用天气和土地利用条件的因素来解释。径流水质分析表明，灌溉水水质对流域径流水质影响较大。结果表明，降雨水质对径流水质的影响也很大。(3) Shinanogawa水系；对位于新泻平原的两个灌区的水量收支分析表明，长明渠的上游水量不一定能满足下游需水量，导致废水流入排水渠，从高效灌溉、简单管理和保持水质的角度来看，中水回用系统是合理的。(4)石卡里川水系；该流域以引水坝为灌溉水源，水田用水不受限制。因此，灌溉水的回用率相对较小。但这一比例近年来有所增加，预计水质会变差。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