Synthetic evaluation of efficiency in hydrological cycle in large watershed

本研究以评价大流域（筑间信浓河流域）的水资源利用效率为目的。结果总结如下。(1)为评价流水流量波动，引入了能反映流域特征的格局指数。(2)“水循环效率”的概念应包含“水循环给社会带来什么和多少”的社会经济观点。“以及身体上的。决定水循环利用效率的一般因素是流量波动、水质波动和水循环利用强度，但也包括对社会的无形影响。(3)研究了影响稻田水分利用的不利因素泥沙输移和低水温的现实。分析结果表明，河床不稳定泥沙的分布是影响泥沙输移的最重要因素，太阳辐射对水温的形成有直接或间接的影响。(4)通过对3年水文观测资料的分析，得出该流域径流率为38%，退水常数为0.043（d^<-1>），洪峰径流系数为0.1 ~ 0.2。结果表明：土壤入渗量大，持水能力差;从这一事实来看，如果从雨水储存的角度考虑，可以解释为给定研究区域的水文效率较低。(5)对坡耕地的退水利用率进行了测定。1990年这些稻田主要用于水、高地两种作物的生产，稻田的产水率为100%，到1992年已下降到66%，退水效率也从290%下降到80%。1990年灌溉水的温度比1992年高得多。

The investigation was conducted aim at the evaluation of Efficiency for water use in large watershed(Chikuma-Shinano river basin). The results are summarized as follow. (1) For the evaluation of discharge fluctuation of flowing water, the pattern index by which characteristics of river basin being explained was induced. (2) The concept of "Water Cycle Efficiency" should involve the socio-economic view-point of "What and how much does a water cycle bring to the society ?" as well as the physical one. The general factors which decide the efficiency are fluctuation in flow rate, water quality and intensity of water recycling, though it include intangible effects on a society.(3) We investigated the reality of sediment transport and low water temperature which are minus factors of water use in paddy fields. As a result of the analysis, it is clarified that the distribution of unstable sediment in river bed is the most important factor for sediment transport, and that the solar radiation directly or indirectly plays an important role for the formation of water temperature. (4) As a result of analyzing hydrology data observed over the 3 years, the author obtained that the runoff ratio is 38%, the recession constant 0.043 (d^<-1>) and the peak runoff coefficient 0.1-0.2. The results indicate that the infiltration is high and the water holding capacity poor. From this fact, if considering from the standpoint of rain storage, can be interpreted that the hydrology efficiency for the given study area is low. (5) The efficiency of return flow using ratio were measured in the area of sloping paddy fields. These paddy fields used for the production of paddy rice and upland crops in 1990, the percentage of paddy ricle was 100% but it decreased to 66% in 1992, and the efficiency of return flow also decreased from 290% to 80%. The temperature of irrigation water rose up much higher in 1990 than in 1992.