STREAM FLOW ANALYSIS BASED ON INTERACTION BETWEEN STREAM AND AQUIFER IN ALLUVIAL FAN

汽水不仅在河道中流动，而且通过进水渗入河床或从含水层渗出，与河岸地下水有一定的联系。尽管河流与含水层之间的这种交换量与雨季的河流流量相比可能相对较小，但两者之间的相互作用是决定枯季和/或取水坝下游流量较小的水流状况的重要因素之一。由于流量的显著减少对水量、水质和温度都有影响，因此可能需要保持最小流量，以保护河流环境，包括生态完整性。本文通过野外观测和水工模型试验，研究了河流与含水层的相互作用及其对水流条件的影响，以求取最小流量。根据对日本靖州河冲积扇的观测，认为河流流量的变化可能是由于与含水层的水交换引起的。水力计算结果表明，该模型是定量评估维持适宜水流条件所需最小流量的有用工具。

Steam-water not only flow in a river channel but also some relationship with riparian groundwater through the influent seepage into a river-bed or the effluent seepage from an aquifer. Although such exchange quantity between stream and aquifer may be relatively small in comparison with the stream discharge in the rainy season, the interaction between both is one of the important factors governing the stream flow condition with small discharge in the dry season and/or in the downstream from the intake dam. Because a remarkable decrease in the discharge affects both water quantity and quality and temperature, it may be necessary to keep a minimum discharge in order to preserve the river environment including ecological integrity. In this paper, for evaluation of the minimum discharge, the stream-aquifer interaction and its effects on the stream flow condition are investigated through field observations and a hydraulic model. According to the observations in an alluvial fan of the Yasu River in Japan, it is thought that variation of the stream discharge may be caused by the water exchange with aquifer. The findings from the hydraulic computations indicate that the model is a useful tool for quantitative evaluation of the minimum discharge required to maintain suitable stream flow conditions.