Research on groundwater flow systems using the concentration of anions

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The studies on groundwater flow system by using the concentrations of anion were carried out. The fields of studies are four areas ; Mt.Yatsugatake, the fluvial fan around the city of Gosen, the fluvial fan in the Nasunogahara, and Mt.Tsukuba.On the mountain slope of Mt.Yatsugatake, the high concentration area of HCO^<3-> and SiO_2 are found at the lower part of the slope, and groundwater in this area is considered that the residence time is large. The concentration of NO^<3-> is an indicator of pollution by fertilizer, and from the comparison of land use map, the polluted water is distributed in the area of farm or pasture, not paddy field.In the Gosen area, the stream lines of groundwater recharged by the Hayatuki River were estimated by the mapping of water qualities, and the lines are coincide with the lines extimated from the geological structure.From the results of the observations in the Nasunogahara, the shallow groundwater is polluted by the excrement of domestic animals, and the pollutant, for example NO^<3->, flows on the same route of the groundwater.On the slope of Mt.Tsukuba, the base flow were sampled and analyzed. The water quality changes remarkably in space, i.e., the concentration of samples of eastern part of the mountains are low and those of western part are high. These differences were caused by the differences of the weathering of rocks.From the results of field observations, there are some remarkable spatial changes in water quality of groundwater, especially in the concentration of anion. These spatial differences are useful to estimate the groundwater flow patterns or systems.The author will make plan for the study on the changes in water quality, especially in anion, to the downstream along the stream line.