Study of the Long-term Change of Groundwater Level and Water Quality in the Vicinity of a Dam

Abstract

This paper describes the groundwater movement indicated by the results of a long-term investigation of the leakage volume, groundwater level and water quality measured since the initial filling of the reservoir. Main results obtained from this investigation can be summarized as follows: 1) The leakage volume tends to decrease with time. In particular, the leakage volume at measuring points where leakage was considerable at initial filling decreased remarkably. 2) The difference in the ratio of transmissivity of the rock mass showed that the sealing zone built during dam construction was functioning soundly. Furthermore, the variation with time of the ratio of transmissivity showed that a natural sealing zone was formed near the reservoir by siltation. 3) The variation of the water quality of groundwater showed that the seepage water from the reservoir arrived at the downstream side after more than one year from the start of filling.