A METHOD TO ANALYSE THE EFFECT OF PRECIPITATION ON THE GROUND WATER STREAM

Abstract

The variation of the level of the ground water table involves the total effect of hydrological elements necessary to determine the budget of water balance under the ground. It then appears that the value of each element can be found by analysing the state of variation in the water level. Long time records of the water level in a well in Beppu City are analysed according to the approximate theory concerning the effect of precipitation on the ground water stream under water table conditions. The result is used to estimate the water budget in the basin. A part of precipitation does not have an effect on the ground water stream and its rate is obtained by the method of analysing the declining state of the water level as being about one-third of the precipitation. This value shows good agreement with the observed effect of precipitation. A part of the supply to the lower confined ground water in the upstream part of the basin does not come back to the upper unconfined aquifer owing to artificial withdrawals from the lower aquifer. Its rate is estimated and compared with the rate of withdrawals of hot water in the city. They recently show a clear tendency to be increased.