Abstract:

Taking account of exponentially and periodically time-varying recharge, water table fluctuation between two parallel ditches was studied. The analytical solution was derived based on the first linearization method of Boussinesq equation, and Duhamel principle. This paper analyzed the characteristics of phreatic water movement by using three kinds of recharge rate functions including exponent-increase, exponent-decay, and sine function. In the first case, water table rises monotonously with the increasing recharge rate; and watershed between the two ditches moves from the higher level side towards the other sides, but will never cross the middle line of the aquifer. In the exponent-decay case, water table goes up at the beginning, then falls after reaching a peak value; watershed firstly moves towards the middle of the aquifer, then turns back to the higher level side due to the declining recharge rate. In the last case, water table periodically fluctuates corresponding to the sine function recharge; and there is a significant time lag between the stimulator and the respond; watershed sways back and forth between the higher level ditch and the middle of the aquifer. The results can be a clue to study the response of groundwater system to climate change, in addition to the transition rule between surface and ground water.

Key words: phreatic water, parallel ditch, unsteady flow, time-varying recharge