Finding of Groundwater Recharge, Transit and Discharge Areas

Abstract

Groundwater recharge, transit and discharge areas for aquifers must be found. Their location depends on the influence of ground surface and hydrographical network (rivers, lakes, sea). It is commonly agreed that the recharge areas are located at hilly places where maximums of infiltration flows and piezometric groundwater levels coincide. Such method was applied for the hydrogeological model of Latvia LAMO. The model provides results for a complex spatial hydrogeological system where conditions even within one aquifer may differ considerably. For this reason, the common method of finding recharge, transit and discharge areas fails to provide accurate results. The new method has been developed. It is based on appliance of the ratio for velocities of vertical to horizontal groundwater flows. The resulting velocity of the vertical flow is found as the difference of velocities of flows on the top and bottom surfaces of the aquifer. The ratio r is the non-dimensional function. Its values r = 1 and r = 0 determine the locations of boundaries for the recharge and discharge areas, accordingly. For the transit area 0 < r < 1. Within the recharge and discharge areas r > 1 and r < 1, correspondingly. The new method provides accurate results even for discontinuous aquifers where the zones of zero thickness appear. Within such zones r = 0. The method will be applied as a tool for investigating complex groundwater processes that are modelled by LAMO. The method was used for extra calibration of LAMO in order to improve its results. The research was supported by the Latvian State Research Program EVIDEnT.