Estimation Of Base Level For An Aquifer From Recession Rates Of Groundwater Levels

A model is presented that calculates a base level for an aquifer, assuming that the aquifer can be approximated by a linear reservoir. The base level is geologically dependent and can be seen as a drainage level for the aquifer that represents the lowest groundwater level that will occur from groundwater flow only. The base level affects groundwater-level variations and can be used to help estimate flow paths. Types of information needed to estimate this parameter are groundwater-level records, from which recession rates are calculated, and a recession curve. The recession curve is a function of the properties of the aquifer, and from it the base level is evaluated together with an aquifer parameter that describes the hydrogeological properties. Data from an area in the Groundwater Network in Sweden are used as an example. The results are consistent with the topography and hydrology of the area. Two factors affect the accuracy of the results: the time resolution of the groundwater-level data and the length of the water-level record.