The groundwater thermal regime in the Flevo polders and Gelderse Vallei (Southern IJsselmeer area, the Netherlands)

Abstract

The relationship between regional groundwater-flow systems and groundwater temperatures has been studied. Temperature/depth profiles were recorded in 70 observation wells. Low temperature gradients were observed in the infiltration areas. In these areas the observed temperature/depth profiles and those calculated with the theory of one-dimensional steady-state heat flow, showed significant correlation. Temperature/depth profiles in discharge areas showed lower shallow vertical temperature gradients than expected. This could be explained with a simple heat-budget equation of the regional groundwater-flow systems. In the area studied recharge of groundwater occurs at a lower temperature than discharge. Part of the geothermal conductive heat flow is used for warming up the relatively cold recharge water. This results in relatively low shallow temperature gradients in discharge areas.