Near-natural stormwater management and its effects on the water budget and groundwater surface in urban areas taking account of the hydrogeological conditions

Near-natural stormwater infiltration can cause rising groundwater tables in urban areas. In order to assess these effects, the area-differentiated groundwater recharge in a real investigation area in Germany and their effects on the groundwater table are modelled using three different computer programs. The first program determines the natural area-differentiated groundwater recharge for the whole study area without considering the infiltration facilities. The second program is used to localise infiltration processes and it calculates the groundwater recharge below the infiltration facilities. The groundwater recharge rates calculated with these two programs are incorporated in the numerical groundwater model. It is used to simulate the groundwater surface level development. By varying the size of additional development areas, the degree of sealing, the infiltration rate and the precipitation different simulation scenarios were conducted. It was found that both the precipitation and the infiltration rate are the most influencing factors concerning the groundwater surface. Further, problems have to be expected especially in areas with low hydraulic conductivities. To ensure sustainable depths to groundwater table calculating the water budget can be recommended, as to name just one of the recommendations presented in this paper.