Kan dagvatten förorena vattentäkten i Hurva?

Sammanfattning: Groundwater is one of our most important natural resources. Therefore, it is important to monitor the groundwater and to protect it from pollution. At Hurva, southern Sweden, the local drinking water is produced by groundwater extraction. In this study the potential impact of storm water on groundwater quality at Hurva is studied in a risk analysis. Mapping of the geology and hydrogeology in the area was made and after that an inventory of the possible pollution sources in the area was done. Based on the result of the inventory and the hydrogeology a modelling of the groundwater flow was made to assess the potential influence of pollutants from three activities at sites within the hydrological catchment. The main groundwater source is fracture zones along dolerite dykes intersecting the clay shale bedrock. The overlying soil is 5-20 m thick and consists mainly of sandy till, possibly with an elevated clay content near the bedrock. The groundwater flow direction is to the north which makes pollutants south of the discharge well the greatest concern. Two agricultural sites and one site in a dike close to a junkyard were analysed in the groundwater modelling. Results showed a slow movement of groundwater, yielding transport times of between 2,5 and 11 years from the modelled sites to the discharge well of the local water plan. Only from within a narrow zone, south of the well, did groundwater from the site reach the discharge well. The local geology provides the groundwater some protection, but there can be a risk of persistent pollutants reaching the discharge well from sites in the southern zone. However, there is a general lack of information concerning the geology and the aquifer and many of the parameters in the model have been estimated.