Evidence of karstification in chalk and limestone aquifers connected with stream systems and possible relation with the fish ecological quality ratio in Denmark

Abstract Although chalk aquifers are not too often associated with conduit flow, they highly productive groundwater systems and, like limestone aquifers, can be vulnerable to contamination when exposed land use activities. The Danish carbonate rocks generally recognized fractured and covered by thick Quaternary sediments. Fissure flow is pronounced, occurring in the upper 50–100 m due Pleistocene glaciations. According recently published maps of distribution karst Europe, Denmark has no karst. However, this study concludes that karstified an important source freshwater Denmark. Four national datasets on features, chemistry, fish ecological quality ratio (EQR) data now indicate more heterogeneous structures preferential pathways than had been conceptualized modelled a water resources groundwater/surface-water model recent past. This provides new qualitative evidence rapid agrochemicals from surface through thinner parts cover layers, sinkholes solution-enlarged fractures may likely impact vulnerability aquifers. Additionally, system, some gaining streams discharged show increased EQR values using observed river daily discharge instead simulated discharge.