USE OF ORGANIC TRACE COMPOUNDS TO IMPROVE WATER MANAGEMENT AT A BANK FILTRATION SITE AT THE RIVER RHINE, GERMANY

Water management at bank filtration sites seems straight forward. In Germany, water demand shows higher variations due to a temporal increase in water demand (especially in agriculture). In combination with an increase of observed extreme water levels in both, the river as well as in groundwater there is a need for new and improvement of water management. We present results on trace organic compounds used for improvement of water management at the urban bank filtration site Flehe in Düsseldorf, Germany.

Hydraulic and hydrochemical measurements were carried out over a period of several years across a study transect on the Rhine riverbanks with up to 15 monitoring wells and the river Rhine itself. Various inorganic and organic compounds, among those fertilizers, pesticides, and pharmaceuticals are monitored. Generally, concentrations of the compounds decrease with increasing distance to the river Rhine. However, this situation changes during extreme events like droughts and floods. The drought in the summer of 2018 with ever-low water levels of the river Rhine led to a significant increase in trace organic compounds in the pumping wells originating from the landward groundwater. On the contrary, the high water levels in winter 2018/2019 hat remarkable impact not only on the flow conditions but also on the organic trace compounds. It is noticeable here that an increased concentration of substances discharged from the Rhine can also be detected at measuring points beyond the well gallery, on the landward side of the measuring point transect. The occurrence of organic trace substances even shows that the flood of the river Rhine pushes the water in the bank filtrate up to the well gallery and far beyond into the hinterland despite ongoing water pumping. These observations are crucial for the subsequent water management during different water levels of the river Rhine.