Groundwater-surface water relations in regulated lowland catchments; hydrological and hydrochemical effects of a major change in surface water level management.

In lowland deltas with intensive land use, surface water levels are human controlled letting in river water during dry periods and discharge by pumping during wet periods. The water levels are usually maintained at a fixed level year-round or at fixed winter and (higher) summer levels. Several water authorities in The Netherlands consider implementing a more natural and flexible water level regime in nature reserves, with low levels in summer and high levels in winter.

Reaction capacity characterization of shallow sedimentary deposits in geologically different regions of the Netherlands.

Quantitative insight into the reaction capacity of porous media is necessary to assess the buffering capacity of the subsurface against contaminant input via groundwater recharge. Here, reaction capacity is to be considered as a series of geochemical characteristics that control acid/base conditions, redox conditions and sorption intensity. Using existing geochemical analyses, a statistical regional assessment of the reaction capacity was performed for two geologically different areas in the Netherlands.

Comparison of selection methods to deduce natural background levels for groundwater units.

Establishment of natural background levels (NBL) for groundwater is commonly performed to serve as reference when assessing the contamination status of groundwater units. We compare various selection methods to establish NBLs using groundwater quality data for four hydrogeologically different areas in the highly populated and developed subcatchment Western River Rhine, The Netherlands: selection of old groundwater (before 1945), of tritium-free groundwater (i.e.