Variability of water quality in a riparian wetland with interacting shallow groundwater and surface water

Abstract

Lowland catchment hydrology is dominated by shallow groundwater with complex interactions between groundwater and surface water. In lowland catchments of N Germany, a high fraction of agricultural land is drained and therefore influenced by fast water transport to discharge systems with resulting alterations to water quality. The investigated catchment area "Kielstau" (approx. 50 km 2 ) in the N of Schleswig-Holstein serves as an example. Detailed investigations on the interactions between groundwater, river, and ditch-water quality were evaluated at a drained riparian wetland area (0.15 km 2 ) used as grassland in the central part of this catchment. The water quality in the drainage ditches showed variability dependent on their hydrological integration. At the far-from-river end, groundwater and ditch-water quality were in most parameters much more alike than at the close-to-river end. The composition of ditch water at the close-toriver end of the ditch was determined by transformation processes and dilution which took place along the ditch much more than exfiltration processes like those that were dominant at the farfrom-river end. In most cases, the mean NH 4 concentrations were higher in the groundwater than in the ditches, but the highest concentrations were found all along the time in the close-toriver sampling points and in the river. The highest NO À 3 concentration was observed in a ditch influenced by an adjacent arable field as well as in the river. The concentrations of phosphate and total P were lower in groundwater than in the ditch water.

Methodologies and Management Framework for Restoration of Wetland Hydrologic Connectivity: A Synthesis

“…Restoration of the vertical HC. The wetland surface watergroundwater interaction is mainly reflected by the water exchange and water quality evolution between the surface water of the wetland and groundwater and becomes the important factor controlling the formation, development, and even extinction of wetlands (Crosbie et al 2009;Schmalz et al 2009). Surface water and groundwater exchange processes play a crucial role in the biogeochemical transformation of aquatic environments.…”

The impact of agricultural Best Management Practices on water quality in a North German lowland catchment

“…Lowland catchments are ecosystems with low flow velocity, a high groundwater table, and flat topography (Müller et al 2004;Krause et al 2007;Schmalz et al 2009). In the past centuries, different melioration measures such as river regulation and pumping stations have been implemented in order to enlarge areas as well as render better cultivation conditions for agriculture.…”

A test of CoupModel for assessing the nitrogen leaching in grassland systems with two different fertilization levels

“…In natural systems, changes in horizontal groundwater flows according to the recharge rate were more typical. Obvious interactions between shallow groundwater and surface-water bodies that can affect inflow rates were observed in the Northern Lowland of Germany (Schmalz and Fohrer, 2009). However, standard deviations between 0.025 and 0.24 indicated more highly variable shallow groundwater levels for the four nearest observation points than for the whole grassland site (minimum s.d.…”