Time series analysis of con nuous streambed temperature during a period of 47 d revealed that discharge to a stream is nonuniform, with strongly increasing ver cal fl uxes throughout the top 20 cm of the streambed-aquifer interface. An analy cal solu on to the transient heat transport equa on was used to analyze several pairs of observed amplitude damping with depth. A nonuniform pa ern in discharge across the stream width was also observed, which could have been caused by lateral or horizontal fl ow. Head measurements in a meadow area and below the stream showed strong convergence of fl ow near the streambed. Seepage meter measurements in the middle of the stream o en resulted in highly variable fl ux esmates, which could have been caused by hyporheic fl ow due to the presence of a gravel layer. Discharge and recharge to the stream at the bank near the meadow was rela vely steady throughout the period. On the other hand, discharge to the stream at the opposite bank near a steep hillslope decreased signifi cantly toward the end of the period (early June), which was a ributed to a drop in the water table on this side of the stream. The results from the me series analysis were compared with seepage meter measurements and the results from a steady-state analy cal solu on to the heat transport equa on. The diff erent methods agreed on the pa ern of discharge across the stream width, and the mean values during the studied period generally agreed well but with diff erent ranges.Abbrevia ons: SWI, sediment-water interface. The European Union (EU) Water Framework Direc ve requires EU membercountries to administer their water resources in an integrated fashion, where the ecological statuses of diff erent water bodies are treated together. In this respect, groundwater-surface water interactions play a central role (Dahl et al., 2007). In the Skjern River Catchment (SRC) in Denmark, groundwater-stream and groundwater-lake interactions have been investigated at various scales. For example, Kidmose et al. (2011) modeled lake-scale seepage patterns at a fl ow-through lake in the upper parts of the SRC to see how seepage is aff ected by lake bathymetry and the depositional character of the lake bed sediments. On-land and off shore geophysical explorations have helped to improve the inclusion of the lake in the regional groundwater fl ow model, improving the model's ability to simulate the observed seepage patterns.Heat has been used in many studies as a natural tracer to assess groundwater-surface water exchange at various scales. Th e seasonal changes in temperature contrasts between the surface water and deeper groundwater make it possible to quantify the direction and magnitude of the exchange (Constantz, 2008). At the kilometer scale, distributed temperature sensing has been used to study groundwater-lake and groundwater-stream interactions (Selker et al., 2006a,b). At the meter scale, point or profi le measurements of temperature have been popular for some time (Constantz, 2008). A number of investigations have relied on ...

A restored riparian zone was characterized to understand the effects of flooding on subsurface hydrological flow paths and nitrate removal in groundwater. Field and laboratory investigations were combined with numerical modeling of dynamic flow and reactive nitrate transport. Flooding enhances nitrate removal in groundwater primarily by two mechanisms. First, by creating a stagnant flow zone beneath the flooded area thereby increasing the residence time and leaving more time for nitrate removal. Secondly, nitrate removal is increased by enhancing upward flow into the highly reactive organic‐rich top layers. Flooding therefore contributes to nitrate removal in “hot spots”, where nitrate is transported to the peat and during “hot moments”, when flow is stagnant. The permeability of the capping peat layer relative to the aquifer is important as it controls both mechanisms. The model shows that the deep‐seated nitrate removal is greater than projected from the laboratory nitrate reduction experiments.

The aim of the present study is to investigate the vertical distribution of the Nitrate Reduction Potential (NRP) at different depths on a natural (Evi

A numerical study demonstrates the effects of flooding on subsurface hydrological flowpaths and nitrate removal in anoxic groundwater in riparian zones with a top peat layer. A series of two-dimensional numerical simulations with changing conditions for flow (steady state or transient with flooding), hydrogeology, denitrification, and duration of flooding demonstrate how flowpaths, residence times, and nitrate removal are affected. In periods with no flooding groundwater flows horizontally and discharges to the river through the riverbed. During periods with flooding, shallow groundwater is forced upwards as discharge through peat layers that often have more optimal conditions for denitrification caused by the presence of highly reactive organic matter. The contrast in hydraulic conductivity between the sand aquifer and the overlying peat layer, as well as the flooding duration, have a significant role in determining the degree of nitrate removal.