Importance of groundwater and macrophytes for the nutrient balance at oligotrophic Lake Hampen, Denmark

Ommen, Daniela Oliveira; Kidmose, Jacob; Karan, Sachin; Flindt, Mogens; Engesgaard, Peter; Nilsson, Bertel; Andersen, Frede Østergaard

doi:10.1002/eco.213

Cited by 29 publications

(9 citation statements)

References 41 publications

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“…The analysis of the nutrient circulation system in oligotrophic lakes is an area of continuing research [ Oliveira Ommen et al , 2011]. At the same time, field experiments that identify the incidence of high‐frequency, large‐amplitude internal waves continue to be carried out and to provide insight into their wave structure, amplitude, and seasonality [ Preusse et al , 2012; Hutter , 2011, chapter 2].…”

Section: Discussionmentioning

confidence: 99%

Fluid circulation and seepage in lake sediment due to propagating and trapped internal waves

Olsthoorn

Stastna

Soontiens

2012

Water Resources Research

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[1] It has long been known that surface gravity waves induce significant seepage through the porous layer found at the lake bottom. Away from coastal regions, however, the pressure signature of surface waves at the lake bottom is weak. We consider fully nonlinear internal gravity waves, whose long wavelength and slow motion implies a sustained and strong pressure perturbation even in the deep regions of the lake. We argue that internal waves can induce significant seepage through the sediment layer, in regions where surface gravity waves have negligible impact. The pressure profile at the fluid-porous layer interface is computed from the ''exact'' Dubreil-Jacotin-Long theory, giving a reliable profile even for large waves. This profile is used in conjunction with Darcy's law to compute the seepage within the porous region. We find that the geometric distribution of seepage is strongly controlled by both the ratio of porous media thickness to the horizontal length of the pressure perturbation, and the bottom topography, when it is present. Based on work on the interaction of internal solitary waves with the bottom boundary layer, we develop a model to account for the changes in permeability due to wave-induced instabilities in the bottom boundary layer and enhanced benthic turbulence. This turbulence acts to unplug the pores near the surface by lifting the detritus that clogs them. The resulting changes in permeability significantly enhance exchange between the free fluid and the porous medium on the downstream side of the wave.Citation: Olsthoorn, J., M. Stastna, and N. Soontiens (2012), Fluid circulation and seepage in lake sediment due to propagating and trapped internal waves, Water Resour. Res., 48, W11520,

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Section: Discussionmentioning

confidence: 99%

Fluid circulation and seepage in lake sediment due to propagating and trapped internal waves

Olsthoorn

Stastna

Soontiens

2012

Water Resources Research

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“…Groundwater, while seeping through lake sediments, may mobilize phosphorous from iron oxides, phosphorous-bearing minerals, and organic matter buried in lake sediments [10,13]. Although phosphorous was long considered to be immobile in groundwater, there is increasing evidence that the eutrophication of lakes is driven by groundwater discharge rich in phosphorous and that this may be an important albeit so far neglected source [47][48][49][50][51]. For instance, studies of the eutrophic Lake Arendsee (Germany) revealed that groundwater discharge was responsible for more than 50% of the total phosphorus supply to the lake [48].…”

Section: Groundwater-borne Phosphorous Fluxmentioning

confidence: 99%

“…For instance, studies of the eutrophic Lake Arendsee (Germany) revealed that groundwater discharge was responsible for more than 50% of the total phosphorus supply to the lake [48]. The importance of groundwater-borne phosphorous may also hold for oligotroph lakes [49].…”

Section: Groundwater-borne Phosphorous Fluxmentioning

confidence: 99%

Phosphorous Supply to a Eutrophic Artificial Lake: Sedimentary versus Groundwater Sources

Förster¹,

Scholten²,

Schubert

et al. 2021

Water

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The eutrophic Lake Eichbaumsee, a ~1 km long and 280 m wide (maximum water depth 16 m) dredging lake southeast of Hamburg (Germany), has been treated for water quality improvements using various techniques (i.e., aeration plants, removal of dissolved phosphorous by aluminum phosphorous precipitation, and by Bentophos® (Phoslock Environmental Technologies, Sydney, Australia), adsorption) during the past ~15 years. Despite these treatments, no long-term improvement of the water quality has been observed and the lake water phosphorous content has continued to increase by e.g., ~670 kg phosphorous between autumn 2014 and autumn 2019. As no creeks or rivers drain into the lake and hydrological groundwater models do not suggest any major groundwater discharge into the lake, sources of phosphorous (and other nutrients) are unknown. We investigated the phosphorous fluxes from sediment pore water and from groundwater in the water body of the lake. Sediment pore water was extracted from sediment cores recovered by divers in August 2018 and February 2019. Diffusive phosphorous fluxes from pore water were calculated based on phosphorus gradients. Stable water isotopes (δ2H, δ18O) were measured in the lake water, in interstitial waters in the banks surrounding the lake, in the Elbe River, and in three groundwater wells close to the lake. Stable isotope (δ2H, δ18O) water mass balance models were used to compute water inflow/outflow to/from the lake. Our results revealed pore-water borne phosphorous fluxes between 0.2 mg/m2/d and 1.9 mg/m2/d. Assuming that the measured phosphorous fluxes are temporarily and spatially representative for the whole lake, about 11 kg/a to 110 kg/a of phosphorous is released from sediments. This amount is lower than the observed lake water phosphorous increase of ~344 kg between April 2018 and November 2018. Water stable isotope (δ2H, δ18O) compositions indicate a water exchange between an aquifer and the lake water. Based on stable isotope mass balances we estimated an inflow of phosphorous from the aquifer to the lake of between ~150 kg/a and ~390 kg/a. This result suggests that groundwater-borne phosphorous is a significant phosphorous source for the Eichbaumsee and highlights the importance of groundwater for lake water phosphorous balances.

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“…This method is elaborate and prone to errors due to the small head differences, which are difficult to measure (Fritz and Mackley 2010). Ommen et al (2012) used a combination of hydraulic gradients between piezometers and the lake in combination with seepage meters to assess the volume of LGD and infiltration.…”

Section: Introductionmentioning

confidence: 99%

Investigating Groundwater‐Lake Interactions by Hydraulic Heads and a Water Balance

2014

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Discharge of groundwater into lakes (lacustrine groundwater discharge, LGD) can play a major role in water balances of lakes. Unfortunately, studies often neglect this input path because of methodological difficulties in its determination. Direct measurements of LGD are labor-consuming and prone to error. The present study uses both spatially variable hydraulic-head data and meteorological data to estimate groundwater input by LGD and lake water output through infiltration. The study sites are two shallow, groundwater-fed lakes without any surface inflows or outflows. Horizontally interpolated groundwater heads were combined with lake water levels to obtain vertical hydraulic gradients between the aquifer and the lake, which are separated by a thick layer of lake bed sediment which has a much lower hydraulic conductivity than the underlying aquifer. By fitting the hydraulic gradient to the results of a simple mass balance and considering the process of clogging, we were able to estimate the hydraulic conductivity of the lake bed sediments. We calculated groundwater inputs by LGD and lake water outputs by infiltration on an annual basis. Although our method requires several assumptions, the results are reasonable and provide useful information about the exchange between the aquifer and the lake, which can, for example, be used for the calculation of nutrient mass balances.

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Importance of groundwater and macrophytes for the nutrient balance at oligotrophic Lake Hampen, Denmark

Cited by 29 publications

References 41 publications

Fluid circulation and seepage in lake sediment due to propagating and trapped internal waves

Fluid circulation and seepage in lake sediment due to propagating and trapped internal waves

Phosphorous Supply to a Eutrophic Artificial Lake: Sedimentary versus Groundwater Sources

Investigating Groundwater‐Lake Interactions by Hydraulic Heads and a Water Balance

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