Lake restoration with and without dredging of phosphorus-enriched upper sediment layers

Abstract

Human activity has been the cause of continuing decline of water quality in most Dutch lakes. Development of lake restoration programmes must take into account the lake functions. Major reduction of the nutrient and pollutant loading is the primary step in lake restoration. Still, the recovery of eutrophic lakes is retarded frequently because of internal phosphorus loading by the lakes' sediments. Sediment dredging, as an additional tool for water quality management to accelerate accomplishing the desired water quality, is studied. In this paper we evaluate the preliminary results of eight lake restoration projects in the Netherlands. The lakes are compared in order to estimate the magnitude of the internal phosphorus loading. Dredging as an additional measure was carried out twice in the peatlake Geerplas. In the Nieuwkoop Lakes only the external phosphorus loading was substantially reduced from 0.9 to 0.2 g P me2 y-'. Provisional results of these two shallow peatlake restoration projects focussed on eutrophication abatement with and without dredging, are presented. Both show a decrease in phosphorus concentration in the lakes. The necessity to dredge the lakes is discussed.

Eutrophication, phase shift, the delay and the potential return in the Greifswalder Bodden, Baltic Sea

“…This approach has been successful in shallow lakes (Kleeberg and Kohl, 1999;Phillips et al, 1999) und would probably help lower the concentration of available phosphate in the Greifswalder Bodden. In studies of (Van Der Does et al, 1992;Van Liere and Gulati, 1992) sediment dredging lead to a marked reduction in phosphate concentration in the upper sediment accompanied by a reduced phosphorus release into the water column and a decline in phytoplankton concentration. However, lake restoration programs showed that sediment removal alone could not provide long-term changes without additional restoration measures (Ryding, 1982;Boers et al, 1992;Kleeberg and Kohl, 1999;Phillips et al, 1999), and they are an expensive restoration tool.…”

“…In studies of (Van Der Does et al, 1992;Van Liere and Gulati, 1992) sediment dredging lead to a marked reduction in phosphate concentration in the upper sediment accompanied by a reduced phosphorus release into the water column and a decline in phytoplankton concentration. However, lake restoration programs showed that sediment removal alone could not provide long-term changes without additional restoration measures (Ryding, 1982;Boers et al, 1992;Kleeberg and Kohl, 1999;Phillips et al, 1999), and they are an expensive restoration tool. Treatment with aluminium-sulfate to bind phosphorus from the sediment (nutrient inactivating) has been successful in reducing the concentration of available phosphorus and improving trophic state (Cooke et al, 1986).…”

Restoration and resilience to recovery of the Lake Loosdrecht ecosystem in relation to its phosphorus flow

“…With significant downward seepage in the lake, the chemical would also move out of the system in weeks or months when the aerobic layer is mixed with the anaerobic part by wind. In a whole lake experiment in a comparable lake, the addition of iron(III)-chloride also failed to improve water quality (Boers et al, 1992).…”

Eutrophication control strategies for three shallow Vecht lakes in the province of North Holland

“…Since 1986 when the waste water treatment plant in the Horstermeer polder became operational, the phosphorus dynamics (sedimentation and release) at the sediment is the most important item in the lakes' phosphorus balance. Therefore, dredging of the lakes' nutrientloaded bottom sediment will be the most effective measures to reduce eutrophication ( Van der Does et al, 1992). A pilot-dredging project in this regard is to commence shortly.…”