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Newsletter and Technical Publications
<Planning and Management of Lakes and Reservoirs:
An Integrated Approach to Eutrophication
Abridged Version- A Student's Guide>

Lake Restoration Methods

A detailed overview of methods applicable to aid recovery of lakes is given in EITC's Technical Publication Series number 11. A summary of restoration methods is given in Table 4, and a few important, relatively cost-moderate, methods are mentioned below.

Siphoning of hypolimnetic water requires installation of a suitable pipeline from the bottom of the lake to the outlet. The method is not recommended if there are downstream lakes unless the water is treated. It is only applicable to lakes with a thermocline (or halocline) for a significant period.

Harvest of macrophytes is recommended, particularly in cases where the macrophytes can be used to feed domestic animals or for production of methane. Herbicides should not be applied as they contaminate water and biota.

Biomanipulation, i.e., removal of small fish feeding on zooplankton and stocking of carnivorous fish, is another cost-moderate method that is only effective in the total phosphorus range of 0.05-0.15mg/l. However, the potential hazards of introduced species must be carefully considered.

Sediment remediation can be carried out either by in situ methods or by removal of the sediment from the bottom of the lake or reservoir. In in situ remediation, air, or a mixture of air and oxygen, is pumped and released at the sediment-water interface to eliminate anoxia in the bottom water. Capping sediments with clean material is one technique for sediments polluted with metals and organic compounds. Chemical treatment has been used to immobilize phosphorus at the sediment-water interface. Additions of chemicals, such as ferric chloride and calcium nitrate, to the sediments can be used as chemical treatment. However, the treatment must be designed for a specific lake.

Table 4. Methods for restoration of lakes and reservoirs.
Method Application Costs
In situ precipitation often not applicable to shallow lakes low
Removal of sediment limited to shallow lakes very high
Algicides not recommended medium
Coverage of sediment general medium-high
Shading by trees has only long-term effects for small lakes very low
Wetlands removal of nutrients from inflow water medium
Aeration only applicable to lakes with thermocline high to very high
Siphoning only applicable to lakes with thermocline medium, high if P- removal is required
Biomanipulation only in the P-range 0.05-0.15 mg/l usually low
Diversion the problem is moved not solved case dependent



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