Benefits and optimization of hypolimnetic withdrawal as a lake restoration technique

Session: 47. - Physical Processes in Lakes

Gertrud Nurnberg, Freshwater Research, [email protected]

Abstract

Hypolimnetic withdrawal is an established lake restoration technique in Europe that has been underused in Great Lake watersheds of North America. Its operating and maintenance efforts are low, because it is based on the damming of surface outflow and discharging of bottom water, thus removing un-wanted substances from the hypolimnion. Since the first application in 1954, hypolimnetic withdrawal has been studied in more than 50 lakes including the deep water withdrawal in large reservoirs, in small man-made ponds, and in remote lakes. Current and new applications include Swedish Bornsjön, the back-up drinking water system for Stockholm Vatten, an urban impoundment in Michigan to treat cyanobacteria blooms, a Californian canyon reservoir, a Canadian agricultural lake, and a project for Finnish Kymijärvi that investigates a novel treatment of the withdrawal water. The comparison of water quality variables before and during treatment indicates decreasing eutrophication in most treated lakes. The current study investigates the working principle of hypolimnetic withdrawal and strives to separate treatment effect from concomitant influences, including external load reduction and climate effects. Potential negative effects of hypolimnetic withdrawal due to influences on the thermal structure of a lake are explored. The importance of treating the withdrawal water is discussed.

1. Keyword
lake management

2. Keyword
phosphorus

3. Keyword
eutrophication

4. Additional Keyword
internal phosphorus load

5. Additional Keyword
physical restoration treatment