Sediment sluicing at LSU University Lake – A proposal for combating urban lake siltation and nutrient enrichment

Abstract                                                                                                 

Many urban lakes are faced with the twin problems of siltation and nutrient enrichment from the runoff of the watersheds. The accumulation of soil and organic particles can exacerbate internal release of nutrients, leading to a degradation of water quality and to the impairment of designated uses. When the water quality issue becomes imminent, dredging of the lake-bottom sediments is often used. However, dredging can be extremely costly, as well as undesirable when a popular lake in a highly urbanized area must be dried out for an extended period of time. The LSU University Lake is a prime example of the situation. Since it was last dredged about 30 years ago, the 184-acre lake has silted up and much of the open water area has become shallower than 2.5 feet (Xu & Xu, 2015). Our water quality monitoring at the lake has shown a considerable increase of nitrogen and phosphorus in the past five years (Xu & Xu, in press). The concentration of chlorophyll a during the summer months has increased by 3-6 times, causing long-hour supersaturation of dissolved oxygen in the lake. Based on the current condition, this lake can be classified as hypereutrophic. The Baton Rouge Area Foundation has recently contracted a group of firms to create a master plan for the restoration of the lake. As a chief solution, dredging of ~800,000 cubic yards of the lake bottom sediments is being proposed. However, cost of such a large-scale dredging project would easily amount to over $100 million, which no agency or private entity would see as realistic. Apart from the unrealistic cost, dredging does not provide a sustainable solution; in other words, should we dredge the lake again in another 30 years when it silts up? Here I propose an engineering solution, sediment and nutrient sluicing, which will cost only a tiny fraction of the amount a dredge project would cost; Yet, the solution will work long term and effectively in reducing both sediment and nutrient accumulations. My presentation will show the current water quality conditions at the LSU University Lake and will discuss the sediment sluicing proposal for combating the problems. 

References:

Xu, Z. and Y.J. Xu. 2015. Rapid field estimation of biochemical oxygen demand in a subtropical eutrophic urban lake with chlorophyll a fluorescence. Environmental Monitoring and Assessment, DOI 10.1007/s10661-014-4171-1.

Xu, Z. and Y.J. Xu. (in press). Determination of trophic state changes with diel dissolved oxygen: A case study in a shallow lake. Water Environment Research.