Identifier

etd-0130102-144242

Degree

Master of Science in Civil Engineering (MSCE)

Department

Civil and Environmental Engineering

Document Type

Thesis

Abstract

City Park Lake is a shallow, subtropical, urban hypereutrophic lake located in Baton Rouge, Louisiana. By the late 1970’s, this artificial lake had experienced extreme eutrophication and suffered from frequent algal blooms and fish kills. Restoration of City Park Lake occurred in 1983 and consisted of dredging nutrient-laden sediments and the rehabilitation of sewage pipelines. Pre- and post-restoration water quality monitoring programs have provided valuable information by which to gage the long-term success of the restoration work. Following the restoration effort, dramatic improvements were observed in the lake including lower nitrogen, phosphorus and chlorophyll-a concentrations, reduced frequencies in algal blooms and fish kills, and an increases in the mean depth and oxygen storage capacity of the lake. The shift from phosphorus- to nitrogen-limited conditions following the dredging of sediments was accompanied by the occurrence of filamentous types of algae. Filamentous algae later pre-dominated algal “blooms” during the 1990’s. With little or no implementation of watershed and lake management strategies for the reduction of phosphorus loadings in the decades since restoration, current water quality data indicates that phosphorus levels now approximate those measured during pre-restoration years. The increase in phosphorus concentrations during the post-restoration accompanied by decreasing nitrogen concentrations were further exacerbated by sediment phosphorus release in the decades since restoration and below-normal precipitation since 1998. Organic decay and an increased hydraulic retention time in the lake have resulted in light attenuation that has apparently crippled the growth of filamentous algae in City Park Lake. A phosphorus management model was developed to address filamentous algae in City Park Lake. The calibrated model was used to simulate the sensitivity of the lake to various loading mechanisms. In addition, several phosphorus management strategies were evaluated with the model to estimate short-term and long-term effectiveness.

Date

2002

Document Availability at the Time of Submission

Release the entire work immediately for access worldwide.

Committee Chair

Kelly A. Rusch

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