Graduation Year

2006

Document Type

Thesis

Degree

M.A.

Degree Granting Department

Geography

Major Professor

Robert Brinkmann, Ph.D.

Keywords

Eutrophication, limnology, BATHTUB, Harmful algal blooms, Reservoirs

Abstract

This work explores the relationship between nutrient loading and changes in water quality in a sub-tropical, above-ground, off-stream municipal water supply reservoir, the C.W. Bill Young Regional Reservoir. The three source waters for the reservoir have varied but high levels of nutrients such as phosphorus and nitrogen. In other reservoirs, these nutrients have been linked to deterioration of water quality and increased expense in water treatment. The need to minimize excess nutrients results led to the primary research question: what allocation of withdrawals from the three sources will minimize the deterioration of water quality? To answer this question, the relationship between nutrient and other water quality data, such as temperature,phosphorus, chlorophyll a, Secchi depth, and trophic state indices were explored. Results indicate that temperature had a correlation with observed water quality.

27.9% of the variability in trophic state index as a function of Chlorophyll a was correlated with average temperature at one foot below water level. Correlation and regression models were developed using available time-series of linear and log-transformed water quality data to predict Chlorophyll a response. The parameters used in the model were selected from correlation matrices and from the P value in the multiple regression. The models developed were significant at P < 0.05. In the developed models, temperature was found to have greater predictive strength than nutrients indicating that this reservoir may be more strongly influenced by season and light than by nutrient limitation. Lastly, the US Army Corps of Engineers' eutrophication model, BATHTUB, was used to simulate different loading conditions and trophic response.

The model results indicate that use of water the middle pool or lower pool of the Tampa Bypass Canal yield similar trophic states with the middle pool slightly lower. Use of water from the Alafia River yielded the highest trophic state and would be expected to have negative impacts on water quality.

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