Civil Engineering

 

Date of this Version

12-2011

Comments

A THESIS Presented to the Faculty of The Graduate College at the University of Nebraska In Partial Fulfillment of Requirements For the Degree of Master of Science, Major: Civil Engineering, Under the Supervision of Professors Bruce I. Dvorak and David M. Admiraal, Lincoln, Nebraska: December, 2011. Copyright 2011 Jake Ross Fisher.

Abstract

Water quality monitoring was conducted in two urban watersheds (Colonial Hills and Taylor Park) located in southeast Lincoln, NE over a three year period spanning from October 2008 through September 2011. In-line probes continuously measured for turbidity, conductivity, dissolved oxygen, and water temperature while other water quality constituents were analyzed for discrete water samples collected using grab and automatic sampling techniques. The water quality data was used to calculate event mean concentrations (EMCs) for sixteen storm events sampled over the duration of the project period. Three types of stormwater quality multiple linear regression models were developed for the estimation of the discretely measured parameters: (1) continuous concentration models using in-line probe and flow data along with climatic data as explanatory variables; (2) EMC models using only climatic data as explanatory variables; and (3) EMC models using in-line probe EMCs along with climatic data as explanatory variables.

Statistically significant multiple linear regression continuous and EMC models resulted for six water quality constituents (i.e., total suspended solids, soluble reactive phosphorus, total phosphorus, nitrate plus nitrite nitrogen, total kjeldahl nitrogen, and E. coli). Generally, the addition of an in-line probe variable in the EMC models improved the model fit over climatic-only EMC models. The results suggested continuous models may be beneficial to urban watershed management through the recognition of important physical watershed characteristics. Because stormwater runoff concentrations change so rapidly in small urban watersheds, the continuous models provided an increased potential to recognize rapid, in-storm changes due to site-specific characteristics. Differences in 2010 mass loading trends for TSS between the two sites during large and small precipitation events suggested that different physical processes were at work (e.g., stream bank erosion may be an important contributing factor during large storm events within the Colonial Hills watershed).

Advisers: Bruce I. Dvorak and David M. Admiraal

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