Date of Award:

12-2011

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Civil and Environmental Engineering

Committee Chair(s)

Darwin L. Sorensen

Committee

Darwin L. Sorensen

Committee

Jeffery S. Horsburgh

Committee

Nancy O. Mesner

Abstract

This study was conducted to provide new and useful data about Pineview Reservoir and its watershed, produce water and phosphorus (P) budgets for Pineview Reservoir, test the validity of conclusions made in the Pineview Reservoir Total Maximum Daily Loading (TMDL) document, and create estimates of nitrogen (N) loading to the reservoir from both surface and ground water sources. The production of the water and P budgets, as well as the N loading estimates, was accomplished by measuring flow, nitrate, ammonium, total phosphorus (TP), and soluble reactive phosphorus (SRP) that was entering and exiting the reservoir through surface water sources and the reservoir outlet over a period of approximately 2 years (2008 to 2010). Estimates of ground water contributions to the reservoir were also made using ground water P and N concentration data from a parallel study and ground water flow estimates from the literature. In order to test the validity of claims made in the TMDL, internal reservoir parameters such as temperature, dissolved oxygen, TP, orthophosphorus (OP), nitrate, ammonium and dissolved iron (Fe) were measured at the surface, thermocline, and hypolimnion of five sampling locations within the reservoir over the same sampling period. Chlorophyll A was also measured near the surface of the sites during each sampling event. Contrary to the conclusions made by the TMDL it was found that the internal cycling of nutrients, especially P, is occurring in Pineview Reservoir and that annually observed phytoplankton blooms can be attributed to the release of benthic nutrients. It was also found that there is a large store of sediment P that is currently or potentially could be made available for transfer into the water column. It was estimated that 14,800 kg of P was exported from the reservoir over the one-year sample period of 4/15/2009 to 4/14/2010. This large P release is due to the practice of exporting P rich hypolimnetic water throughout the summer irrigation season. It was shown that more P could be exported if outflows were increased during this period. P budgets indicated that P may not currently be building up within Pineview Reservoir, but given the limited amount of ground water data available for the Reservoir’s watershed, further ground water flow and nutrient data are necessary to substantiate this claim. This study has helped to provide a clearer picture of the trophic status and internal P cycles of Pineview Reservoir. It has also helped to answer questions about the reservoir that have been overlooked in previous studies, such as the magnitude of internal P loading and the importance of Spring Creek and Geertsen Creek in the reservoir’s water budget. This and other information gathered during this study could prove to be a useful benchmark for measuring the effectiveness of future efforts to improve water quality in the reservoir.

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Comments

Publication made available electronically January 24, 2012.

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