Date of Graduation

12-2011

Document Type

Thesis

Degree Name

Master of Science in Biological Engineering (MSBE)

Degree Level

Graduate

Department

Biological and Agricultural Engineering

Advisor/Mentor

Haggard, Brian E.

Committee Member

Scott, J. Thad

Second Committee Member

Costello, Thomas A.

Keywords

Applied sciences; Earth sciences; Water quality trends; Watersheds

Abstract

Northwest Arkansas contains two Section 319 Priority Watersheds that the Arkansas Natural Resources Commission (ANRC) has identified as being impacted by point and nonpoint sources of pollution (i.e., phosphorus, nitrogen, and sediment), and the Arkansas Water Resources Center (AWRC) has monitored the water quality at several sites within these watersheds. Water-quality data has been collected over the last decade within the Illinois River Watershed (HUC #11110103) and the Upper White River Basin (Beaver Reservoir HUC# 11010001), each watershed containing three sampling sites. The Illinois River Watershed sites are located on the Illinois River, Osage Creek, and Ballard Creek, and the Upper White River Basin sites are located on the West Fork of the White River, White River, and Kings River. The objective of this study was to determine monotonic water quality trends at these six sites from water-quality data accumulated between 1997 and 2010. Specifically, the study used flow-adjusted constituent concentrations (i.e., SO4, Cl-, NO3-N, TN, NH4-N, SRP, TP, and TSS) to examine long term trends in the water-quality data with parametric (i.e., linear regression) and non-parametric (i.e., Seasonal Kendall test and Sen's slope estimator) statistical techniques. The goal was to understand if constituent concentrations have increased, decreased, or not changed over time. These changes in water quality were then compared with changes in watershed management as to suggest how certain actions have influenced these streams and rivers. Overall, TN, SRP, TP, and TSS have shown significant decreases in flow-adjusted concentrations (FACs) across these two watersheds over the defined study period, based upon both statistical approaches. The decrease in phosphorus was likely the most important observation, because most water quality concerns in this region have focused on elevated phosphorus concentrations in these trans-boundary watersheds.

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