Date of Award:

2013

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Civil and Environmental Engineering

Advisor/Chair:

Jeffery S. Horsburgh

Abstract

The quality of water of our nation’s rivers and streams is important to many vital uses including drinking water treatment, recreation, and the natural environment. Water quality can be severely impacted by the quantity and type of suspended sediment found therein. Because suspended sediment can be associated with many other contaminants that degrade water quality, it is noted as the most common impairment to water quality in the United States. Suspended sediment can cause significant ecological impacts to the chemical and biological characteristics of surface waters. The ability to accurately quantify suspended sediment concentrations at the appropriate time(s) and location(s) is critical in assessing whether streams are meeting their designated beneficial uses and in implementing and evaluating watershed management and mitigation plans and restoration efforts. Currently, new methods for quantifying suspended sediment concentrations use mathematical and statistical techniques to relate turbidity and suspended sediment and have been shown to be affected by several factors, including the size and characteristics of suspended sediment particles. In this research we used turbidity as a surrogate (substitute) for suspended sediment at six locations in the Little Bear River, Utah, U.S.A. We also examined the differences between single-point and width and depth integrated suspended sediment sampling at two sites. This was used to develop a method to account for the differences and improve the resulting estimates of suspended sediment concentrations. Statistical techniques were used to assess—in probabilistic terms—the duration and magnitude of potential water quality criteria exceedance. Findings highlight that among some monitoring locations with wide geographic distances, turbiditysuspended sediment relationships are not site-specific for the more frequent (90th percentile) but lower (<50 NTU) turbidity values. Comparisons of point measures of turbidity and width and depth integrated suspended sediment samples revealed that suspended sediment is homogenous at their respective stream cross sections for 90% and 99% of the time at sites 2 and 6, respectively. The results are applicable to water managers who are charged with the determination of attainment or exceedance of water quality standards.