Document Type

Thesis

Date of Degree Completion

Fall 2020

Degree Name

Master of Science (MS)

Department

Cultural and Environmental Resource Management

Committee Chair

Clay Arango

Second Committee Member

Jennifer Lipton

Third Committee Member

Anthony Gabriel

Abstract

Water in Kittitas County is extremely valuable since it supports farming, recreation, and cultural activities, as well as environmental processes and a diversity of biological life while providing many ecosystem services. However, land conversions required by agricultural and urban land uses can negatively impact water quality and the biological function of the stream. I studied how forested, agricultural, and urban land use affect six streams. Fourteen sites were sampled, once each in July, August, and September 2019. Land use was calculated as a percentage of forested, agricultural, and urban land use within a 100-m buffer of the stream, upstream of the sample site. Measurements of the streams at the sample sites, including thalweg depth, discharge, bank full width, and a substrate analysis, were taken as well as temperature, pH, and dissolved oxygen. Suspended sediment, specific conductivity, and turbidity were also determined, and samples were collected to measure ammonium, nitrate, and phosphate concentrations. An analysis of EPT percentage and HBI scores for aquatic benthic macroinvertebrates were used to infer biological condition. I found that land use had a significant effect on depth, discharge, temperature, specific conductivity, nitrate, phosphate, EPT, and HBI. Agricultural and urban land uses had deeper channels with high flows, and high temperatures. Temperatures in agricultural and urban land uses never went below 13°C and had the highest peak at 21°C, while forested sites had a low temperature at 10°C and never went above 14°C. Also, I found that nitrate and phosphate concentrations, as well as HBI, were highly correlated with a higher percentage of agricultural and urban land use. High EPT percentages were highly correlated with high forested land use. Management recommendations include best management practices (BMPs) for different agricultural and urban sites. These BMPs are targeted to reduce nutrient inputs and increase habitat heterogeneity for the restoration of sensitive macroinvertebrates. Overall, this study highlights how land use is associated with degraded stream habitat showing the biological consequences observed in the aquatic macroinvertebrate community in Kittitas county.

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