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Date Permissions Signed
Date of Award
Master of Science (MS)
Matthews, Robin A., 1952-
Bodensteiner, Leo R., 1957-
Helfield, James M.
Nonpoint source pollution is a concern in many streams nationwide. Puget Sound cleanup efforts have increasingly focused on targeting nonpoint sources of pollution, including nutrient and bacterial sources resulting from agricultural activities. Skagit County, Washington hosts a robust compilation of agricultural activities from large scale row crops and dairy operations to small hobby farms. It is also home to the Skagit River, the most important river system for Puget Sound salmon, and Samish Bay, the largest shellfish growing area in the north Puget Sound. Enormous efforts have been made to assess the health of Washington's waterways and to find an effective way to ensure clean water without threatening the historic agricultural sector. The Skagit County government established a monitoring program in 2003 for the express purpose of assessing agricultural effects on streams. Surface water quality data from 40 sites on 28 streams, collected from 2003-2011 as part of this program, were used in these analyses. The objective of this research was to augment Skagit County water quality reports in order to determine the influence of agricultural land-use and precipitation on regional surface water quality. Median fecal coliforms, salinity, and turbidity were higher at sites at the downstream end of agricultural areas as compared with upstream sites, and dissolved oxygen concentrations were lower. Sites downstream from agricultural activities were more likely to have detectable levels of total suspended solids, orthophosphate, ammonium, and total Kjeldahl nitrogen than midstream, upstream, or reference sites. Precipitation was only correlated with fecal coliforms at a quarter of the sites, though precipitation events were associated with higher median fecal coliforms at downstream sites. Land-use characteristics were more deterministic of median fecal coliforms than were inherent watershed characteristics.
Western Washington University
Skagit County (Wash.)
Copying of this thesis in whole or in part is allowable only for scholarly purposes. It is understood, however, that any copying or publication of this thesis for commercial purposes, or for financial gain, shall not be allowed without the author's written permission.
Carruthers, MarySutton, "An analysis of agricultural land-use effects on surface water quality in Skagit County streams" (2012). WWU Graduate School Collection. 250.