title: Dairy Farming and the Effects of Agricultural, Nonpoint-source Pollution on Stream Water Quality, Johnson Creek Watershed, Whatcom County, Washington
Creators: name: Wills, Max Thomas
Publisher: name: Western Washington University
Year: 1998

description: <p>The Johnson Creek watershed, which supports one of the highest densities of dairy farms in Washington State, suffers from degraded stream water quality, primarily in the form of high fecal coliform concentrations, elevated nutrients, and low levels of dissolved oxygen. Despite the implementation of best management practices (BMPs) over the past two decades, poor stream water quality has persisted. The Washington State Department of Ecology (DOE) is therefore required under section 303(d) of the federal Clean Water Act, to establish a Total Maximum Daily Load (TMDL) policy for the basin as a means of remediating the impaired water bodies. The current project was undertaken to assist DOE with this task by conducting a water quality study to determine the present quality of the surface waters and determine the location and mode by which farm waste enters the stream. BMP effectiveness was also reassessed by conducting historical water quality comparisons.</p>
<p>Currently, stream water quality within the watershed remains impaired by fecal coliform, ammonia, nitrates, phosphates, and dissolved oxygen. An examination of standard box plots shows a redundant pattern of water quality impairment at specific sampling sites, indicating the general location of potential source areas. Box plots arranged by sampling date also show that stream water quality is most severely impaired during the wettest portion of the year and tends to improve as precipitation diminishes through the summer months. This suggests that runoff from fertilizer-laden fields is the primary mode by which dairy waste enters the stream. Stream water models, constructed to predict nutrient transport, confirm the box plot interpretations and show, through a process of load-accounting, that the majority of the nutrient loading originates from specific dispersed (nonpoint) source areas.</p>
<p>Historical comparisons of median data values, substantiated with Maim-Whitney hypothesis testing, showed decreasing trends for ammonia and fecal coliform concentrations, and improvements in the dissolved oxygen levels over the past 20 years, indicting BMPs have been at least partially successful at preventing the direct input of farm waste into the stream. Numerous farms within the basin, however, are presently operating without up-to-date farm waste management programs and a correspondence was found between these operators and the portions of the stream identified as farm waste input source areas. In addition, increasing trends were observed for nitrates and phosphates, which corresponds with a nearly two fold increase in the total herd size and subsequent manure production within the basin over the last two decades.</p>
<p>To approach stream water quality compliant with state and federal regulations, at a minimum, all of the dairies operating within the watershed need to adhere to prudent waste management techniques. To attain complete water quality compliance, future regulatory policies within the Johnson Creek watershed may need to be more intrusive and could include herd size caps, a moratorium on winter manure spreading, or the establishment of a stream buffer.</p>