Wilson Creek Sub-basin Bacteria, Total Maximum Daily Load, First Water Quality Post-TMDL Monitoring Report
Date published: October 2013
Authors: Bohn, Gregory, and Jane Creech
Reference:
Bohn, Gregory, and Jane Creech. 2013. Wilson Creek Sub-basin Bacteria, Total Maximum Daily Load, First Water Quality Post-TMDL Monitoring Report. Washington State Department of Ecology. Olympia, WA. Publication No. 13-10-043. October.
Abstract:
n 2005, the Washington State Department of Ecology (Ecology) completed the Wilson Creek Sub-basin Bacteria Total Maximum Daily Load (TMDL), which is a water quality cleanup plan for fecal coliform (FC) bacteria in the Wilson Creek sub-watershed, near Ellensburg, Washington.
The Wilson Creek sub-basin is a highly agricultural area, irrigated by many canals and creeks that wind their way through valley. The TMDL found that the highest FC levels in the creeks occurred during the irrigation season.
This report summarizes a follow-up to the earlier TMDL, in which water samples were collected at most of the sites used in the TMDL and were then analyzed for FC. The new data was then compared to the data from the original study. A total of 16 sample sites – three background sites and 13 downstream (non-background) sites – were comparable between the TMDL and this study.
The TMDL identified two types of reduction targets for FC: a geometric mean target and a 90% value target. The current study found that all 16 comparative sites met the first interim TMDL target for the geometric mean. Additionally, 94% of the sampling sites complied with the TMDL’s second interim geometric mean target, due in October 2015.
About 75% of the comparative sites complied with the first interim 90% value target. However, only 6 of 16 (37.5%) of the sites are in compliance with the corresponding second interim 90% value target, due in October 2015. This should accentuate the importance of continued implementation of best management practices (BMPs).
Contact person/agency: Washington State Department of Ecology
File Format: pdf
Associated Data:
Spatial Data
- Summary: Contains the sampling locations that were used in 2005 and/or 2011.
- File Format: ESRI Shapefile
- Coordinate System: WGS 1984
- Contact: Washington State Department of Ecology
