Oregon Department of Environmental Quality
Date of Award
Master of Environmental Management (MEM)
Environmental Science and Management
Water -- Pollution -- Total maximum daily load -- Oregon, Water quality -- Testing, Amazon Creek Watershed (Or.), Water quality -- Management
In this project, I analyzed the status and trends of water quality data describing fecal bacteria (E. coli) and DO in the Amazon and Coyote Creek watersheds of the Southern Willamette Valley, Oregon. I also examined TMDL implementation plans produced by DMAs, determined if and how implementation activities corresponded to changes in water quality, compared management and planning of DMAs in the watersheds, discussed aspects of the current TMDL, and compared state regulations and standards in other states. I concluded by making management recommendations to better facilitate future status and trend analysis.
Amazon Creek, Amazon Diversion Channel, A-3 Drain, and Coyote Creek are listed year-round on Oregon’s Category 4A 303(d) list for exceeding State bacteria criterion for E. coli. Upper Amazon Creek, Amazon Diversion Channel, and Coyote Creek are listed on Oregon’s 303(d) Category 4A list for exceeding the State DO criteria. These stream segments were separated by watershed (Upper Amazon Creek, Lower Amazon Creek, and Coyote Creek) and analyzed at each sample station and as a whole with available data.
Ultimately, the lack of data hindered my status and trend analyses. However, existing data indicated Upper Amazon Creek and Coyote Creek continue to be impaired for DO, while DO concentrations in Lower Amazon Creek have increased above state single sample exceedance criterion for cool water (5.0 mg/L). The current protocol for monitoring bacteria and DO in these streams makes detecting exceedances difficult. The sample stations and seasons which are near exceedances can only be assumed to exceed 7-day criterion because grab sampling does not necessarily capture the lowest level of DO nor the highest level of bacteria concentration on the day of sampling. Sparse grab samples only convey instantaneous measures, which makes detailed assessments of seasonal or annual trends in water quality incomplete.
Coyote Creek had not been tested for TMDL-related water quality parameters since 2003 until sample collection was conducted as part of this project by ODEQ during the summer of 2015. Data obtained through the 2015 collection could therefore only be used to help inform the current status of water quality. Furthermore, the A-3 Drain allocated bacteria concentration reduction set by ODEQ (decrease 33%) was determined from data taken during December of 2002. The allocated reduction percentage was difficult to analyze due to the season which reduction was calculated for. Bacteria concentration reduced by 48% overall, on average, when comparing data collected before and after 2008, but when comparing data collected after December of 2002 until present, during late October through the end of December, E. coli concentration only decreased by 3%. It is recommended that the TMDL be reassessed to minimize any confusion toward the allocated reduction percentages.
DMAs in the Amazon and Coyote Creek watersheds have implemented BMPs or water quality management actions for decades prior to TMDL issuance, and have continued those actions. Therefore, analyzing and linking any water quality trends before and after the 2008 TMDL could not be directly attributed to specific implementation activities. The paucity of data and sample stations also minimized the ability to understand pollutant sources, loading locations, and trends in water quality data. If data are to be used to assess water quality status and trends or determine if TMDL implementation activities are achieving load allocations, sampling procedures and requirements in both Amazon Creek and Coyote Creek watersheds needs to be improved. Neither Amazon Creek nor Coyote Creek had flow measurements. Without flow measurements, agencies cannot assess where specific loading is occurring nor whether certain areas are affected during high flow events or low flow events. Using seasonality as a surrogate for flow measurements does not portray possible rain or system flush events.
Based on my analysis, I recommend that TMDL implementation plans require DMAs to describe specific responses anticipated for implementation activities and timelines for attainment to each implementation activity. This would help ODEQ as well as DMAs assess implementation success and areas for improvement. In order to fully achieve these objectives, updates to ODEQ and DMA data collection requirements for 303(d) listings are needed by increasing data collection and the number of sampling sites.
Zydek, Stosh, "Assessment of TMDL Implementation and Water Quality Status and Trends in Amazon Creek and Coyote Creek Watersheds" (2016). Master of Environmental Management Project Reports. 49.