irrpren Quality in the State of Orecion: Likelihood of animal pathogenic presence using enterococci Maltha S. Nasik*, Thmefliy G. Waief, Daniel T. Bfeggeim% Robert K, Hal*, & Donald Ebert* *U.S. EPA, P.O. Box 93478, Las Vegas, Nevada 89193-3478, USA (nash.maliha@epa.gov) fU.S. EPA, E243-05, Research Triangle Park, North Carolina 27711, USA Introduction Livestock grazing is a widespread and persistent ecological stressor in the western United States. Livestock impact surface water quality by introducing nutrients and bacteria, and by damaging stream banks or removing vegetation cover leading to increased sediment loads and tempera- tures. The objective of this study is to test the viability of grazing potential index (GPI) (Heggem et al. 2004) to predict spatial distribution and concentration of animal born bacteria (enterococci). GPI is an index that uses Geographic Information Systems (GIS) to identify locations likely to support grazing. It is based on distance to water, forage availability and land ownership. Further analyses are underway to investigate spatial distribution of livestock and its relationship to landscape metrics (e.g., percent riparian cover, natural cover, etc.) and surface water nitrogen and phosphorous loadings. Study Area Description Oregon state encompasses 251,415 km2 in surface area with a wide range in elevation and vegetation cover from the coast on the west to the dry- land in the east (Figure 1). Elevations range from the sea level at the coast to 3,426 m (11,100 ft) at Mount Hood. Climate data for the state of Oregon spanning the last 100 years, indicates wet/dry cycles of 20- 30 years. Dry periods were noted in the years from 1920 through 1945 and from 1975 through 1994. A wet cycle appears to have begun in 1994. Wafer 8J»si4y BSafeis Environmental Monitoring and As- sessment Program (EMAP) water data were obtained for the years 1990 through 1994 to coincide with the 1992 remote sensing data (National Land Cover data; NLCD). Only water quality data for the growing season (June — September) were used. To ensure adequate coverage of temporal and spatial water data, a site with at least two years of measurements (n = 197) were extracted from the Oregon EMAP project and used for the analyses of enterococci. General linear model (proc GLM in SAS) and Arc View were used for analyses and presentations of results. Recently, EPA (1986) recommended using enterococci bacteria to in- dicate the presence of human and/or animal fecal materials. Water is safe for drinking when a single sample contains no more than 104 colony-forming units (cfu) per 100 ml or when the geometric mean of multiple samples (minimum time interval of 24 hours) is less than 35 cfu/100 ml for freshwater. From the 197 sample sites, 25% (49 sites) exceeded the standard geometric mean (35 cfu/100 ml, Figure 2). These sites were further investigated to identify trends over time (increasing/decreasing). Increasing or decreasing enterococci concentration at a site may represent the impact of livestock presence or absence in the area. A total of 35 sites exhibited a positive or negative trend; only 13 sites had a significant positive trend and one site had a significant nega- tive trend (Figure 2). The relationships of enterococci and water temperature, dissolved oxygen, organic ni- trogen, total nitrate, total nitrite, total phosphate, and dissolved phosphate were studied in sites where the overall geometric mean of the enterococci was higher than 35. The relationships for a few of the sites are presented in Table 1. Figure 3 shows the GPI (2003) map and enterococci sites in the Johnson Creek South at Glenbrook River Mile 1.1. Although the geometric mean for the enterococci concentra- tion is high (840 cfu/100 ml), the trend of enterococci over time is decreasing signifi- cantly. In spite of a positive trend (not significant) in temperature and nitrogen com- pounds, the significant positive trend in the dissolved oxygen may indicate improving conditions at this site. This site is within a low GPI area. Red and orange dots indicate sites with a geometric mean of enterococci more than 35 cfu/100 ml located mostly within areas of high GPI (Figure 3). Fig 3. 2003 grazing potential index map. ^Joh-isor Creek tbli.r dot) Figure 1. 1992 national landcover (30 m) for the study area. Fig 2. Trend direction in sites where the geometric mean of enterococci concentration is highterthan 35 cfu/100 ml. Table 1. Overall geometric mean of the enterococci concentration (cfu/100 m), temporal trend for the eneterococci, and direction of relationships between enterococci and other surface water measurements for selected sites. Discussion We presented a simple method as a means to validate the GPI by synchronizing the likelihood of livestock presence from the GPI map with that of high values of entero- cocci concentrations in surface water (Figure 3). Enterococci data were used to accomplish one of our objectives; that is to examine the temporal trend in enterococci in an effort to link the behavior with that of the human and/or livestock. This method may be useful as a targeting tool to identify priority areas for implementation of Best Management Practices (BMP) to prevent or reduce the runoff and transportation of animal waste to surface water as a means for improving/ preserving the quality of surface water in the western part of the USA. Acknowled g m ent s We are very grateful to Tony Selle, Scott Augustine and Peter Leinenbach for their input and discussions. Reference Heggem D.T., T.G. Wade, P. Leinenbach, S. Augustine, A JR. Selle, A Calderon, J.M. Viger, KA Hermann, R.K. Hall, A. Weiss, and V Haack. 2004. Demonstration of Potential Grazing Impact to Water Quality in the Western United States. Poster presentation, EPA 2004 Science Forum, Healthy Communities and Ecosystems, June 1-3, 2004, Washington, DC, USA. U.S. EPA. 1986. Ambient water quality criteria for bacteria-1986. EPA-A440/5-84-002. U.S. Environmental Protection Agency, Washington, DC. Notice: Although this work was reviewed by EPA and approved for publication, it may not necessarily reflect official Agency policy. Mention of trade n; ir commercial products does not constitute endorsement or recommendation by EPA for u ------- |