Multi-scale landscape factors influencing stream water quality in the state of Oregon

• Published in: Environmental monitoring and assessment 2009-09, Vol.156 (1-4), p.343-360
• Main Authors: Nash, Maliha S, Heggem, Daniel T, Ebert, Donald, Wade, Timothy G, Hall, Robert K
• Format: Article
• Language: English
• Subjects: Animal, plant and microbial ecology; Animals; Applied ecology; Applied sciences; Atmospheric Protection/Air Quality Control/Air Pollution; Bacteria; Biological and medical sciences; Cattle; Earth and Environmental Science; Ecology; Ecotoxicology; Ecotoxicology, biological effects of pollution; Enterococcus; Enterococcus - isolation & purification; Environment; Environmental Management; Environmental monitoring; Environmental Monitoring - methods; Exact sciences and technology; Feces; Freshwater; Freshwater ecology; Fundamental and applied biological sciences. Psychology; GPI; Grazing; Grazing potential index; Human influences; Humans; Land cover; Land ownership; Land use; Landowners; Landscape; Landscapes; Livestock; Logistic Models; logit analysis; Mathematical models; Monitoring/Environmental Analysis; Nitrogen; Nitrogen - analysis; Nutrients; Oregon; Pathogens; phosphorus; Phosphorus - analysis; Pollution; Regression analysis; Rivers - chemistry; Rivers - microbiology; Runoff; Sediments; Spatial distribution; Stream banks; Stream water; Streams; Studies; Surface water; Surface water data; Thresholds; United States; Urban agriculture; Urban areas; Vegetation; Vegetation cover; Water - analysis; Water Microbiology; Water quality; Watersheds; Wetland agriculture
• ISSN: 0167-6369; 1573-2959
• DOI: 10.1007/s10661-008-0489-x

Enterococci bacteria are used to indicate the presence of human and/or animal fecal materials in surface water. In addition to human influences on the quality of surface water, a cattle grazing is a widespread and persistent ecological stressor in the Western United States. Cattle may affect surface water quality directly by depositing nutrients and bacteria, and indirectly by damaging stream banks or removing vegetation cover, which may lead to increased sediment loads. This study used the State of Oregon surface water data to determine the likelihood of animal pathogen presence using enterococci and analyzed the spatial distribution and relationship of biotic (enterococci) and abiotic (nitrogen and phosphorous) surface water constituents to landscape metrics and others (e.g. human use, percent riparian cover, natural covers, grazing, etc.). We used a grazing potential index (GPI) based on proximity to water, land ownership and forage availability. Mean and variability of GPI, forage availability, stream density and length, and landscape metrics were related to enterococci and many forms of nitrogen and phosphorous in standard and logistic regression models. The GPI did not have a significant role in the models, but forage related variables had significant contribution. Urban land use within stream reach was the main driving factor when exceeding the threshold (>=35 cfu/100 ml), agriculture was the driving force in elevating enterococci in sites where enterococci concentration was