Seasonal and Urban Signatures of Fecal Contamination on the Provo River

Escherichia coli and coliform bacteria are consistently used as indicators of fecal contamination in water, but contamination monitoring efforts are generally concentrated on urban sites in the spring and summer, disregarding potential variation associated with time, urbanization, or built infrastructure. After the Provo River originates in the Uinta Mountains, its middle section passes through rapidly urbanizing areas. To assess how land use and seasonal change affect fecal bacteria concentrations in the middle Provo River, we evaluated E. coli density, coliform bacteria density, and water characteristics along the river’s urbanization gradient. We measured E. coli and coliform bacteria with IDEXX Colilert Quanti-Trays, and water chemistry (including temperature, dissolved oxygen, and turbidity) with real-time sensor technology at four locations spanning the Provo’s mountain-to-urban transition twice a month. Unexpectedly, we found that E. coli and coliform bacteria density was highest in the summer at the montane site (298 ±153 colony forming units (cfu), and 1562 ±403 cfu, respectively) and relatively high below the Jordanelle Dam (119 ±59 cfu, 1266 ±327 cfu). Although neither of these measurements exceed the Utah Division of Water Quality standard for drinking water or primary contact recreation (668 cfu), our results suggest that active wildlife in high elevation sites may contribute significantly to fecal contamination and reservoirs may do little to curb fecal contamination and may actually act as fecal bacterial incubators under warm temperatures. One urban site also contained high levels of E. coli and coliform bacteria in the spring (204 ±104 cfu, 1508 ±596 cfu) and fall (49 ±20 cfu, 1085 ±296 cfu). This site was punctuated by another monitoring site following the dam, indicating that urbanization and/or farming practices between the two urban sites introduce feces into waters. Based on linear regression models, E. coli concentrations increased as waters warmed (R2 = 0.06, P = 0.02) and as dissolved oxygen levels declined (R2 = 0.08, P = 0.01). Coliform bacteria density followed the same patterns but these variables explained substantially more of the variation (temperature: R2 = 0.20, P \u3c 0.001, dissolved oxygen: R2 = 0.21, P \u3c 0.001). Our findings demonstrate a strong seasonality, built infrastructure, and wildlife component to fecal contamination in addition to human waste and offers insights in the chemical environment affecting fecal contamination