Irrigation return flows from grazed rangelands generate concerns about potential water quality impacts from temperature changes, nutrient enrichment, bacterial contamination, and sediment discharge. The Upper Feather River watershed, in California's northern Sierra Nevada, includes approximately 60,000 acres of irrigated range lands, located primarily within Sierra Valley, Indian Valley and American Valley. The objective of this project is to determine the current status of pollutant levels above and below the major irrigated agriculture systems in the Upper Feather River Watershed. During the 2005 and 2006 summers, water samples were collected from nineteen sites. Electrical conductivity, pH, total nitrogen (N), nitrate (NO₃), ammonium (NH₄), total phosphorus (P), phosphate (PO₄), total and dissolved organic carbon (TOC/DOC), turbidity, total suspended solids, and E. coli were measured by standard methods. Data from the initial sampling (2005) suggest that water quality is not impaired at most sites for most of the time. (Mean values for all sites are given in parentheses following the constituent.) In general, no site contained appreciable PO₄ (0.01 ppm) or NH₄-N (0.01ppm).  Electrical conductivity was low at all locations (131 μS/cm).  NO₃ (0.09 ppm), N (0.28 ppm) and DOC (2.77 ppm) showed increased concentrations associated with decreased flows. This trend is expressed spatially, from above the valley to below, and temporally, from May to September.  E. coli concentrations (123cfu/100ml) did not follow any spatial pattern, but during late summer low flows, concentrations at some sites greatly exceeded the state mandated threshold of 235 CFU/100 ml. Future sampling will focus on pinpointing sources of E. coli within the watershed. Also, sampling on ranches will help bracket pollution sources and assist in developing cost-effective best management practices to reduce water quality impairment.