This study relates Colorado watershed condition with downstream water quality. Water quality is characterized by selected variables (e.g., suspended sediment) measured at a gauge or other inventory point along a river (together, these are called water quality measurement sites, WQMs, or simply “sites”). Watershed condition is characterized by the existence of stressors and other land cover measures for the watershed upstream of the WQM. Thus we are attempting to explain downstream water quality (the response/dependent variable) in terms of watershed condition (predictor/independent) variables.
Two separate analyses are planned, a spatial analysis using water quality data for only one point in time within the period 2000 to 2009 at each WQM, and a trend analysis at selected WQMs that offer measurements for many years during the period 1981 to 2012. Data for the spatial analysis come from two, one-time assessments conducted by the EPA plus selected stream USGS gauges. Data for the trend analysis will come from selected USGS stream gauges.