Ranking contributing areas of salt and selenium in the Lower Gunnison River Basin, Colorado, using multiple linear regression models

Abstract

COVER. Inset left: Measuring the streamflow of a tributary in the Lower Gunnison River Basin, Colo. (Photograph taken by Laetitia Linard); Inset right: Example geospatial data used in the report (Photograph taken by Joshua Linard, U.S. Geological Survey); Background: a field typical of those found in the Lower Gunnison River Basin, Colo.

Groundwater quality and hydrology with emphasis on selenium mobilization and transport in the Lower Gunnison River Basin, Colorado, 2012–16

“…Previous investigations estimated that the amount of irrigation water applied to fields in the lower Gunnison River Basin ranged from 40 to 84 in. (3.3 to 7 ft) depending on land use, irrigation method, and crop type (Linard, 2013). A study conducted in the Grand Valley estimated a mean value of 1.27 acre-feet of the 3.79 acre-feet of irrigation applied (around 30 percent) was deep percolating (Mayo, 2008).…”

Salinity and selenium yield maps derived from geostatistical modeling in the lower Gunnison River Basin, western Colorado, 1992–2013

“…Salinity is often measured as total dissolved solids (TDS). The U.S. Environmental Protection Agency (EPA) has established a primary drinking-water standard for selenium of 50 micrograms per liter (μg/L) (EPA, 2003(EPA, ), and, in 1997 Leib and others (2012) and Linard (2013) included Colorado River Basin drainages outside the lower Gunnison River Basin. the U.S. Department of Agriculture Natural Resources Conservation Service (NRCS), are implemented to reduce salinity levels in the Colorado River (Colorado River Basin Salinity Control Forum, 2020).…”

“…Models have also been developed to inform the prioritization of mitigation projects. Linard (2013) refined the MLR models to estimate yields of salinity and selenium for the lower Gunnison River Basin by using geospatial basin characteristics. The use of yields (mass per time per unit of area) instead of loads was chosen to address collinearity of the explanatory variables and the weight of subbasin area as a predictor.…”

“…The use of yields (mass per time per unit of area) instead of loads was chosen to address collinearity of the explanatory variables and the weight of subbasin area as a predictor. The study produced salinity and selenium yield estimates for subbasins within the lower Gunnison River Basin and ranked each subbasin so that high-yield areas could be identified (Linard, 2013). A SPAtially Referenced Regressions on Watershed attributes (SPARROW) dissolved solids model (Schwarz and others, 2006) was implemented by Kenney and others (2009) by using water-quality data for water year 1991 and basin characteristics that were related to climate, land use, and geology for the Upper Colorado River Basin.…”

“…The U.S. Geological Survey (USGS), in cooperation with the Colorado Water Conservation Board and Reclamation, has refined the existing lower Gunnison River Basin salinity and selenium models developed by Linard (2013) in an attempt to better identify areas of greatest salinity and selenium yield. This effort is intended to provide a more accurate assessment of areas in the lower Gunnison River Basin with the highest salinity and selenium yields as well as provide more flexibility to assess yield information from user-defined areas (polygons).…”