Salinity trends in the upper Colorado River basin upstream from the Grand Valley Salinity Control Unit, Colorado, 1986-2003

Substantial Declines in Salinity Observed Across the Upper Colorado River Basin During the 20th Century, 1929–2019

“…Results corroborate many other studies that report significant decreases in dissolved‐solids loads and concentrations in the UCRB during the 1900s, when widespread decreasing trends were observed for the Green River sub‐basin before 2013 (Thiros, 2017; Vaill & Butler, 1999), for the Colorado River headwaters sub‐basin prior to 2003, with many decreasing trends occurring upstream, or prior to the implementation, of salinity‐control projects (Bauch & Spahr, 1998; Butler, 1996; Leib & Bauch, 2007; Liebermann et al., 1989; Vaill & Butler, 1999), and for the San Juan River sub‐basin pre‐1983 (Liebermann et al., 1989; Moody & Mueller, 1984). In a recent assessment of national trends, Oelsner et al.…”

“…The Salinity Control Forum estimates that from 1980 to 2019, salinity mitigation efforts had reduced dissolved‐solids loads by 23.8 million tonnes in the UCRB, less than half of the observed change that occurred at these sites over the same period (52.9 million tonnes). This finding, along with substantial decreases in dissolved solids preceding the implementation of salinity‐control efforts, indicates there are additional land‐cover, land‐use, or climatic processes in the UCRB that significantly affect dissolved‐solids transport in the basin (Bauch & Spahr, 1998; Butler, 1996; Leib & Bauch, 2007; Rumsey et al., 2017). Factors thought to affect salinity in the UCRB include erosion, channel evolution, hydrologic variation, shifts in land cover, changes in land use, and the construction of large reservoirs.…”

“…Butler (1996) identified decreasing trends in dissolved‐solids loads and concentrations near Grand Valley, CO from 1970 to 1993 and concluded that trends were, in part, caused by salinity‐control projects, but that natural or other anthropogenic effects in the UCRB likely also played a role in decreasing salinity. Decreases in dissolved solids observed upstream of salinity‐control projects from 1970 to 1993 (Bauch & Spahr, 1998) and from 1986 to 2003 (Leib & Bauch, 2007), indicated that various watershed processes may have led to observed decreases, such as stream channel evolution, hydrologic variation, changing land‐use practices, or fluctuations in groundwater discharge and quality. Additional trend analyses have specifically investigated the effects of salinity‐control projects in the UCRB (Schaffrath, 2012; Thiros, 2017), finding that salinity reductions coincide with areas where projects have been implemented upstream.…”

Analysis of annual dissolved-solids loading from selected natural and irrigated catchments in the Upper Colorado River Basin, 1974-2003

“…When considering local processes, it is important to understand that dissolved-solids yield (the amount of load per area) in a given basin is not static in time. Trends in dissolved-solids concentrations related either to salinity control projects or natural processes have been identified during the period of study (Liebermann and others, 1989;Chafin, 2002;Anning and others, 2007;Leib and Bauch, 2008).…”

Flow-adjusted trends in dissolved selenium load and concentration in the Gunnison and Colorado Rivers near Grand Junction, Colorado, water years 1986--2008

“…Although salinity loads and concentrations have been previously characterized for the U.S. Geological Survey (USGS) streamflow-gaging stations at Colorado River near Colorado-Utah State line and Gunnison River near Grand Junction, Colo. (Kircher and others, 1984;Butler, 1996;Vaill and Butler, 1999;Butler, 2001;Leib and Bauch, 2008), trends in selenium at these two stations have not been studied. The Gunnison Basin and Grand Valley Selenium Task Forces have expressed a need to better understand selenium trends in the Gunnison and Colorado Rivers (Gunnison Basin & Grand Valley Selenium Task Forces, 2012).…”