Surface-water salinity in the Gunnison River Basin, Colorado, water years 1989 through 2007

Estimated dissolved-solids loads and trends at selected streams in and near the Uinta Basin, Utah, Water Years 1989–2013

“…The calculated dissolved-solids concentrations and streamflow values were logarithmically transformed to help meet the assumptions of normality and constant variance (Hirsch and others, 1991). This report follows methodology presented in Schaffrath (2012).…”

“…The gaging stations selected for analysis are listed in table 1 and the location of each site is shown on figure 2. A similar assessment of trends in dissolved-solids loads in the Gunnison River Basin in Colorado was conducted by the USGS in collaboration with the Colorado River Basin Salinity Control Forum (Schaffrath, 2012). For consistency and comparability of results, methods used in that study to calculate dissolved-solids loads and flow-normalized loads at selected sites were used in this study.…”

“…Variations in residuals over time are not expected in the final regression model with time included as an explanatory variable because the effects of the variable are accounted for within the model. A qualitative interpretation of the LOWESS smooth line included an estimation of when the minimum and maximum modified residuals occurred, based on the year when the slope changed, and the direction of the trend before and after the date of the minimum or maximum modified residuals (Schaffrath, 2012).…”

“…A smaller p-value provides stronger evidence that the null hypothesis is unlikely to be true. The following criteria from Schaffrath (2012) were used to determine the significance of the model coefficients: p≤0.01, highly significant; 0.01<p≤0.05, significant; 0.05<p≤0.10, marginally significant; and p>0.10, not significant.…”

“…Streamflow at each site was determined from the stage-discharge relation method (Rantz and others, 1982), where area-velocity discharge (streamflow) measurements are associated with stage (height of The mean daily streamflow value determined for a period longer than 1 year includes a range in streamflow variability and represents the average streamflow condition for the period (Schaffrath, 2012). The mean annual streamflow is the sum of the 365 mean daily streamflow values for a period.…”