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Scientific Investigations Report 2013–5075

Prepared in cooperation with the Bureau of Reclamation and the Colorado River Water Conservation District

Ranking Contributing Areas of Salt and Selenium in the Lower Gunnison River Basin, Colorado, Using Multiple Linear Regression Models

By Joshua I. Linard

Thumbnail of and link to report PDF (15.8 MB)Abstract

Mitigating the effects of salt and selenium on water quality in the Grand Valley and lower Gunnison River Basin in western Colorado is a major concern for land managers. Previous modeling indicated means to improve the models by including more detailed geospatial data and a more rigorous method for developing the models. After evaluating all possible combinations of geospatial variables, four multiple linear regression models resulted that could estimate irrigation-season salt yield, nonirrigation-season salt yield, irrigation-season selenium yield, and nonirrigation-season selenium yield. The adjusted r-squared and the residual standard error (in units of log-transformed yield) of the models were, respectively, 0.87 and 2.03 for the irrigation-season salt model, 0.90 and 1.25 for the nonirrigation-season salt model, 0.85 and 2.94 for the irrigation-season selenium model, and 0.93 and 1.75 for the nonirrigation-season selenium model. The four models were used to estimate yields and loads from contributing areas corresponding to 12-digit hydrologic unit codes in the lower Gunnison River Basin study area. Each of the 175 contributing areas was ranked according to its estimated mean seasonal yield of salt and selenium.

First posted September 23, 2013

For additional information contact:
Director, Colorado Water Science Center
U.S. Geological Survey
Box 25046, Mail Stop 415
Denver, CO 80225
http://co.water.usgs.gov

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Suggested citation:

Linard, J.I., 2013, Ranking contributing areas of salt and selenium in the Lower Gunnison River Basin, Colorado, using multiple linear regression models: U.S. Geological Survey Scientific Investigations Report 2013–5075, 35 p., http://pubs.usgs.gov/sir/2013/5075/.



Contents

Abstract

Introduction

Purpose and Scope

Description of Study Area

Types of Information Used

Statistical Analysis Methods

Multiple Linear Regression Models

Rankings of Contributing Areas

Summary

References Cited

Appendix: Estimates of Hydrologic Unit Code seasonal salt and selenium yields and their corresponding ranks


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