7997

• UCREFRP Catalog Number: 7997
• Author: Nash, L. L. and P. H. Gleick.
• Title: The Colorado River Basin and Climatic Change, The Sensitivity of Streamflow and Water Supply to Variations in Temperature and Precipitation.
• USFW Year: 1993.
• USFW - Doc Type: EPA 230-R-93-009,
• Copyright Material: NO

THE SENSITIVITY OF STREAMFLOW AND WATER SUPPLY
IN THE COLORADO RIVER BASIN TO CLIMATIC CHANGES

INTRODUCTION

Background

Human activities are substantially increasing the atmospheric concentration of greenhouse

gases. These gases, in turn, are expected to increase the overall average temperature of the Earth's surface

and alter precipitation patterns worldwide. The magnitude of increases in global average temperature is

predicted to range from 1.5' C to 4.5' C over the next century (lPCC, 1990). The regional impacts of these

changes will vary and cannot yet be predicted with much confidence; however, existing global climate

models indicate that temperature increases in central North America will exceed the increase in the global

mean, and will be accompanied on average by reduced summer precipitation and soil moisture (lPCC; 1990;

Manabe and Wetherald, 1980; Rind, et aI., 1990).

Such global climatic changes may have substantial impacts on water resources. Higher

temperatures, new precipitation patterns, rising sea level, and changes in storm frequency and intensity will

alter water availability, quality, and demand. Despite recent advances in modeling the atmosphere, large

uncertainties remain about the details of regional hydrological changes. Until large-scale climate models

improve both their spatial resolution and their hydrologic parameterizations, information on the effects of

global climatic changes on hydrologic sub-basins can best be produced using detailed, basin-specific

hydrologic models. In this study, we analyze the potential impacts of climatic change on the hydrology and

water resources of the Colorado River Basin. First, we use a regional hydrologic model to study the effect

of changes in temperature and precipitation on runoff in several sub-basins of the Upper Colorado.

Subsequently, we analyze the impact of changes in runoff on water supply, water deliveries, and water

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