WSP03145

• File Number: 8271.300
• Description: Colorado River Basin Salinity Control Program - General Information and Publications-Reports
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 1/1/3000
• Title: Salinity Loading to the Colorado River
• Water Supply Pro - Doc Type: Report/Study

r,

**

L
I

.....
~
....,
~

SALINITY ~OADING TO THE COLORADO RIVER

Introduction

As part of the geothermal reservoir testing program performed
for the Reds1:one Corporation, an analytical model of the
reservoir was developed. Ac1:ual tes1: da1:a was used to calibrate
this model, which was used to predict drawdowns anywhere in the
reservoir a1: various discharge ra1:es and pumping times. Using
accep1:ed relationships between drawdown and discharge, changes
in discharge of various documented thermal springs were
calcula1:ed. These calculated changes compare favorably with
,observed reduc1:ions in spring flow during the reservoir test.

,

Using both observa1:ions and calcula1:ed effects to the existing
geothermal system, we conclude that there will be no net
salinity increase in the Colorado River due to discharge from
the Redstone geothermal well. The "no net salinity increase"
agrument is expanded and documented in this section.

Analytical Model

THEORY
The Theis well equation, one of the mos1: widely used equations
in hydrogeology, is 1:he basis for 1:he analy1:ical model used in
this s1:udy. The equation predicts drawdown from a discharging
well in an infinite, homogeneous, confined aquifer. By.using'
the theory of superposition, one can simulate variable discharge
wel.ls or springs, boundary conditions, and injection wells. The
theory of superposition says that the drawdown ata point in an
aquifer that is affected by several wells (or spings) is the sum
of the drawdowns for each of the wells at that point. By using
image well theory, various types oT hydrologic boundaries,
including discharge and recharge, can be simulated.. Most
hydrogeology texts discuss the use of these theories in
analytical analyses (Walton, 1970; Davis and DeWiest, 1969;
Free%e and Cherry, 1979).

A more detailed discussion of the model, its equa1:ions, and i1:s
opera1:ion is in Appendix A.

MODEL SET-UP AND CALIBRATION
All known discharging points, including springs, seeps, and
wells (Redstone), were represented by discharging wells with an
assigned discharge. The assigned locations and discharges Tor
these points were based on work by Barrett and Pearl (197B).
These values are listed in Table 1 and their locations shown on
Plate 1. In addition to the documented springs, two additional
springs were included with estimated discharge. The addition of
these springs is based on field observations. At several
10ca1:ions, one well was used 1:0 simula1:e 1:wo or more closely

1

-