WSP08953

• File Number: 8273.300
• Description: Colorado River Basin Salinity Control - Federal Agencies - USGS
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 3/1/1995
• Author: USGS
• Title: Using Geochemical Data to Identify Sources of Salinity to the Freshwater Navajo Aquifer in Southeastern Utah - Aneth Technical Committee Fact Sheet
• Water Supply Pro - Doc Type: Publication

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Salinity Increases in the Navajo Aquifer in Southeastern Utah

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TREND LINE THROUGH
NAVAJO AQUIFER
DATA

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IODIDE- TO-CHLORIDE RATIO .
TYPICAL OF HALITE-SOLUTION
BRINES (RlCH1ER AND KREITLER, I::.
1991) ~ I::.A

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1 10 100 1,000 10,000 100,000
CHLORIDE CONCENlRATION, IN
MILLIGRAMS PER KILOGRAM

EXPLANA TION

A NAVAJO AQUIFER
. OIL-FIELD BRINE--Number
above symbol refers to
multiple samples.

Figure t Iodide-ta-Chloride Weight, Ratios Compared with Chloride Concentration in Water Samples
from the ,Navajo Aquifer and Oil~Field Brines in the Study Area.

Iodide-to-chloride weidht ratios in samples from the
Navajo aquifer trend ~ward lower ratios characteris-
tic of non-OFB (halite solution brine) ratios (Fig;
ure 7), The best fit liqe through the Navajo aquifer
samples trends toward'the composition of halite solu-
tion brines and is far rElmoved from the composition of
OFB in the study area! (Figure 7), Results of the bro-
mide and iodide data are in agreement and indicate
that OFB is not causing the salinity increases in the
Navajo aquifer. .

Stable Isotopes

discounting the role of OFB as even a minor. source of
salinity to water in the Navajo aquifer, additional geo-
chemical evidence is needed to verify these initial
results. The stable isotopes of oxygen and hydrogen in
water provide a useful geochemical tool to 4etermine
water sources (Drever, 1988) and hence salinity.
sources, The stable isotopes of oxygen (180 and 160)
and hydrogen (2H and lH) have been used in numer-
ous OFB studies to differentiate salinity sources
(Richter and Kreitler, 1991), The application of 11180
and IlD values to differentiate salinity sources is par-
ticularly well suited to this study area because of the
large differences in isotopic composition between OFB
and other ground and surface waters (Figure 8),
The isotopic composition of ground- and. surface-
water samples in the study area was compared with

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Although the bromide-to-chloride and iodide-to-
chloride weight ratios' provide strong evidence for

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WATER RESOURCES BULLETIN

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