WSP00735

• File Number: 8220.117.J
• Description: Grand Mesa
• State: CO
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 12/1/1971
• Author: Environmental Protec
• Title: Water Quality Evaluation of the Grand Mesa Project-Colorado
• Water Supply Pro - Doc Type: Report/Study

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as shown in the tobulation below. The assuMptions used in calculatin~
the minimuM flO\'/ requirements are as follO\.s:

1. The Project area's population in 2010 ~lill be 5,450.

2. Each pop,ulation equivalent contributes 0.17 pounds of
five-day 200C biochemical oxyncn demand (GODS).

3. There will always be~/aste treatment facilities in the
Project area capable of removing 85 percent of the BOD5
contributed by the entire population.

The 1m/est flOl. recorded at the U. S. Geological Survey qaqinq stations
nearest the Project area has been 115 cfs, which is more than adequate
to meet the minimum flow required for waste assimilation.

\~ater Ouali.ty Standards for r,unnison River

Des i qnated ~Iater Use
for Gunni son Ri ver
from Confluence with
',Iorth Fork to Confl uence
with Colorado River

S tanda rds of Qua 1 i ty JI
Di ssol ved
Oxyqen Temp.
(mq/l) of pH

\Iam \Ia ter Fi shery

:::-5

< 90 6.5-8.5

Indus tri a 1 via ter Supply

Salinity is the water quality parameter of major importance out-
side the Project area. The averaqe annual oresent modified total
dissolved solids concentrations of the Gunnison River at Grand Junction
and of the Colorado River at Lake r1ead are about 646 and 760 rlCI/l,
respectively. (3) The total dissolved solids concentrations in the,
Gunnison River at Grand ,Junction and in the Colorado River at Lees
Ferry and all ooints downstream nresently exceed U. S. Public Health
Servi ce recomended 1 imi ts for dri nki no water. Project development
will cause an increase in these salinity concentrations. The averane
annual 5 a 1 i ni ty i Ilcreasei s expected to be 18 mq/l in the Gunni son
River at r,rand Junction and 3 moll in the Colorado River at Lake ',1ead.

The mineral quality of water discharged from Hoover Dam does not
fluctuate nreatly from month to month because of the large amount of
\'/ater stored in Lake Powell and Lake f1ead. 1I00'lever, the l'1ineral
quality of the Gunnison River at Grand Junction does fluctuate ~lidcly
durin" the vear. One of the effects of the Pro.iect on ~/ater quality,

1/ /ldanted frOM State of Colorado :Jater ()nality Standards documents;
refer to state standards for specifi c 1 anf1uaf1e and additional
. ~ . .
crl _erla.