7983

• UCREFRP Catalog Number: 7983
• Author: U.S. Department of the Interior.
• Title: Quality of Water, Colorado River Basin.
• USFW Year: 1993.
• USFW - Doc Type: Progress Report No. 16,
• Copyright Material: NO

12 Chapter 3-Causes and Impacts of Salinity

resulting salinity of spoil derived waters ranges
from approximately 3,000 mgIL to 3,900 mgIL.
The variability in concentration depends on
water residence time and the chemical and
physical properties of the spoil.

Saline water is also a byproduct of oil and gas
production in the Basin. It is not uncommon to
produce several times the amount of saline
waters as oil. Oil and gas operators in Colorado
produced approximately 25 million barrels of
saline water during December 1985. The
salinity of production waters varies greatly from
location to location and is dependent upon the
producing formation. Common disposal
techniques include evaporation, injection, and
discharge to local drainages.

The future development of the oil shale
resources in Colorado, Utah, and Wyoming has
the potential to increase salt loading to the
Colorado River. Salt increases can be attributed
to the consumptive use of good quality water,
mine dewatering, and, if surface retorting is
used, the leaching of spoil materials similar to
that of surface coal mining.

Reclamation and others are attempting to
identify abandoned exploration wells that are
leaking and develop plans to control the leaks.
The Meeker Dome Salinity Control Unit
identified and plugged several abandoned wells
along the White River to prevent a salt dome (a
geologic formation) from discharging saline
water into the river.

Erosion

Several researchers[8-11] have shown that
erosion of saline shales and dissolution of
efilorescence (surface salts) increase salinity
during thunderstorms. Low-elevation snowmelt
on saline geologic formations may also
contribute significantly to salinity. Analyses of
the Green River near the Green River station
indicate that salinity remains unusually high
during peak. flows associated with snowmelt
runoff events.

Reclamation studies on the McElmo Creek
Salinity Control Unit found that approximately
32 percent of the total salt load could be related

to runoff events. Other studies by Reclamation
show that 21 percent of the Price River salt load
and 14 percent of the San Rafael River salt load
are related to natural runoff events.

Studies[12] conducted on Mancos Shale in the
Upper Colorado River Basin have demonstrated
a positive relationship between sediment yield
and salt production. Sediment yield increases as
a result of either upland erosion or streambank
and gully erosion. Upland erosion is attributed
to rill and inter-rill flow. Salt and sediment
yields are dependent upon storm period,
landform type, and the soluble mineral content
of the geologic formation.

Studies[13] conducted in the Price River Basin
have demonstrated that the highest salt and
sediment concentrations occur in the first
streamflow event following a long period of no
discharge. The accumulation of salts in the
channel is attributed to efilorescence resulting
from the drying of the channel. Salt yields
occurring after the initial flushing of the channel
are similar to those found in the surrounding
watershed soils.

Sediment and the resulting salt yield are highly
dependent upon landform type. Three major
landform types-badlands, pediments, and
alluvial valleys-are associated with the Mancos
Shale terrain.

Badlands are the most erosionally unstable,
with sediment yields as high as 15 tons per
acre [14]. Rilling accounts for approximately
80 percent ofthe erosion[13]. Because salt
production is closely related to sediment yield
and the badland soils have not been leached of
their soluble minerals, they produce the greatest
amount of salt of the landform types.

Pediments are gently inclined planate erosion
surfaces carved in bedrock and generally
veneered with fluvial gravels. The surface
slopes of pediments are gentle, making them
relatively stable. Pediments have deeper soils
and higher infiltration rates than badlands, thus
they support a greater vegetation cover and are
less erosive.

Alluvial valleys are formed by a change in
gradient and the deposition of sediment. They
are stable except along the channel where