WETLANDS IN NORTHERN SALT LAKE VALLEY, SALT LAKE COUNTY, UTAH—AN EVALUATION OF THREATS POSED BY GROUND-WATER DEVELOPMENT AND DROUGHT
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Resource ID
8411
Resource Type
Document
UGS Program
Wetlands
Title
WETLANDS IN NORTHERN SALT LAKE VALLEY, SALT LAKE
COUNTY, UTAH—AN EVALUATION OF THREATS POSED BY
GROUND-WATER DEVELOPMENT AND DROUGHT
Author
Sandow M. Yidana, Mike Lowe, and Richard L. Emerson
Date
-
County
Salt Lake
Country
USA
Keywords
Drought, Ground-Water, Development, Salt Lake Valley, wetland, monitoring, assessment, EPA, Great Salt Lake, hydrology, core element, water quality, UGS, Utah Geological Survey
Document Type
Report
Original Filename
WTLND0063.pdf
Geotechnical Database
Not Included
Abstract / Description
ABSTRACT
Salt Lake Valley is a largely urban area with a growing population.
Most of the development in Salt Lake Valley uses
municipal water sources, principally wells completed in the
basin-fill aquifer system. The population growth and concomitant
increase in municipal ground-water pumping could
significantly decrease the amount of ground water discharged
from the principal aquifer system (where most wells are completed)
to the shallow unconfined aquifer system.
The shallow unconfined aquifer overlies confining beds above
the principal aquifer system in the central and northern parts
of the valley, and provides water to springs and approximately
58,000 acres (23,500 hm2) of wetlands in ground-water discharge
areas. Decreased recharge to the shallow unconfined
aquifer from the principal aquifer due to increased groundwater
pumping could reduce water supply to these springs
and wetlands. Also, water supply to the springs and wetlands
is affected by climatic conditions and Great Salt Lake level.
Drought conditions during 1999–2004 reduced the amount of
recharge to ground-water aquifers across the state, including
the Great Salt Lake area, negatively impacting the Salt Lake
Valley wetlands. In 2005 and 2008, the elevation of Great Salt
Lake declined to near its historic lowstand reached in 1963,
allowing some parts of the Salt Lake Valley wetlands to dewater.
To evaluate the potential impacts of drought and increased development
on the Salt Lake Valley wetlands, we used existing
data to estimate a water budget and develop regional, threedimensional,
steady-state and transient MODFLOW models
to evaluate water-budget changes for the wetland areas; these
efforts focused on wetlands around the margins of Great Salt
Lake, although the results may apply to all of the wetlands
in Salt Lake Valley. The modeling suggests that subsurface
inflow into the wetland areas would be most affected by decreased
subsurface inflow due to long-term (20-year) drought
conditions, which would also cause changes in Great Salt
Lake levels, but subsurface inflow would also decrease due to
increased municipal and industrial well withdrawals over the
same time period. Therefore, the worst-case scenario for the
wetlands would be a combination of both conditions. If the
U.S. Environmental Protection Agency’s goal on no net loss
of wetlands is to be met, the Salt Lake Valley wetland areas
should be managed to maintain their current budget of water
(estimated at about 52,420 acre-feet per year [65 hm3/yr] of
recharge).
We also installed shallow monitoring wells in the Salt Lake
Valley wetland areas to determine hydraulic gradient and
ground-water quality in the shallow unconfined aquifer. The
magnitude and direction of the hydraulic gradient are similar
to those documented previously, where ground water in the
wetland areas flows north toward Great Salt Lake. Total-dissolved-
solids concentrations for water samples collected from
two shallow monitoring wells are 6786 and 21,324 mg/L.
This model-dependent study indicates that wetlands in Salt
Lake Valley may be stressed in the future. Drought and increased
development due to population growth could dramatically
reduce the amount of water the wetlands receive. Measures
to reduce the potential for degradation of the Salt Lake
Valley wetlands include development restrictions, re-use of
wastewater upgradient of the wetlands, and implementation
of water conservation practices.
Marker lat / long: 40.876497, -112.018764 (WGS84)