Wetlands in Tooele Valley, Utah: An Evaluation of Threats Posed by Ground-Water Development and Drought
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Resource ID
8375
Resource Type
Document
UGS Program
Wetlands
Title
Wetlands in Tooele Valley, Utah: An Evaluation of Threats Posed by Ground-Water Development and Drought
Author
Neil Burk, Charles Bishop, and Mike Lowe
Date
-
County
Tooele
Country
USA
Keywords
Tooele, Ground-Water, Developement, Drought, Wetland, land use, monitoring, assessment, EPA, Great Salt Lake, Hydrology, water quality, function, core element, UGS, Utah Geological Survey
Document Type
Report
Original Filename
WTLND0067.pdf
Geotechnical Database
Not Included
Abstract / Description
ABSTRACT
Tooele Valley, Tooele County, Utah, is a mostly
rural area at the south end of Great Salt Lake experiencing
a rapid increase in residential development,
resulting in less agricultural land use. While most of
the development in the incorporated areas of Tooele
Valley uses municipal water sources, principally wells,
development in the unincorporated areas primarily
relies on single-family domestic wells. This change
from agriculture to domestic water use could significantly
decrease the amount of ground water discharged
from the confined aquifer system, where most wells
are completed, to the shallow unconfined aquifer system,
which provides water to springs and wetlands in
ground-water discharge areas. Additionally, drought
conditions over the past six years have reduced the
amount of recharge to ground-water aquifers across the
state, also impacting Tooele County’s wetlands. Also,
in early 2005, the elevation of Great Salt Lake declined
to near its historic lowstand reached in 1963. Tooele
County is in the process of creating a Special Area
Management Plan (SAMP) for the wetlands in Tooele
Valley to balance development with wetland conservation.
To evaluate the potential impacts of drought and
increased development on Tooele Valley wetlands, we
investigated the current status of the wetlands and used
a ground-water flow model of the aquifer system in
Tooele Valley to investigate how further drought and
development would affect the water budget of the wetlands.
Delineation of the wetland boundaries was performed
by SWCA Environmental Consultants who
created maps of the wetland areas using remote sensing
data.
We documented the current status of the wetlands
by performing a functional assessment of three wetland
areas, and by installing shallow monitoring wells
in the three wetland areas. The results suggest that the
wetland hydrology has been impacted the most by the
numerous roads, canals, and ditches in the area, and
that agricultural land use is more beneficial to wetland
health and functionality than industrial or urban land
use. We found that the magnitude and direction of the
hydraulic gradient were similar to those documented
previously, where ground water flows from the mountains
toward Great Salt Lake. Water samples collected
from the shallow monitoring wells indicate no downgradient
improvements exist in water quality, as totaldissolved-
solids (TDS) concentration typically
increases downgradient.
To determine the potential impacts posed by increased
ground-water development and further
drought, we used and altered the regional, three-dimensional,
steady-state and transient MODFLOW models
for Tooele Valley to estimate the water budget for
the wetland areas. As a conservative goal, the Tooele
Valley wetlands should be managed to maintain their
current budget of water, which is estimated to be
98,000 acre-feet per year (120,900,000 m3/yr) as subsurface
inflow and 6600 acre-feet per year (8,140,000
m3/yr) as discharge from springs for the entire wetland
region in the transient model. The modeling suggests
that subsurface inflow into the wetland areas would be
most affected by increased ground-water withdrawals,
and discharge from springs that feed the wetlands
would be most affected by further drought conditions.
Therefore, the worst-case scenario for the wetlands
would be a combination of both conditions. These
results will be useful in guiding land-use and development
decisions in Tooele Valley.
This study indicates that wetlands in Tooele Valley
are endangered. The threats posed are from drought
and increased development due to population growth,
which could dramatically affect the amount of water
the wetlands receive. As development continues, we
recommend placing restrictions on the areas of development,
such as allowing development only in upland
environments or placing a non-development buffer
around the wetland areas. The use of single-family
domestic wells and septic-tank systems should also be
discouraged because of the contamination threat in the
shallow unconfined aquifer posed by septic-tank discharge.
Use of municipal sewer and water lines should
be required; this would help confine urban sprawl and
contamination threats would be lower because the
wastewater is treated prior to environmental discharge.
Wastewater from sewers should, where possible, be
reused or discharged to the environment upgradient of
the wetlands so that the septic-tank component of
ground-water recharge is not lost. Enactment of water
conservation practices would also be beneficial for the
wetland environments.
Marker lat / long: 40.645837, -112.386806 (WGS84)