For much of Idaho, the Snake River is the lifeblood. The 1,040 mile
tributary of the Columbia River provides water for drinking,
irrigating, and generating approximately 50 percent of the state’s
energy through hydropower. The Snake River flows from Yellowstone
National Park through a series of mountain ranges, canyons, and plains
in Wyoming, Oregon, Idaho, and Washington. For Idaho Power Company,
owner and operator of 17 hydroelectric power plants, preservation of
the river is of utmost importance.
Idaho Power is involved in the generation, purchase, transmission,
distribution, and sale of electric energy in a 24,000-square-mile area
in southern Idaho and eastern Oregon with an estimated population of
982,000. It is one of the nation’s few investor-owned utilities with a
predominantly hydroelectric generating base in addition to two
gas-fired plants and shared ownership of three coal-fired generating
plants.
“Since we use the river system for power generation and for public
recreation, we are committed to being good stewards of our natural
resources and environment,” said Mike Butler, GIS expert with Idaho
Power.
Each of the 17 dams Idaho Power operates along the Snake River is
subject to a federal license through the Federal Energy Regulatory
Commission (FERC). Each license is for a specified term and must be
renewed over time. Idaho Power is in the process of relicensing dams
throughout its system and complying with new licenses received in 2004
for Bliss Dam and Lower Salmon Dam, where a study is under way to
ensure the viability of the Bliss Rapids snail, a species listed as
threatened under the Endangered Species Act.
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The Bliss Rapids Snail is listed as a threatened species under the Engangered Species Act.
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FERC is not allowed to grant licenses that might adversely affect
any listed species without consulting with the U.S. Fish and Wildlife
Service (USFWS). This formal consultation with the USFWS occurs when an
action is likely to adversely affect a listed species.
If Idaho Power restricted operations of its Snake River Dam, the
utility could potentially lose substantial revenues and would need to
seek costly alternate sources of energy to meet the needs of its
customers. Instead, Idaho Power takes a proactive approach to
relicensing its dams by employing a large staff of experts in biology,
engineering, and geographic information system (GIS) technology. The
team primarily studies and monitors hydraulic, recreational, aquatic,
and terrestrial resources within the utility’s service territory as
defined by FERC.
Looking at Impact on Bliss Rapids Snails
In 2004, Idaho Power began its five-year study of the Bliss Rapids
snail. The gastropod may be considered an indicator species, one that
defines the overall health of its habitat and the river system.
Invertebrate biologists and hydraulic engineers at Idaho Power are
charged with trying to locate and study habitats including the
hydraulic environments of threatened or endangered snail colonies in
the middle Snake River reach.
“We want to learn where and under what hydraulic and environmental
conditions do we find listed snails,” Butler said. “We need to be able
to answer questions related to snail reactions as the water levels
change during seasonal river flows and normal flow fluctuation from
power generation.”
Idaho Power’s team of experts had to answer important questions.
What are the habitats the snails occupy and what environmental
conditions do they need? What hydraulic variables impact the snails? If
the water level goes up or down, are the snails able to migrate to the
new environment? Does the utility’s operation cause harm to the snails?
If so, how will the utility alter operations to minimize its impact?
“Our mission is to collect the data necessary to accurately model
the river flows and locate snail habitats,” Butler said. “From there,
we will be able to determine how best to minimize possible operating
impact to the snails—if any impact is found.”
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| Idaho Power has a boat equipped with a wide reange of sensors to measure and monitor the health of the Snake River. |
Here you can see the data returned from the sonar instrument and thermal sensors for water temperature and bathymetry. |
Determining Data Layers
The utility’s GIS houses a comprehensive set of layers for studying
the river. A substrate layer identifies changes in the riverbed surface
from boulders, cobbles, gravels, sands, silt, and muck. A channel
classification layer distinguishes each region of the river as a bar,
pool, riffle, glide, or rapid. Water temperature is tracked with a
temperature data logger. Solar radiation tools in the ArcGIS Desktop
Spatial Analyst extension help determine places on the ground within
the river system where temperature changes need to be understood and
monitored.
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| This detailed map of the Snake River shows the effect of solar radiation on water temperature for this stretch of the river. |
Since Bliss Rapids snails are approximately the size of a pinhead,
or 2 to 3 mm, and therefore difficult to spot, the team used Global
Positioning System (GPS) techniques to locate the populations.
Population locations are stored in the enterprise geodatabase along
with data for substrate layers, channel classification, water
temperature, and water velocity.
“GIS allows us to look at the potential area of impact by flow and
even duration of wetting and drying so we can try to minimize that area
and simultaneously maximize operating potential,” Butler said. “This is
essential to our company not only during the relicensing process, but
as we continue to produce affordable, renewable energy for the rate
payers.”
Mapping and Modeling the Snake River
By linking GIS-based 3D terrain models with results from Danish
Hydraulic and Water Institute (DHI) 1D hydraulic models, the Idaho
Power team is able to simulate through animation and portray with maps
all flow regimes the company may encounter through normal operations.
Researchers are able to overlay inundation polygons with known snail
locations, mapped habitats, and channel classification polygons to
quantify how much area of preferred snail habitats are wetted or
dewatered at different operational flows.
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This
flood simulation shows the water flow potential at a low stage of 4,500
cubic feet of water per second (CFS) versus a flood stage at 20,000 CFS.
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With ESRI’s ArcGIS Desktop Spatial Analyst and 3D Analyst extensions,
the team created a series of triangulated irregular networks (TIN) and
surface grids that combine underwater topography, aerial
photogrammetry, and various ground surveys into a seamless physical
representation of the riverbed. Sonar devices are used to collect
underwater topography, or bathymetry. Ground surveys are conducted by
engineers who map the bed surface and water surface elevations using
sonar, Real Time Kinematic (RTK) GPS, and traditional survey techniques.
Pressure transducers were also installed in the river to log water
surface elevations related to discharge. The river stage data was used
to calibrate several one-dimensional hydraulic models that are
ultimately used to simulate water flows.
“Now we have the physical environment mapped in GIS and modeled with
hydraulic modeling software,” Butler said. “We import results from our
modeling work into our GIS to create inundation flood maps for specific
dam discharges.”
GIS analysts at Idaho Power developed a series of Visual Basic
models to streamline the flood mapping process and geodatabase design
and implementation. When the inundation polygons are compared with the
channel classification and substrate layers, suitable and unsuitable
snail habitats are identified for each operating flow.
“We are now able to visualize the inundation area versus discharge
relationships for the entire river reach and how they relate to snail
habitats,” Butler said. “Laboratory studies have determined that the
snails being studied have high mortality above certain temperatures and
under freezing conditions. So if we can alter operations to minimize
exposing critical snail habitats to ambient air temperature and solar
radiation, then we can benefit the snail populations by reducing
potentially harmful conditions, improve our stewardship in the river
system and still generate electricity at some of the lowest energy
rates in the country."
Jessica Wyland is a writer at ESRI; e-mail:
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