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Upper Henry's Fork Subbasin
Assessment Contact
Troy Saffle
DEQ Idaho Falls
Regional Office
900 N. Skyline,
Suite B
Idaho Falls, ID 83402
ph: (208) 528-2650
fx: (208) 528-2695
troy.saffle@deq.idaho.gov
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Surface Water: Upper Henry's Fork
Subbasin Assessment
| > Link to document
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| The Subbasin at a Glance |
| Hydrologic
Unit Code |
17040202 |
| Area |
1,068 square miles |
| §303(d)
Listed Stream Segments |
Henry's Lake, Henry's Fork River |
| Beneficial
Uses Affected |
Cold water biota, salmonid spawning |
| Pollutants of
Concern |
Dissolved oxygen, sediment |
| Major Land Uses
|
Agriculture, recreation, forestry, recreational
development |
| Date
Approved by U.S. EPA |
Subbasin assessment only;
no EPA approval required |
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| Background |
| The federal Clean Water Act requires that
states and tribes restore and maintain the chemical, physical, and
biological integrity of the nation's waters. States and tribes must
adopt water quality standards necessary to protect fish, shellfish,
and wildlife while providing for recreation in and on the waters whenever
possible. Section
303(d) of the Clean Water Act establishes requirements for states
and tribes to identify and prioritize water bodies that are water
quality limited (i.e., water bodies that do not meet water quality
standards). States and tribes must periodically publish a priority
list of impaired waters, currently every two years. For waters identified
on this list, states and tribes must develop water quality improvement
plans known as total maximum daily loads (TMDLs) that establish
allowable pollutant loads set at levels to achieve water quality
standards.
The first step in this process
is the development of a subbasin assessment. The subbasin assessment
describes the physical, biological, and cultural attributes of the
subbasin and summarizes available water quality information, among
other things. If a subbasin assessment demonstrates that a water
body identified on the §303(d) list is actually not water quality
impaired, the water body will be recommended for removal from the
§303(d) list during the next listing cycle and a TMDL will
not be developed. Such is the case of both water bodies in this
subbasin assessment. |
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| Overview |
| The Upper Henry's Fork Subbasin, located in
eastern Idaho, is the origin of the Henry's Fork of the Snake River.
Parts of the subbasin are also located in Wyoming and Yellowstone
National Park. The quality of surface waters within the subbasin is
generally good, with almost half of the water derived from springs
in nearly pristine condition. The northern portion of the subbasin
is geologically rich in phosphorus, and the highly enriched waters
of Henry's Lake support a trophy trout fishery. The
information presented in the assessment indicates the development
of TMDLs for the two water bodies is not necessary. Season depletion
of dissolved oxygen in Henry's Lake is a function of naturally high
concentrations of phosphorus in the lake's watershed. Sediment loading
was due to a distinct event associated with drawdown of Island Park
Reservoir in 1992. Both Henry's Lake and Henry's Fork support the
beneficial uses of cold water biota and salmonid spawning. Therefore,
TMDLs were not developed and the water bodies were recommended for
removal from the §303(d) list.
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| Subbasin Assessment |
| View entire
document including appendices (pdf 3.7 mb, 149 pages). |
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