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Scientific Investigations Map 3229

Prepared in cooperation with the Shoshone-Bannock Tribes

Bathymetry and Capacity of Blackfoot Reservoir, Caribou County, Idaho, 2011

By Molly S. Wood, Kenneth D. Skinner, and Ryan L. Fosness

Thumbnail of and link to report PDF (2.5 MB)Abstract

The U.S. Geological Survey (USGS), in cooperation with the Shoshone-Bannock Tribes, surveyed the bathymetry and selected above-water sections of Blackfoot Reservoir, Caribou County, Idaho, in 2011. Reservoir operators manage releases from Government Dam on Blackfoot Reservoir based on a stage-capacity relation developed about the time of dam construction in the early 1900s. Reservoir operation directly affects the amount of water that is available for irrigation of agricultural land on the Fort Hall Indian Reservation and surrounding areas. The USGS surveyed the below-water sections of the reservoir using a multibeam echosounder and real-time kinematic global positioning system (RTK-GPS) equipment at full reservoir pool in June 2011, covering elevations from 6,090 to 6,119 feet (ft) above the North American Vertical Datum of 1988 (NAVD 88). The USGS used data from a light detection and ranging (LiDAR) survey performed in 2000 to map reservoir bathymetry from 6,116 to 6,124 ft NAVD 88, which were mostly in depths too shallow to measure with the multibeam echosounder, and most of the above-water section of the reservoir (above 6,124 ft NAVD 88). Selected points and bank erosional features were surveyed by the USGS using RTK-GPS and a total station at low reservoir pool in September 2011 to supplement and verify the LiDAR data. The stage-capacity relation was revised and presented in a tabular format. The datasets show a 2.0-percent decrease in capacity from the original survey, due to sedimentation or differences in accuracy between surveys. A 1.3-percent error also was detected in the previously used capacity table and measured water-level elevation because of questionable reference elevation at monitoring stations near Government Dam. Reservoir capacity in 2011 at design maximum pool of 6,124 ft above NAVD 88 was 333,500 acre-ft.

First posted September 5, 2012

For additional information contact:
Director, Idaho Water Science Center
U.S. Geological Survey
230 Collins Road
Boise, Idaho 83702
http://id.water.usgs.gov/

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Suggested citation:

Wood, M.S., Skinner, K.D., and Fosness, R.L., 2012, Bathymetry and capacity of Blackfoot Reservoir, Caribou County, Idaho, 2011: U.S. Geological Survey Scientific Investigations Map 3229, 1 sheet.



Contents

Abstract

Introduction

Previous Investigations

Methods

Quality Control and Quality Assurance

Effect of Wind on Reservoir Surface Slope

Revised Stage-Capacity Relation

Acknowledgments

References Cited


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