U.S. Department of the Interior
U.S. Geological Survey
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Peak-flow characteristics for unregulated streams in Wyoming are described in this report. Frequency relations for annual peak flows through water year 2000 at 364 streamflow-gaging stations in and near Wyoming were evaluated and revised or updated as needed. Analyses of historical floods, temporal trends, and generalized skew were included in the evaluation. Physical and climatic basin characteristics were determined for each gaging station using a geographic information system. Gaging stations with similar peak-flow and basin characteristics were grouped into six hydrologic regions. Regional statistical relations between peak-flow and basin characteristics were explored using multiple-regression techniques. Generalized least squares regression equations for estimating magnitudes of annual peak flows with selected recurrence intervals from 1.5 to 500 years were developed for each region. Average standard errors of estimate range from 34 to 131 percent. Average standard errors of prediction range from 35 to 135 percent. Several statistics for evaluating and comparing the errors in these estimates are described. Limitations of the equations are described. Methods for applying the regional equations for various circumstances are listed and examples are given.
Abstract
Introduction
Purpose and scope
Acknowledgements
Previous investigations
Description of study area
Methods
Streamflow-gaging stations
Basin characteristics
Data compilation
Determination of basin characteristics
Frequency analyses
Historical data
Base discharge
Trend testing
Skew evaluation
Map of skew isolines
Skew prediction equation
Mean of gaging station skew values
Previous investigations
Regional relations
Delineation of regions
Regression analyses
Results
Regional equations
Rocky Mountains
Central Basins and Northern Plains
Eastern Basins and Eastern Plains
Eastern Mountains
Overthrust Belt
High Desert
Limitations
Applications
Ungaged site on an ungaged stream in one region
Ungaged site on an ungaged stream in two regions
Gaged site
Ungaged site near a gaging station on the same stream in one region
Ungaged site between two gaging stations on the same stream
Summary
Selected references
Supplemental information
PLATES
1. Map showing locations of streamflow-gaging stations and hydrologic regions used in study
2. Map showing soils hydrologic index data
FIGURES
1. Location map of study area
2-3. Graph showing:
2. Comparison of mean basin elevation determined using a geographic information system with mean basin elevation in the U.S. Geological Survey National Water Information System
3. Comparison of mean-annual basin precipitation determined using a geographic information system with mean-annual basin precipitation in the U.S. Geological Survey National Water Information System
4. Example annual peak-flow frequency curve
5. Generalized skew map for Wyoming and surrounding states
6-7. Map showing:
6. Physiographic provinces and sections for Wyoming and surrounding states
7. Hydrologic regions for determining peak-flow characteristics of Wyoming streams
8. Graph showing example of relation between cross-correlation coefficients of annual peaks and distance between sites
9-10. Map showing:
9. Mean March precipitation, Eastern Mountains Regions
10. Mean January precipitation, Overthrust Belt Region
11. Graph showing joint distribution of mean basin elevation and basin drainage area for gaged sites in the Rocky Mountains Regions
TABLES
1. Equations for estimating peak-flow characteristics, Rocky Mountains Regions, Wyoming (Region 1)
2. Equations for estimating peak-flow characteristics, Central Basins and Northern Plains Region, Wyoming (Region 2)
3. Equations for estimating peak-flow characteristics, Eastern Basins and Eastern Plains Region, Wyoming (Region 3)
4. Equations for estimating peak-flow characteristics, Eastern Mountains Regions, Wyoming (Region 4)
5. Equations for estimating peak-flow characteristics, Overthrust Belt Region, Wyoming (Region 5)
6. Equations for estimating peak-flow characteristics, High Desert Region, Wyoming (Region 6)
7. Applicable ranges of basin characteristics for use in regional regression equations
8. Exponents for drainage-area ratio in equation for estimating peak-flow characteristics at an ungaged site near a gaging station on the same stream in one region
9. Streamflow-gaging stations used in study, Wyoming and surrounding states
10. Basin characteristics, selected streamflow-gaging stations, Wyoming and surrounding states
11. Peak-flow characteristics, selected streamflow-gaging stations, Wyoming and surrounding states
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