thumbnail

Methods for estimating selected flow-duration and flood-frequency characteristics at ungaged sites in Central Idaho

Water-Resources Investigations Report 94-4120

Prepared in cooperation with U.S. Bureau of Indian Affairs
By:

Links

Abstract

Methods for estimating daily mean discharges for selected flow durations and flood discharge for selected recurrence intervals at ungaged sites in central Idaho were applied using data collected at streamflow-gaging stations in the area. The areal and seasonal variability of discharge from ungaged drainage basins may be described by estimating daily mean discharges that are exceeded 20, 50, and 80 percent of the time each month. At 73 gaging stations, mean monthly discharge was regressed with discharge at three points—20, 50, and 80—from daily mean flow-duration curves for each month. Regression results were improved by dividing the study area into six regions. Previously determined estimates of mean monthly discharge from about 1,200 ungaged drainage basins provided the basis for applying the developed techniques to the ungaged basins. Estimates of daily mean discharges that are exceeded 20, 50, and 80 percent of the time each month at ungaged drainage basins can be made by multiplying mean monthly discharges estimated at ungaged sites by a regression factor for the appropriate region. In general, the flow-duration data were less accurately estimated at discharges exceeded 80 percent of the time than at discharges exceeded 20 percent of the time. Curves drawn through the three points for each of the six regions were most similar in July and most different from December through March. Coefficients of determination of the regressions indicate that differences in mean monthly discharge largely explain differences in discharge at points on the daily mean flow-duration curve. Inherent in the method are errors in the technique used to estimate mean monthly discharge. Flood discharge estimates for selected recurrence intervals at ungaged sites upstream or downstream from gaging stations can be determined by a transfer technique. A weighted ratio of drainage area times flood discharge for selected recurrence intervals at the gaging station can be used to estimate flood discharge at the ungaged site. Best results likely are obtained when the difference between gaged and ungaged drainage areas is small.

Geospatial Extents

Additional Publication Details

Publication type:
Report
Publication Subtype:
USGS Numbered Series
Title:
Methods for estimating selected flow-duration and flood-frequency characteristics at ungaged sites in Central Idaho
Series title:
Water-Resources Investigations Report
Series number:
94-4120
Year Published:
1998
Language:
English
Publisher:
U.S. Geological Survey
Publisher location:
Reston, VA
Contributing office(s):
Idaho Water Science Center
Description:
iii, 10 p.
Number of Pages:
14
Country:
United States
State:
Idaho
Other Geospatial:
Salmon River Basin;Clearwater River Basin;Weiser River Basin;Payette River Basin;Snake River
Scale:
1000000