WSP11762

• File Number: 8443.600
• Description: Narrows Unit - Studies
• State: CO
• Basin: South Platte
• Water Division: 1
• Date: 7/25/1974
• Author: Donald Miller
• Title: Inflow Design Flood Study - Narrows Damsite
• Water Supply Pro - Doc Type: Report/Study

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es-ti...,.._
graph derivation for mountainous watersheds for which e~~"l~

tion.of direct runoff -(surface runoff plus'interflow)

requires determination of a rising base flow. The Uinta

River watershed above Neola, which drains the south slope of

the Uintah Mountains, is considered similar to the moun-

tainous watersheds draining the east slope of the Rocky

Mountains. The stream gage near Neola at about 6900 feet

elevation is located' on the Uinta River just downstream from

where it emerges from the mountains. The river heads along

a divide which rises to elevations exceeding 12,000 feet.

Lag curves. - Bureau procedure for estimating lag times for unitgraph

development XX for basins for which lag time data are not available

is selection of a lag curve previously derived which is considered

applicable to the watershed under study, These lag curves have been

drawn using results of flood hydrograph analyses for lag times;

plotting on log-log paper as abscissa a basin .factor,

L Lea -l- ;-r (see main
I -
~(..,. ':"p.l ~
in hours as ordinates.

text for definition of terms) versus lag times

Curves drawn

by these plottings have the
"
L L r"" ,~ .v "'/
C ( ca 11'.
= . Experience has

vT
range

shown.

general equation form:

lag, hours

that these analyses have yielded a broad

of lag time,va1ues for

respective watershed

basin factors' and hence,the use of
'. ' ;< (s.....Jh:)
having different C and ;Ie., values fo'r

several

different lag curves

the lag

equation. The selection of an appropriate lag curve for watersheds

where runoff data are scare is always a problem.

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