9376

• UCREFRP Catalog Number: 9376
• Author: CH2MHill.
• Title: Duchesne River Hydrology and Water Availability Study.
• USFW Year: 1997.
• USFW - Doc Type: \
• Copyright Material: NO

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CHAPTER 4
Flow Analysis of Duchesne River

Introduction
The purpose of the flow analysis was to determine historical flows on the Duchesne River
-for the period of USGS flow records and to the extend that record to earlier years, if
possible. The actual USGS flow records at the Randlett gauge exist from 1943 to 1994. Flow
statistics developed for this period of record include average flows, percent exceedance
flows, recurrence intervals, and extreme flows.
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An examination of impacts with changing upstream operation was done by dividing the
record into two periods (pre-1970, post-1970) to develop statistics for each period. The
pre-project period was assumed to represent historical flow regime, and the post-project
period was assumed to reflect current flow regime with increased diversions from such
projects as CUP. There is no defined date when the flow regime changed from the
historical flow regime because the change was incremental. Major changes occurred with
the CUP project coming online in 1970. Thus, the pre-project and post-project periods are
assumed to be pre-1970 and post-1970, respectively. To assist in determining pre-project
flows and the effects of longer term records, the Myton gauge was used to extend the flow
record of the Randlett gauge to earlier periods with less development. An analysis of flows
was also performed to differentiate the impacts of projects from the hydrologic effects in the
post-project period. Gauges not significantly impacted by development were used to
accomplish this task.
The information is summarized in the tables and figures at the end of the chapter. This
information can be used to make statistical inferences and draw conclusions to the historical
flows.
Flow Statistics at Randlett for 1943 through 1994
Average monthly flows for the Randlett gauge are shown in Tables 4-1 and 4-2 in both CFS
and acre-feet, respectively. Flows statistics for the various periods are summarized in the
table below.
Table 4-1
USGS Randlett Average Monthly Flows (CFS}

Period Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Yearly Total
AC-FT
1943-1994 299 382 410 401 443 492 419 1,022 1,881 468 206 191 398,578
1943-1969 254 389 449 442 485 517 511 1,301 2,127 482 213 172 442,068
1970-1994 347 374 368 356 397 465 320 722 1,615 453 198 224 351,607
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