WSP07965

• File Number: 8446
• Description: Cache La Poudre Project
• State: CO
• Basin: South Platte
• Water Division: 1
• Date: 7/1/1983
• Title: Cache La Poudre Project Study and Related Correspondence
• Water Supply Pro - Doc Type: Report/Study

I
I
I
I
I
I
I
I
I
I
I
I

CHAPTER III
HYDROLOGY AND WATER RIGHTS

A. INTRODUCTIOIi

This chapter contains a discussion of the hydrology of the water supply
for the Cache la poudre River Basin, as well as inflow design flood estimates
and sediment production estimates which are essential to the planning of
facilities for a potential Cachela Poudre Project. It also contains a dis-
cussion of the water rights considerations involved in the management of the
water supply. This material is intended to provide a basis for projecting
future water supply and its management with and without a potential Cache la
poudre Project.

B. WATER SUPPLY HYDROLOGY

1. General

Hydrology is the study of the occurrance and distribution of water
and is used in the planning, design and operation of water resource projects.
As part of this study, a hydrological analysis was performed with historic
precipitation, streamflow, and reservoir operation records for the purpose of
estimating the future availability of water within the basin.

As noted in Chapter I I, the bulk of the total water supply for the
Cache la Poudre Basin is produced by native waters from rainfall and snowmelt
in the upper basin catchment area and by importation of water from adjacent
river basins. The remaining water supply is produced by rainfall and snowmelt
in the lower basin and by groundwater inflow into the lower basin. The avail-
ability of water from the upper basin as measured at the mouth of the canyon
represents the developable flows for a potential Cache la poudre Project.

I
I
I
I
I

The catchment area of the upper basin of the Cache la poudre River
above the mouth of the canyon is shown on Figure III-l. The location and
periods of record of all gages used in the analysis of the upper basin catch-
ment; including streamgages, gages on transbasin import facilities and gages
on the major diversion facilities in the upper basin, are also shown on Figure
II 1-1.

2. Recorded Annual Flows

a. Mouth of the Canyon

A plot of the annual streamflows as measured at the mouth of the
canyon is shown on Figure 111-2. The measured streamflows include effects of
transbasin imports, diversions out of the upper basin, consumptive uses in the
upper basin, and regulation due to existing storage reservoirs. Referring to
Figure 111-2, a period of high flows is evident, beginning in 1890 and ending
in 1923. Following this period the average annual recorded streamflow dimin-

I
I

III-1