WSP09401

• File Number: 8056
• Description: Drought Preparedness
• State: CO
• Basin: Statewide
• Date: 8/28/1986
• Author: CDM
• Title: Phase I - Drought Study - City of Loveland Raw Water Supply System
• Water Supply Pro - Doc Type: Report/Study

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4.3.1 Hydrologic Data Used in Augmentation Process

Precipitation and streamflow from other areas were examined to determine if

long-term historical records existed which could be correlated with the Big

Thompson native flows for augmentation purposes. The records used in this

analysis included monthly native flows of the Cache La poudre River and

monthly precipitation data collected at the Vaterdale Treatment Plant (in

Loveland); Fraser, Colorado; and Grand Lake, Colorado weather stations.

Only data recorded concurrently with the Big Thompson native flows and

which were also available for periods when Big Thompson flow data were

missing were considered. The selected records were sufficient in length to

generate a 58-year historical record of Big Thompson River native flows for

the period 1927 to 1984 (calendar year).

Precipitation records for the three weather stations mentioned previously

were selected due to their length of record and possibility of

demonstrating good correlation to Big Thompson native flows. Records from

the Vaterda1e station should reflect precipitation that has fallen in the

Big Thompson watershed, and thus streamflow as a result of precipitation,

although they will not necessarily correlate to spring runoff as a result

of snowmelt. Runoff resulting from winter snowfall may be better

represented by precipitation records from high mountain weather stations.

The station located near Estes Park would have been the obvious candidate

for this analysis, however, its location has been changed at times and its

use is generally not considered appropriate for long-term record analyses.

The Grand Lake and Fraser stations are located on Colorado's Vestern Slope

near the Continental Divide. These were the nearest high mountain stations

to the Big Thompson watershed for which records were available. Runoff

resulting from melting of winter snowfall are more adequately represented

by these stations than the Vaterda1e station.

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