WSP01414

• File Number: 8449.918
• Description: South Platte Projects
• State: CO
• Basin: South Platte
• Date: 8/1/1982
• Author: CWCB
• Title: South Platte River Basin Assessment Report
• Water Supply Pro - Doc Type: Publication

The locations of the major tributary and key mains tern gaging stations used

in the study's hydrologic analyses are shown on Figure 1. Mean annual

flows at selected stream gaging stations for the periods of the 1928

through 1952, 1953 through 1979, and 1928 through 1979 water years are

shown in Table 8. II. shift in annual flow volumes between 1952 and 1953 for

many of the long-term streamflow records in the basin corresponds to the

beginning of major transbasin imports by the Colorado-Big Thompson

Project. These imports have increased the flows of St. Vrain Creek, the

Big Thompson River, the Cache la Poudre River, and the mainstem South

Platte River downstream from Henderson. Primarily for this reason, the

period of the 1953 through 1979 water years was selected for description

and analysis of long-term, historical streamflow conditions throughout the

basin. Annual flows at the selected stream gaging stations on the mainstem

South Platte River for the 1953 through 1979 water year period are shown in

Table 9.

Surface Water

The South Platte River at the South Platte gaging station is the uppermost

point in the study area (Figure 1). At this location, the South Platte

River drains an area of about 2,600 square miles. Major tributaries in the

drainage area upstream from the gage include the South, Middle and North

Forks of the South Platte River and Tarryall Creek. Flows measured at this

gaging station are affected by the irrigation upstream of about

45,000 acres of land and by transbasin imports through the Boreas Pass

Ditch and the Harold D. Roberts Tunnel (U.S. I\.rmy Corps of Engineers,

1977). The mean annual flow at the South Platte gaging station was about

254,000 acre-feet during the 1928 through 1979 water year period

(Table 8). Between the gage at South Platte and the gage at Waterton,

located 8 miles downstream, the municipalities of Denver and Aurora divert

their water supplies. As a result, mean annual streamflow of the SOuth

Platte River at the Waterton gage was about 127,000 acre-feet for the 1928

through 1979 water year period (Table 8).

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