WSP11022

• File Number: 8149.911
• Description: Miscellaneous Small Projects and Project Studies - SE Needs Assessment and PSOP
• State: CO
• Basin: Arkansas
• Water Division: 2
• Date: 12/10/1998
• Author: GEI Consultants Inc
• Title: SECWCD Arkansas Basin Future Water and Storage Needs Assessment
• Water Supply Pro - Doc Type: Report/Study

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Water and Storage Needs Assessment
SECWCD/Assessment Enterprise
December 10,1998

2. DESCRIPTIONS OF EXISTING WATER SYSTEMS

2.1 Primary Water Supply Sources

Water users in the SECWCD obtain water from three primary sources: I) native surface water
supplies, 2) imported water supplies from the Fryingpan-Arkansas (Fry-Ark) Project and other
transmountain diversions, and 3) ground water, including springs, alluvial wells, and non-
tributary wells. A general description of these sources is provided in Sections 2.1.1 through
2.1A In Section 2.2, water supply sources and general system characteristics are presented for
25 larger municipal and industrial (M&I) water supply entities (23 larger municipal entities in
the SECWCD, plus Public Service Company of Colorado and the City of Aurora) and
summarized for the numerous smaller M&I entities within the SECWCD. The City of Aurora,
while not located within the SECWCD, has extensive water holdings in the Basin. Similar
discussions are provided in Section 2.3 for the agricultural water supply entities. Like many
river basins in Colorado, the majority of water use in the Arkansas Basin is for irrigated
agriculture. The arrangement of canal and ditch systems, and the development of alluvial wells
for irrigation, has resulted in a substantial amount of agricultural "re-use" in the lower Basin,
because irrigation return flows are made available to down-gradient irrigation systems.

As population growth continues (Section 3), M&I water use is projected to increase in proportion
to agricultural water use, which is anticipated to remain fairly constant (or decline somewhat)
over the planning horizon (year 2040). This situation may result in the need to develop
additional water supplies and to change how existing water sources and supply facilities are
operated.

2.1.1 Native Surface Water Supplies

As shown on Figure 2.1, which serves as a key map for this report, the Arkansas River rises in
the Rocky Mountains, near Leadville, in central Colorado. From its source to Canon City,
Colorado, the stream is a typical mountain torrent, descending from Elevation 11,500 to
Elevation 5,300. This section is characterized by a succession of narrow valleys separated by
short canyon sections. Between Canon City and Pueblo, the valley widens slightly and is flanked
by foothills as it descends to Elevation 4,700 at Pueblo. Here the river emerges into a plains
section and the stream course is characterized by low banks and a broad, sandy bed that shifts
frequently. Elevation of the streambed at John Martin Dam is 3,765 feet and from there descends
gradually to 1,800 feet at Great Bend, Kansas. Slopes vary from a maximum of about 110 feet
per mile in the mountain reaches to about 7 feet per mile in the plains section. Above John
Martin Dam, these slopes result in flood flows characterized by rapid rise, high peak discharge,
and short duration, while the more moderate slopes between the dam and state line tend to flatten
the peaks and extend the duration of a flood wave. The river above John Martin Dam is 300

974II\Fin:IUITEXT..... WPD

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~ GEl Consultants. Inc.

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