WSP06451

• File Number: 8460.500
• Description: Platte River Recovery Plan - SPDSS Studies ‎(see also 8483)‎
• Basin: South Platte
• Date: 6/5/1991
• Author: Univ. of Colorado
• Title: Colorado's Law of Underground Water" - A Look at the South Platte Basin & Beyond
• Water Supply Pro - Doc Type: Publication

584 .UNIVERSITY OF COWRADO LAW REVIEW

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FIGURE 2. ANNUAL INSTALLATION AND CUMULATIVE TOTAL OF
LARGE-CAPACITY IRRIGATION WELLS IN THE SoUTH PLATIE
VALLEY
Source: "NU"h' Schneider & Minges, Hydrology of the South Platte River Valley
art eastern Colorado .
CoJorado Water Resources Circular No. 28 (1975).

.

COLORADO LAW OF "UNDERGROUND W."

stream from about Henderson, Colorado) (shown in Figure I) varies
in width from about one mile to over ten miles. The aquifer in this
reach is estimated to contain as much as eight million acre-feet of
water.IO

1988]

585

As early as the 1890s farmers began to draw water from this un-
derground source to supplement their surface diversions. II As shown
in Figure 2, the number of wells increased gradually at first, reaching
about 250 by 1933, then grew rapidly to 3,200 in 1970.'2 Major bursts
of growth occurred in the 1930s and 1950s as a result of periods of
drought. Improvements in well technology and the increased availa-
bility of low cost electricity supported the growing use of wells during
this period, Groundwater development proceeded without control un-
til the mid 19605. Of the 1.4 million acre-feet of water estimated to
have been diverted for irrigation as an annual average between 1947
and 1970, groundwater supplied an estimated 420,000 acre-feet or
about 30 percent of the total. IJ
The growth in groundwater withdrawals caused a reduction in
the annual groundwater discharges to the South Platte, declining from
about 800,000 acre-feet in 1947 to about 550,000 acre-feet in 1970.14
The expected corresponding reduction in surface flows did not appear.
however, apparently because of concurrent increases in transmountain
diversions adding new water to the basin and because of decreases in
surface diversions from the river," In the late 1950s the Colorado-Big
Thompson Project began adding over 200,000 acre-feet of water per
year into the system, In addition, direct diversions from the river de-
creased about 130,000 acre-feet on an annual basis from 1947 to
1970.'6
Although overall surface flows were not substantially reduced by
groundwater development, problems were developing in certain ar-

10. Woodward.Clyde Consultants, SoUTH PLATTE RIVER BASIN AssESsMENT REl'ORT 27 (Aug.
1982) (hereinafter Soutb Platte Study).
II. HUff, Effects of Water-Management Practices on the Flow of the South Platte Riper. ColoroJio
in SciENCE COUNCil OF JAPAN AND INTEltNATlONAl Ass'N OF HYDROLOGICAL SciENCE, INTERNA.
nONAL SYMPOSIUM ON HYDROLOGIC CHARACTERISTICS OF RIVER BASINS 613 (Dec. 1975) (held in
Tokyo, Japan) (hereinafter Hurr).
12. [d.
13. South Platte Study, supra note 10, at 41. Bredehoeft and Young point out that the amount of
installed well capacity in the South Platte Valley in 1970 substantially exceeded that necessary to "max-
imize expected net benefits" from agriculture. They conclude that this "overcapacity" i.s a fonn of
insurance which fanners determined to be worthwhile to assure a dependable water supply. Bredehoeft
& Young, Conjunctive Use of Groundwater and Surface Water for lm'gared Agricut(u~: Risk Aversion,
19 WATER RESOURCES JIJ!, illS (l98J).
14. Hurr, supra note II, at 613.
15. Id.
16. ld. at 614.