WSP06362

• File Number: 8210.470
• Description: Pacific Southwest Interagency Committee
• State: CO
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 11/1/1971
• Author: PSIAC
• Title: Pacific Southwest Analytical Summary Report on Water and Land Resources based on Framework Studies of Four Regions - November 1971
• Water Supply Pro - Doc Type: Report/Study

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It is concluded that:
I. Drainage requirements will increase as a result
of prolonged and more intensive use of
irrigation and expansion of irrigated lands.

Drainage

Status

About 1.8 million acres of the 13.3 million
irrigated acres are drained. Some 1.5 million acres still
needed drainage in 1965.
Existing facilities vary from open ditches to tile
drains and are most prevalent in the older irrigated
areas, where high water tables and salt balance
problefilll reduce the pro<luctivity of the land. Over an
extensive area, irrigation practices have kept the
water table below the root zone and prevented an
accumulation of salt in that zone. Reuse of drainage
water for irrigation is widely practiced by returning
the drainage flows to a stream or aquifer. Use of the
drainage water is repeated until the salt content of
the remaining supply limits its use for efficient crop
production.

Needs and Problems

In addition to about 1.5 million acres of land
needing drainage in 1965, an additional 3.5 million
acres of irrigated land will require drainage by 2020.

Plan Response

ment measures, are shown in figure 14. Operation and
maintenance costs are shown in figure 15.

Conclusions

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., 3.5
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The framework plans contemplate solving drainage
problems as they are generated by the expansion and
intensification of irrigation on new and presently
irrigated lands. The area drained in 1965 and the
lands to be drained are shown on figure 13.
All of the plans also provide for onfarm measures
for the dual purpose of drainage and better
application of water. These. measures are discussed in
this report as a part of Land Management.
Systems will be constructed to control both
surface and subsurface drainage resulting from
irrigation. Subsurface drains will vary from open
ditches to tile drains. Irrigation water also will be
reused under current practices. The problems of
ultimate disposal of drainage water are discussed at
length in the Water Quality portion of this report. 5
O.

Costs

Scheduling is indicated by figure 13 showing acre-
ages to be drained and by time frames. Installation
costs for drains, other than those for land manage-

o

1965 1980 2000 2020

Figure 13.-Area to be drained.

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