WSP06206

• File Number: 8278.200
• Description: Title I - Wellton-Mohawk
• Basin: Colorado Mainstem
• Date: 8/1/1988
• Author: USDOI/SCS
• Title: Wellton-Mohawk ON-Farm Irrigation Improvement Program Post-Evaluation Report
• Water Supply Pro - Doc Type: Publication

I. SUMMARY

The WELLTON-MOHAWK ON-FARM IRRIGATION IMPROVEMENT PROGRAM was implemented
under Title 1 of the Colorado River Basin Salinity Control Aet
(Public Law 93-320).

The Soil Conservation Service (SCS) ffiaintained a fully-staffed project office
in ~ellton, Arizona, fron February 1975 until May 1986. A follow-up progran
with emphasis on irrigation water management is now being conducted by the SCS
Yuma Field Office staff, located in Yuma, Arizona.

The on-farm irrigation improvement program treated about 48,000 acres which
were planned in 366 contracts. The land treatment practices were combined as
appropriate to meet specific field requirements. They were:

conservation cropping sequence
crop residue use
irrjfation systems
irrigation water management
irrigation land leveling (laser)
irrigation ditch lining
soil swapping
underground barriers
water control structures

48,000 acres
48,000 acres
48,000 acres
48,000 acres
44,000 acres
263 miles
3,000 acres
22,000 feet
10,635

The SCS assisted farmers plan, apply, and evaluate land treatment. As a
result, water is applied faster and with more uniformity. Yields are
generally larger. Irrigation labor was less. The amount of irrigation water
used ~as reduced. Therefore, water percolating through the soils of
irrigation fields was reduced. This resulted in less flows in the drainage
ditch which re-enters the Colorado River.

Toe cost to install the land treatment was a little over 29 .illion dollars.
This averages about S600 for each acre. Amortizing this value at current
interest rates, plus the operation, maintenance, and replacement, results in
average annual costs of $73 per acre. The average annual benefits were
estimated to be $150 per acre. The average aonual benefit to cost ratio is 2
to 1.

The estimated average annual benefits considered increased yields, worth
$2.7 aillion, decreased amounts of irrigation water spplied, valued at
$4~2 aillion, and decreased irrigation labor worth $0.3 aillion.

Research agencies advanced the application of new technolgy. They improved
the designs, management, and operation of irrigation systems. They measured
movement and concentration of aalt in the soil. Several systems were
automated and water -.asuring structures were improved.

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