WSP12980

• File Number: 8210.140.20.C
• Description: Imperial Irrigation District ‎(IID)‎
• State: CA
• Basin: Colorado Mainstem
• Date: 1/9/1996
• Author: Imperial Irrigation District
• Title: Water Requirements and Availability Sutdy ‎(draft)‎
• Water Supply Pro - Doc Type: Publication

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a number of subjective assumptions have been made as a basis for determining potential water
availability. These assumptions are intended to approximate a water conservation program
targeted at the maximum amount of conservation obtainable. Subjective assumptions are, of
course, always open to discussion. Regarding tailwater:

1. Drip, linear move sprinklers, and tailwater return systems offer the most direct
verifiable conservation of tailwater and, if available in a water transfer program,
would be chosen first by water users.

2. Drip and linear move systems would be evenly distributed across major soil
classifications. According to the Soil Survev of ImDerial County. California,
approximately 80 percent of Valley agricultural soils are heavier soils such as clays,
silty clays, and clay loams. 20 percent are lighter soils such as sands, sandy loams.
and loamy soils.

3. No more than 50 percent of agricultural acreage can be put under drip or linear move
systems due to capacity limitations in IID's delivery system. Drip and linear move
systems are assumed to lower tailwater to one percent of delivered water. It should be
noted that, although drip and linear move systems may reduce tailwater, improved
crop yields may increase consumptive use of applied water, reducing potential net
water conservation.

4. The remaining 40 percent of heavier soils could select a tailwater return system.
Tailwater return systems could capture 67 percent of available tailwater.

5. Irrigation management measures and increased delivery flexibility could be applied to
the remaining 10 percent of lighter soils where tailwater return systems may not be as
cost effective and where deep percolation might be more of a problem than tail water.
These measures would reduce tail water and deep percolation losses by an amount
equal to 50 percent of average District tailwater.

Assuming 100 percent acreage participation, the estimated maxImum on-farm conservation
potential is estimated to be 283,200 acre-feet per year.

Based on the Boyle Report (On-Farm Irrigation FJficiencv. Imperial Irrigation District, Boyle
Engineering Corp., 1993.), approximately 45 percent of operational water can be recovered with
additional concrete lining, lateral interceptors, and additional reservoir storage. The remaining

Draft: Subject To Revision 1/3/96

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