WSP00945

• File Number: 8442.400
• Description: Missouri Basin - Pick Sloan Project - Reports
• State: CO
• Basin: South Platte
• Water Division: 1
• Date: 2/28/1985
• Author: DoI, BoR
• Title: Lake Andes - Wagner Unit Planning Report / draft Enviromental Statement
• Water Supply Pro - Doc Type: Report/Study

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Irrigation Management System

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It was determined early in the planning process that application of water

to the project should be limited such that deep percolation is minimized.

A primary reason is that installation of the subsurface (closed) drains can

be deferred longer with reduced deep percolation. The application of only

that water needed will reduce the amount of deep percolation and delay, or

possibly eliminate, need for these drains.

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The annual cost for an irrigation management program was incorporated into

the project and included in the farm budgets at a cost of $5 per acre. The

local sponsors are aware of the need for this program and are in support of

it. The irrigation district will provide the irrigation management program

and assess the water users in a similar fashion to OM&R assessments. Water

applications will be quantified and soil moisture levels will be monitored.

Individual fields will be monitored for consumptive use and available soil

moisture. This process will optimize the use of irrigation water on the

project and keep operational and onfarm wastes to a minimum.

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If an irrigation management system were not used, the high efficiency

obtainable with this system would not be realized and drainage, pumping,

and project facility costs would be increased. These cost increases have

been estimated to be $5 to $20 per acre. If these efficiencies are not

obtained during peak use, some shortage will occur. In view of this, it is

incrementally feasible to include an irrigation management system as an

integral part of the project.

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Project Water Requirements

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Crop Irrigation Requirement.--The crop irrigation requirement used in the

early formulation studies was developed by weighting climatic data from a

number of stations in the area. For the Planning Report, a new crop irri-

gation requirement (CIR) was computed using climate data from three

stations--Pickstown, Wagner, and Armour, South Dakota. The results of

these computations were compared and it was found that there was no signi-

ficant difference between the three stations. Since the record for the

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