WSP10371

• File Number: 8111.805
• Description: Arkansas River Compact Administration - Keesee Ditch
• Basin: Arkansas
• Date: 1/1/1986
• Author: HRS Engineering
• Title: Keesee Ditch Change of Water Rights Vol 1 - Historical Operation of Kessee Ditch
• Water Supply Pro - Doc Type: Publication

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Water Budget Analysis

Consumptive use of irrigation water is a function of the amount and timing
of the available water supply, the amount and timing of irrigation water
requirements, and the carryover effects of soil moisture storage. Essentially,
the amount of consumptive use can be considered as the lesser of either the
irrigation water requirement or the available irrigation supply, which may include
both diversions and soil moisture. In order to combine the components of irrigation
requirements and irrigation supply in the determination of historical consumptive
use, a water budget analysis was performed.

The water budget analysis incorporated a monthly accounting of irrigation
supply, storage and use to model the movement of water out of and back into
the combined Arkansas River/alluvial aquifer system. In terms of this combined
stream/aquifer system, consumptive use of irrigation water _ was considered as
the net removal of water from this system on a monthly basis. Based on this
concept, consumptive use of irrigation water occurs as either soil moisture storage
or evapotranspiration, since both result in removal of water from the stream/aquifer
system. Evap.otranspiration of stored soil moisture at a later time is not considered
an additional consumptive use, since this irrigation water has already been
accounted for. This concept provides a realistic approach to accounting for all
uses of irrigation water in the water budget analysis.

Under the water budget system of accounting, the total available irrigation
water supply for each month was calculated based on an irrigation efficiency
of 70 percent and the available soil moisture at the start of each _Jllilnth.
{E~apot~spiration losses w;;;;-then calculated - as-the l~;;e-r~:;;-f irrig'~~i<l.~_\V~~~~\

L:;:;:.~:~:;i'~th:;;o;;;::!~::~::";:;;pp!::,:,, th:,:::;' ::::;oo"~, ::'::: --1l:!

maximum storage capacity. Irrigation water in excess of this amount was
considered to return to the stream/aquifer system as deep percolation to ground
water. The monthly results of the water budget accounting included the
end-of-month available soil moisture, the total consumptive use, and the total
amount of irrigation. water returning to the stream/aquifer system due to delivery
losses and excess irrigation.

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