WSP00944

• File Number: 8407
• Description: Platte River Basin - River Basin General Publications
• State: CO
• Basin: South Platte
• Water Division: 1
• Date: 3/1/1982
• Author: Arthur D Little Inc
• Title: Six State High Plains-Ogallala Aquifer Regional Resources Study - Study Element B-3 - Agricultural and Water Use Management and Technology Assessment
• Water Supply Pro - Doc Type: Report/Study

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Conveyance System - all those structures, facilities and operations needed
to convey irrigation waters from water source (well, reservoir, stream,
etc.) to field of application.

Cubic foot per second (cfs) - a common measurement of rate of flow in
irrigation, equals 448.831 gallons per minute or 28.32 liters per
second.

Deficit (Stress) irrigation - optimizing the relationship of water applied
with respect to crop yield by scheduling the time and amount of water
application in accordance with the minimum water requirements at the
several stages of plant growth. Some crops can be stressed during cer-
tain stages of growth with minimal effects on yield. Simple reductions
in water application rates or frequencies without corresponding con-
sideration of plant growth and yield effects do not meet the criteria
for planned deficit irrigation. Other definitions of deficit
irrigation--e.g. keeping the evapotranspiration requirements of plants
(ETp) below the total ET losses from applied waters (ETa < ETp) are also
commonly used.

Evaporation (E) - the physical transformation and movement of water from
a liquid state to a gaseous (vapor) state in the atmosphere. Evaporation
from water surfaces (Ew) and evaporation from wetted soil surfaces (Es)
make up the major portions of water losses to evaporation, though evap-
oration from plant surfaces (Ep) and from spray droplets in the air also
contribute to total E losses. At some stages of plant growth, the evap-
oration loss from plant surfaces (Ep) can exceed all other evaporative
losses. Temperature (solar radiation), relative humidity and wind
velocity all play direct roles in the rate of evaporation. Evaporation,
along with plant transpiration, make up the two principal sources of
nonrecoverable water losses (see below).

Evapotranspiration (ET) - a combined measure of water evaporated from the
soil (Es) and plant surfaces (Ep) plus that water transpired (T) by
growing plants. Irrigation water requirements for crops are commonly
expressed in units of ET per unit of time (day, month, growing season).

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