ABE 1-CWR Flashcards
defined as the depth of water needed to meet the water consumed through evapotranspiration by a disease-free crop,
growing in large fields under non-restricting soil conditions including soil water and fertility, and achieving full production potential under the given
growing environment
Crop water requirements (CWR)
rate of evapotranspiration of a given crop as influenced by
its growth stages, environmental conditions and crop management to achieve the potential crop production
crop evapotranspiration (ETc)
sum of ETc for the entire crop
growth period
CWR
When management or environmental conditions
deviate from the optimal, then that rate of evapotranspiration has to be adjusted to the prevailing conditions and is called ________________________
-actual crop evapotranspiration (ETc)
-the property of plants used in predicting actual evapotranspiration
-value varies with the
development stages of the crop
Crop Coefficient (kc)
Date of sowing
Length of the total growing season
Duration of the initial stage (germination to 10% ground cover)
Duration of crop development stage (from 10% to 80% ground cover)
Duration of the mid season stage (from 80% ground cover to start of
ripening)
Duration of the late season stage (from start of ripening to harvest)
Information required on crops
Both ______and _____ concepts apply to either irrigated
or rainfed crops.
-CWR
-ETc
For irrigated crops, the concept of CWR has to be
complemented by that of ____________________
irrigation water requirement (IWR)
-is the net depth of water [mm] that is required to be applied to a crop to fully satisfy its specific crop water
requirement.
-It is the fraction of CWR not satisfied by rainfall, soil
water storage and groundwater contribution
irrigation water requirement (IWR)
-defined as the quantity or depth of irrigation water in
addition to precipitation required to produce the desired crop yield and quality and to maintain an acceptable salt balance in the root zone (NEH, 2003)
-strongly influenced by the amount and timing of
precipitation
Irrigation water requirements
USES of __________________-
irrigation scheduling for a specific field
seasonal water needs for planning, management, and
development of irrigation projects
Irrigation water requirements
-A procedure to record the additions and withdrawals of
water from the crop root zone and to determine the amount of available water remaining in the root zone at a desired time
-In flooded areas, the capillary rise is usually neglected because of the continuous percolation from the puddled layer
SOIL WATER BALANCE
Δ moisture in the soil =
input – output
is a critical measure of irrigation performance in terms of the water required to irrigate a field, farm, basin, irrigation district, or an entire watershed.
Irrigation efficiency
is a basic engineering term used in irrigation science to characterize irrigation performance, evaluate irrigation water use, and to promote better or improved use of water resources, particularly those used in agriculture and turf/landscape management.
Irrigation efficiency
Irrigation efficiency is a function of the following:
-irrigation method used
-physical condition of the irrigation system
-physical condition of the soil
-plant or crop type, spacing and population
-timing and amount of irrigation water applied
-water management level and skill
-environmental condition at the time water is applied
economics of irrigation
amount of water needed to irrigate a specific land area
spatial uniformity of the crop and its yield
amount of water that might percolate beneath the crop root
zone
amount of water that can return to surface sources for
downstream uses or to groundwater aquifers that might supply other water uses
amount of water lost to unrecoverable sources (salt sink, saline aquifer, ocean, or unsaturated vadose zone).
Things that affects Irrigation efficiency
The ratio between the water delivered to the farm and the water diverted from a river or reservoir expressed in percent
Ec = (Wf / Wr) x 100
where:
Wf = water delivered to the farm
Wr = water diverted from the river or reservoir
Water conveyance efficiency (Ec)
-result primarily from Seepage from ditches, canals, and pipelines
-Leakage through and around headgates and other structures
-Operational spills
Conveyance losses
Some loss in conveyance is ___________.
unavoidable
Losses may be greatly reduced by (1) lining earth ditches and canals or converting to pipelines and (2) by repairing and maintaining canals and pipelines, headgates, and other structures
Some loss in conveyance is unavoidable.
The ratio between water stored in the soil root zone during irrigation and the water delivered to the farm expressed in percent
Ea = (Ws / Wf) x 100
where:
Ws = water stored in the soil root zone during irrigation
Wf = water delivered to the farm
Water application efficiency (Ea)
A concept that combines a measure of uniformity and Ea and provides for adequacy considerations
Application Efficiency of the Low Quarter (AELQ) or the Application Efficiency of the Low Half (AELH).
ratio of the average of the lowest one-fourth of measurements of irrigation water infiltrated to the average
depth of irrigation water infiltrated, expressed as a percentage.
AELQ
ratio of the average of the low one half of
measurements of irrigation water infiltrated to the average depth of irrigation water
AELH
A measure of the uniformity of irrigation water distribution over a field
Water distribution efficiency (Ed)
Methods to compare the uniformity of water application between different irrigation methods and systems
-distribution uniformity (DU) for the average low-quarter or low-half depth
-Christiansen coefficient of uniformity (CU)
is the ratio of the average of the lowest one-fourth of measurements of irrigation water infiltrated to the average depth of irrigation water infiltrated, expressed as a percentage
DU of low one-quarter
is the average of the lowest one-quarter of all measured values each of which
represent an equal area of the field
A similar definition is used for high quarter depth and low half depth
Average low-quarter depth of water infiltrated
also use to evaluate application uniformity
Christiansen’s coefficient of unformity (CU)
When CU is greater than 70%, test data typically form a _________________ that is normally distributed and symmetric about the mean
bell shaped curve
The ratio of water beneficially used on the project, farm or field to the amount of water delivered to the farm expressed in percent
Water use efficiency (Eu)
The ratio of water stored in the root zone during the irrigation to the water needed in the root zone prior to irrigation, expressed in percent
Water storage efficiency (Es)
The ratio of the normal consumptive use of water to the net amount of water depleted from the root zone
Consumptive use efficiency (Ecu)
