Water use characteristics of irrigated crops in the
southern MDB:
weather-based irrigation scheduling
D. Whitfield, M. O’Connell, L. McClymont
A. McAllister, M. Abuzar, K. Sheffield
Satellite-based Water Use Applications:
• Field/crop scale irrigation scheduling
• Farm/region/industry scale water use benchmarking,
planning, reporting
Irrigation Water Use:
SUPPLY = CROP DEMAND (± LF)
SUPPLY: irrigation, rainfall
CROP DEMAND:
CWR = Kc ETo
crop type, weather (ETo)
Kc : crop type, condition/status
CROP DEMAND:
CWR = Kc ETo
long-running questions associated with both Kc and ETo in Australia:
Highly structured, discontinuous tree/vine crops (stone/pome fruits, vine,
nut and citrus) are major crops in Riverland, Sunraysia, GMID:
ETo: the most appropriate measure of reference crop evapotranspiration?
Allen RG, Pereira LS, Raes D & Smith M (1998):
Crop evapotranspiration - Guidelines for computing crop water
requirements
FAO Irrigation and drainage paper 56
Allen RG, Walter, IA, Elliott RL, Howell, TA, Itenfisu D; Jensen, ME &
Snyder RL (2005):
The ASCE Standardized Reference Evapotranspiration Equation
Meyer, WS (1999):
Standard Reference Evapotranspiration calculation for inland SE
Australia.
CSIRO Land and Water Tech Report 35/98
DEPI/NWI Water Use Measurement, Monitoring, Reporting project:
applied satellite-based SEBAL-METRIC measures to major crops grown in major
irrigation districts of MDB in period, 2007-2010.
Aims:
• Characterise water use of irrigated crops in MDB
•
implications for improved irrigation water management, reporting, planning.
Methods:
Kc approach (FAO56, ASCE-EWRI):
• Quantitative.
• Scalable, with consistent application of supply/demand principles across the
range of areal and time scales relevant to irrigation water management and
planning at field-farm/regional-industry scales.
Methods (cont.):
• METRIC developed by Allen et al (from SEBAL)
• water use characteristics of all major crops in major irrigation areas of
southern MDB
• Compare Australian crops with existing Allen Idaho data: Tasumi et al
(2005) related METRIC ET to vegetation cover (NDVI) in Idaho crops
GV dairy pasture
ET/ETr
GV dairy pasture
ET/ETo
3 classes crop water use in southern MDB:
Stone/pome, citrus, grape, nut
• Strong increase in ET/ETr with increase in NDVI
• ETmax = ETr
Perennial dairy pastures
• Strong increase in ET/ETr with increase in NDVI
• ETmax = ETo
Rice
• ET/ETr = 1 pre-emergence
• ET/ETr < 1 post-emergence
• ETmax = ETr in full-grown crop
Class 1 well-watered crops (ET/ETr > irr refill line):
Kc = ET/ETr
Kc depends on canopy cover (NDVI):
Project: crop-specific relationships between crop water use (ET, CWR),
weather(ETr) and vegetation cover (NDVI).
Soil water balance – irrigation scheduling
Can therefore provide satellite-based fieldscale irrigation scheduling advice/services
based on weather data, satellite ET, and
vegetation data (NDVI)
VicDEPI FarmWeb Irrigation scheduling
NDVI + weather  Satellite-based irrigation schedule
Soil water balance – irrigation schedule