Water use characteristics of irrigated crops in the southern MDB:

weather-based irrigation scheduling

D. Whitfield, M. O’Connell, L. McClymontA. McAllister, M. Abuzar, K. Sheffield

Satellite-based Water Use Applications:

• Field/crop scale irrigation scheduling • Farm/region/industry scale water use benchmarking, planning, reporting

crop type, weather (ETo)

Kc : crop type, condition/status

SUPPLY = CROP DEMAND (± LF)

CROP DEMAND: CWR = Kc ETo

Irrigation Water Use:

SUPPLY: irrigation, rainfall

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:

CROP DEMAND: CWR = Kc ETo

Meyer, WS (1999):Standard Reference Evapotranspiration calculation for inland SE Australia.CSIRO Land and Water Tech Report 35/98

Allen RG, Walter, IA, Elliott RL, Howell, TA, Itenfisu D; Jensen, ME & Snyder RL (2005):The ASCE Standardized Reference Evapotranspiration Equation

Allen RG, Pereira LS, Raes D & Smith M (1998):Crop evapotranspiration - Guidelines for computing crop water requirementsFAO Irrigation and drainage paper 56

ETo: the most appropriate measure of reference crop evapotranspiration?

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

Perennial dairy pastures

Rice

• Strong increase in ET/ETr with increase in NDVI• ETmax = ETr

• Strong increase in ET/ETr with increase in NDVI• ETmax = ETo

• 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 depends on canopy cover (NDVI):Kc = ET/ETr

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 field-scale irrigation scheduling advice/services based on weather data, satellite ET, and vegetation data (NDVI)

VicDEPI FarmWeb Irrigation scheduling

Soil water balance – irrigation schedule

NDVI + weather Satellite-based irrigation schedule