Some studies have been carried out to estimate LAI in 
terms of vegetation indices derived from spectral 
measurements either using hand held instruments by 
physically being in the field or from remote sensing 
images. Colombo et al., (2003) derived LAI in terms of 
different vegetation indices for five different vegetation 
types: soybean, corn, vineyards, poplar plantation and 
deciduous forest in Colombano region, Italy. They used 
spectral data from an IKONOS  panchromatic- 
multispectral image to derive different spectral 
vegetation indices. Haboudane et al, (2004) also 
developed the predictive equations in the same way to 
predict LAI for three crop types: corn, beans, and peas in 
Canada but they used ground measured reflectance data 
to derive vegetation indices. The simple and common 
approach to derive LAI from remote sensing is to 
develop empirical equations between LAI and vegetation 
indices (Yi et al., 2008) as remote sensing measurements 
are more reliable due to its spatial and temporal 
distribution. NDVI is one of the vegetation indices 
which is simple and frequently used to estimate LAI (Qi 
et al, 2000). Moreover, it is required to establish 
individual empirical equations for each vegetation type 
as the empirical coefficients of equations vary with the 
vegetation type (Colombo et al., 2003) 
This paper deals with the development of empirical 
relationships between ground based LAI (LAlg) and 
NDVI measured from satellite images for three common 
   
  
  
  
  
   
  
   
   
  
   
   
   
  
  
  
   
   
   
    
    
  
   
   
  
  
irrigated crops (com, wheat and rice) grown in the 
Murray Darling Basin (MDB). 
2. METHODOLOGY 
The study was carried out in the Coleambally Irrigation 
Area (CIA) located in southern MDB in Australia (Figure 
1). The Murray Darling Basin is the Australia’s most 
important agricultural region, and contains 65% of total 
amount of Australian irrigated areas (ANCID, 2005) 
Principal summer crops grown include rice, soybeans, 
maize (corn) and grapes (November — April), while 
principal winter crops include wheat, oats, barley and 
canola (May — October). The CIA covers approximately 
79,000 ha of intensive irrigation. Surface water is 
diverted to the area from the Murrumbidgee River at 
Gogeldrie Weir. The average annual precipitation and 
evapotranspiration is about 396 mm and 1677 mm 
respectively. 
LAI on ground measurements, spectral data for NDVI 
and other corresponding crop-growth measurements were 
collected in the site during the summer and winter 
seasons of 2010-11. Every seven to ten days during the 
cropping seasons, field visits were planned to coincide 
with the important phenological development stages of 
the crops, satellite overpass day and favourable weather 
conditions in order to guarantee cloud-free satellite 
images on important growth stages of crops (Table 1). 
  
  
S e: 
  
Legend 
: CIA LAt and MSR Measurement Sites 
  
Roads 
Coleambally Irrigation Area farms 
  
  
  
  
  
      
0 
1 
i 
UIT 
  
  
I > 
a N N Coleambally Irrigation Area - All Farms 
Kitometres À Where LAI and MSR Data Has Been Collected 
  
  
Figure 1: Locations of LAI and MSR data collection in the CIA 
   
  
  
  
Nl =] =] ==] SN] A 
Ti