Is a Simple, Leaf Area Index Based Water Balance a Reasonable way to Predict Catchment Discharge in Montane Regions of Australia?

Leaf area index (LAI) has been linked to catchment processes and geomorphology, such as precipitation and elevation. Hence, satellite derived LAI, in particular, is a suitable resource for water balance modeling in large catchments due to extensive, instantaneous coverage. Using the Corin Catchment in eastern Australia (CC) as a case study, we initially investigated the quality of fine temporal moderate resolution imaging spectroradiometer (MODIS) 8 day derived LAI and fine spatial 30 m Landsat satellite derived LAI. Preliminary results indicate that, at a mean pass rate of 44 per year, MODIS is most suited for catchment modeling because it has a temporal resolution 5 times higher than Landsat (approximately 5 per year). However, the LAI range of MODIS is 8 times larger than Landsat and no detectable relationship existed between the MODIS and Landsat derived LAI within several days pass of each other. Ground-based LAI photography collected this year is being analyzed to validate the use of MODIS and/or Landsat. Focusing on the MODIS data for CC, two LAI populations can be discerned from a probability density function of over 400000 interpolated data points, where the LAI threshold appears to be 2 m2/m2. Although the coefficient of variation above the threshold (42.1) is higher than below (33.2), both LAI populations demonstrate a similar temporal trend. Spatially, the two populations are not dissimilar over elevation, slope, or aspect. Cross correlations indicate significant relationships between random component temperature, random component rainfall, and interpolated random component LAI. Similarly, the random component of CC discharge appears to lag interpolated random component LAI changes by 1 - 4 months. We use this as a justification to construct a simple, distributed water balance model, with rainfall and LAI as dynamic inputs. The measured CC discharge will be used to validate this model. Further efforts will concentrate on exploring relationships between regolith and climatic data in the CC relative to LAI.