Horler et al. (1983) and Miller et al. (1991) have focused on the 'red-edge. The region where leaf reflectance rises frm low reflectance in the red to high reflectance in the near infra-red. Laboratory studies with spectroradiometers have found movements in the inflection point and changes in the slope and amplitude of the 'red-edge caused by water, nutrient and heavy-metal toxicity stresses. Therefore a series of CASI images taken over the growing season provides the means for separation of changes in reflectance due to changes in leaf chlorophyll concentration, from those caused by changes in leaff stacking (ie.LAI)' as affected by affected by phenology or stress.
During the spring-summer of 94-95 CASI imagery will be obtained three times over areas which have mix of groundwater recharge and discharge patches to monitor plant physiological response to natural seasonal change coupled with conditions arising from groundwater discharge. We expect the CASI to detect early stress conditions and to separate areas where the vegetation has access to deeper salinised ground water as opposed to areas where plants extract soil water whch originates solely from precipitation. This will indicate areas in the landscape which may be partially waterlogged but not exhibit surface salt. Mapping currently salt affected lands (high albedo) within paddocks of grasses (lower albedo) is routine, we are attempting to do more than this.
3.2 Local Scale (LANDSTA Data)
LANDSAT Satellites have carried the MSS sensor since 1972 (i.e. satelllites 1 to 5) and the TM sensor since 1983 (satellites 4 and 5) For sensor and satellte characteristics refer to Harrisison and Jupp (1989). Three scenes are required to cover the entire LCC, dates of TM imagery currently available are:
| PATH 94 | PATH 93 | |
| Date 1 : 8 Dec 1989 Bands 2,3,4,5 | Date 1:7 Mar 1990 Bands 2,3,4,5,7 | Row 85 |
| Date 2: 1 Jan 1993 Bands 2,3,4,5 | Date 2: 10 Jan 1993 Bands 2,3,4,5 | |
| | Date 1: 6 Feb 1991 Bands 2,3,4,5 | ROW 86 |
| | Date 2: 16 Apr 1993 Bands 2,3,4,5 | |
LANDSAT TM data will be atmosphericallly corrected to radiance values to allow regional plant growth models to be validated and to identify anomalies between the predicted radiance, as modelled by plant growth models (reference in here), and the observed signal. This will enable us to determine focus areas for more detailed data collection, usually remotely sensed (CASI) with syupporting field data, to assist in the detailed modelling.
MSS data has been used to provide base line mapping of land use within the L/CC the dates of the MSS data, all obtained from LANDSAT 4, are as follows.
| PATH 94 | PATH 93 | |
| Date : 2 Feb 1984 Bands 4,5,6,7 | Date: 10 Jan 1984 Bands 4,5,6,7 | Row 85 |
| | Date: 23 Nov 1983 Bands 4,5,6,7 | ROW 86 |
3.3 Regional Scale (AVHR Data)
Daytime thermal AVHRR data is used to provide measures of moisture availability through Normalise Difierence Temperature Index (NDTI) images. Daytime reflective AVHRR data is used to provide Normalised Difference Vegetation Index (NDVI) images. Eighty (80) day-night pairs, approximatelyu monthly from June 1986 to present have been archived for all South-East Australia. The theory am application of linking water balance to energy balance by thermal remote sensing have been outlined in previous research (Mc Vicar et al., 1991, 1992, 1993, Jupp et al. 1990, 199222a, 1994a)
The AVHAVHR data for the 212188 pointsoints Thermal remote ending I an intantaneou observation of the tatu of the energy balance hich rovide the mean to gain information about oil moiture. Vartiation in daytime AVHARR data I governed by the amount of ater and the ease ith hich it I transferred from the surr2af2ace to the atmosphere, via ET (Jupp et al 1990)
The NDTI has the form as follows, see (Mc Vicar et al 1992, Jupp et al 1994a:
NDTI= (T¥ - Ts) (T¥ - T0) (4)
Where T is the modeled surface temperature if there is an infinite surface resistance, that is, ET a is zero Ts is the surfacr temperature observed from the AVHRR sensor, and T0 is the modelled surface temperature if there were zero surface resistance; hence Eta equals Etp T and T0 can be though of a the physically-limited upper and lower temperatures for given meteorological conditions and surface resistances. Thy define an envelope in which meaningful AVHRR derived surface temperatures must fail If Ts is close to the T0 it is an indication of conditions being wet, whereas if Ts is close to the T value dryness is signified.
Calibrated NDVI images allow regional estimates of LAI to Provided to the plant Growthmodellen the correction of ndvi for the estimation of lai is a routine procedure for remote sensing and will not be detailed further in this paper (gutan 1991)
3.4 Ancillary Data Used with Remotely Sensed Data
Ancillary data used in the project includes a discharge data base (DDB) in which location, severity size of the salinised disharge areas were record areas of high infiltration and very high infiltration been mapped for 7 of the 16 1:100 000 scale maps which cover the LCC. This mapping has only been done for the Ordovician Sediments. Daily meteorological data, consisting of maximum and minimum air temperatures and rainfall, from Jan 1980 until the present was obtained from the Bureau of Meteorological fo the four sites within the LCC. Daily micrometerological parmenters, such as solar radiation and potential evapotranspiration, were modelled from tis data using the methods outlined in Mc Vicar et al (1991, 1992) and Jupp et al (1994a) The 6 year lead period between the start of the water balance modelling (1980) and the comparison with AVHRR thermal observations (1986) means that the importance of the initial water storeage (W0) is reduced.
