A contrast to the landcover change that we found in the established Murrumbidgee
Irrigation Area is that apparent near Emerald in the Central Highlands of
Queensland. During the period over which we can look back here, an entire
irrigation development was established.
The Emerald Irrigation Project was initiated by the Queensland Government
and funded, in part, by the Federal Government. The first sign apparent
in the image of 29/08/72 is the filling of the Maraboon Dam on the Nogoa
River. The water has a cobalt blue colour in FCC because of the high level
of sediment carried by it. Most of the bottom lands have been cleared of
trees, mostly brigalow (Acacia harpophylla) to establish sown pastures or
for dryland cropping. The dark clay soils of the cultivated fields in this
area show as black as firescars in the image. The uncleared eucalypt woodlands
on the uplands are the greenest landcover in the image. No fields of lush,
vigorous vegetation (brilliant crimson in FCC) are present.
Use your browser to open each image
in a new window to compare them.
Three FCC images showing the landcover change that has occurred in the Emerald
irrigation district of the Central Highlands of Queensland during the period
29/08/72 to 01/08/91
By the time of the modern image, 01/08/91, the Maraboon Dam has filled
and the distinctive signature in FCC of fields of irrigated crops is scattered
throughout the cleared bottom lands. There is an overall change in greenness
across this scene because of differing seasonal conditions; however, just
eyeballing these two images shows that there has been considerable clearing
of the woodland present in the earlier scene. If you look carefully, you
can also detect the presence of a new open cut coal mine on the northern
edge of the image.
The colours within the Difference FCC are easy to interpret. The image is
dominated by the filling of the Maraboon Dam and by the creation of irrigated
fields. These fields have the blue signature of an increase in greenness.
The dark tones of landcover (tree) clearing are extensive and spread across
the image.
It will be very interesting to look back on this area in a decade's time,
in the year 2000. I predict that the rate of change of landcover will have
slowed, and that the types of agricultural landuse will have also changed.
