Farm cadastral data were sourced from Victorian Department of
Sustainability and Environment (DSE). Measures of water
supplied to farms in the period, January to April 2009, were
sourced from the Victorian Water Register (VWR), maintained
by DSE (http://www. waterregister.vic.gov.au/). Farm-scale data
were aggregated to district (pod) scale for regional reporting
purposes.
Seven cloud-free images of Landsat 5 were acquired for the
study (Table 1). The images were sourced from the USGS
(http://earthexplorer.usgs.gov). The selection of images
represented the traditional irrigation period during spring,
summer and autumn seasons in northern Victoria (irrigation is
not normally required in the period, June — August, when
rainfall usually exceeds evaporative demand). All images were
radiometrically corrected prior to analysis. Digital numbers
were converted into physical units of at-sensor-radiance, top-of-
atmosphere (TOA) reflectance, and at-sensor brightness
temperature to a 30 m spatial resolution, using the current
equations available for Landsat-5 (Chander et al 2009).
Acquisition Date | Scene (Path / Row)
10 Oct 2008 94 / 85
04 Nov 2008 93/85
14 Jan 2009 94 / 85
23 Jan 2009 93/85
13 Apr 2009 93/85
20 Apr 2009 94/85
08 May 2009 92/85
Table 1. Landsat 5 TM images used in the study.
3. RESULTS
Spatial distribution of CWR showed significant variation at
pod-level during Jan-Apr 2009 (Figure 1). Large parts of
Pyramid-Boort and Torrumbarry areas in the west had CWR
under 1000ML. Higher numbers of CWR (reaching up to 9440
ML) were in Central Goulburn, Shepparton and Murray Valley
irrigation areas.
Total water supply at pod-level varied from near zero to over
5000 ML during January-April 2009 (Table 2). Spatial
distribution of TWS (Figure 2) showed similar pattern as of
CWR (Figure 1). Parts of eastern Torrumabrry, Central
Goulburn, Shepparton, and Murray Valley had fairly high water
supply whereas large parts of Pyramid-Boort areas received
very little water.
The ratio of TWS and CWR ranged between near zero and 13
(Table 2). TWS and CWR showed a strong relationship (Figure
3), which supports the use of these data to underpin a
benchmark. The regional distribution of the ratio showed a
considerable spatial variation. Lower values (=1.0) where
supply is near or below demand, were found in the eastern part
of the Catchment. Pyramid-Boort and the western part of
Torrumbarry irrigation area showed higher values of the CWR:
TWS. Irrigation intensity (ML/ha) ranged between O0 and 20
ML/ha. Western areas had higher irrigation intensities as well as
those on the edge of the irrigation systems. A large part of the
Catchment had water use <5 ML/ha in Jan-Apr 2009.
International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XXXIX-B8, 2012
XXII ISPRS Congress, 25 August — 01 September 2012, Melbourne, Australia
Crop Water Requirement (ML)
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April 2009 in Goulburn-Murray catchment.
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Crop Water Demand (ML)
Figure 3. Crop water requirement vs water supply in Goulburn-
Murray catchment during January — April 2009. The line shows
the relationship, TWS = CWR, where farm water supply and
water demand are in approximate balance.
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