water applied to meet the crop water requirement over a land
unit (e.g., a farm). In this study, the land units were, in fact, the
irrigation water delivery units administered by irrigation water
licenses. A land unit receiving irrigation water any time during
the season (from spring through summer to autumn) was con-
sidered “irrigated.” The satellite-based measures in pixel form
were aggregated within the management unit for the purpose
of analysis and comparison with water delivery information.
Study Area
The study area is known as Central Goulburn Irrigation District
(CGID) that forms a part of Goulburn-Murray Irrigation Catch-
ment in the State of Victoria, Australia (Plate 1). This 1,900 sq.
km. area supports major irrigation-based industries. It is located
between the southern latitudes of 36°04'41" and 36°38"26", and
between the eastern longitudes of 144°46'37" and 145°23'41".
Its gravity irrigation system, established in the early 1900s,
is currently being modernized. The area has fairly flat terrain
and shallow natural drainage, overlaid by a network of irriga-
tion channels and drains (Plate 1d). The area is generally dry,
with average annual rainfall ranging between 200 and 400 mm.
Most of the rain falls during the winter season (June to August).
The average maximum temperature ranges between 12 to 15°C
in winter, increasing to 27 to 30°C in summer (December to
February). The average minimum temperature varies from 3
to 6°C in winter to 12 to 15°C in summer. Irrigation generally
commences in spring (September through November), and
continues through summer and into autumn (March through
May). Most of the agricultural crops in this area are irrigated
except the winter crops (e.g., wheat and barley oats) which are
largely rain-fed. Winter crops have not been considered in this
study. The major irrigation system adopted is flood or fur-
row irrigation though other systems (e.g., movable sprinklers,
self-propelled irrigators, and micro- and mini-sprinklers) are
also prevalent. The main industries are dairying, horticulture,
cropping, and grazing. To support dairy, pastures principally
comprise a mix of white clover (
T. repens L.
) and perennial
ryegrass (
L. perenne L.
). Treed horticultural crops and perennial
pastures are irrigated throughout the seasons. Annual pastures
(e.g., white clover) are irrigated generally in autumn. Summer
crops (e.g., tomatoes) are irrigated only in summer.
Material and Methods
The approach to irrigation mapping was implemented in three
broad steps (Figure 1). First, the satellite images were pro-
cessed to generate surface temperature and vegetation index.
(a)
(b)
(c)
(d)
Plate 1. Location of study area: (a) Study area and the surroundings shown on the map of Australia, (b) Major rivers and water bodies that
surround the study area; also shown are the weather stations, which provided information used in this study, (c) The yellow line shows the
extent of the Central Goulburn Irrigation Area (
cgia
) on an
aster
image which is a mosaic of four scenes dated 09 and 18 December 2012;
the band combination is RGB: VNIR 321; Vegetation appears as red and water as blue, and (d) Main irrigation channels in
cgia
.
230
March 2015
PHOTOGRAMMETRIC ENGINEERING & REMOTE SENSING
