PAST AND FUTURE TREND OF IRRIGATION DEVELOPMENT IN THREE CATCHMENTS OF THE WHITE VOLTA SUB-BASIN - Sustainable Irrigation Development in the White Volta Sub-Basin - page 161

reservoirs developed, 20 are used for irrigation (Table 7.1). The records
include the years that the systems were developed but not the irrigated areas
developed. Due to the lack of records on the irrigated areas, an average
figure from an earlier study was used. Birner et al. (2005) investigated 25
small reservoirs in the Upper East Region and identified that the average
size of land irrigated by a small reservoir was 8.5 ha.
7.3.2 Satellite Image Analysis of Irrigation
Development in the Study Area
The satellite image analysis is intended to trace the irrigation footprints
within the study area. The Google Earth images obtained over the years
(2003, 2005, 2007 and 2010) were limited in aerial coverage over the study
area. For consistent analysis, observation windows common to all the years
were outlined for all three catchments (see the red outlines in Figure 7.1 and
Figure 7.2) and used as the area of analysis. Thus the trend of irrigation
development was analysed for about 30% of the Anayari catchment, 100% of
the Atankwidi and 30% of the Yarigatanga catchment. The image analysis
for the Anayari catchment could be carried out on all the four years but for
the Atankwidi and Yarigatanga catchments it could be carried out for 2005,
2007 and 2010.
In the Google Earth image, all irrigation systems observed are traced and
coloured. These include the large-scale irrigation, small reservoir irrigation,
shallow wells irrigation and riverine pump irrigation. Irrigation activities are
grouped into two types: government-led and private-led irrigation systems.
There are two reasons for grouping these irrigation systems as such. Firstly,
the driving forces behind the development of these technologies are different.
Differentiating the two types gives more clarity as to which type of
investment is behind the expansion of irrigation in the study area. Secondly
some of the shallow groundwater technologies such as temporal shallow wells,
permanent shallow wells and riverine alluvial dugouts are mixed up in the
same location and as such cumbersome to distinguish on the image. To make
the distinction between irrigation technologies simple a common factor for
these technologies is used. The common factor amongst these technologies is
that they are all private-led, thus the choice of private-led and government-
led irrigation systems.