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 163

reservoir irrigation scheme. Farmers make use of return flows from the large-
reservoir irrigation scheme for private irrigation farms. A consistent
expansion of private-led irrigation systems is observed from the Google earth
images from 2003 to 2010. The irrigation developments along the streams
continue to expand over the years. However, there are some stream channels
and flood plains where more irrigation can be developed but which currently
remain untouched.
Irrigated areas observed in the satellite images were estimated. Due to the
methodology used in producing images in Figure 7.1 and Figure 7.2, the
scale of the images could not be determined. However, knowledge of the size
of the Vea irrigation scheme was used as a benchmark in estimating the area
of other irrigation sites. The irrigated areas were divided into smaller pixels
and the trapezoid method was applied in estimating the area. Table 7.2
shows the irrigated areas estimated from the satellite images.
Table 7.2: Estimated irrigated areas from satellite images

Catchment Anayari Catchment (ha) Atankwidi Catchment (ha) Yarigatanga Catchment

(ha)

Observed
Area (%)

30% 100% 30%

Irrigation
Type

Government-
led Irrigation

Private-led
Irrigation

Government-led
Irrigation

Private-led
Irrigation

Government-
led Irrigation

Private-led
Irrigation

2003 60 380 n/a n/a n/a n/a

2005 65 420 2 191 153 20

2007 44 485 2 230 326 104

2010 40 483 2 224 355 155

The observed irrigated areas for Anayari and Yarigatanga catchments are
extrapolated to cover the total catchment area based on ground observations.
In the extrapolation, the irrigated area by small reservoirs in the satellite
observation is considered to be proportional to the total catchment area.
Private-led irrigation is more intense at the downstream portions of the
catchment, as a result in the extrapolation, the intensity of private-led
irrigation in the unobserved areas is estimated to be half of the observed.
Table 7.3 shows the irrigated areas for the extrapolation.