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 170

social, health and environmental aspects, and international relationships,
notably regarding the sharing of waters (IFPRI, 1995). It is an important
indicator to help assess future irrigation development.

Few studies on irrigation potential have been conducted in the study area.
The first study was conducted by the Water Research Institute of Ghana as
part of the Water Resources Management Study of the Volta Basin. In this
study the irrigation potential of the White Volta sub-basin of Ghana was
estimated as 314,000ha (6% of the catchment area) (Wiafe, 1997).
It is not the objective of this chapter to conduct a detailed irrigation
potential assessment of the study area. Therefore the study adopts the
irrigation potential of 6% estimated by the Water Resources Management
Study. Since the study area is located in the White Volta sub-basin it is
likely to have similar irrigation potential characteristics as the basin in
general.
Comparing the potential with the developed area implies that over 80% of
the potential irrigable area is still undeveloped. Thus there is high
opportunity to upscale irrigation in the study area.
The question should be asked whether there are sufficient water resources to
realise the irrigation potential. Here only some general calculations will be
made.
The average annual rainfall in the study area is about 1100mm/a. The
average annual groundwater recharge in the study area is about 66mm/a
(Martin, 2006). Using a crop water requirement of about 900mm/season
(including transpiration and evaporation) the groundwater irrigation
potential of the study area amounts to 6.3%. It should be noted that other
competing groundwater uses can reduce this potential.
The annual runoff coefficient in the study area is about 13% (Martin, 2006).
If, say, only 10% of this runoff could be stored in reservoirs the irrigation
potential can be further boosted by 1.6%.
This simple analysis shows that there are sufficient water resources to fully
support the irrigation potential of about 6% of the catchment area.

7.4.2 Drivers for the Upscaling of Irrigation

Development

Literature has shown that several drivers led to the large public investments
in irrigation in the second half of the 20 th century. The drivers include global