16
H. Baleta et al.
These forested upland areas store and contribute a very high proportion of the water in
some of Africa’s major rivers. Some of these areas are under threat from, for example,
deforestation, which will have major impacts on the quality and quantity of available
water in these areas. Many of these towers provide water in transboundary basins so
that their fate—protection or destruction—has impacts across national borders. The
400,000 hectare (ha) Mau Forest Complex in Kenya, for example, is the largest of
Kenya’s five water towers. It is the single most important water catchment in the Rift
Valley and western Kenya. Water from the Mau Forest Complex supports agriculture,
hydropower, urban water supply, tourism, rural livelihoods and wildlife habitats all
through western Kenya. The water flows into Lake Victoria and ultimately the White
Nile (MEWNR 2015). The total economic value of the Mau Forest Complex is
estimated to be in excess of 1.3 billion USD a year (Cameron 2010).
In Africa, water use differs by sector, and also by geography and infrastructure development. Water use across Africa is categorized by green
1 water use and
blue
2 water use. The amount of blue water available on an annual basis is linked
closely to the level of water storage in a country. Africa, as a continent, has severely
underdeveloped storage infrastructure, except in South Africa where the volume of
water stored per capita is relatively high. The lack of storage infrastructure to ensure
water during dry years means that most of the continent is vulnerable to variations
in annual rainfall. This is a significant vulnerability on a continent that is subject to
regular and often devastating droughts. Different economic sectors depend on either
green of blue water for their operations as shown in Fig. 3. For instance, agriculture in Africa is more dependent upon green water use (>95% of food production in
sub-Saharan Africa is from green water), while industry or domestic use is (by definition) dependent on blue water use. Within these generalities, there are some regional
distinctions across the continent. For example, of the blue water used for agriculture,
75% of irrigation takes place in South Africa, Madagascar and Sudan (WWF and
IFC n.d). Therefore, the potential to grow the agricultural sector across the continent
is significant. In terms of industrial water use, marginally more industrial water is
used in northern Africa (WWF and IFC n.d).
The distinction between blue and green water footprints is particularly relevant to variability, resilience, institutional governance and infrastructure development going forward. The blue water footprint represents the volume of available
blue water that is used and evaporated in the process. If we take into account environmental flow requirements, the actual volume of freshwater available for human use
is significantly lower (Mekonnen and Hoekstra 2016). Blue water scarcity, measured
as the ratio of blue water footprint to available blue water after accounting for
environmental flow requirements, is presented in Fig. 4.
1 Water from precipitation that is stored in the root zone of the soil and evaporated, transpired or
incorporated by plants. It is particularly relevant for agricultural, horticultural and forestry products.
https://waterfootprint.org/en/water-footprint/what-is-water-footprint/.
2 Sourced from surfac.e or groundwater resources and is either evaporated, incorporated into a
product or taken from one body of water and returned to another, or returned at a different time.
Irrigated agriculture, industry and domestic water use can each have a blue water footprint. https://
waterfootprint.org/en/water-footprint/what-is-water-footprint/.
H. Baleta et al.
These forested upland areas store and contribute a very high proportion of the water in
some of Africa’s major rivers. Some of these areas are under threat from, for example,
deforestation, which will have major impacts on the quality and quantity of available
water in these areas. Many of these towers provide water in transboundary basins so
that their fate—protection or destruction—has impacts across national borders. The
400,000 hectare (ha) Mau Forest Complex in Kenya, for example, is the largest of
Kenya’s five water towers. It is the single most important water catchment in the Rift
Valley and western Kenya. Water from the Mau Forest Complex supports agriculture,
hydropower, urban water supply, tourism, rural livelihoods and wildlife habitats all
through western Kenya. The water flows into Lake Victoria and ultimately the White
Nile (MEWNR 2015). The total economic value of the Mau Forest Complex is
estimated to be in excess of 1.3 billion USD a year (Cameron 2010).
In Africa, water use differs by sector, and also by geography and infrastructure development. Water use across Africa is categorized by green
1 water use and
blue
2 water use. The amount of blue water available on an annual basis is linked
closely to the level of water storage in a country. Africa, as a continent, has severely
underdeveloped storage infrastructure, except in South Africa where the volume of
water stored per capita is relatively high. The lack of storage infrastructure to ensure
water during dry years means that most of the continent is vulnerable to variations
in annual rainfall. This is a significant vulnerability on a continent that is subject to
regular and often devastating droughts. Different economic sectors depend on either
green of blue water for their operations as shown in Fig. 3. For instance, agriculture in Africa is more dependent upon green water use (>95% of food production in
sub-Saharan Africa is from green water), while industry or domestic use is (by definition) dependent on blue water use. Within these generalities, there are some regional
distinctions across the continent. For example, of the blue water used for agriculture,
75% of irrigation takes place in South Africa, Madagascar and Sudan (WWF and
IFC n.d). Therefore, the potential to grow the agricultural sector across the continent
is significant. In terms of industrial water use, marginally more industrial water is
used in northern Africa (WWF and IFC n.d).
The distinction between blue and green water footprints is particularly relevant to variability, resilience, institutional governance and infrastructure development going forward. The blue water footprint represents the volume of available
blue water that is used and evaporated in the process. If we take into account environmental flow requirements, the actual volume of freshwater available for human use
is significantly lower (Mekonnen and Hoekstra 2016). Blue water scarcity, measured
as the ratio of blue water footprint to available blue water after accounting for
environmental flow requirements, is presented in Fig. 4.
1 Water from precipitation that is stored in the root zone of the soil and evaporated, transpired or
incorporated by plants. It is particularly relevant for agricultural, horticultural and forestry products.
https://waterfootprint.org/en/water-footprint/what-is-water-footprint/.
2 Sourced from surfac.e or groundwater resources and is either evaporated, incorporated into a
product or taken from one body of water and returned to another, or returned at a different time.
Irrigated agriculture, industry and domestic water use can each have a blue water footprint. https://
waterfootprint.org/en/water-footprint/what-is-water-footprint/.