Availability of Water

Angola

The available surface and groundwater resources in Angola are relatively abundant. The total renewable surface water availability in the country is estimated at almost 184 km³/year, equivalent to around 8 213 m³ per inhabitant per year (m³/c/a). Most of the rivers flowing westward have their sources in the Central Plateau region. Much of the surface water drains into the Atlantic, which receives approximately 41 % of annual flows. A total of 119 km³ per year is flowing into the neighbouring countries of which the Democratic Republic of Congo receives 84 km³, Zambia about 25 km³ and Namibia 10 km³, while Angola itself does not receive any external water resources (Source: Aquastat, 2005). Thus, Angola’s dependency ratio (The parameter that describes the part of the total renewable water resources originating outside the country) is 0 %.

The renewable groundwater resources have been assessed at 72 km³ per year. Groundwater levels are found at depths between 10 to 30 m in the Central Plateau, 5 to 30 m in the coastal zone and over 200 m in the semi–arid areas and low well yield of the south.

Namibia

The water resources that Namibia has access to can be divided into internationally shared water resources and internal water resources. The international water sources are the northern and southern perennial and ephemeral border rivers: 

• Northern perennial rivers: Kunene, Okavango, Zambezi and Kwando;
• Northern ephemeral river: Cuvelai river draining from southern Angola into the Etosha Basin;
• Southern perennial river: Orange-Senqu.

All rivers are shared between Namibia and the other riparian states on the above mentioned rivers.

Total natural renewable water resources of Namibia are estimated at 45 km³/yr, of which only 6.2 km³/yr (4.1 km³/yr surface water and 2.1 km³/yr groundwater) are internally produced. A total natural renewable water resources is the sum of internal renewable water resources and external natural renewable water resources (including surface and groundwater). It corresponds to the maximum theoretical annual amount of water actually available for a country at a given moment. Natural resources are considered stable over a long period.

Over half of the external water resources come from the Zambezi River, while smaller amounts are contributed by the Orange, Kunene, Kwando and Okavango rivers. From the total accounted natural flow (Accounted natural flow of border rivers: As a general rule, 50 percent of the total river flow is assigned to each of the bordering countries) of the transboundary rivers Zambezi, Kunene and Orange of 28 km³/yr, only 0.255 km³/yr is secured through treaties (0.07 from the Orange River and 0.185 from the Kunene River) and should thus be considered as total accounted actual flow. This reduces the natural renewable water resources of 45.5 km³/yr to actual renewable water resources of 17.7 km³/yr, equivalent to about 8 800 m³ per inhabitant and year. The dependency ratio for Namibia is relatively high (65%).

Long-term Availability of Water Resources in Angola and Namibia

Long-term annual average precipitation	Angola	Namibia
Depth (mm/yr)	1 010	285
Volume (km³/yr)	1 259	235
Long-term average annual renewable water resources
Internal renewable water resources (km³/yr)	184	6.2
External renewable water resources (km³/yr)	0	11.6
Total renewable water resources per capita (m³/c/yr) (2000)	8 213	10 211
Dependency ratio (%)	0	65.7

The internally produced surface water sources of Namibia are all ephemeral, meaning they only exist for a short period following precipitation. The internal water sources of Namibia also comprise the groundwater and the utilisation of unconventional water sources. The total internal renewable water resources per capita are estimated at 2 892 m³/yr (FAO 2010b).

Total exploitable or manageable water resources: This is defined as that part of the water resources which is considered to be available for development, taking into consideration factors such as: the economic and environmental feasibility of storing floodwater behind dams or extracting groundwater, the physical possibility of catching water which naturally flows out to the sea, and the minimum flow requirements for environmental services, aquatic life, navigation etc. It is also called water development potential. Methods to assess exploitable water resources vary from country to country depending on the country's situation. In general, exploitable water resources are significantly smaller than natural water resources.

Namibia's water resources have a total assured safe yield of 660 Million m³/yr, distributed as follows: groundwater 300 Million m³/yr, ephemeral rivers 200 Million m³/yr, perennial rivers 150 million Mm³/yr and unconventional sources 10 Million m³/yr. Of the potential from ephemeral rivers about 90 Million m³/yr have been developed. It is also estimated that the long term sustainable safe yield of the groundwater sources is 300 Million m³/yr and of this potential 150 Million m³/yr have been developed.

Availability and Mobilisation of Freshwater Resources in Namibia (Mm³/yr)

Source	Remark	Potential	Mobilised
Groundwater	Long-term sustainable safe yield	300	150
Ephemeral surface water	Full development at 95 % assurance of supply	200	90
Perennial surface water	Installed abstraction capacity	150	150
Unconventional	Reclamation, re-use, recycling	10	10
Total		660	400