GENERAL BACKGROUND INFORMATION by GD Burmeister

NTRODUCTION

Offers for the consultancy services were submitted late in 1994, the study only commenced on the 1st July 1995. The study can be divided into three distinct phases. The first phase were concluded in October 1995 with the submission of the Inception Report and the Comparative Study. The Inception Report basically defined the approach and methodology for the execution of the project and contains specific details as to how the work will be performed. In the Comparative Study all the potential damsites (or hydro schemes) between the Epupa Falls and the Marienfluss were investigated and compared, whereafter a selection was made of the schemes that would be further investigated in the next phase. This phase will be concluded with the submission of the Formulation Report which will be submitted in October 1996. This part of the study include aspects like aerial photography, geological drilling and mapping and the EIA components. The Formulation Report will make a recommendation as to which scheme should be selected for the final phase which is then the actual Feasibility component. During this phase the hydropower scheme will also be compared to alternative energy sources, which will include other renewable energy sources and a thermal station at Walvis Bay.

AGREEMENTS

Use of the Cunene River water is regulated in terms of various agreements, concluded initially between Portugal and Germany, later Portugal and South Africa, and currently negotiations are in process between Angola and Namibia. A joint technical commission has been set up for this purpose. Although Namibia and Angola are still busy with negotiations on water use rights, the outcome is expected to have little effect on the feasibility of a hydro power scheme in the Cunene River.

HYDROLOGY, SILTATION AND DEMAND FORECASTS   

The rainfall in the Cunene river catchment area varies from 1 300 mm p.a. in the northern highlands of the Lubango Area in Angola to almost nothing at the river mouth. The rainfall in the Epupa region is in the order of 300 mm p.a. The evaporation ranges from 300 mm p.a. in the upper highlands to ± 2 000 mm p.a. in the lower catchment area. In the project region the evaporation is in the order of 1 750 mm p.a. or 4,8mm per day.

As the damsizes vary, the evaporation losses will also vary. In the case of one of the big dams the evaporation losses will be in the order of 525 million cubic metres p.a. which represents approximately 6% of the total storage capacity of that dam, this is based on the dam being full. In the case of another scheme where a smaller dam is investigated, the evaporation losses will be in the order of 95 million cubic metres p.a. which represents some 3,4% of the total storage of that dam. The level of the water in the dam obviously has a direct effect on the evaporation losses, in the case of the first dam referred to which has a wall hight of 90m, drop in water level by 20m would reduce the surface area of the water by 40% which would obviously has a direct effect on the evaporation losses.

Hydrological data for the Cunene basin exist from 1933 but sufficient rainfall stations was only available from 1945 onwards, which could mean that the records before that time may be questioned. These records were used to calculate the mean annual runoff which is in the order of 5 000 million cubic metres p.a. or 160 m 3 /s which is almost double the figure which was referred to in the agreements between the two countries. However, the figure referred to in the agreement between the two countries is based on the storage capacity of the Gove Dam which is about 2 500 million cubic metres. The probable maximum flood is some 12 500 m 3 /s, while the regional maximum flood is in the order of 8 200 m 3 /s. The spillways however, will be designed for a flood of 100 years which is in the order of 6 - 8 000 cubic metres per second.

In the hydrological model provision was made for all consumptive users in development scenarios that could be established at this point in time. As far as Angola is concerned, this include water for potential mines, livestock, households, etc. and it also includes provision for new irrigation schemes of up to 40 000 hectares. In the case of Namibia, provision is made for a withdrawal of 6 m3/s at present, which could be increased to 12 m 3 /s in future.

It is estimated that the sedimentation yield in the Cunene basin would be in the order of 100 ton/km 2 p.a. and with an effective catchment size of 75 000 km 2 , a total yield of ± 5,5 million cubic metres p.a. is expected. Taken into account that the dead storage volume of the smallest scheme is 800 million cubic metres, it will take 145 years to fill the dead storage in that case and over 400 years in the case of the largest scheme. Sedimentation therefore does not pose a major thread to the large reservoir on the Cunene river.

The following table shows the expected growth in the peak load requirements of Namibia. This forecast is based on the identification of specific developments and forecasting the actual requirements of such developments rather than using a percentage growth. However, if the percentage growth is calculated, it can be seen that up to the year 2000 the expected growth is in the order of 5,6% whereafter it reduces to approximately 3,2%. This compare very favourably with the 3,5% which is generally excepted by the World Bank.

Year

Peak Load (MW)

Year

Peak Load (MW)

1981

138

1995

282

1982

158

1996

295

1983

169

1997

308

1984

183

1998

338

1985

178

1999

372

1986

181

2000

410

1987

205

2001

451

1988

211

2002

496

1989

213

2003

546

1990

225

2004

601

1991

241

2005

661

1992

253

2010

718

1993

242

2015

781

1994

275

2020

849

 

COMPARATIVE STUDY

A total of six alternative hydropower schemes were investigated between Epupa and the Marienfluss. After submission of the report three schemes were selected for further studies during the formulation report. The following are some of the relevant statistics of each scheme phase.

SCHEME

DAMS

RESEVOIR

HIGH WATER

LEVEL (MSL)

TOTAL

STORAGE

(MM3)

AREA (ha)

HIGH

WATER

SURFACE

DAMM WALL

HEIGHT (m)

INSTALLED

CAPACITY

(MW)

A

A

710

 

 

90

 

 

C

580

8760

30200

75

430

B

B

705

8900

29500

145

430

C

E

580

2800

5500

200

430

Scheme A consists of two dams with Dam A approximately 4km upstream of Epupa and Dam C approximately 10km downstream of Epupa, with a high water level equal to the toe level of the falls.

Scheme B consists of one dam approximately 6km downstream of Epupa, which will cover the falls.

Scheme C consists of one dam approximately 40km downstream of Epupa, with a high water level equal to the toe level of the falls.

ENVIRONMENTAL IMPACT ASSESSMENT

Due do the high international profile of this potential scheme, it was a requirement in the ToR for the Consultancy Services that the EIA must be dealt with as a separate entity and the following organogramme show the make-up of the EIA team. As can be seen the team is divided in three separate groups i.e. a group for the Physical Environment which falls directly under the EIA manager, with a separate team and a separate team leader for the Ecology and the Social Impact analysis. At this stage most of the studies are still in progress although a few of the studies have been completed. All the studies and the reports will however be available at the time the Formulation Report is considered so that the Environmental Impact will be assessed together with the technical features of the various alternatives to decide on the scheme which will be proceeded with in the Feasibility Study Phase.

One of the reports that has been completed is the Environmental Study of the Cunene river mouth. This study basically concluded that the Cunene river has no estuary and function as a river mouth. As such the regulation of the flow will have no affect on the marine species or the marine eco-systems. The study also determined that the dry season flow is capable of keeping the river mouth open. It is, however, not clear what the role of floods play in removing of the wind-blow sand from the south, and what the affect of the full regulation of the river will be in this regard. It is, however, important to note that since Ruacana became operational, the flow in the river has been regulated for an average of 10 months in the year, while in the last four years it was basically regulated for the full year, due to the fact that the river was very low. The present regulation of the river varies from day to day and from week to week. One can virtually see the differences on a hourly basis in the level of the river. With a big dam and a hydro scheme this regulation will be much more stable.

Interesting features of the Cunene mouth is the fact that a large number of green turtles are living in the river mouth and sea and are apparently attracted as a result of the warm water coming in from the Cunene. One of the main problems could be with a big dam, that the temperatures in the river downstream of the dam could drop which may have a negative affect on the green turtle population. Another interesting feature is the fresh water prawns which apparently go up as high as Epupa. Normally these prawns need the brackish water, that is where the sea and the fresh water meet, for breeding purposes, but in this case it seems that they have adapted to fresh water breeding.

From an environmental point of view the one aspect that need to be taken into account is the possibility that an irrigation scheme of 30 - 40 000 ha may be developed in Angola in the middle Cunene region. Such a development will have a very negative effect on the environment, not only would that require regulation of the Cunene water, but also will it result in up to 40 m3/s of the water of the Cunene being used for consumptive use. In addition to that serious pollution that will occur as a result of the fertilizers that will be used.

Two other reports that deals with the social issues has also been completed. It is true that very strong opposition exist within a group of the Ovahimba people against a development at Epupa, but it is also true that there are differences of opinion in this regard. People living further away from the Cunene e.g. Purros area are supportive of the development of the Kaokoland region and see the potential development of a hydro power scheme as a very important stepping stone. Chief Kapika, the local headman, is very strongly opposed to any the development of any scheme within the Cunene river, and it could be partly due to the fact that he's been put under tremendous pressure from both sides e.g. from people for and people opposed to this scheme. However, the headman on the Angolan side, which is in fact a brother of Chief Kapika, has a different approach. He basically agrees that any development at Epupa itself would not be acceptable, but will accept developments downstream of Epupa on the condition that the Himbas are compensated for any losses that they may suffer.

From an archaeological point of view no important new findings were made sofar. Rock engravings are found in the region of Epupa and while initially it was thought to be 5 to 10 000 years old, it was later determined to be about 500 years old, which is about the time that the Himba's spend in the region. Himba graves are very important and in this regard Councillor Katjhira, provides great assistance because he basically will remember the positions of all the graves in the region and can give a full history of each grave.

CONCLUSION

The environmental studies will be completed by the time the Formulation Report is considered. All relevant data will then be available for the purposes of taking the decision as to which scheme will be selected for the final Feasibility Study. Study findings will be made public for comments, and a public hearing will be held for further consultations with the public before the final selection is made.

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