|Divundu hydro power plant||
|Alt. A||Alt. B|
|Total capacity at mean head||MW||19||20|
|Total energy production||GWh||150||160|
|Total cost primo 1999||mill. N$||297||345|
|Unit Investment cost 1)||Ncent/kWh||23||25|
1) Annually distributed investment cost plus cost of operation and maintenance divided by the average annual production. 10% discount rate, 40 year lifetime, annual maintenance/operating cost 0.03 N$/kWh.
4.2 Project Description
4.2.1A Description of Alternative A
Appendix 1: Alt A; Map 1:50 000
The weir will be located approximately 2 000 m upstream of the "Popa Falls" in Okavango River close to Divundu village in Caprivi. A gross head of 9 m in the wet season and 10 m in the dry season will be obtained by construction of the 6 m high weir (from surface riverbed to to the highest regulated water level, HRWL). The weir will be 930 m long. The reservoir inundates 1.4 km2 of land. The water surface will normally be kept close to HRWL with option of 0.5 m regulation. The scheme will not affect Angola (inundation of land), and only marginally affect Botswana due to approximately 1.5 mill m3 annually increased evaporation. The power plant will be located at the outlet in the river downstream of the "Popa Falls". The total length of the waterway is 2 500 m. The access to the plant will be from the existing road, B 8. The plant will be connected to the local grid by a short transmission line.
4. 2.1B Description of the Alternative B
Appendix 2: Alt B; Map 1:50 000
The weir is located on the Popa Falls. The power station is located downstream of the rapids similar to alt. A. The gross head is approximately 9 m. The weir is 6 m high and the length is 2 150 m. The reservoir will inundate 2.1 km2 of land, and evaporation will be approximately 2 mill m3 annually.
4.2.2 Catchment Area - Runoff
|Approx 203 000||1.8||365||11500|
The inundated area is measured to 1.4 km2 in alt A, and 2.1 km2 in alt B. The transport of sediments in the river is unknown, but arrangement for flushing is assumed. A gravity-concrete weir is assumed (rockfill can be used as an alternative at both sides).
The weir will be 8 m high (from cleaned damfoot to HRWL) and the crest 930 m long. The total volume will be 6 000 m3.
The weir will be 8 m high (from cleaned damfoot to HRWL) and the crest 2 150 m long. The total volume will be 35 650 m3.
Rock is exposed at the damsites. Some excavation and grouting are necassary to obtain a watertight and stable damfoot.
Diversion during construction will be obtained by means of cofferdams, culvert(s) and gates. It is assumed that some overflow during construction will be accepted.
The spillway is calculated as a fixed concrete weir. The alternative could be fixed labyrinth weir or with inflatable rubber gates. The Q1000 flood is estimated to be 8 000 m3/s with a max flood level up to HRWL+2,5 m in alternative A, and HRWL + 2 m in alternative B. The alternative with inflatable rubber gates will reduce the increase of water level during floods, and give an option for increased head during low flow periods.
Section (from – to)
Inntake – cone
Headrace tunnel / canal
(2 x 5) m
Turbine – outlet
(2 x 5) m
Turbine – outlet
4.2.5 Power Station
The station will be located downstream of the "Popa Falls" on the left river bank.
Underground / open powerhouse
Capasity at max head
Type of turbine
Number of units
Tailwater (Dry/wet season)
996 / 998
996 / 998
4.2.6 Peak Power
The future value of peak power will probably give a higher optimum capacity. The plant can be operated to meet daily peak power demand.
4.2.7 Data on the powerplant (with restrictions; 20 m3/s water release during 5 months)
Divundu Hydro Power Plant
Dry / wet
Dry / wet
Mean annual inflow
Reservoir volume as % of annual
mill m3 / %
Power Station data
Mean gross head
Mean energy equivalent
0.024 / 0.022 2)
Max flow at mean head
Max capacity at mean head
Energy production, firm
Energy production, surplus
Energy production annual
Cost estimate primo 1999
Unit investmentcost 4)
1) 60 % of the year is estimated as dry season and 40 % as wet season.
2) The energy equivalent is based on the net head, which is lower in Alt A than B due to energy loss in a longer waterway.
3) The output during the dry season will be 15 - 19 MW and 16 - 20 MW in the wet season.
4) 10% discount rate, 40 years lifetime, annual maintenance / operating cost 0.03 N$/kWh.
4.2.8 Access roads
The power plant will be located close to the existing infrastructure, which are: roads, grid, restcamps, shops, hospital, airport (small aircrafts) etc. The need is only to build short access roads to the powerstation and the weir.
Section (from – to)
Upgrad./new tarred road
Exist. road- weir
The powerplant is located close to the local 33 kV-grid, which also connects Divundu to Rundu through a 200 km 33 kV-line The connection to the local 33 kV-grid will be permanent. The power from Divundu will mainly be used in the Caprivi area, but will also be a supplement to national demand. The need for upgrading the transmission line to Rundu has not been evaluated. However, the Divundu scheme will enhance connection of the Eastern Caprivi (Catima Mulilo) to the Namibian transmission network.
Capacity existing transmission line
Powerstation - grid
4.2.10 Tele Communication
Local grid will be used.
4.2.11 Location of (Tunnel) Masses
The tunnel/canal masses will be placed near the power station. As an alternative the masses can be used for construction of roads or for other purposes.
4.2.12 Borrow pit - Mass – Quarry
It is assumed that the aggregates for the concrete work can be taken from suitable places in the neighbour-hood.
Costs (mill N$) pr 01.01.99 (10% pa interest during construction period)
Divundu Alt. A
(Dam wall above the rapids)
Divundu Alt. B
(Dam wall on the rapids)
Reservoir, weir cost
Waterway (Penstock included)
Power station (civil works)
Power station (mechanical)
Power station (electrical)
Access roads, Temporary lines, Transportation
Permanent transmission lines
Housing. Workshop. Admin. block. Storage, etc.
Landscape design, etc
Financing costs (I of 1-12)***
Total estimate cost
1) Included in reservoir costs.
Specific cost: Alt A: 1.98 N$/kWh, Alt. B: 2.16 N$/kWh,
Based on mean annual production.
* Planning/administration are calculated with 10% for civil work, and 5% for electrical and mechanical work.
** 4% of 1 – 6 is used, which is normal according to experiences from other hydropower scehemes.
The mitigation for each scheme will decide the actual level.
*** Calculation formula:
I = (1.05(1.10 t - 1))/(0.10 t) - 1, "t" is construction period in years
"I" is to be multiplied with the sum of 1 – 12
Unit investment cost with different discount rate (Ncent/kWh)
4.3 Hydrology, Consequenses
4.3.1 Use of reservoir
The level of the reservoir will be held close to HRWL most of the year. (If peak power is needed, a small regulation (0.5 m) can be used. The length of the reservoir at HRWL will be approximately 4 km in alt. A, the surface area is 2.9 km2, and the inundated land area is 1.4 km2. The length of the reservoir at HRWL is 6 km in alt. B, the surface area is 4.5 km2, and the inundated land area is 2.1 km2.
The capasity of the plant is 68 % of Q mean. This means that in approximately 70 % of the year there will be water over the weir and so in Popa Falls. The rest of the year at least 20 m3/s compensation water is included in the calculations. This is released through the weir.
Implementing the reservoir will not make any influence on the floods or waterlevel in the river downstream of the plant. Upstream of the weir a certain backwater will occur, but in this case the effect will be small and will not affect Angola.
4.4 Compensated Initiatives
4.4.1 Planned Compensation
Resettlement of directly affected people is included in the costs. This cost will depend on the local situation. In this case we have used 4% of 1 – 6 in the cost to come up with a general figure. The 4% is normal according to experiences from other hydropower schemes. The mitigation for each scheme will decide the actual level. In the cost estimate 8 mill N$ for alt A, and 9 mill N$ for alt B is assumed to be used for compensation.
The minimum amount of water release is assumed to be 20 m3 / s in approximately 5 months.
4.4.2 Possible Compensation
Peak power operation is possible during the day, and should be discussed in later studies in order to highlight possible negative environmental impacts and actions to reduce them.
5 Socio-economic and Environmental Considerations
The plant will have a long utilization time, and be in operation nearly all the year. The reservoir created by the weir is not big enough to manipulate the river flow, therefore it will always be water in the river downstream of the scheme.
The inundated area is approximately 1.4 km2 in alt A, and 2.1 km2 in alt B. The scheme will not affect Angola. Approximately 75 huts, 15 houses and 4 campsites around Divundu will be affected by the increased water level. A socio-economic programme must therefore be established to secure new land and improved life for the people directly affected. Due to the increased water surface, the annual evaporation will increase by approximately 1.5 mill m3 (alt A) and 2 mill m3 (alt B), and thereby have a minor impact on the flow into the Okavango Swamps. However this flow is 11 500 mill m3 annually at Divundu.
The rapids inhabit a small-sized rare fish species, which could be negatively affected during construction, and later operation of the plant. The biological life in the river between the dam and the outlet from the powerstation must be thoroughly studied and measures taken to prevent severe impacts.
The scheme will enhance the connection of the Caprivi to the main grid in Namibia. Secured electricity supply is a prerequisite to develop the agriculture potential in Caprivi. This added value to the local society should be investigated.
6 Other alternatives
The plant has not been optimised. In addition to the two described alternatives there are several alternative heads, capasities, damsites, spillways and combinations that should be investigated at later stages of the planning.
NWL Normal Water Level
HRWL Highest Regulated Water Level
LRWL Lowest Regulated Water Level
masl meter above sea-level
Output 1 MW = 1000 kW
Energy 1 GWh = 1 mill kWh
Voltage 1 kV = 1000 V