SANCOLD is pleased to announce that the South African Register of Large Dams can now be downloaded from the SANCOLD website at this link (Excel spreadsheet). This provides the facility of being able to sort the information easily and to draw interesting conclusions.
The South African Register of January 2009 contains information pertaining to 1 082 large dams. To qualify for inclusion in the Register, a dam must meet the following criteria:
- The dam must have a height of not less than 15 m reckoned from the lowest point of the foundation.
- Dams between 5 m and 15 m impounding more than 3 million m3 are also included, but limited statistical information is provided.
Dam Safety: Small and Large Dams
South Africa has a greater number of dams classified as “small” than those classified as “large”. These dams are mostly owned by the agricultural sector, primarily for irrigation and stock watering. Some local authorities also own such dams for water supply to towns. All dams with a safety risk in South Africa with a height (measured from the downstream toe) of 5 m and greater and a storage capacity of more than 50 000 m3 are subject to the dam safety regulations in terms of the National Water Act (No 36 of 1998).
Owners of such dams are required to register the dams with the Department of Water and Sanitation. The dams are then classified into different categories depending on their hazard potential rating which considers potential loss of life and potential economic loss that may result from dam failure. Three dam safety classifications are defined
- Category I dams are small dams with low hazard potential rating.
- Category II dams are of an intermediate nature and also require the involvement of dam professionals.
- Category III dams have the highest potential rating and require the most attention from a dam safety perspective.
The current (August 2008) information on the number of South African dams and their classifications is given below and has been kindly supplied by the Dam Safety Office (DSO) of the Department of Water and Sanitation (DWS).
The total number of registered dams is 4 457 of which 4 173 (94%) have been classified into the different dam safety categories. Information on this register of dams can be downloaded from the DSO page of the DWS website (www.dwa.gov.za/DSO/ ). Note that some of the information in the DSO Register differs from that in the SANCOLD Register and arises because of differences in definition of terms. The height of a dam is different for the reason given above. The registration of dams commenced in 1986 and after a 5-year build-up period, the rate of annual registrations has remained essentially steady. There are currently 49 mine and industrial residue deposits (tailings dams) registered and included in the list.
The distribution of registered dams according to size class and reservoir capacity is given in the tables below.
| Size class | Number | Percentage |
| Small (5 m – 12 m) | 3 323 | 73 % |
| Medium (12 m – 30 m) | 1 033 | 23 % |
| Large (30 m and higher) | 192 | 4 % |
| Total | 4 457 | 100 % |
| Capacity (x 106 m3) | Number | Percentage |
| 0.00 – 0.05 | 149 | 3.3 % |
| 0.05 – 0.10 | 1 108 | 24.9 % |
| 0.10 – 0.25 | 1 591 | 35.7 % |
| 0.25 – 1.00 | 995 | 22.3 % |
| 1.00 – 10 | 423 | 9.5 % |
| 10 – 100 | 129 | 2.9 % |
| 100 – 1 000 | 54 | 1.2 % |
| 1 000 – 10 000 | 8 | 0.2 % |
| Total | 4 457 | 100 % |
Almost 75% of dams are small (lower than 12m) and 85% have a storage capacity of less than 1 million m3.
The distribution of existing dams classified according to hazard potential rating and category is given in the tables below.
| Size class | Low hazard potential | Significant hazard potential | High hazard potential | Total |
| Small | 2 294 (55 %) | 758 (18 %) | 41 (1 %) | 3 093 (74 %) |
| Medium | 293 (7 %) | 499 (12 %) | 134 (3 %) | 926 (22 %) |
| Large | 1 (0 %) | 19 (0 %) | 134 (3 %) | 154 (4 %) |
| Total | 2 588 (62 %) | 1 276 (31 %) | 309 (7 %) | 4 173 (100 %) |
| Category classification | Number of dams | Percentage |
| Category I | 2 353 | 56.0 % |
| Category II | 1 558 | 37.3 % |
| Category III | 280 | 6.7 % |
| Total | 4 173 | 100 % |
Interesting Facts about South African Dams
Interesting information abstracted from the South African Register of Large Dams is:
- The oldest dam is the Upper Mpate built near Dundee in 1880. It is an earthfill embankment with a height of 18 m and crest length of 293 m.
- The total storage capacity of the 1 086 dams is 31 619 million m3 which is about 65 % of the mean annual runoff of South Africa of 49 000 million m3.
- The development of major dams over time is shown graphically below. The figures illustrate that there was a lull in dam development during the Second World War, but accelerated in the period from 1970 to 1980 with the construction of the Orange River Project and the Thukela-Vaal Project. There has been a progressive decline in dam development from 1980. While the rate of development has reduced, dams will still be required to provide water for various purposes to meet future rising demands.
- The percentage distribution of dam types in South Africa is shown below. Some dams consist of a combination of dam types such as a concrete gravity spillway plus earth flanks. Changing technology and the dam site characteristics (geology, floods and topography) influence the selection of dam types. Most dams in South Africa are constructed from earthfill.
| Dam type | Percentage |
| Earthfill | 74 % |
| Rockfill | 2 % |
| Concrete gravity | 12 % |
| Concrete arch/buttress | 10 % |
- The distribution of the heights of large dams in South Africa is tabulated below. Most large dams in South Africa are lower than 30 m in height.
| Height range | Number of dams | Percentage |
| < 30 m | 950 | 85 % |
| 31 m – 50 m | 27 | 11 % |
| 51 m – 70 m | 28 | 2 % |
| 71 m – 90 m | 8 | 1 % |
| > 90 m | 2 | 0.2 % |
- The highest dam in South Africa is the Vanderkloof Dam on the Orange River with a height of 108 m.
- The Big Five Dams in South Africa are given in the table below.
| Dam (alphabetic) | Height (m) | Wall volume (million m3) | Storage capacity (million m3) | Water surface area (km2) |
| Vanderkloof Dam | 108 | 1.3 | 3 187 | 133 |
| Vaal Dam | 63 | 1.4 | 2 610 | 323 |
| Sterkfontein Dam | 93 | 19.8 | 2 617 | 67 |
| Pongolapoort Dam | 89 | 0.6 | 2 267 | 132 |
| Gariep Dam | 88 | 1.4 | 5 343 | 352 |
- The storage capacity of the Sterkfontein Dam in the upper Vaal River catchment is virtually the same as that of Vaal Dam, while its water surface area is only 20% of that of Vaal Dam. The evaporation losses from Sterkfontein Dam are accordingly far lower than those from Vaal Dam. Water is therefore kept in reserve in the more efficient Sterkfontein Dam and only released once Vaal Dam is at its minimum operating level thus saving appreciable evaporative losses.
- The dam with the largest storage capacity is the Gariep Dam on the Orange River with a capacity of 5 343 million m3.
- The dam with the longest crest is Bloemhof on the Vaal River with a length of 4 270 m.
- The shortest dam is Hellsgate near Uitenhage built in 1910 with a crest length of only 4 m. This concrete dam with a height of 26 m is built in a narrow gorge.
- The dam with the largest wall volume (volume of material) is Sterkfontein near Harrismith with an earthfill volume of 19.8 million m3. Sterkfontein Dam is the only South African dam in the ICOLD Register of the World’s Largest Dams on account of this characteristic.
- The largest floods are expected in the Vaal River and provision has been made in Vaal Dam for a spillway capacity of 25 000 m3/s. The two major dams on the Orange River each have a spillway capacity of 20 400 m3/s.
- The dam with the largest water surface area is Gariep at 352 km2 (352 million m2).
- The Woodhead Dam on Table Mountain constructed in 1897 (50 m height) was recently awarded the American Society of Civil Engineers (ASCE) International Landmark status in 2008 (see SAICE Journal October 2008).
Contents of SA Register of Large Dams
The information in the Register is as follows with the various abbreviations used in the tabulation are given below:
- Number: A sequence number to track the number of dams.
- Locality Number: Based on the Drainage Regions in South Africa and a unique number for the specific dam. The 1999 Drainage Region map is on the DWS website here although there have been some problems in accessing the large file. Some dams have not been allocated a number yet.
- Name of dam: The current dam name is given. An asterisk (*) after the name indicates that Notes are included in the appropriate column which might pertain to previous dam name/s or other matters.
- Special features:
- A abandoned
- H heightened (raised)
- L lowered
- U unchanged
- R rebuilt
- C under construction.
- International:
- I if dam abutments are in different countries
- O if dam abutments are in the same country
- River: Tr = Tributary.
- Dam type: Combinations of dam types are common:
- CB buttress
- BM barrage
- ER rockfill
- MV multiple arch
- PG gravity in masonry or concrete
- TE earth
- VA arch
- XX unlisted
- Sealing: The position and type of watertight member is described as follows.
- Position:
- f upstream facing
- h homogenous dam
- i core
- x unlisted
- Type
- a bituminous concrete
- c concrete
- e earth
- m metal
- p plastic
- x unlisted
- Foundation:
- R rock
- R/S rock/soil
- S soil
- X unlisted
- Height of dam: Height in metres (m) above lowest foundation.
- Length of dam: Length in metres (m) measured at crest.
- Volume of dam body: Expressed in thousands of cubic metres (103 m3).
- Reservoir capacity: Expressed in thousands of cubic metres (103 m3).
- Area of reservoir: Expressed in thousands of square metres (103 m3).
- Length of reservoir: Expressed in km at the longest point.
- Purpose(s) of reservoir: In order of decreasing priority:
- C flood control
- F fish farming
- H hydroelectricity
- I irrigation
- N navigation
- R recreation
- S water supply
- X other or unlisted
- Area of reservoir: Expressed in square kilometres (km2).
- Spillway capacity: Expressed in cubic metres per second (m3/s).
- Spillway type:
- L free overspill
- L/V gated-free overspill
- V gated
- X other
You can download the Excel file here.