SA Register of Large Dams

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SOUTH AFRICAN REGISTER OF LARGE DAMS

South African Register of Large Dams

SANCOLD is pleased to announce that the South African Register of Large Dams can now be downloaded from the SANCOLD website.  The Register is given in the form of an 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 15m reckoned from the lowest point of the foundation.
  • Dams between 5m and 15m 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 5m 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 Affairs and Forestry.   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 with Category I dams for small dams with low hazard potential rating.  At the other end of the scale Category III dams have the highest potential rating and require the most attention from a dam safety perspective.  Category II dams are of an intermediate nature and also require the involvement of dam professionals.

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 Affairs and Forestry (DWAF):

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 DWAF website (www.dwaf.gov.za/DSO/publications.asp ).  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.

Distribution of dams registered according to size class

Size class

Number

%

Small (5 m – 12 m)

Medium (12 m – 30 m)

Large (30 m and higher)

3 232

1 033

192

73%

23%

4%

Total

4 457

100%

Distribution of registered dams according to reservoir storage capacity

Capacity (x 106 m3)

Number

%

0,00 – 0,05

0,05 – 0,10

0,10 – 0,25

0,25 – 1,00

1,00 – 10,00

10,00 – 100,00

100 – 1 000

1 000 – 10 000

149

1 108

1 591

995

423

129

54

8

3.3%

24.9%

35.7%

22.3%

9.5%

2.9%

1.2%

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.

Classification of existing dams according to size class & hazard potential rating

Size

class

Hazard potential rating

Total

 

Low

Significant

High

Small

Medium

Large

2 294 (55%)

293 (7%)

1 (0%)

758 (18%)

499 (12%)

19 (0%)

41 (1%)

134 (3%)

134 (3%)

3 093 (74%)

926 (22%)

154 (4%)

Total

2 588 (62%)

1 276 (31%)

309 (7%)

4 173 (100%)

 

Category classification of existing dams

Category

Classification

Number

of dams

%

Category I*

Category II

Category III

2 335

1 558

280

56.0%%

37.3%

6.7%

Total

4 173

100%

* 33 of these dams are actually medium size dams that have been classified as Category l dams, in terms of regulation 3.2 of the dam safety regulations.

Interesting South African Dam Facts

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 18m and crest length of 293m.
  • 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.

graph1 graph2

 

  • 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 type.  Most dams in South Africa are constructed from earthfill.

Dam type

% of Total

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

m

Number

of dams

% of total

 

%

<30

950

85%

31-50

27

11%

51-70

28

2%

71-90

8

1%

>90

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 order)

Height

 

m

Volume

 

million m3

Storage

capacity

million m3

Water

surface area

km2

Gariep

88

1.4

5 343

352

Pongolapoort

89

0.6

2 267

132

Sterkfontein

93

19.8

2 617

67

Vaal

63

1.4

2 610

323

Vanderkloof

108

1.3

3 187

133

  • 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 270m.
  • 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 volume 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 (50m height) was recently awarded the American Society of Civil Engineers (ASCE) International Landmark status in 2008.  See SAICE Journal October 2008.


Contents of the 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 DWAF website although there have been some problems in accessing the large file.   Some dams have not been allocated a number yet.

http://www.dwaf.gov.za/BI/MapServices/WRC/map.asp?mapserv=base

http://www.dwaf.gov.za/BI/MapServices/

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.

Please download the excel file here

 

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Workshop and Technical Tour in China: October 2017

To promote the “World Declaration on Hydropower and Dams for African Sustainable Development” launched at the ICOLD 80th Anniversary in 2008 in Paris as well as the “World Declaration on Water Storage for Sustainable Development” launched at the ICOLD 24th Congress in 2012 in Kyoto, CHINCOLD has been carrying out annual workshops and study tours for members of the African Regional Club since 2009. This year CHINCOLD has invited members of the African Club to the 10th Workshop and Technical Tour in October 2017 in Changsha, Hunan Province of China.

Kindly contact the Secretary for more details. Submissions in the correct format to the Secretary of SANCOLD is required by 15 May 2017

Please download CHINCOLD CV Template here

 

The Annual South African National Committee on Large Dams (SANCOLD) Conference in 2017 will be held in Centurion, Tshwane between Wednesday 15 and Friday 17 November 2017

 SANCOLD invites all from Africa and the wider family of ICOLD to participate in the Conference which will include technical presentations, technical panel discussions and an exhibition. This event will offer dam and water resources engineers as well as all contributing to the dam engineering industry important international, regional and local linkages, networking and the exchange of knowledge and experiences.

SANCOLD 2017 will be an ECSA Continuing Professional Development (CPD) accredited event and attendance for the three days will receive 3.0 credits (1 credit /day).

Please download the Abstract format 2017 V1 file here

Please download the First Announcement 2017 file here

 

 

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