, Water History

Blyderivierspoort – dam of extraordinary beauty Chris Snyman Chris

The Blyderivierspoort Dam in north of Hoedspruit. The outbreak of the Second World is situated in one of the most spectacular Modern irrigation started in the War stemmed any further develop- Lower Valley in the late ment, and it was only in 1948 that the surroundings in . Lani van 1800s following the settlement of Irrigation Department again inves- Vuuren takes a peek into the history of this Voortrekkers in the area. However, tigated the possibility of establishing dam. Tsetse fly and malaria as well as skir- a dam and bulk irrigation infra- mishes with local populations kept structure here. The only irrigation significant tributary of the irrigation development to a minimum. of consequence could be found on Olifants River, the Blyde Only after the introduction of DDT in the farm Moriah, where an irrigation River rises on the western the 1930s and 1940s did permanent furrow taking water directly from the slopesA of the , near Sabie crop farming take off. The first inves- in Mpumalanga. It flows northwards tigations towards the establishment of past the town of Pilgrim’s Rest for a large irrigation scheme were under- History in the making more than 100 km through a region taken prior to the Second World War. of extraordinary beauty along the In the subsequent Irrigation Depart- n 1972, history was made when the eastern escarpment and through the ment report published in 1936, Circle IDepartment of Water Affairs’ first Blyderivierspoort. Here the Blyde Engineer MA Kean proposed the con- female engineer to work on a construc- River cascades down a steep series struction of a dam on the farm Rietvley tion site, A Mouton, joined the team at of rapids to its lower reaches, where 25 in the Lower Breede River Valley Blyderivierspoort­ Dam. it again flows northwards to join the with a capacity of 333 million m3.

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Left: An artist’s illustration of the Blyderivierpoort Dam made prior to its construction.

Below: A close-up of the energy dissipaters situated in the dam wall. DWA

Blyde River had been established. At irrigation scheme would be contem- this stage there were still only around plated by the government. 200 whites living in the valley (the The mining com- population of 5 000 black people were plex was established in the 1950s, not considered), of whom only 31 and subsequently the Phalaborwa were farm owners. Barrage was constructed in 1966 to This proved not motivation supplement water to the complex. enough to warrant such significant The supply from this 235 m-long expenditure. The Irrigation Depart- concrete structure was controlled by ment was also demotivated by the the Phalaborwa Water Board, which results of soil studies, which indicated had the right to abstract 28 127 290 that soil conditions were mostly not m3/day from the Olifants River. conducive for irrigation. It was conse- However, upstream developments, quently decided that, until such time such as the raising of the Middelburg that the (white) farming community and Loskop dams later caused the had increased considerably and had water supply to the mines to fall short. become experienced in local farm- This pushed the idea of a dam on the ing and irrigation methods, no large Blyde River back onto the table. The DWA/eWISA

Origin of the name ‘Blyde’

he naming of the Blyde River is of Dutch origin meaning ‘happy river’. It was so called because in 1844 Voortrekker Tleader Hendrik Potgieter and others returned safely from Delagoa Bay where they had gone in search of a harbour for trading to the rest of their party of trekkers who had considered them dead. While still under this misapprehension they had named the river, where they had been encamped, Treurrivier, or ‘river of weeping’. Source: New Dictionary of South African Place Names by PE Raper. Wikipedia

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sources

• Union of South Africa (1948) Irrigation Department. Regional report (preliminary) on Blyde River, Transvaal. Government Printer: Pretoria. Report No: 119A • South African National Committee on Large Dams (1994) Large Dams and Water Systems in South Africa. JP van der Walt and Son: Pretoria • Turton, AR, Meissner, R, Mam- pane, PM and Seremo, O (2004) A Hydropolitcal History of South Africa’s International River Basins. Water Research Commission Report No. 1220/1/04. Water Research Commission: Gezina. • Republic of South Africa (1969) Chris Snyman Chris Secretary for Water Affairs report on the proposed Blyde River Gov- ernment Water Works (Blyderivier Poort Dam). Government Printer: Pretoria. Report No: WP Q-‘69

double curvature dam could be con- structed, but later this was changed to a concrete gravity arch. This was decided as the most suitable type of structure because the massive but weathered and jointed condition of the foundation necessitated a good distribution of load over a wide area. The maximum height of the dam is 71 m, with a crest length of 240 m and a maximum wall thickness of 30 m. Blyderivierspoort Dam has a maximum capacity of 54 million m3. The availability of alluvial depos-

Chris Kirchhoff/Media Club South Africa Club South Kirchhoff/Media Chris its allowed the crusher to be located inside the dam basin, thus avoiding 1969 White Paper suggested the con- establishment of roads and houses Top: The Blyde unnecessary scarring of the natural struction of a dam on the farm Blyde by the Department of Water Affairs. River rises on the area. An aerial ropeway transported western slopes of the River Poort in the district of Pilgrim’s Excavation blasting started a year the aggregate from the crusher to Drakensberg, near Sabie Rest with the purpose of stabilising later in April 1971. By June, con- in Mpumalanga. the batching plant. Aggregate was the supply of water to irrigators in the struction of the cofferdam started. stockpiled in the works area to facili- Blyde River irrigation district while, at This was completed in April 1972, Above: A spilling tate early withdrawal of the crusher the same time, increasing the quantity despite setbacks caused by unprec- Blyderivierspoort Dam. from the basin. The batching plant The dam is 71 m high, of water available to the Phalaborwa edented floods (1 200 m3/s). In comprised aggregate bins into which with a crest length of Water Board. August 1972, the first concrete was 240 m. the ropeway buckets discharged their The proposal was approved by placed via cableway, and two years loads, recovery tunnel and conveyor Parliament and preliminary work later the river diversion gap through belts leading up to the top of the 30 m- on the dam site just below the con- the wall was closed and the crusher high batching and mixing tower. The fluence of the Blyde and Ohrigstad removed out of the reservoir basin. dam was completed in 1975, and rivers started in April 1970 with the Originally it was thought that a spilled for the first time a year later. 

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