Loskop Dam Interesting Facts
- The dam wall was originally between 1934 and 1938, and was built entirely by hand.
- In 1978/9the dam was drained raised by 9 meters to its current height of 54 meters.
- The bas is ₊/₋24 meters thick and length is 506 meters long.
- The entire dam wall rests on a solid rock base.
- The canal entire engineer “Col. DF Roberts” has his remains cemented into the wall.
- The canal, which runs down the left hand side of the river measures 480km.
- The canal system irrigates about 1600 hectors of farmland; the lowest point of the is only 107 meters below the dam wall.
- If the dam wall gates are reopened the maximum amount of water is 29,000 liters per second.
- The dam itself is able to supply framers with water for up to three years without rain.
- The catchment area of the Olifants River, which flows into the dam , is some 1225 million hectors including areas such as Hendrina, Dacel, Ermelo and Bronkhorstspruit. Included in this catchment area is the Wilger and Klein Olifants River that also contributes to the dam.
- On the 15th of February 1996 at 3am dam registered at 117,63%At this point the water flowing from the Oliftants River was 3.2 million cubic liters per hour.
- At 100% the dam olds 348 million cubic litters with the surface area of 2385 hectares.
LOSKOP DAM – Early Local Engineering Ingenuity
( An article in The Water Wheel dated September / October 2008 )
Despite being constructed more than 70 years ago , the Loskop Dam , situated across a gorge on the Olifants River , about 32km south of Groblersdal , in Mpumalanga , remains one of the largest dams in South Africa.
Lani van Vuuren reports
The history of Loskop Dam can be traced back to the 1840`s when the first Voortrekkers settled in the Kruis River valley not far from the present dam site. The first farms in the Olifants River valley , including Lagersdrift and Kalkfontein , were pegged out as long ago as 1886. Back then , the farmers cultivated mainly wheat under dry-land conditions.
Notwithstanding the establishments of these farms , due to malaria and cattle diseases like East Coast fever , initial development was slow until the turn of the nineteenth century. In the early Twentieth century , many farmers trekked with their cattle from the Highveld to the Olifants River valley during winter. Each winter they stayed a little longer until they eventually settled in the area in greater numbers. This was particularly during the years 1917 and 1924.
It was in 1917 that the first private dam in the area was completed on the farm Rooikraal with government assistance. Thanks to irrigation , the wheat crop on this farm increased from 150 to 8000 bags a year. Around 1925 , other small irrigation schemes were completed involving both weirs and pumping water from the river. This led to the establishment of the Hereford Irrigation Board to serve an area of about 10km downstream of the present Loskop Dam.
The proposed Hereford Scheme included an improvement of the diversion weir at Kameeldoring , and also a 41km-long canal extending as far as the Moses River. After a loan of R 70 000.00 was granted by the Land Bank , work started during 1928 under the supervision of the Department of Irrigation. The various contracts were completed in 1930.
The early success of this scheme gave rise to a petition by farmers for the establishment of the Loskop Irrigation District. The old Transvaal Irrigation Department had undertaken a reconnaissance survey of such an irrigation scheme on the Olifants River between 1905 and 1907. However , back then it was recommended that an irrigation scheme should not be implemented until the valley was more densely populated , and not before there was the prospect of a railway service to the area.
Construction of the Loskop Dam on the farms Loskop and Vergelegen started in 1934. As was the case with many other government projects at the time , only white married white men were employed on the Loskop Dam construction site. They were paid five shillings a day and provided with free accommodation , food and medical attention.
The number of labourers employed at the end of March 1935 was 440 men. Throughout 1935 and 1936 the Director of Irrigation noted in his report that there was a shortage of labour , especially concerning the construction of the Loskop Dam. The department then asked the Department of Labour to allow single white men on the site as well.
By the end of 1937 the dam was nearly complete , except for a number of minor tasks on the superstructure. Good rains fell in December 1937 and January 1938. This resulted in the dam being filled and it overflowed in January 1938.
( The estimate cost of the entire project was 1.5 million British Pounds.
In June 1935 , a start was made on the canal system , which was eventually completed in 1948 , after an interruption in the work as a result of the outbreak of World War 2. The total length of the canals is 480km.
The Loskop Irrigation Scheme also resulted in the establishment of a town , Groblersdal , laid out on a farm owned by W.J. Grobler. The town was proclaimed in 1938.
Development in the Witbank-Middelburg area necessitated the raising of the dam wall so that the portion of the assured yield which had in the meantime become affected as a result of the construction of upstream dams such as Rondebosch , Witbank and Doornpoort dams could be restored. By 1971 , when the recommendation to raise the dam wall was made , the Loskop Dam system of canals served about 25 000 ha of farmlands.
Between 1974 and 1980 the dam wall was raised by nine meters to a height of 54m above the lowest foundation level.
The full supply capacity of the dam is 362 million cubic meter.
The ashes of Lt Col Robert (He was the resident engineer at the Department of Irrigation`s very first hydraulics laboratory near the dam site ) were originally buried on an island in the dam. As the raising of the wall was to result in the inundation of the island , the ashes were removed and reentered in a niche on the left flank of the dam wall.
FACTS AND FIGURES
| Year of completion | 1938 ( raised in 1979 ) |
| Purpose | Irrigation , domestic, industrial |
| River | Olifants River |
| Nearest town and province | Groblersdal , Limpopo |
| Type | Mass concrete |
| Net storage capacity | 348 million cubic meter |
| Wall height above lowest foundation | 54m |
| Crest length | 506m |
| Material content of dam wall ( original & raised ) | 415 000 cubic meter |
| Type of spillway | Uncontrolled |
| Capacity of spillway | 7 750 cubic meter / second |
| Surface of dam at full supply level | 2 350 ha |
