Driekloof Spillway Traditional Cache
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Difficulty:
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Terrain:
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Size: 
(small)
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The cache is on the opposite side of the road from the designated view point. Be careful and enjoy the easy find. The cache container is small plastic labeled container.
Driekloof Dam, the upper reservoir of the Drakensberg Pumped Storage Scheme, is located in an arm of the Sterkfontein basin. Pumping from the Tugla River will first fill the Driekloof Dam and the water for inter-basin transfer will flow over the spillway into the Sterkfontein Dam. There will be a rapid fluctuation of water levels up to 22 m below full supply in the Driekloof reservoir over a weekly cycle of pumping and generation of electricity.
The dam is of the rock fill type with a central clay core. The spillway is a baffled apron placed centrally on the embankment .
Main Data
Type -Rock f ill
Height above lowest foundation -46,6 m
Length of crest -500 m
Volume content of dam wail -843 000 m³
Gross capacity of reservoir -35,6 million m³
Capacity of spiliway -312 m³/s
Type of spillway -Baffled apron on embankment
Non-overflow crest -AL 1 702,44 m
Spiliway crest -AL 2 700,0 m
Maximum operating water level -AL 1 702,0 m
The spillway - visible from this view point.
The run-off from the Driekloof catchment is insignificant and does not require a spillway. But, as the secondary function of the dam is to convey the water for the
inter-basin transfer to the Sterkfontein basin, Driekloof had to be provided with a spillway. The solution adopted after extensive investigations is a baffled apron spillway centrally placed on the embankment
The spillway has to perform a dual function, viz:
1. To convey water being pumped from the Tugela River for the inter- basin transfer from Driekloof to Sterkfontein. The maximum discharge of water over the spillway in this direction is 200 m³
2. To convey 312 m³ from Sterkfontein to Driekloof when water levels in the Driekloof reservoir drop below the spillway crest during power generating cycles and when the Sterkfontein Dam is at full Supply level.
To provide the necessary resistance against sliding of the baffled apron slabs, precast concrete beams were placed horizontally into the rockfill during the fill operation. The stabs were then cast in situ on a blinding layer after the completion of the fill and after allowing for initial settlement of the embankment and the foundations. Subsequently the baffles were cast in place as well.
The Driekloof Dam was completed in 1979 and has been in operation since.
Additional Hints
(Decrypt)
Gur juvgr qbg ba gur terra fde jnf na nppvqragny vaqvpngbe.