Knellpoort_Dam=The 50 m high Knellpoort Dam  was completed in 1988. It was the first arch gravity Roller Compacted Concrete (RCC) dam in the world and has a gross storage capacity of 137 Mm³a.
In order to prevent similar siltation problems to those experienced at the Welbedacht Dam, the Knellpoort Dam functions as an off-channel storage dam with a relatively small catchment area of only 798 km² and corresponding MAR of approximately 20 Mm³a. Water from the Caledon River is pumped to Knellpoort Dam from the Tienfontein Pumping Station via a 2 km long canal which is equipped with a silt trap to reduce siltation in the main reservoir.
The Knellpoort Dam is currently used to supplement the water in the Welbedacht Dam for abstraction to Bloemfontein via the Caledon Bloemfontein pipeline as well as to support Rustfontein Dam via the Novo Transfer Scheme. Water will then be transferred directly from the Knellpoort Dam into the Rustfontein Dam catchment.
The capacity of the Novo Transfer Scheme which is transfering water from the Knellpoort Dam to the Modder River, will in future be increased in stages in accordance with the needs of Bloemfontein and Botshabelo and is expected to reach a maximum transfer capacity of 150 Mm³ by the year 2030.
Image: McKenzie