The ‘Muela Hydropower Station is situated mid-way between the Katse Dam in Lesotho and the Ash River Outfall in South Africa. The powerhouse houses three Francis Turbines that use water transferred from the Katse and Mohale Dams through the Katse Intake Tower to generate 72 megawatts of electricity for domestic and export purposes.
Muela Hydropower Station and Tailpond Dam
The ‘Muela Hydropower Station is situated mid-way between the Katse Dam in Lesotho and the Ash River Outfall in South Africa. The water enroute to South Africa uses three Francis Turbines that are installed in the powerhouse to generate 72 megawatts of electricity for domestic and export purposes.
Before the station was built, Lesotho was 100% dependent on South Africa for electricity.
After generation of electricity, water exits from the three (3) 24MW turbines into the ‘Muela Tailpond, a 55 metre high dam which provides the headwater for the continuation of water delivery to South Africa. This dam has an intake tower which first takes water into the Delivery Tunnel South which is connected with the Delivery Tunnel North for delivery to the Ash River Outfall at Clarens in South Africa.
Water from the ‘Muela reservoir can be released into the Little Caledon River for through two outlet valves. The Little Caledon bypass allows water to be diverted down the Caledon River to supply emergency water to the Eastern, Central and Southern Free State, as well as Lesotho border towns during severe drought conditions.
The by-pass system is installed around the power station from the Transfer Tunnel to the Tailpond Reservoir. It is a requirement in the Treaty to ensure continued delivery of water during outage or service requirements on the Hydro-Power Station.
The 37km long Delivery Tunnel is made up of two sections as follows:
Delivery Tunnel South
The 15km long Delivery Tunnel South, comprises of the portion which starts from the ‘Muela Tailpond in Lesotho to the Lesotho-South Africa Border. Water is transferred from the Katse Reservoir via the ‘Muela Intake works into the Delivery Tunnel and then into the Delivery Tunnel North from the border to the Ash River Outfall in South Africa.
Enroute to the Ash River Outfall, water passes through two flow metres installed in the measuring chamber, excavated as part of the Ngoajane drill and blast river-crossing siphon on the Delivery Tunnel South.
These measuring devices measure the volume of water delivered from Lesotho to South Africa. Data from the metres is transmitted by telemetry to the main control centre at ‘Muela.
Flow is once again measured at the measuring weir built into the Ash River Outfall in South Africa.
Delivery Tunnel North
The Delivery Tunnel North represents the 22 km waterway system which starts from the Lesotho-South Africa Border to the delivery point on the Ash River Outfall at Clarens in South Africa.
THE ASH RIVER OUTFALL
The Ash River outfall is a concrete tunnel outlet structure which is built on the gradient so that water has to flow uphill to slow the flow of water that enters into the Ash River watercourse. This helps to dissipate the energy of the increased water volume in the area, thereby mitigating the environmental impact in the area.
From the Ash River Outfall, the water follows the natural watercourse into the Liebenbergsvlei and Wilge Rivers as they wind towards the Vaal Dam, over a distance of 200 km.
|Principal Statistics of the ‘Muela Dam|
|Dam Type||Double Curvature Concrete Arch|
|Maximum height above foundation||55m high|
|Concrete Volume||65,000 m³|
|olume reservoir||6 million m³|
|Spillway Crest Length||72m|
|Capacity of spillway||584 m³ per second|