Theewaterskloof Dam is an earth-fill type dam located on the

Sonderend River The Sonderend River, also known as the Riviersonderend (Afrikaans for ''River without an end''), is a main tributary of the Breede River, located in Western Cape Province, South Africa. The village of Riviersonderend is believed to have taken its ...

near

Villiersdorp Villiersdorp is a town of approximately 10,000 people located in the Western Cape province of South Africa in the Overberg region. Unlike most of the geographical region which specialises in wheat and canola farming, the Villiersdorp Valley is no ...

Western Cape The Western Cape is a province of South Africa, situated on the south-western coast of the country. It is the fourth largest of the nine provinces with an area of , and the third most populous, with an estimated 7 million inhabitants in 2020 ...

South Africa South Africa, officially the Republic of South Africa (RSA), is the Southern Africa, southernmost country in Africa. It is bounded to the south by of coastline that stretch along the Atlantic Ocean, South Atlantic and Indian Oceans; to the ...

. Administratively it is located within

Theewaterskloof Local Municipality Theewaterskloof Municipality is a local municipality (South Africa), local municipality located within the Overberg District Municipality, in the Western Cape province of South Africa. As of 2007, the population was 108,790. Its municipality code i ...

. It was established in 1978 and is the largest dam in the

Western Cape Water Supply System The Western Cape Water Supply System (WCWSS) is a complex water supply system in the Western Cape region of South Africa, comprising an inter-linked system of six main dams, pipelines, tunnels and distribution networks, and a number of minor dams ...

with a capacity of 480 million cubic metres, about 41% of the water storage capacity available to

Cape Town Cape Town ( af, Kaapstad; , xh, iKapa) is one of South Africa's three capital cities, serving as the seat of the Parliament of South Africa. It is the legislative capital of the country, the oldest city in the country, and the second largest ...

, which has a population of over 4 million people. The dam mainly serves for municipal and industrial use as well as for irrigation purposes. The hazard potential of the dam has been ranked high (3).

Dam characteristics

Theewaterskloof Dam water extraction point

Theewaterskloof Dam's earth-fill wall is long and high. An inlet tower and conduit through the wall allow for releases of water into the

. The

spillway A spillway is a structure used to provide the controlled release of water downstream from a dam or levee, typically into the riverbed of the dammed river itself. In the United Kingdom, they may be known as overflow channels. Spillways ensure th ...

can handle a maximum flood of . The Charmaine intake tower draws water from the reservoir into the Franschhoek Tunnel, which conveys it under the Franschhoek Mountains into the Berg River catchment and ultimately into Cape Town's water supply. In winter the tunnel can operate in reverse, conveying surplus water from the Berg River into Theewaterskloof. An additional intake tower supplies water to the Vyeboom Irrigation Board for irrigation of areas around the dam.

Water restrictions

Theewaterskloof Dam 2018 02 10 (28425520089)

Below-average rainfall since 2015 have seen the Theewaterskloof water level drop to critical levels. Water restrictions were imposed by the City of Cape Town in 2016 to meet a target of 600 million litres of water per day, with residents limited to 100 litres of water per day and a ban on car washing, watering gardens and topping up swimming pools with municipal water. By the end of the 2017 dry season, Theewaterskloof had declined to a level of 12.9%, with the last 10% mostly unreachable. A storm in June 2017 brought heavy rain, increasing the level to 15%, but overall rainfall in 2017 remained very low. Media footage of the declining dam level sparked the importance of conserving water. Water restrictions in Cape Town were increased from Level 4 to Level 4b on 1 July 2017, limiting consumption to 87 litres of water per person per day. Rainfall in 2017 remained well below average, and by early 2018 the dam was again approaching critically low level, resulting in water consumption being limited to only 50 litres per person per day, and plans for a possible "Day Zero" in April 2018 when Cape Town's municipal water supply was predicted to be shut off. As a result of good rains in the winters of 2019 and 2020, the Theewaterskloof water level reached 100% in October 2020.

Rainfall and capacity

Theewaterskloof dam has a capacity of of water, and when full the reservoir covers an area of . The catchment area of is served by streams emanating in the Hottentots Holland mountain range. This area has a long-term average of 69 days with precipitation per year. Historically records show we are in a dry period 1mm of rain per square meter equates to 500 000 000 litres falling on this area. Hence it requires a full metre of rainfall with 100% runoff to fill the dam from totally empty, which is unlikely to happen in any single year. It takes a few days for all the runoff to reach the dam. Evaporation and how saturated the ground is affects the amount of water reaching the dam. An average amount of between 9% and 15% is used to offset the values against evaporation and soil absorption. A deeper dam has less evaporation due to less surface area per volume. Theewaterskloof dam.png, Location of the dam Theewaterskloof Dam catchment map.svg, Catchment area of the dam

Social events

The Theewaterskloof Dam is also the home of the annual Synergy Live music festival, one of the biggest outdoor music festivals in South Africa, which typically takes place on the last weekend of November or the first weekend of December.

References

External links