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 is predicted to be shut off. It is predicted that at least 3 years of good winter rainfall is necessary for this dam to return to previous healthy levels.
Rainfall and capacity
Theewaterskloof dam has a capacity of 480 million cubic metres of water. The catchment area of 500 square kilometres 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.
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.
