Reservoirs in Orange Farm, Ennerdale and Lawley are very low.
As a result, Johannesburg Water said it is placing measures in place, such as closing outlets at night.
The local water utility also said it is monitoring the Lenasia Cosmos, Lenasia Hospital Hill and High level reservoirs.
Interventions to increase water are closing at night, as well as rescheduled openings throughout the day.
Systems that are stable are the Commando, Randburg/Roodepoort, Central Systems, Soweto and Midrand.