The dial shows Christchurch's residential water use for the previous day, this includes commercial users but not usage from private wells. The personal use information is just residential use.
Green zone (0 to 140 million litres): We all need to work together to make sure our water use stays within the green zone. This zone represents an average day's water use. Lower water use means we can take more wells out of service, upgrade well heads faster and then stop chlorinating the water sooner.
Yellow zone (140 to 200 million litres): If our water use gets into the yellow zone this could affect our ability to upgrade well heads. We can only upgrade well heads when water use is low and they’re not being used.
Red zone (over 200 million litres): If our water use stays in this zone for a number of days we may need to impose water restrictions. It's not that we’re going to run out of water, it's that when demand for water is high we can only supply so much through the network. The pumps, pipes and reservoirs can only deliver a certain amount of water at any one time. If people use too much there could be a pressure loss in the system, shortages or not enough to fight fires.