Currently, the Clearwater blend is very similar to the average groundwater most of our customers use. As it moves through our drinking water system, the blend mixes repeatedly with groundwater from other sources. Because of this, there is no way to use water quality characteristics to “track” the Clearwater supply as it flows through the drinking water system.
The primary purpose of using the blend of recharged Colorado River water and groundwater is to allow the City to shut down wells in central Tucson that have caused groundwater declines and contributed to land subsidence. Because of this, the blend is first directed into those areas of town where these wells were located — mostly in central Tucson. Since 2001, more than 80 wells were taken out of service or put in standby mode (shut off, but kept ready for use to meet any emergency). This has allowed groundwater levels in central Tucson to begin to recover naturally. Any of the blend that is not used up in the area where the wells have been put on stand-by flows or is pumped wherever it is needed to meet customer demand or to fight fires.
Since 2001, the amount of Clearwater blend has risen to approximately 50% of the water Tucson Water delivers annually. During the summer months, when average daily demand for water is around 130 MGD, the water supply from Clearwater will be used up relatively quickly, before it can spread very far across our service area. During the winter months, when average daily demand is less than 80 MGD, the blended water will spread over a much wider area. On some low-use days, most Tucson Water customers have at least some of the Clearwater blend reach their taps.