CAP water comes from the Colorado River by agreement, not by right
The Central Arizona Project (CAP) channels water from the Colorado River to cities and towns in Arizona. CAP gets its water from Lake Mead. CAP has an agreement with six other states and Mexico.
The amount of water Arizona is allowed to take for CAP is designated by agreement with two other states, Unfortunately, a huge water hog, California, drinks from the same trough. Nevada, another water hungry state (how many water displays are in Las Vegas?) also partakes.
CAP water came to Oro Valley in 2012
CAP water was not used by Oro Valley until six years ago. That was because there was no way to get water to Oro Valley from the reservoirs in Avra Valley. First, the reservoirs had to be built; then the City of Tucson had to get the water. Oro Valley Water signed an agreement with Tucson Water to "wheel" water through
CAP water is a significant contributor to Oro Valley's water supply
Oro Valley uses CAP water to recharge its wells. As this chart shows, Oro Valley now uses less groundwater than its target maximum groundwater use. Prior to CAP becoming accessible, this was most certainly not the case.
Oro Valley now depends on CAP water to replenish its wells. Oro Valley can not provide water at a "safe well usage" level without it.
The prolonged western states drought threatens the Colorado River water supply
There is a prolonged drought in the West that has reduced available water levels.
"The U.S. Bureau of Reclamation, responsible for divvying up Lake Mead’s water and electric power, in August reported a 57 percent chance that Lake Mead’s water levels would be so dismal in 2020 that Arizona and Nevada would face cutoffs." (Source)
Specifically, Lake Mead and Lake Powell that feeds it, are at 38% and 45% of maximum levels. (Source) The sources that feed these lakes aren't in much better shape. (Read more about the CAP water situation here and here.)
Our conclusion: Be good for the town to consider whether it really is wise to encourage growth in total water consumption given the possibility that CAP water could be restricted.
