Phoenix mostly doesn't drink Colorado River water

Chandler is about the same (50-something% SRP, 30-something% Colorado, < 10% groundwater). Some groundwater use is sustainable, by the way; the cities do calculations of how much water seeps into the ground from rain or irrigation, and the idea is you're supposed to pump up less than that amount, minus a 5% "cut to the aquifer" to make sure there's extra margin to avoid depleting the aquifer.

> For the City of Phoenix (the political city, plus about half of Paradise Valley), the tap water breaks down like this: roughly 60 percent originates as Salt and Verde River water, delivered through the Salt River Project. A little under 40 percent originates as Colorado River water. A very small amount is groundwater, pumped from local wells. That is the portfolio. The number that gets cited in most coverage (41 percent groundwater, 36 percent Colorado, the rest split) is the statewide figure, the whole of Arizona averaged together. It is not Phoenix. Phoenix is its own arrangement, and the arrangement is unusual.

p.s. good article, by the way. It highlights a lot of the byzantine quirks of water management in Arizona.