They can take wastewater (which is no longer fresh), clean it up for use, and return it back to the system.
While Arizona is landlocked there's also not a ton of distance between it and the Gulf of California so they could do desalinization, although I imagine that's too costly to consider at the moment.
> It has its own water treatment plant at its Ocotillo campus in Chandler that’s similar to a municipal plant. There’s also a “brine reduction facility,” a public-private partnership with the city of Chandler, that brings 2.5 million gallons of Intel’s wastewater a day back to drinking standard. Intel uses some of the treated water again, and the rest is sent to replenish groundwater sources or be used by surrounding communities.
They're taking raw untreated river/lake/aquifer water, purifying it to an incredible degree for the fab. When they use the water it gets cleaned again.
Now that water can either be returned to the river/lake/aquifer or if you clean it sufficiently well it can go straight into municipal drinking water supplies. That's how this fresh water comes out of nowhere.
Maricopa and Pinal counties have lots of agricultural water that either comes directly off the Colorado river via canal, or is pumped from shallow alfalfa field runoff groundwater that is too full of nitrates to be even remotely potable.
We also, unlike the CA Central Valley or the Midwest who are apparently cool with depleting their resources as fast as humanly possible, are acutely aware of our groundwater supply constraints, given that we live in a desert, and practice a lot of aquifer recharge and management.
Intel cleans it, uses it, and dumps it into aquifer recharge, which cleans it even further.
The midwest gets more than enough water via rain, so nobody worries about water. Farmers don't irrigate crops, they just accept lower profits in drought years. You might be thinking of the west where water is a problem.