Depends on the aquifer. The assumption you're making is "natural precipitation recharges aquifers" and that assumption is not always true. Sometimes it's true,

Depends on the aquifer. The assumption you're making is "natural precipitation recharges aquifers" and that assumption is not always true. Sometimes it's true, but it takes 10,000 years so if you mean "recharges while our current civilization exists" then it's effectively false. This is the case for the Ogallala aquifer which supplies 27% of the irrigated land in the US. https://en.m.wikipedia.org/wiki/Ogallala_Aquifer https://en.m.wikipedia.org/wiki/Ogallala_Aquifer Sometimes it's just completely false because the groundwater exists as a sealed bubble of water put there during the last ice age. That glass of water you just drank? Congratulations! It's 25,000 years old, and we know this through isotopic analysis. Your drinking water was mined and once it's gone it's gone forever. https://en.wikipedia.org/wiki/Fossil_water https://en.wikipedia.org/wiki/Fossil_water Sometimes recharge can happen but only via snowmelt at high altitudes (and of course Tucson doesn't get much snow). Sometimes it's completely true. The Edwards aquifer in Texas gets recharged every time it rains. https://en.m.wikipedia.org/wiki/Edwards_Aquifer https://en.m.wikipedia.org/wiki/Edwards_Aquifer So it's complicated. Generally speaking, deeper groundwater sources take longer to recharge if they recharge at all. I don't know the particular groundwater situation around Tucson. > why are we building projects that need tons of power and water in the Sonoran desert instead of next to the Great Lakes Evaporative cooling is effective and cheap where humidity is low. It doesn't work well where humidity is high.