NZ does a lot of geothermal so i know a little more about it than most but i'm no geologist. couple points - first, don't confuse depleting the ground water wi

NZ does a lot of geothermal so i know a little more about it than most but i'm no geologist. couple points - first, don't confuse depleting the ground water with depleting the heat. a lot of geothermal taps the heated groundwater and yes, you can screw that up by extracting more than is re-plenished. luck/geology is your guide for what the ratio is though. binary systems fare better as you pull the water out, suck off the heat and then inject the liquid back in. secondly, the big problem with geothermal is that the wells cost 10s of millions of dollars. the financial decisions far outway the technical ie, you have to spend $30-40M to get a well that's active upfront but it may take decades to get it paid back. hot dry wells are like throwing money into a pit and then paying someone else to burn it. if you're relatively small then you can eliminate this risk by running your own fluid up and down but remember these wells are only 20-30 cm in diameter. oh - and don't forget that if you mess it up, presurised ground water or mud will use your well to get through an impermeable rock layer and into an aquifer. there's some well head in Indonesia that's been pumping out cubic km's of hot mud for the last 20 years...