Wow, amazing, I thought underground water was the same temp from north to south (I assumed a little variation) based on the insulating qualities of land? The gypsum mines by us are used for 'cold storage' for business records and data tapes etc since they stay about 52 degrees year around.
If you went 100 feet down and created a storage cavern in N florida wouldn't the air temps in that cavern still be 52 degrees? If so how does the ground water stay at 72-74?
I do notice that our ground water does get colder in winter somehow. I say that only because the water from the tap (well) is much colder sooner when taking a drink or brushing teeth in winter and the setting on the hot water heater has to be turned up a fuzz to get to the same setting on the shower mixer handle. It takes more hot water to mix with the colder cold water to get the same comfort temp in the shower so you notice the mixer handle is at a different position.
You probably save lots of energy when your hot water heater brings the temp from 72 to 102 deg or 103 deg vs our 48 or 50 to 102 or 103!
Can you imagine if you had access to a warm spring up here in the northern wastelands and could pump 78 deg water into your pond all winter. You would have an awesome growing season and fish would love their 'hottub'
