> How long does it take for that water to re-enter the ecosystem in a usable way? It depends on where you got the water from. If you got it from a river or la

> How long does it take for that water to re-enter the ecosystem in a usable way? It depends on where you got the water from. If you got it from a river or lake, probably "until the next time it rains". If you got it from an aquifer, then it depends on how long it takes water to filter down into the aquifer, assuming it can do so at all. > Water isn't just destroyed, yeah? In the case of aquifers it actually can be, effectively. Per https://en.wikipedia.org/wiki/Aquifer#Human_dependence_on_groundwater https://en.wikipedia.org/wiki/Aquifer#Human_dependence_on_gr... second paragraph: Fresh-water aquifers, especially those with limited recharge by snow or rain, also known as meteoric water, can be over-exploited and depending on the local hydrogeology, may draw in non-potable water or saltwater intrusion from hydraulically connected aquifers or surface water bodies. This can be a serious problem, especially in coastal areas and other areas where aquifer pumping is excessive. In some areas, the ground water can become contaminated by arsenic and other mineral poisons. https://en.wikipedia.org/wiki/Ogallala_Aquifer#Aquifer_water_balance https://en.wikipedia.org/wiki/Ogallala_Aquifer#Aquifer_water... is a worthwhile read with specific numbers for a specific aquifer that illustrates some of the possible problems. All of which is to say that in some places (and in particular in much of the Western US) water may closer to a non-renewable resource than a renewable one if it comes from an aquifer. At least on years-to-decades timescales.