How to slake a planet's thirst.
D003247:Conservation of Natural Resources / Q000191:economics / Q000379:methods / Q000639:trends; D006801:Humans; D011057:Politics; D011634:Public Health / Q000639:trends*; D018508:Water Purification / Q000191:economics / Q000379:methods; D014881:Water Supply / Q000191:economics / Q000592:standards* / Q000706:statistics & numerical data