It is because it is so vital that we should get a clear signal of its value. We should be paying for what it is worth. I don't think the supply of ground wate

It is because it is so vital that we should get a clear signal of its value. We should be paying for what it is worth. I don't think the supply of ground water and the demand for it vary wildly. And that is what market prices are based on. But a sudden change in prices would definitely occur when it is depleted. Rain water is a different thing. The supply varies greatly. But it is also completely renewable. Industries that use it should adapt to its potential scarcity and prices help to do that.