"One interesting idea that has emerged in dry places (notably Australia and Israel) is water markets. These make sense on a pretty basic level: if something is scarce and valuable, I should be able to buy, sell, and speculate on it."
Given that water is a fundamental necessity, it's supply should not be subject to rigged markets and monopolistic pricing, which is the norm when private investors try to take over natural monopolies (i.e. there's no 'competition' in water supply systems, rather like electricity markets.)