A growing population in some of the world's driest areas is leading many people to study the economics of water. Why is a diamond expensive and water free? It's a famous question posed in economics.
Actually that may not persist much longer.
Here is the main category for the economics of water.
To get an idea of how much renewable water a country has, go to Worldbank/World Development Indicators database.
Type freshwater as a search term.
Or check p.142 of the paper copy of World Development Indicators.