Growing enough food to feed the world depends on water supply. The challenge can be met, though there are conditions. 

Microbial pollutants of water are a major source of health and economic problems the world over. Scientific methods are being developed to trace pathogens and make water cleaner, though it is an uphill struggle. 

To most people, water is a public good, like air. Yet in practice, its proper management and distribution raise inherent challenges of allocation, which is where economic principles can help. Supplying water costs money. Moreover, though a renewable resource, it is fragile and can be spoiled.

The OECD might not be thought of as playing a role in water supply and management, but in fact it has a leading role, as it does in all areas of sustainable development.