JAY FAMIGLIETTI:

That's right and I'm glad you mentioned that because one of the one of the issues in Cape Town is the lack of development of groundwater and so the future I think in many cities around the world is a combination of surface and groundwater use managed jointly, some sewage recycling, some desalination if possible, lots of conservation of course maybe changes in water water pricing. We'd like to say there's no there's no silver bullet there's no one size fits all. So there will be region by region solutions. That said I think cities are sustainable. I think the bigger challenge for the global population is growing food in these conditions that we're seeing globally and satellites have revealed as you've shown in the animations the disappearance of groundwater. So I think on the one hand we have sustainable cities in terms of water supply for drinking and economic growth and energy production but not necessarily for food production. So this is this is a big issue that I don't think that desalination and sewage recycling are going to resolve.