There are two Dams in Manabi La Esperanza and Honda.
here are a couple of clips I just found on youtube, 210 m3/second
https://www.youtube.com/watch?v=BRuwBFfNurkhttps://www.youtube.com/watch?v=GVi0PKoIRu8
Most towns on the coast are supplied from these sources,The Desal plants in Manta that I am aware of are for private developments/gated communities.
In Bahia the problem is not the water but the water storage reservoir is to small, its on a 4 day cycle, so each house or business needs at least a four day water tank/cistern.
I have a hotel and water shortage has never been a problem. even with over a 100 guests last month.
If you go further north up the coast towards Jama its quite dry again, but I have personal found many springs and aquifers, One 25 minutes inland on a farm where I keep my horses. another a few minutes north of Bahia 50 meters back from the beach, one next to Las Olas 1 km inland 54 meters above sea level. and another North of Canoa before Jama, I drank water from them all and even sent samples to a lab in Manta just for fun.
Another concern I keep reading about is power, The power where I live is very consistent., much more then Vancouver. although with these mega developments popping up all over Ecuador the Government is ramping up their power with six new hydroelectric plants.
One major shocker for you guys who are considering a cheap place to retire, it wont be Ecuador, The good old days are coming to an end. property prices are high and soon everything else will be too when the government ends natural gas subsidies.