Why not install a national pipeline where sea water is supplied.  Then people can connect to it for flushing toilets, forest fire prevention, even creating an inland fish culture, etc. Aside from the freshwater savings, the private sector will be encouraged to develop water filtration systems to obtain fresh water. I suggest using ceramics and gravity, or perhaps using sea water circulating on dome roofing system where distillation can occur and excess heat from buildings can be dissipated while salt becomes another byproduct. 

I must admit that this could be feasible only on bay areas.  Until drainage system is sure not to end in fresh water rivers, etc.  This brings us then to another environmental problem at hand, where chemicals and other wastes find their way to the rivers.