People who live in drought afflicted areas always point to desalination as the answer to all their problems.
Desalination may solve their problems but only by creating additional problems elsewhere. We don't have a lot of experience with desalination plants in Canada because we usually have enough rain and groundwater. Parts of the US, however, aren't so blessed. Now, with large tracts of the American south facing drought and water depletion, the clamour for desalination is getting louder and more strident.
Desalination - the production of freshwater by removing salts and other ingredients in sea water - sounds like the perfect solution. It's not. Desalination plants create enormous environmental problems. They're expensive to build and expensive to run. They use an awful lot of energy, typically fossil fuel, and generate a lot of greenhouse gases. The pipes tend to leak and saltwater causes immense problems once it gets into groundwater supplies (remember how the Romans took revenge on Carthage?)). The worst part, however, is the brine effluent that's left over.
The standard approach is to simply pump the brine, along with all the other chemical residue from the desalination process, right back into the coastal sea. There it plays utter havoc with the marine environment ranging from turbidity, salinity imbalances, destruction of fish habitats and stocks and algae blooms.
In North America, our coastal waters already face enough challenges. We don't need to add the consequences of desalination to the mix.