Could they build a hydo close to the coast and use seawater as the water source, this is done in Japan. Endless water supply which could also balance peek and off peak demand whereby we run efficient coal fired stations flat out and close some of the inefficient ones. Would change the environment of the storage reservoir which may be a problem so not sure if that cost/benefit worthwhile. This is some info on the Okinawa project.
Could do the same with floodwaters by building dams on high ground and harvesting in flood and releasing water in drought.
