What "ought" to be done about Townsville's heat

There was this great research and pilot scheme done for a system of taking cold waters from the deep (4 degrees C) and using the temperature differential with shallow tropical water to generate electricity. The pilot scheme (in Hawaii) showed reasonable effectiveness in generating electricity, but also a great many other uses for the cold water. For instance, pumping cold water through underground pipes under crops to improve their productivity, and using the cold water for air-conditioning. My "scheme" for Townsville would be a simple heat exchange for the water already being pumped to all the houses. The salt water would cool a hunk of metal, and the purified dam water would be cooled significantly by the metal, and the cold water being distributed to the whole city would cool everything down. The main problem with Townsville as I understand it is that there is no deep water nearby. The water would have to be piped in from a hundred kilometers away. This shouldn't really be a problem though - we are piping in gas from further than that for electrical generation. Once the initial "cold water" scheme is shown to be successful, all sorts of applications will become obvious, as well as generating electricity. And the considerable advantage over electrical air-conditioning is that there is a net reduction in heat.