Well, they use gas for the primary cooling, but my understanding is that the gas heats water -> vapor turbine -> condense water -> repeat. It is unclear to me how do you condense much water without cooling towers.. Normally lets say 40% of the thermal energy is transformed to electricity, and the rest is lost (needs to be cooled). So basically you still need to cool a lot of water, maybe 200MW worth of heated water.

But this is a conventional issue, a gas or coal generator has similar cooling requirements.