Experiments have shown that adding a very thin layer of certain compounds to reservoirs slows evaporation significantly, thus conserving water for consumption and power. It would be terrific if it also suppressed mosquitoes too - the article made no claims, but covering the water with a thin layer of certain compounds can suffocate mosquitoes in their larval ("wiggler") stage.
Downside? Evaporation cools the reservoirs so they'll run a bit hotter. No doubt other phenomena remain to be discovered. But it will be interesting to see where this goes.