On the road to a clean energy future, there are many road blocks. There is political resistance driven by those that benefit from the current system. The enormous financial cost of transitioning to new power sources and meeting rising energy demands in an era of ballooning deficits and tightening budgets also presents a major challenge.

But one constraint that is often overlooked is the need for large amounts of water in places where supplies are already short. Given rising populations and over-allocated water resources, the construction of a renewable energy infrastructure will inevitably bump up against water constraints.

Energy developers in the west are already learning this lesson. Just yesterday, Solar Millennium, a German developer that is proposing a new solar thermal plant near Las Vegas, announced that it would alter its plans in order to reduce water consumption. Solar thermal plants use the sun’s rays to heat water and drive turbines. Wet cooling allows the heat to escape through evaporation, while dry cooling employs fans and heat exchangers and keeps the water from escaping. The latter uses 90% less water but is typically 5% more expensive to build while also reducing energy output 5%. For a technology that is already struggling to be cost competitive with dirtier fuel sources, these additional costs can be prohibitive.