One of the things that happens when you write a book is that people quickly ask when you’re going to write your next one and what it will be about. Funny thing is, despite my busy schedule I’ve actually given this some serious thought. Not that I’m committing to anything just yet, but I’ve thought about what the subject matter might be.

I think it might be water. Fresh water in particular. Global warming has a real chance of causing fresh water to become something we will have in short supply. Although some areas of the world are getting too much rainfall, others are getting hit with unprecedented drought (e.g. the southwestern US), and those trends are only getting worse.

I believe most people think a little bit about fresh water and recognize the importance of being careful with it. Nobody wants to waste it unnecessarily and almost everyone hates the idea of dumping industrial waste into fresh water lakes. But there are still a lot of people who aren’t as smart with it as they should be. For example, the best time to water lawns isn’t in the middle of the daytime with the sun beating high overhead, because much of the water quickly evaporates. It’s better to do so early morning before sunrise, or after sunset. That way, the water stays where it’s supposed to and waters the lawn, rather than simply disappearing into the air. We may think about how precious fresh water is, but we don’t necessarily do much about it.

Even more importantly than just thinking about watering the lawn properly, a lot of people aren’t aware of how much fresh water is used in the generation of electricity. The statistics are rather alarming. According to a US Geological survey in 2005, 53 percent of the fresh water Americans use is for the production of electricity.

Coal uses the most, a reason the US statistics are as high as they are since Americans get more electricity from coal than any other energy source. Each megawatt-hour (MWh) of electricity generated from the combustion of coal uses more than 16,000 gallons and consumes almost 700 gallons, all for cooling purposes. But don’t forget that water is also used in the mining process, creating a sludge that can totally pollute the freshwater source the water is drawn from because that’s usually where it returns.

Nuclear power is in second place for fresh water use. Nearly 15,000 gallons of water are used with nearly 600 gallons consumed per MWh of electricity generated. Mining of uranium again uses water similar to the mining of coal, and water is also needed for the storage of the fuel rods.

Renewable sources of energy will help this degree of water consumption. Solar panels and wind turbines require no significant water consumption. Hydroelectric power, a common source of electricity in Ontario and Quebec, even has a degree of water inefficiency about it, although it’s not the same as the pollution of water that goes along with mining of coal or uranium, or the consumption of water involved in the cooling processes associated with those particular sources of energy. The “inefficiency” associated with hydroelectric power is because about 9 billion gallons of water evaporates behind hydroelectric dams every day, enough for the needs of 50 million people. Of course, that water isn’t consumed or polluted; it’s simply returning to the atmosphere, to fall as precipitation somewhere else.

I think this is yet one more reason why the traditional energy sources comprised of fossil fuels are worth avoiding. Everyone is aware of the greenhouse gas emissions and the way those are affecting global warming and climate change, although certainly some skeptics and deniers argue to the contrary on that point. But now we’re realizing what it’s doing to our sources of fresh water too.

Some people suggest that desalination plants will be our way to combat this issue in the future when fresh water is becoming more scarce. By removing salt the oceans’ saltwater, we can have a nearly endless supply of fresh water. What people don’t realize, however, is the nearly astronomical amount of energy required to power desalination plants, enough to provide fresh water for the more than 7 billion people living on the planet, let alone alone the other species dependent on fresh water. And if we need more water to be used in the generation of electricity, it will become an endless loop of silliness, ad infinitum.

If the 20th century was the century dominated by oil, future centuries may very well become dominated by fresh water. It may become the most precious commodity on our planet. We’d better respect it and be more careful with it while we still have a good supply around. Renewable sources of energy are one other way for us to help preserve it.