In a previous post here, I raised the population and water issue in a general way. My point was that ignoring the population component of our resource challenges was a mistake, certainly in the long term and in some places, in the short term. I think this is indisputable — resource constraints are worse than they would otherwise be if populations are large and growing rapidly rather than small and growing slowly, or even shrinking.
I also made the point, which I repeat here, that addressing water problems in the face of population growth comes down to three choices: (1) increase the water supply, (2) decrease the water demand per person, and (3) change the number of people. We must do all three, in the right way.
Over the past 100 years, our water policy has focused on (1) — expand supply. Even today, some people cannot imagine any other approach to water, and so we get the knee-jerk calls for new dams in California, even when they cannot be shown to provide the solutions we need. Some people just cannot imagine any other approach. In many parts of the world, expanding supply is still critically important, but ultimately, supply is limited (by either the availability of water, or by its ultimate economic and ecological costs) if demand is not constrained. Sure, desalination is effectively unlimited — at least for rich, coastal communities. But desalination is not an option for the vast majority of our water use, which is for agriculture, far from our coasts. There are true limits to supply.
Then what about (2) — decreasing per-capita demand? Many of my previous posts, and much of the research of the Pacific Institute, look at this issue. The key point is figuring out how to do what we want (grow food, wash clothes, make semiconductors, flush toilets, and so on) more efficiently. And as I’ve often noted, the potential to reduce our water use without any hardship is vast. This is great news, and the ability to improve efficiency has saved our butts (to use a technical term) over the past 30 years.
Water Numbers: In 1980, each person in the U.S. used around 1,940 gallons per day (including our share of power plant cooling water, irrigation water, plus our home and commercial use). Today there are 80 million more Americans than in 1980. If each American still used 1,940 gallons per day, population growth would have caused the U.S. to use an additional 155 billion gallons per day. Per DAY. This is equal to more than ten new Colorado Rivers. But we aren’t using this water. Improvements in efficiency have let us serve these new people without increasing our total water demand, and our current national water use is well below 1,500 gallons per person per day. Fantastic improvement.
I believe there is still enormous room for improving efficiency. But, ultimately, water use in the U.S. will start to grow again if the rate we improve water-use efficiency falls below the rate our population grows. And the limits to water will come closer and closer.
So, what about item (3) above: change the number of people? This is happening too. The rate of population growth is slowing, here and around the world, but population continues to rise. As women in developing countries improve their educational status, family size drops. As poverty is reduced and health services improve, family size drops. As information about options for birth control, and actual access to birth control, expands, family size drops. There are many reasonable and voluntary approaches to population policy, but we still face a world that is growing fast — faster than we are able to provide adequate water services, education, jobs, and health care. So I believe more must be done to address population growth, despite it being such a loaded topic, and this requires talking about birth control, sex education, and other issues that make some squirm. Ignoring the problem, however, will not make it go away. It is an issue even in this country, and we’ve ignored the discussion for far too long.
Finally, to those readers who always try to personalize this, yes, I took personal responsibility for my own role in population many years ago, thank you.
Dr. Gleick’s blog posts are provided in cooperation with the SFGate. Previous posts can be found here.