Like our use of oil, our use of water has the potential to reach peak limits. EarthSky spoke with world-renowned water expert Peter Gleick, head of California’s Pacific Institute. He said:
As much as 40% of the water humans use comes from non-renewable resources, like northern China groundwater, or groundwater in the state of California, or in the Great Plains of the United States, or groundwater in India – any place where we’re pumping groundwater much faster than nature recharges it.
Gleick spoke of depleting finite groundwater resources – and taking too much from water from sources like rivers, before they can be renewed by rainfall or glacier melt. He said:
There’s an average flow of any river, and it goes up and down. We have wet years and dry years, but there’s an average flow. For a river like the Colorado, or the Nile, or the Yellow in China, humans are now taking the entire flow of the river. No water reaches the mouth of the Colorado, except in a really, really wet years. No more water is reaching the mouth of the Nile, anymore, because we’re using it all.
Peak water, he said, is when the rate of our water demand is higher than the rate at which a particular water supply is replenished. Gleick said in many parts of the world, humans have already hit peak limits on water use. He said that he does think there are things we can do.
One of the things we can do, for example, is rethink where we take water. And rethink where we do the things we do with water. It might not be possible to grow food in this basin or that basin, if it’s not sustainable in the long run, but we might be able to grow food somewhere else.
A third option is: let’s rethink how we use water. One of the things we do at the Pacific Institute is look at the connection between water efficiency and water demand. It turns out that we can do the things we want to do. We can grow the food, make the semi-conductors, wash our clothes – all with a lot less water that we’re currently using. And if we’re in areas where we’re reaching peak water, then improving efficiency becomes a very powerful tool, letting us do the things we want, but reducing the demands on the system.
Dr. Gleick explained that another component of peak water has to do with economics:
There’s another constraint that I think is really important. And we call it peak ecological water. That’s where the next gallon that we take out of a system – a river or a lake or a wetland – provides more ecological benefit. In other words, when we first start to take water out of a system, and use it to grow food, or make semiconductors, or residential use, it provides a benefit to society.
It also causes a little bit of ecological harm, and, at first, we don’t pay much attention to that. But we are now reaching a point – and I would argue we’ve passed the point in most hydrologic basins – where we now are causing more ecological damage with every unit of water we take than we are getting economic benefit. It’s a hard thing to measure that point, but it’s a reality. And that point, we call it peak ecological water.
He said we’re not as good at measuring ecological damage as we are at measuring economic benefit. That is why this particular category of peak water is a tricky one to explain. He gave an example:
Look for example, at the Ural River, in Russia. It’s a major hydrologic basin. Two rivers flow into it. The USSR, when it existed, decided that they would take those rivers and they would use it to grow cotton. And they were able to grow a great deal of cotton, and that produced an economic benefit. But by taking the flow of those rivers, the Ural started to dry up. It got saltier and saltier, and all 24 species of fish native to the Ural – that lived nowhere in the world – are now extinct. I would argue that that’s a great example of exceeding peak ecological water.
Gleick said that the concept of peak water is a valuable one for letting us understand where we’re running into problems, and how to figure out how to move to successful sustainable solutions.
That’s an important part of the answer to peak water challenge, he said.
Beth Lebwohl researches, writes and helps produce science content in audio and video formats for EarthSky. She is one of the authors on EarthSky.org, a script-writer for our podcasts, and helps host our English science podcasts in 90-second, 8-minute and 22-minute formats. Beth came to EarthSky in 2006 from the American Museum of Natural History's Department of Astrophysics, where she was surrounded by some of the greatest telescope-building, equation-wielding, code-writing physicists of our time. And they made her think . . . this science thing . . . it's pretty cool.