Water securityWe’re (not) running out of water – a better way to measure water scarcity
Water crises seem to be everywhere. In Flint, the water might kill us. In Syria, the worst drought in hundreds of years is exacerbating civil war. But plenty of dried-out places aren’t in conflict. For all the hoopla, even California hasn’t run out of water. There’s a lot of water on the planet. What is critical is managing water to meet current and future demand. Biophysical indicators, such as the ones we looked at, can’t tell us where a water shortage is stressful to society or ecosystems, but a good biophysical indicator can help us make useful comparisons, target interventions, evaluate risk and look globally to find management models that might work at home.
Water crises seem to be everywhere. In Flint, the water might kill us. In Syria, the worst drought in hundreds of years is exacerbating civil war. But plenty of dried-out places aren’t in conflict. For all the hoopla, even California hasn’t run out of water.
There’s a lot of water on the planet. Earth’s total renewable freshwater adds up to about 10 million cubic kilometers. That number is small, less than one percent, compared to all the water in oceans and ice caps, but it’s also large, something like four trillion Olympic-sized swimming pools. Then again, water isn’t available everywhere: across space, there are deserts and swamps; over time, seasons of rain and years of drought.
Also, a water crisis isn’t about how much water there is – a desert isn’t water-stressed if no one is using the water; it’s just an arid place. A water shortage happens when we want more water than we have in a specific place at a specific time.
So determining whether a given part of the world is water-stressed is complicated. But it’s also important: we need to manage risk and plan strategically. Is there a good way to measure water availability and, thereby, identify places that could be vulnerable to water shortages?
Because it measures whether we have enough, the ratio of water use to water availability is a good way to quantify water shortage. Working with a group of collaborators, some of whom run a state-of-the-art global water resources model and some of whom work on the ground in water-scarce places, I quantified just how much of our water we’re using on a global basis. It was less straightforward than it sounds.
Water consumption, water availability
We use water for drinking and cleaning and making clothes and cars. Mostly, however, we use water to grow food. Seventy percent of the water we pull from rivers, streams and aquifers, and nearly 90 percent of the water we “use up,” is for irrigation.
How much water we use hinges on what you mean by “use.” Tallying the water we withdraw from rivers, lakes and aquifers makes sense for homes and farms, because that’s how much water runs through our taps or sprinkles onto farm fields.
