“Water water every where, nor any drop to drink,” wrote Samuel Taylor Coleridge in his 1798 poem, “The Rime of the Ancient Mariner.”

The world is awash in water. Seventy percent of the planet’s surface is covered by water, and a significant amount of water is frozen and in gaseous forms. Further, the volume of water on planet Earth has remained roughly constant at 344 million cubic miles for more than 1 billion years. By almost any account, water is quite literally everywhere.

Yet we constantly hear of impending shortages. Why? To begin, 97.5 percent of the water on Earth is in oceans — and therefore salty and unfit for human consumption. If all of the planet’s water filled a typical one-gallon milk container, less than a teaspoon of it would be freshwater.

The Earth is constantly recycling the water we use. But we’re stressing the system by not allowing it adequate time to replace the growing amounts we demand. “Can’t we just make new water?” you might ask. Well, our galaxy is actually creating new water molecules all the time — enough to fill the oceans of Earth multiple times per hour. Unfortunately, this is happening far from our planet, and it won’t be efficient — at least for the foreseeable future — to transport it here. Our heavy use of freshwater certainly appears to be a problem without an easy solution. And worse, the pressures are building: demand for water is predicted to exceed supply by 40 percent by 2030.

The already scarce supply of the freshwater consumable by plants, animals and humans is being further limited by climate change, which is changing historical rainfall patterns and increasing the severity of storms. Meanwhile, demand is driven by agriculture, which accounts for more than 90 percent of freshwater use each year. The same forces driving demand for food — namely a global population boom and increasing preferences within that population for animal protein — are placing unsustainable pressure on water supplies.

Climate change and food-driven water demand are creating a toxic cocktail that may shock global stability. We are already flirting with severe water shortages on a regular basis. Consider that one in four large cities are “water stressed,” according to the Nature Conservancy. Barcelona came within days of running out of water in 2008 and was forced to import a tanker of drinking water. California, which has been warming for the last 30 years, has been suffering its worst drought in 1,200 years, one study found. In South Africa, another terrible drought has forced Johannesburg to impose restrictions on water use. By 2025, two-thirds of the world’s population could be living under water-stressed conditions.

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Water wars are coming. The U.S. National Intelligence Strategy, released in September of last year, highlights an elevated potential for water scarcity to generate instability. And a U.S. intelligence community report on Global Water Security released in 2012 warned: “During the next 10 years, many countries important to the United States will experience water problems — shortages, poor water quality, or floods — that will risk instability and state failure, increase regional tensions, and distract them from working with the United States on important U.S. policy objectives.”

Might water wars already be brewing? Pakistan, one of the most water-stressed countries in the world, has an ongoing dispute with India over access to water in which radicals have called for “water jihad.” New Delhi also fears that a new Chinese dam project in Tibet could be used to restrict water supplies downstream in northern India. In March, an Ethiopian dam under construction that could have limited Egyptian and Sudanese access to water nearly generated conflict. In central Asia, there is a similar ongoing disagreement over a Tajikistani dam that could restrict water access in Uzbekistan. These are but a few of the water tensions bubbling globally.

The sad reality of the situation is that it may soon be time to update the Coleridge quote with which I began this piece to “Water wars everywhere, nor any drop for peace.”