As we all know, without water there is no life – on earth or beyond. Annual precipitation on the US averages 2 quadrillion gallons (30 inches/year) and we currently use 0.11 quadrillion gallons of it (6%). The rest soaks into the ground, runs off to the oceans, and evaporates back into the atmosphere. But 6% is a lot; since 1950 our water use has doubled. Within the many generalities, the inequities are great. For example, Hawaii averages of 64 inches per year while Nevada averages only 9. Phoenix is sucking its groundwater dry. Its water table dropped 400 ft by 1990 (go too deep and you get saltwater), while Louisiana builds levees to stay dry. Food production uses almost 50% of US freshwater while people use another 15% around the house. California uses a disproportionate 16% of all US water (5% for utilities and 40% for agriculture) but only gets 2/3 of the US average precipitation. To meet this large demand California is a leader in water reuse and, sometimes to the dismay of others, Colorado River use. Droughts can be devastating. California’s recent 4 year drought was bad, but in the first Millennium, the Midwest had a drought for 500 years.
The US is water rich but water sloppy compared to much of the world. We use a per capita average of 156 gal/day while thirsty Mali uses an average of 3 gal/day. The driest area on earth is the Atacama Desert in Chile, which gets an average of 0.6 inches of precipitation a year, although there are spots where it hasn’t rained in 100 years. And getting water in the US is really convenient, whereas Water For People estimates that 1.4 billion people don’t have any direct access to safe water and over a billion people spend more than 4 hours a day getting water.
As the world population grows to almost 10 billion by mid-century, water issues will undoubtedly become more severe. Will there be water wars? Will desalination overcome its energy limitations (http://www.pri.org/stories/2015-05-15/desalination-expensive-energy-hog-improvements-are-way) to become salvation? Right now it takes 10 times more energy to supply water from the sea than it does to supply it from a freshwater source. Some day you might have to choose between lights or water (the choice will be obvious) or you may have to fight for your water.
Besides the energy linkage to water, there is also a pollution linkage. The more we contaminate our water supplies, the more expensive it becomes to produce safe drinking water. Right now, we generate 12 trillion gallons/year of wastewater sent through 2.3 million miles of sewers to be treated at 16,000 sewage treatment plants, in addition to industry-treated waste, and we dispose of another 1.5 trillion gallons/year into septic systems. Although these wastewaters are treated before recharging reservoirs, they still contain contamination. At present, household water costs about a half cent per gallon (still one of the best deals around), which covers the cost of procurement, treatment (usually limited to filtration and chlorination), and distribution. If supply reservoirs get too contaminated, treatment costs will rise, although maybe not 300-fold, which is the current price of the cheapest bottled water.
“Safe” is the operable word for drinking water. Americans have come to expect it. In 1900, pathogenic drinking water caused terrible cholera epidemics involving widespread death. Chlorination and sanitary sewerage fixed that. In 2000, minute concentrations of lead and other hazardous chemicals caused more subtle but still serious health effects (it did also in 1900, but we had bigger problems then). More careful monitoring and, when needed, advanced treatment or alternative supplies can fix that today. Better monitoring and better understanding of even subtle health effects keeps ratcheting down our views of “safe” drinking water, however. But don’t run to the market for a bottled water alternative just yet – an EPA study several years ago found that at least 1/3 of bottled waters failed federal drinking water standards. And worse, there is no monitoring requirement for bottled water as there is for publicly-supplied water. In its study, EPA even found several bottled waters being filled by garden hoses in parking lots – a bit disingenuous considering their pastoral mountain spring labels.
Before you panic, support conservation and reuse. There is a lot of mileage left in both those approaches. Drip irrigation, compared to flood- and sprinkler-irrigation, can save 40% of water used. More greywater (everything but your toilet) can be reused for things like irrigation via dual piping systems. More of tomorrow’s houses will have such dual systems. And even toilets can get better – Australia uses dual flush toilets (2 different flush volumes by pressing one button over another) for Number 1 vs Number 2. Fortuitously, advanced treatment technologies do exist for ultimate treatment of any wastewater, but they can be expensive. Taken all together and applied in various ways for various needs, my guess is we can get twice the mileage out of our water. But at a higher cost, so be prepared. And then there’s always NASA.