8. Mimicking the Water Cycle: Making Water Potable
“Irrigation of the land with seawater desalinated by fusion power is ancient. It’s called rain.”
—Michael McClary
“Filthy water cannot be washed.”
—African proverb
“In every glass of water we drink, some of the water has already passed through fishes, trees, bacteria, worms in the soil, and many other organisms, including people.... Living systems cleanse water and make it fit, among other things, for human consumption.”
—Elliot A. Norse, in R.J. Hoage, ed., Animal Extinctions, 1985
We have seen the various forms the water on the Earth takes—as seawater, glaciers, groundwater, aquifers, humidity, in living creatures, and as renewable freshwater as rain, lakes, rivers, streams, and so on. And we have seen which nations and regions enjoy the highest concentrations of this last category of renewable freshwater—Total Actual Renewable Water Resources (TARWR). Now let’s look at how that water cycles from each region and back into it or others—typically, having been filtered by Nature and once again fit for consumption.
I swear Figure 8.1 is the same illustration I first saw in my fifth-grade physical geography class. Because The Water Cycle hasn’t changed in a few thousand millennia, I guess the intervening years of my life are but an eyeblink in time, and this diagram is still as valid today as it was back then. It illustrates rather well the process of water passing “through fishes, trees, bacteria, worms in the soil, and many other organisms, including people.” Then it transpires or evaporates into the atmosphere, where it is stored until it again rejoins the Earth as rain, snow, fog drip, or Seattle mist.
Figure 8.1. The Water Cycle1
Source: U.S. Geological Survey
The Water Cycle has no beginning and no end. It doesn’t “start” as rain, and then “become” a river, and then “ascend” as transpiration. It’s a cycle, without beginning or end, that defines the movement of water on the surface of, underground, and above the Earth itself, constantly moving and constantly changing from liquid (water) to gas (water vapor) to a solid (ice) and back again.
Since I live in the high country in the Sierra Nevada, I’ll start, arbitrarily, at that point in the cycle. As snow gently falls in the Sierra, it accumulates and is stored during the winter as snow. Where the sun or water touches it, it refreezes, some as ice. Most people, if they think about snow and ice at all, know that snow melts. Eventually. Really, it does. (Those of us in rural mountain areas with lots of sunshine think about melting snow favorably, if not often. Those living in cities think of snow often and unkindly, as some disgusting, sooty, freezing mass to be gotten through until spring.) Here in the mountains, the melting snow forms creeks that become streams that become rivers for spring kayaking and wonderful hiking and rock-hopping. But this is only one way snow takes a different form by becoming water again. The other way is via sublimation (which has nothing to do with hiding your true feelings about snow).
Sublimation is the process in which snow turns to vapor without passing through the liquid stage first. Out West, we have Chinooks—dry warm winds in midwinter that sort of zap the snow and turn it into its gaseous form without passing through liquid. It’s typically very dry here in the Sierras. Our winter humidity ranges around 20% to 30%. That’s one reason why we don’t mind winter so much. Even though the temperature is low, the sun is shining on our faces, and it isn’t a “wet” cold. Living at just under 7,000 feet, the combination of lower air pressure at this altitude, bright sunshine, and dry winds creates the right environment for Chinooks. People in the Rockies think they have a monopoly on them, but we steal a little of their thunder, or at least terminology, for our own version.
Whatever you call them, these winds are basically straight from the Pacific (when they are wet, we call them “Honolulu Expresses”). Some of the moisture gets wrung out as the wind passes over the Sierras, and the rest as the wind tries to get over the Rockies. Once these winds come down from the mountains onto the high plains (Reno and Denver are both mile-high cities), they can actually become quite mellow—as warm as 60 or 70°F with a relative humidity of 15%, 10%, or less. Here you are in midwinter and suddenly, for a short respite, anyway, you are peeling off layers of winter clothing. The air in these winds is so devoid of moisture that when it hits a snowpack, the frozen water evaporates, rather than melting.
Melting not only fills our streams, rivers, and high-country lakes but also contributes hugely to the supply of groundwater and refreshes who knows how many aquifers. In the springtime, I begin to water my smaller plants, but my big trees and well-established mature bushes I never worry about. I know that their taproots are reaching down to find that water moving at a snail’s pace from the 9,000-foot peaks around me to the 6,223 feet that roughly defines the natural rim at Lake Tahoe. Since I live between those two elevations, I figure the snowmelt I can see above the surface is only part of the story. The rest is slowly moving through my taproots on its way to fill Tahoe another 6 feet or so for the summer.
The story is the same elsewhere in the country, although other areas may receive more or all of their precipitation as rain rather than snow. In either case, the effect is the same. The cycle of water coming back to Earth is continual. Some of it is stored, and much of it is used. But it never stops moving in any case. As humans, animals, and plants breathe, we release some of that water we drank, or water that the plants picked up from the groundwater, as water vapor. When the sun heats water, it’s called evaporation; when plants are heated by the sun and release moisture, it’s called transpiration.
If you don’t believe plants release huge amounts of moisture into the atmosphere, just put a plastic bag around a plant that’s in direct sunlight. As it heats up, you’ll see the plant perspiring—OK, “transpiring”—as the bag begins to collect water vapor on the inside. Or you can just believe the U.S. Geological Survey website, which says that a single acre of corn gives off about 3,000 to 4,000 gallons of water each day!
All of this respired, perspired, and transpired moist air joins that which has evaporated from the land, lakes, and seas in the bright sunlight. It rises into the atmosphere, where cooler temperatures cause it to condense into clouds. Air currents move clouds around the sky, where cloud particles smack into each other or join to form bigger clouds. Sooner or later, all that smacking or becoming heavier by joining cause the water to fall from the sky as rain or snow all over again.
Of course, as I alluded to in mentioning snow melting into the ground and moving as groundwater through the dirt and rock underneath rather than into streams and rivers, a lot of precipitation soaks into the ground as “infiltration.” Some infiltrates deep into the ground to (slowly) attempt to replenish the aquifers that store huge amounts of freshwater for long periods of time and that we humans are now emptying as if there were no tomorrow. On the other hand, some infiltration stays close to the land surface and can seep back into surface-water bodies (and the ocean) as groundwater discharge. (Or it can be sucked up by big trees, which then transpire it back into the atmosphere.)
Because we humans are so blasé about stealing the water from these aquifers without concern for future generations, I think an illustration (see Figure 8.2) and explanation are in order.
Source: U.S. Geological Survey
To quote the USGS website:2
Natural refilling of deep aquifers is a slow process because groundwater moves slowly through the unsaturated zone and the aquifer.
Large amounts of water are stored in the ground. The water is still moving, possibly very slowly, and it is still part of The Water Cycle. Most of the water in the ground comes from precipitation that infiltrates downward from the land surface. The upper layer of the soil is the unsaturated zone, where water is present in varying amounts that change over time, but does not saturate the soil.
Below this layer is the saturated zone, where all of the pores, cracks, and spaces between rock particles are saturated with water. The term groundwater is used to describe this area. Another term for groundwater is “aquifer,” although this term is usually used to describe water-bearing formations capable of yielding enough water to supply peoples’ uses. Aquifers are a huge storehouse of Earth’s water, and people all over the world depend on groundwater in their daily lives.
The top of the surface where groundwater occurs is called the water table. In the diagram, you can see how the ground below the water table is saturated with water (the saturated zone). Aquifers are replenished by the seepage of precipitation that falls on the land, but there are many geologic, meteorologic, topographic, and human factors that determine the extent and rate to which aquifers are refilled with water. Rocks have different porosity and permeability characteristics, which means that water does not move around the same way in all rocks. Thus, the characteristics of groundwater recharge vary all over the world.
To access freshwater, people have to drill wells deep enough to tap into an aquifer. The well might have to be dozens or thousands of feet deep....
In an aquifer, the soil and rock is saturated with water. If the aquifer is shallow enough and permeable enough to allow water to move through it at a rapid-enough rate, then people can drill wells into it and withdraw water. The level of the water table can naturally change over time due to changes in weather cycles and precipitation patterns, streamflow and geologic changes, and even human-induced changes, such as the increase in impervious surfaces, such as roads and paved areas, on the landscape.
The pumping of wells can have a great deal of influence on water levels below ground, especially in the vicinity of the well.... Depending on geologic and hydrologic conditions of the aquifer, the impact on the level of the water table can be short-lived or last for decades, and the water level can fall a small amount or many hundreds of feet. Excessive pumping can lower the water table so much that the wells no longer supply water—they can “go dry.”
Whether the water in The Water Cycle is visible, as in lakes, streams, or oceans, or invisible, as in groundwater, there is no getting around this simple truth that should guide us in our wise use of water: The cycle of water and the cycle of life are inextricably intertwined; indeed, they may as well be one and the same.
So much for how the finite amount of water in the world cycles and recycles itself endlessly and forever, cleaning and purifying as it goes. If mankind will not stop making babies to fill every plot of available earth, we need to do something that shortcuts but imitates what Mother Nature does every day. That is, we need to find ways to purify putrid or fetid or disease-carrying water and wastewater in seconds rather than years, decades, and eons. We also need to figure out how to “evaporate” just the nonsalty part of seawater and make it a life-giver rather than a killer when ingested.
It’s ironic that the one substance that has no replacement on Earth is also the one substance that, in its less-pure forms, kills more human beings than any other every single year. Waterborne pathogens exist in such diverse forms and colossal numbers because everything we recognize as life needs water to live—humans, animals, fruits, vegetables, everything. And to survive, these pathogens must find a host and a means of sustenance themselves. Perhaps that is why 80% of infectious diseases are waterborne and only 20% are airborne or caused by animal-to-human or human-to-human contact.
There is a reason why people around the world, regardless of their level of education or sophistication in the field of pathogenic microorganisms, learned to drink water that was malted (as in beer), fermented (as in wine), or boiled (as in tea, coffee, mate, and other herbal drinks). To this day, those of us who have served tours of duty in the Middle East know that the culture calls for many bladder-distending cups of tea to provide and return hospitality and thanks. Like most religious or cultural food and beverage rules, this tradition flowed from a survival instinct long before it served as a sign of welcome and repose.
Today, there are numerous ways to ensure clean water, free from most, if not all, pathogens. But such methods may be impractical in the developing world. As any good backpacker knows, with the tools we have available in developed nations and the knowledge we’ve gained on the subject, we can ensure the best outcome.
We know we need to make certain that the containers in which we place our water are themselves free of parasites or bacteria by cleaning the containers with soap and water—preferably water we know to be good! After rinsing, we know we still need to submerge the containers in a solution of 1 teaspoon of bleach to every quart of water, and then rinse again with a progressively weaker mixture of bleach and water.
We know to strain the water through a cloth to capture large foreign bodies and then let what we’ve strained settle and gently pour off the water above the sediment, tossing the sediment. Then we boil the water, or add chlorine to it in small quantities (yuck), or leave it in full sunlight in a clear container for 6 hours or more.
I make this slight digression not to turn us all into Ranger Rick buddies but to point out that, while this may work for American or European backpackers concerned about giardia or some other major inconvenience, it is just too much trouble to implement in most of the developing world. Worse, the attitude in many parts of the developing world is, “My parents drank that water and lived. I am drinking that water and living. So something else must be making my child sick.”
We’ll deal with this in greater depth as we begin to discuss investment approaches and opportunities. For now, two approaches that must go hand in hand if we are to make water more potable and safer in much of the world. The UN estimates that some 2.5 billion people on this planet do not have toilets. La toilette is an open ditch next to the creek that provides drinking water. The first step is education, and that doesn’t come easily without empirical evidence that things must change. The other element is portable purification systems that will provide that empirical evidence. Although it sounds counterintuitive to any caring, giving aid worker, the first systems should be given to only a few people—those who will actually use them. Quietly let others see that these systems work, and make them come forward to ask for the systems. Trying to change a thousand generations of belief in a week or month is a losing proposition.
It isn’t my intent, or within my knowledge and ability, to explain how contaminated water, wastewater, and water carrying terrible diseases may be rendered pure. But I know that pure water comprises 90% or 95% or 99% of all bad water. And I know there are methods to purify it of whatever small percentage of bad stuff is in there. And I also know that lack of water (or dirty water) is by far the largest disease problem in the world; that only 20% of the world’s population enjoys the benefits of indoor running water; and that every year, the amount of global water polluted equals the water consumed. That makes this science worth pursuing. The social benefits are there, and the economics are there.
I also know that, in general, there are physical processes like the ones I discussed earlier, biological processes such as the sand-and-charcoal filters I’ve used in my aquariums, chemical processes such as flocculation and chlorination, and the use of ultraviolet light. (That’s the only thing we do to our natural snow water in my own water district—no chemicals, no filters, just UV light.)
All these processes mimic what Mother Nature does over a more extended time frame. Some companies today do this and do it well. Indeed, whole industries have come into existence to purify water on scales both small and large, local and international. With luck and pluck, we may yet be able to vastly increase the amount of potable water available to all—albeit at a higher price than scooping up a handful of freshly fallen snow or catching a raindrop on your tongue.
An even more ambitious endeavor is removing the salts and other minerals from sea water and turning seawater into potable drinking water. This technology is well-proven. Although it too comes at a higher cost than free water falling from the sky, nations such as Saudi Arabia and Yemen have no alternative. Nations such as Israel have some alternatives but want to control the safety and purity of their water and have the engineering prowess and technology to do so.
The U.S. Navy (and other navies, as well as a number of commercial vessels) have been desalinating water for a long time. With water weighing over 8 pounds per gallon, the weight of the water that would have to be carried on a vessel, at great cost in fuel and space, to sustain just a 6-week deployment would be too daunting—let alone a 6-month deployment. The average person uses about 120 gallons of water a day, and an aircraft carrier has some 5,000 crew members. And that’s just one vessel in a task force. Do the math!
You can see why, for some applications, desalination makes the most economic sense.
On the other hand, large-scale desalination typically uses huge amounts of expensive energy, as well as very expensive infrastructure, and incurs relatively high maintenance costs. But it is cost-effective enough that, according to the International Desalination Association, well over 13,080 desalination plants produce more than 12.5 billion gallons of water a day worldwide. That’s a bunch of water.
And desalination must be cost-effective in order to make the economies of scale work in this business. Economies of scale yield more R&D, and more R&D yields greater economies of scale, less energy consumption, and a better and cheaper way to ensure a product that tastes just like that raindrop on your tongue.
And they’d better. There is no way you can do this job halfway. I know from personal experience just how dangerous salt water can be. First I’ll tell you about the physiology of it all, and then how I know firsthand.
Salt water in nature isn’t just the teaspoon of NaCl table salt you pour in a glass of warm water to gargle when you have a sore throat. Salt water in ocean and sea is composed of all kinds of elements and minerals we call “salts”: Epsom salts, potassium salts, iodine salts, and lots more. Ocean water is about three times as salty as your blood. So if you ingest ocean water, the water in your body (which makes up 60% to 70% of your weight) floods out of your cells in a fruitless effort to dilute the salt you just ingested. Since all cells need water, this outward flood leaves them perilously dehydrated. Drinking salt water results in cellular dehydration, with symptoms including hallucinations, muddled thinking, seizures, unconsciousness, brain damage, and, finally, as the overwhelmed kidneys shut down, death. Period.
I recently had reason to think about all this a bit more. On a scuba dive on the USS Vandenberg, 12 miles off Key West, I found I needed extra weight to descend with a new buoyancy compensator (BC) I hadn’t used before. With my dive buddy on the anchor line at the bow, I went to the stern and took off my fins to climb aboard for more weight. The next thing I remember is being 100 yards down-current in 3-foot seas (so, out of sight and earshot of my dive partner) with no fins. It seems that the transom had lifted on a rogue wave and slammed down on the back of my head as I reached down to remove my weight belt to climb aboard.
I’m one of the lucky ones. As a former member of Special Forces, I had the opportunity to attend a special Water Survival School. I was also a Red Cross water safety instructor, and I taught and certified lifeguards. So I’m not as likely to panic just because the back of my head is bruised and I’m all alone 12 miles from shore. Plus, I had a collapsible dive flag and a “sausage”—basically an air sack that stands up in the air—sometimes. Sort of. And I knew my dive partner would alert the cavalry. It was only 2 p.m. So I figured my rescuers would soon be out looking for a diver, or at least the body of one. If push came to shove and the sharks weren’t too curious, I could jettison the tank I’d kept to ward off those pesky creatures, and my weight belt, deflate my BC a little, and start kicking. With luck, I could make Key West by midnight.
Now comes the saltwater part. I knew that ingesting salt water would muddle my brain. The waves were so strong that I kept getting seawater in my snorkel. Although I kept spitting it out, I inevitably swallowed some. After 45 minutes out there alone, waving my collapsible dive flag (it stood 6 feet—my head was 2 feet below the waves), I realized I was fascinated by watching my dive flag move back and forth like a metronome. I wondered who was waving a dive flag. Just that short a time and that little seawater, and already I was starting to lose it.
I had 4 ounces of freshwater and a candy bar as emergency supplies in case something like this happened. I’d planned to save them until I needed them for energy on a swim to shore. Instead, I downed both of them right then and there. Either the concern that I was losing it or the dilution of freshwater or the sugar rush got me focused. Seconds later a charter boat came into view less than a half-mile away, and I waved that flag for all it was worth. I’m no expert on saltwater ingestion, but I’m the closest thing I’ve got. Been there, done that, didn’t get the T-shirt, and don’t need to do it again.
Desalination using reverse osmosis membrane technology has become a viable option for the development of new water supplies. You may be surprised at the number of countries—and nations—staking their future on desalination. (And, if they ever make a portable desalination model, they’ll be richer than Croesus, because every diver and sailor will line up to buy one. I’ll be the first in line.) These countries need to test the water and never get nonchalant or lazy about ensuring that the salts that steal the body’s fluids and mess with the brain have been completely removed.
No matter the method used, all desalination plants basically mimic Nature in some way. Reverse osmosis is the most complex method, but also one of the most effective (see Figure 8.3).3 A semipermeable membrane serves as an extremely fine filter. (Think GORE-TEX fabric, which allows sweat to pass through it but has pores too small to allow rain to penetrate it.) The salty water is put on one side of the membrane, and pressure is applied to stop, and then reverse, the osmotic process. It generally takes a lot of pressure and is fairly slow, but it works.
Figure 8.3. Reverse osmosis desalination
Source: BBC News Online
The two biggest desalination plants in the world are in the Middle East. No surprise there. The largest reverse osmosis seawater plant in the world is at Ashkelon, on Israel’s southern coast. It provides more than 100 million cubic meters of desalinated water per year at a cost of about US$0.60 per cubic meter. Since one cubic meter equals just over 264 U.S. gallons, and since the average price of water in the U.S. is about $1.50 per 1,000 gallons, it would cost U.S. residents about $0.40 for a cubic meter. (I should point out that this compares Ashkelon’s cost to produce water to U.S. consumers’ cost to buy water. Farmers pay considerably less, and Ashkelon’s output goes to agriculture as well.)
Still, for consumers at least, if water costs not a penny a gallon, but 2 cents or more, so what? Water is essential, and we will pay what is fair, given our circumstances. Israel’s circumstances are that for both security and access to water, it must pay for desalination.
Of the world’s water, we know that less than 1% is available as freshwater, polluted or not. And less than 1% of that amount is available to the entire Middle East (yes, that includes the flow from the once-mighty Tigris, Euphrates, and Jordan Rivers). Yet 5% of the world’s people live there. Worse, every major river within the Middle East crosses at least one international border. Is it any wonder that Israel chooses not to rely merely on rainwater resident in the Sea of Galilee and the Jordan River, its few aquifers, and recycling? Or that the Golan Heights, which look flat on a sixth-grader’s map, actually provide not just the high ground any military commander seeks, but also greater water security for Israel?
The world’s largest desalination plant is Jebel Ali (Phase 2) in the United Arab Emirates. Unlike Ashkelon, the technology used here is multistage flash distillation and can produce three times as much—300 million cubic meters of water per year. (For comparison, the biggest desalination plant in the U.S. is operated by Tampa Bay Water, which produces about 35 million cubic meters of water per year.)
I use these two merely as examples of what can be done when necessity demands it—and the cost can be brought down to not that much more than rainwater if the project is big enough. The politics of water ensures that freshwater sources will be increasingly in doubt for many nations. Desalination remains the only viable alternative. It may not be too big a stretch to suggest that desalination may prevent more wars than the United Nations ever has.
The initial capital investment for desalination is quite expensive, but consider the alternatives. Why have nations moved cautiously? Many have enough freshwater today. Of those that don’t, there are environmental considerations. Removing scores of different salts, minerals, and pesticides from brackish or sea water leaves us with the issue of what to do with all that stuff. It can’t simply be pumped back into the ocean. As every longtime diver knows, we’ve done enough harm to our oceans without adding that insult. So all this stuff, some of it benign in minute and necessary concentrations in the oceans but toxic when concentrated, has to be dealt with. And that, too, costs money.
The initial research, which must be proven in larger-scale analysis, is actually heartening. As the U.S.’s National Research Council recently reported, “Limited studies suggest that desalination may be less environmentally harmful than many other ways to supplement water—such as diverting freshwater from sensitive ecosystems.... Desalination also has raised concerns about greenhouse gases because it uses large amounts of energy. Seawater reverse osmosis uses about 10 times more energy than traditional treatment of surface water, for example, and in most cases uses more energy than other ways of augmenting water supplies. Researchers should investigate ways to integrate alternative energy sources—such as the sun, wind, or tides—in order to lower emissions from desalination....”
I am completely in favor of using sun, wind, or tides, but our water problems are pressing now, not in 20 years. What is available now is nuclear and natural gas, and dirty old coal and oil. You want water? Acknowledge that it takes energy, and the energy sources we hope to replace are still the energy sources that we have in abundance—with a transportation and distribution infrastructure already in place.
That’s the decision many nations will have to make, and I imagine that’s the conclusion many of them will reach. Pure water gives life. Bad water kills. Seawater kills. If we have to use natural gas until these things become more efficient, so be it.
That wraps up where the water is, who’s got it and who doesn’t, how The Water Cycle has always worked and always will work, and the alternatives that might open new sources of pure water. What could possibly gum up the works? Politics, of course!
Endnotes
1 The Water Cycle - Water Science for Schools. U.S. Geological Survey. http://ga.water.usgs.gov/edu/watercyclehi.html.
2 “The Water Cycle: Infiltration.” U.S. Geological Survey. http://ga.water.usgs.gov/edu/watercycleinfiltration.html.
3 Leyne, Jon. “Water factory aims to filter tensions.” http://news.bbc.co.uk/2/hi/middle_east/3631964.stm.