Part 2 of 4
Water security is not an idle curiosity and it may be the leading edge of the climate crisis for many people. Without water civilization degrades rapidly. This article from the Washington Post documents how one Indian city of more than 9 million people, Chennai, is grappling with the problem in real time. Three other Indian cities are on the cusp of a similar situation.
Perhaps the first thing to consider about the impending, actually unfolding, global water emergency, is that we’ve been here before. Not you and me, but the human race. Water insecurity is one form of existential crisis that happens as a result of population increases. Other forms of crisis that our species has successfully faced include finding enough arable land and local food availability.
When population increases stressed the food supply of foragers, they moved to less populated areas where the pickings were better and when they ran out of places to move, they slowly invented permanent settlements based around cleared lands where they grew food crops part of the year or tended semi-wild livestock. Converting from foragers to farmers was a slow process that likely took generations but at some point, we were foragers no more, or more precisely small bands of foragers had moved on deeper into the forests. You can still find some in places like the Amazon basin today.
Modern Homo sapiens have been on the earth for about 200,000 years, yet only within the last twenty thousand years or so have people formed large groups and lived in permanent settlements. A lot of benefits come from settling down, like inventing agriculture, law and the rules of how people should live together, religion, property rights and much more.
For most of that 200,000 years our species lived as foragers. We call them hunter-gatherers but essentially, they were opportunists: they survived by foraging sometimes finding nuts, berries, and tubers, and other times snagging a rabbit, spearing fish, or digging clams.
Farming didn’t solve our food problem because population increases have always stressed food supplies. When our ancestors settled down, they had to invent ways to preserve food from times of plenty to get themselves through the next times of need. They invented ways to smoke, salt, and cure meat and fish and learned how to gently roast grains so that they would not sprout in storage. We also carried over from our forager ways the ability to anticipate the seasons of this or that berry and when the salmon or shad might next swim up river.
The transition from foraging to domestication involved supplementing ecosystem services, the things we could expect to get from nature without more effort than it takes to fill a bucket, spear a fish, or pick a berry. Supplementing meant planting berry bushes and fruit trees but also domesticating and planting grasses for their seeds, irrigating land and building ponds using primitive dams.
Perhaps the last ecosystem service we have is fresh water, but we’ve already been augmenting water supplies for thousands of years to supplement steadily increasing demand brought on by population growth and seasonal variation. You might not think of it as supplementing the supply, but every time people build a reservoir, a dam, a water tower, and every water treatment plant, every time we discover and tap an aquifer, we’re supplementing the supply of water that nature gives us. We manage it so that it’s available to us in dry times and to keep excess amounts of it away from our homes and buildings.
We’re rapidly approaching a time when we’ll need to begin adding to the water supply that nature gives us.
What tomorrow looks like
In part 1 of this series we noted that countries like Nigeria, Somalia, and Iranand more than a score of others face very high water stress by 2040. With water stress comes food stress as agriculture is compromised and with that some populations will be on the move like our ancient ancestors searching for new hunting grounds. Unfortunately, other people already live in those places and they aren’t likely to be very welcoming so we need to do what we can to stave off big water emergencies.
It’s a good bet that we’ll need to desalinate sea water to supplement the natural water supply. When we say desalinate, it also means treating some grey water that we use for daily living and recirculating it. If this offends your sensibilities, it’s what nature does and what long space travel relies on.
About 70 percent of the world is covered by water but most of it is salt water in the oceans. Freshwater only makes up 2.5 percent of the water on the planet and a lot of that is bound up in glaciers and snowfields. If they were to completely melt, the resulting water would make its way to the oceans. So, astoundingly, only 1 percent of our freshwater is easily accessible.
There are several ways to desalinate seawater and the most obvious is to distill it by boiling it and condensing the vapor. This approach is energy intensive and works well for small quantities but to desalinate huge quantities of water, we need to turn to osmosis, a process invented in California in the 1950s. Osmosis uses membranes and high pressure to strain salt and other impurities out of the water and what’s left is fresh.
The energy needed to desalinate water through osmosis comes from electricity, which is good, because that energy can easily be derived from renewable sources. In current dollars it costs $2,000 to produce one acre-foot of fresh water from seawater. There are 325,851 gallons in 1acre-foot, enough to supply the water needs of a family of four for a year (and one acre equals 43,560 square feet). A desalination plant built in Carlsbad, CA in 2016 produces 50 million gallons per day for San Diego County.
An on line story in Bloombergsaid that energy is the “…largest single expense for desalination plants, accounting for as much as half of the costs to make drinking water from the sea…”. Indeed, the energy needs are significant, but not overwhelming. Getting a million gallons of freshwater from the sea uses about 15,000 kilowatt-hours of power.
So desalination is one of many technologies that’s available given a supply of energy for the effort. Other tech is sitting on shelves or making its way through R&D and to the market. The discussion isn’t about whether to invest in new tech and new industries it’s about ow to efficiently implement and manage. That’s how a disruption happens in an economy. It’s happening now and it’s an example of the age of sustainability taking shape.
Last words (for now)
The more renewable energy we can put to use in desalination the lower the cost of freshwater will be. That’s why, as we consider the future energy paradigm, we need to consider a good deal more than simply replacing fossil fuels in transportation and heating, for instance. The more energy we can focus on problems like fresh water, the more we can raise earth’s human carrying capacity. This isn’t a permanent solution to the carrying capacity problem, but it could help avert disaster as we contemplate many dry nations armed with nuclear weapons.
It’s been true throughout history that population catches up with technological advances that temporarily provide adequate solutions for basic human needs like food and water. Desalination should be viewed as a way to manage a crisis in the same way we manage many maladies today with drug treatments that don’t cure people but prevent them from succumbing to diseases like diabetes, some forms of arthritis, hypertension and even AIDS.
We need to do much more too. Fortunately, some of the poorest countries are in sunny climates and are located close to the ocean. What’s needed to supply complete solutions where they are needed goes beyond technology though. It requires implementation of good government and that might be the hardest paradigm to shift.
In the next part of this series we’ll take a closer look at water management which includes desalination but goes further.