Freshwater: Earth’s Most Precious Liquid

If someone in outer space were to cast their view away from the vast, stary tapestry of the cosmos, and back to our home – Earth – they would see a bright blue-green orb hanging in contrast with the black void surrounding it. Our beautiful, blue planet looks that way because it’s mostly water. The surface is roughly 71% water, with the rest being land, and some ice at the poles and at the peaks of a few mountain ranges. 

Yet, we still see, hear and read of water scarcity, drought, and places where people struggle to find this necessity of life. How can this be?

The reality is that most of that water we see is unusable for drinking, farming or industry, and there’s a pretty good reason. 

When you look at the vast reservoirs of water this planet holds, a staggering 97% of it is saltwater – undrinkable, no good for farming, and corrosive if applied industrially. Only 3% of our planet’s water is freshwater. Not much, is it?

When we look closer at that 3% of freshwater, only a fraction is available for our civilization to use. About 69% is locked up in glaciers and ice caps, and about 30% is groundwater. Less than 1% of freshwater is found in lakes, rivers, wetlands, soil moisture, near-surface aquifers, and the atmosphere.

The truly accessible water that humans, wildlife, and ecosystems rely on is therefore a tiny fraction of the planet’s total water supply.

Let’s look at this in a slightly different way to help put it in perspective. If all of Earth’s water fit into a 1-litre bottle, only about 30 millilitres would be freshwater. Of that, most would be trapped in ice or deep underground. The water readily available in rivers, lakes, and wetlands would amount to only a paltry few drops.

So, Why are Oceans Salty?

The oceans weren’t always salty, but over time, a perfectly natural process made them that way. Rain itself is naturally fresh. It came from clouds of water that evaporated from places perhaps thousands of kilometers away. That rain falls on the ground, some collecting in rivers and lakes cutting through rocks and soil. Recall one of water’s quiet miracles – the ability of it to dissolve other compounds due to the polarity of the water molecule itself. 

During the course of water running from soil, to stream, to lake and river on long, often meandering paths to the ocean, it dissolves mineral salts along the way, before ending up in one of the Earth’s mighty oceans.

Of course, water will evaporate from the oceans as well, and when it does, it leaves those dissolved salts behind. Repeat that cycle countless times over hundreds of millions of years, and all those dissolved minerals left behind in the oceans as water evaporates, create oceans of increasing salinity.

The oceans are a great collection basin. Water leaves, but the dissolved minerals largely stay behind.

Nature tirelessly performs a giant distillation process, every day, every week, month, year, across millennia, spanning epochs of our planet’s history.

• Ocean water evaporates. 
• Salt stays behind. 
• Water vapour forms clouds. 
• Rain falls as fresh water on lands far way
• Water flows back to the seas, picking up more salts along the way. 

The hydrologic cycle continuously creates fresh water, and this is one of the most elegant natural systems on Earth.

How Little Fresh Water Is Actually Available

Let’s come back to our examination of freshwater. We noted that only roughly 3% of the world’s water is freshwater. Surely that’s more than enough, given how much water in total the world has, but astonishingly, and perhaps frighteningly, it is not so.

The water locked up in glaciers and ice caps is inaccessible, in practical terms, for us to use, given location and distance. And while melting glacial runoff does make it to communities downrange of the glaciers, it is already accounted for as rivers.

As for groundwater, have we not considered the use of wells? Yes, but that is considered as near-surface availability. Most groundwater is actually too deep to access economically, some is saline, and some trapped in rock formations which replenish very slowly. Only a tiny fraction exists in lakes, rivers, wetlands, and shallow groundwater, that humans can readily use.

If we consider that tiniest allotment of water that we are so privileged to use, we must also consider that it is not evenly distributed across our planet. Much of the landmass is desert, or mountain, or frozen tundra and icecaps – places where readily accessible freshwater is scarce or practically non-existent.

Freshwater is scattered unevenly across the world, the largest being the rift lakes in Africa, and the Great Lakes of North America. Mighty rivers such as the Nile, the Tigris, Euphrates, the Yangtze, the Congo and Amazon rivers to name a few, allowed for human civilizations to grow and thrive.

As we discussed earlier – fresh water equals life. Here in Southwestern Ontario, surrounded by the Great Lakes and nourished by rivers like the Sydenham and Thames, it’s easy to believe fresh water is limitless. In reality, we are among the fortunate few who live beside one of the greatest freshwater systems on Earth.

Access to freshwater is foundational to our survival, and to the survival of the ecosystems upon which we, not only as a civilization, but as a species, rely.

We’ve talked about how every glass of water represents a journey millions of years in the making. It may have fallen as rain on a prehistoric forest, flowed through ancient rivers, rested beneath a glacier, or travelled through the Great Lakes before arriving at our tap. We take it so much for granted, but it’s foolhardy and shortsighted to see water as nothing more than an infinite and readily available resource. It is the product of one of Earth’s oldest and most remarkable cycles. Though our planet appears blue from space, the fresh water that sustains us is surprisingly scarce, and that makes it worthy of both gratitude and stewardship.

In our next piece, we will examine what can happen to societies when we don’t heed this – cautionary tales of misuse, misfortune, and how it affected the people and ecosystems around them.

Sources:

U.S. Geological Survey (USGS). Where Is Earth’s Water?
U.S. Geological Survey (USGS). The Water Cycle.
National Oceanic and Atmospheric Administration (NOAA). The Water Cycle.
UNESCO. United Nations World Water Development Report.
Food and Agriculture Organization of the United Nations (FAO). AQUASTAT Global Water Information System.
Environment and Climate Change Canada. Freshwater in Canada.
International Groundwater Resources Assessment Centre (IGRAC). Groundwater Resources and Aquifers.