Climate Science, Change And Our Daily Lives - Part 2: Under Water

News flash: The water supply in the Upper Colorado River Basin is in severe shortage and will cause consumption restrictions in Nevada, Arizona, New Mexico and West Texas. It’s getting closer to us.

We need fresh water to live, and so do many other creatures and life forms around us. Water is also an important part of managing our Earth’s temperature because it stores heat really well.

In this article, Part 2 of my climate change series, we’ll take a look at the effects of changing temperatures on this vital resource.

Our water supply

Water (H2O) comes in three forms: liquid, gas and solid. While the Earth’s surface is mostly water, only about 2.5% is freshwater. Of that, even less is considered potable, i.e., safe to drink and cook with.

Most of our Earth’s water is in our oceans and seas (96%), but that’s all saltwater. Less than half a percent of our freshwater is found in lakes, rivers, streams and swamps. Almost 70% is in ice caps and glaciers. About 30% of all freshwater is in groundwater (underground), which provides half of America’s drinking water (99% in rural areas) and 25%-40% worldwide. Freshwater water vapor also exists in the atmosphere as well as in clouds and precipitation. Of course, all this water is constantly moving, changing and circulating in the hydrologic cycle. (USGS)

From these basic facts, we can see that freshwater is scarce and precious. Groundwater, though our main source of drinking water (and irrigation), is not evenly distributed around the world; half of the world’s freshwater is concentrated in only six countries. Nor is it evenly distributed within our country (e.g., Michigan vs. Nevada). Where freshwater is limited, people have used many technologies like wells, dams and canals to store and move it, mostly locally. Water storage is thus essential for our food security.

The US is disproportionally endowed with freshwater, having 7% of global renewable freshwater resources for just 4% of the world’s population. But this doesn’t guarantee we will have enough in the future. Generally, drinking water supplies in the US are among the safest and most well-regulated in the world, yet coherently managing this scarce supply has been problematic.

Our water demands

Although a bit dated, a 2012 U.S. Intelligence Community Assessment Global Water Security report predicted that by 2030, humanity’s annual global water requirements will exceed current sustainable supplies by 40%.

Globally, freshwater for agriculture, industry and municipal use has increased by a factor of six since 1900. As of 2015, 322 billion gallons of water per day were used in the US. The three largest usage categories were irrigation (118 Gal/day), thermoelectric power (133 gal/day) and public supply (39 Bgal/day), cumulatively accounting for 90% of the national total. (For more details, see USGS or this factsheet.) Conservation efforts have led to declining consumption rates here in the US; on average, each of us now uses 80-100 gallons per day. But supply and demand vary considerably across regions and states.

In the delicate balance between global supply and demand for freshwater, some areas already suffer from water insecurity. When something upsets that delicate balance – like increased temperatures due to climate change – we can quickly develop a water-related crisis. Approaches to maintaining this highly complex balance differ depending on location and have seen varying degrees of success.

Our water reflects dangers of climate change better than our air

Unlike our problems with too much CO2 in the atmosphere, the impacts of climate change and pollution can be seen more easily inn our world’s water supply.

According to NASA, the Earth’s global sea level has risen about 8 inches in the last century. The rate in the most recent 20 years, however, has been accelerating more quickly.

At the same time, global sea surface temperature has risen more rapidly in the last 30 years (1.5 degrees F since 1901). Under the surface, temperature increases and pollution have contributed to decimating a variety of species. (In our first article, we showed how fast the Earth’s temperature is rising due to human effects.) This is because Earth stores 90% of its extra energy in the ocean.

Surface ocean waters have also become about 30% more acidic since the beginning of the Industrial Revolution, not to mention the problems caused by plastic pollution and destructive fishing practices. The ocean has absorbed between 20-30% of total human generated CO2 emissions in recent decades (7.2 to 10.8 billion metric tons per year).

Sea-level rise from melting snow, glaciers, ice sheets, etc., is also threatening coastal communities and their water supplies, which often draw their freshwater from aquifers. A rising ocean creeping inland can contaminate this groundwater. To add to our troubles, the Clausius-Clapeyron equation shows that for every 1.8 degrees of warming, the atmosphere can hold 7% more moisture â