The dynamic & fickle lives of water by George Sibley

By George Sibley

There’s nothing like dry times to make us think about water. For most of us, access to water is so convenient (it comes out of a faucet) that it’s easy to take it for granted – until we’re told that there’s cause to start worrying about it.

Thus our awareness of water is usually worrying about it, which is too bad; it’s worth contemplating in itself – here on our planet that, had we seen the planet first from a satellite’s perspective, we would probably have named “Water” rather than “Earth.”

The first thing to think about is the fact that we live on a planet at just the right distance from our sun to enable water to exist simultaneously in its solid, liquid and gaseous states – the three lives of water. A few million miles farther from the sun, toward Mars, our water would all be frozen in its solid state. A few million miles closer to the sun, the water would all be a gaseous cloud mass suffocating the planet. In neither of those situations could life as we know it exist; all life on the planet depends on water in its liquid state.

It’s also worth noting that all of us land-based life forms depend entirely on a very small portion of the planet’s water. Most of Planet Earth’s water – 97 percent – is too “salty’ with dissolved solids for land-based life; we need “freshwater,” distilled as vapor from the salty oceans, then drifted in clouds over the land, condensing as it cools, and dropping as nearly-pure precipitation. But at any given time, only two to three percent of Earth’s water is freshwater – and two-thirds of that in the present age is “frozen assets” in glaciers and ice sheets, remnants of much larger “solid water” masses caused by a mere wobble and tilt in the planet’s relationship to the sun.

Most of the remaining third is invisible groundwater, some of which is accessible for plants through roots and for humans through wells. But the visible liquid water we think of as “our water resource” – the rivers and

streams, lakes and marshes – is only a little over one percent of that two to three percent of the planet’s total freshwater. Our freshwater resource is an almost ignorable fraction of the planet’s total water resource.

So there’s not a lot of freshwater to start with, and here in the upper Gunnison River basin, we are not ideally situated to get a share of it. The main source of the water we get in the Southern Rockies is water vapor evaporated from the tropical Pacific Ocean a thousand miles west. That warmed water vapor rises, cooling and condensing to liquid or solid precipitation, some of which is carried east and north by the trade winds into the so-called Temperate Zone. There, prevailing west winds push it toward the West Coast’s coastal ranges, causing it to rise again and cool further, condensing to “orographic precipitation” that falls on those mountains. Flowing down the mountains’ east slope into the Central Valley, it warms again and absorbs moisture rising off the irrigated fields. Then it encounters the steep young Sierras, where the rising, cooling and precipitating cycle happens again, often with massive dumps of snow and rain.

Between those two California mountain ranges, most of the Pacific moisture is squeezed out of the air. Descending the lee slope of the Sierras, the air warms again and “recycles” whatever moisture it can absorb in its long trip over the arid Great Basin, where small rivers form in the small uplifts of that basin-and-range region but eventually just disappear, either evaporated back into the air or soaked into the ground.

Finally, nine hundred miles inland from the West Coast, the air reaches the Southern Rockies, and only two factors make it possible to squeeze the remaining moisture out of that mostly dried-out air: the great height of the mountain ranges and the deep winter cold at those elevations.

Thus the majority of the precipitation

Dusty Demerson

for the entire Colorado River region falls in the winter as snow on the headwaters basins of the Southern Rockies, above 8,000 feet elevation. It is a fraction of what falls on the California mountain ranges: some readers will remember hearing of a storm in January 2021 that dropped nine feet of “Sierra cement” on the Sierras; but by the time the remaining moisture got to the Southern Rockies, it only had a foot of “Colorado champagne powder” left for us – a relatively dry snow that only yields an inch of water from a foot of snow. Well, we go with what we get and are grateful for that.

Snow falling on the mountains is just where our water story starts, though. What happens to that solid or liquid water after it falls? In 2020 a group of scientists at the Western Water Assessment, based at the University of Colorado in Boulder, published an in-depth report on the Colorado River (“Colorado River Basin” link at https:// wwa.colorado.edu). The report states that approximately 170 million acre-feet of water (enough water to cover an acre of land one foot deep) fell over the Colorado River Basin in an average 20th-century year, and 85 percent of that fell in the river’s headwaters basins, like our Upper Gunnison country above the 8,000-foot elevation, the majority of it as winter snow.

Colorado River records show, however, that only about 10 percent of that large quantity of precipitation actually makes it into the Colorado River by the time the river has collected its major tributaries. Where does the rest of that precipitation go – 85-90 percent of it?

Almost all of it goes back into the atmosphere in its gaseous state – a lot of it pretty quickly, before it even gets down to where humans begin living off of it. As much as a fourth of the total precipitation that falls as solid-state water (snow) is sublimated by wind and sun – water taken from its solid to its gaseous form without even going through the liquid stage. Windblown snow in the high rocks-and-ice region loses part of its mass to sublimation; snow caught on the darkcolored branches of conifers in the mountain forests is vaporized off the branches as the sun warms the dark branches under the snow. Sublimation is sometimes even visible – “steam” rising from the edge of a snow mass on a sunny day, even when the air temperature is below freezing.

When the snow melts and turns to water, water that stays on or even near the surface of the land is vulnerable to evaporation by sun and wind. Less evaporates in the higher elevations than lower down in the hot, dry deserts, and the mountain forests and grasslands help protect water from evaporation; nonetheless, evaporation returns a significant portion of water back into the atmosphere, even in the high country. (In

Rebecca Ofstedahl

Mary Schmidt

the summer, some of the water evaporating out of the Colorado River system reservoirs is carried back up to the peaks and orographically cooled to fall again in the river basin as showers and thunderstorms – natural recycling.)

Plant shade protects some of the snow or water from evaporation, but the plants themselves give even more water back to the thirsty atmosphere. Plants transpire groundwater up through their roots and stems to every leaf; a fraction of that water is used by the leaf for its own vitality and for the photosynthesis processes that ultimately feed us all. But at least 90 percent of what a plant carries up from the groundwater is transpired through leaves into the atmosphere as more vapor to cool their immediate environment. This can be quite a lot of water. A mature lodgepole pine transpires around 10-12 gallons of water a day, depending on temperature; an Engelmann spruce transpires 18-20 gallons a day, and a mature cottonwood (below 8,000 feet) more than 100 gallons a day. Not only does water not “grow on trees”; trees substantially diminish the supply of liquid freshwater, just like we do.

Between sublimation from the solid state in the high country, and evaporation and transpiration of the liquid state everywhere, water does show a disquieting tendency toward its gaseous rather than its liquid state – the more disquieting as we warm up the global climate.

Temperature obviously drives the dynamic transitions among these three lives of water, solid, liquid and vapor, leading scientists today to distinguish between dry droughts, when the atmosphere carries insufficient water vapor to condense as precipitation, and heat droughts, when precipitation has occurred but high temperatures escalate the vaporizing processes and quickly return more of the water to the atmosphere. We’ve experienced both types in the 2021 water year. Current estimates are that each one-degree increase in average temperatures will reduce the amount of freshwater collected in arid-land rivers and lakes four to eight percent.

Tracy Schwartz

Trevor Bona

But that gets into a larger story – one in which we will all be involved for the foreseeable future. My hope here, beyond fueling readers’ curiosity, is to convey a stronger sense of why that involvement needs to be wholehearted and serious. b

Freelance writer George Sibley has been watching the water in our valleys since the mid-1960s and his time on the Crested Butte Ski Patrol (skiing on water in its solid state). He has followed “our” water from the high alpine to where, after many uses and abuses, it finally disappears in the desert cities and fields of the deep Southwest.