Click the link to read the article on the Sibley’s Rivers website (George Sibley):

July 17, 2024

In the last post, I suggested that the Colorado River Compact with its ‘temporary equitable division’ into two basins could now be considered irrelevant (or worse, obstructive) because we have finally effectively accomplished, over the past century, the goal that brought the seven-state Compact commission together in 1922, but which they were unable to achieve then: a seven-way division of the use of the river’s waters.

They wanted a legally constituted seven-way division that would override the appropriation doctrine at the interstate level, to avoid a seven-state horserace for water in which California was already lapping the field, but in 1922 they lacked, for that goal, both a sufficient knowledge of the river’s flows and reasonable expectations for their own growth. Finally they settled on the two-basin division that was, from the start, problematic (Arizona refused to even ratify it), but which sufficed to persuade Congress that the states were enough in agreement so that Congress could go ahead with funding the big mainstem structures the Bureau of Reclamation was champing at the bit to build (perhaps the real goal of the Compact).

But now, after a century of Colorado River development, we ought to be able to say, with resignation if not confidence, that, yes, we have accomplished an eight-way division of use of the river’s waters (seven states plus Mexico). We can say this because all of the waters of the river have been put to use; what each state has to use now is almost certainly all the water it will ever have to use – at best.

Is it an ‘equitable’ division? The Compact intended for each basin to have the use of half of the river’s waters; what has evolved over the century is roughly two-thirds of the river being used by the Lower Basin, one third by the Upper. But a huge majority of the 35-40 million people served by the river live in the Lower Basin; the majority of the best land irrigable by the river is there. Speaking as an Upper Basin inhabitant, I would rather see the water go where the people are, than the people coming to where the water is (although too much of that is happening anyway).

But to my point: the seven-way (plus Mexico) division of the use of the waters that the Compact commissioners wanted has been achieved – like it or not. (Water for the 30 First People tribes is shoehorned into the state allotments.) So can we not finally jettison the two-basin division that has really proven to be nothing but divisive? As indicated by the current situation, with each basin producing a plan for the future that is unacceptable to the other basin?

We seem to have two options for the post-2026 operation and management of the river systems and structures at this point: one, add another set of ‘Law of the River’ modifications, corrections, crutches and bandaids to the beat-up Compact. Or two, start to do what we keep telling ourselves we need to be doing today: ‘thinking outside the box’ – the Compact being the box we’re in. Nested in a larger box, the appropriation doctrine as the ultimate answer, no matter what the question.

So with the seven states currently deadlocked in the two-basin box, we might take the moment to at least haul ourselves up onto the edge of the box to look around – and we might find a start in looking at the basic nature and function of our river, underneath all the physical, legal and economic structures we’ve laid over it to control and contain its basic nature. There is also some interesting science happening around the river I want to get into….

The basic function of every stream is to collect and carry off water from precipitation that the precipitation ‘catchment basin’ could not ‘catch’ and put to work in some way nurturing other life, soaking into the root zone of the plant life or accumulating in surface pools and lakes. When it comes too fast (as when a snowpack is melting), or the slope is too steep or rocky, the ‘catchment basin’ becomes a ‘watershed,’ shedding water. This is not to say that a living stream is just a ‘drainage ditch’; the water itself gives intimations of trying to stay with the land, slowing itself with picking up everything from sand and gravel to whole trees; and when the slope gentles enough, it drops what it is carrying in its own path and forces itself into looping meanders and wetlands that maximize contact with the land and opportunities to stay there.

A stream becomes a ‘gaining’ or ‘losing’ stream, depending on what is happening in the watershed it is moving through: precipitation causes direct runoff from the land, and also raises the water table, the level of saturation in whatever geological structures underlie the watershed. Both of those can add water to the stream, making it a ‘gaining’ stream. If there is no precipitation, or only enough to wet the root zone for whatever plant life is trying to hold the watershed together, and if the stream is carrying a flow that is higher than the water table in the stream’s riparian zone, then the stream will give some of its water to its riparian zone in what hydrologists call a ‘hyporheic exchange,’ making it a ‘losing’ stream. (Personally, I think of it as a ‘giving stream.’)

You can probably see where this is going for a river in an arid region like most of the Colorado River Basin. Humid-region rivers like the Mississippi and its eastern tributaries tend to be ‘gaining streams’ all the way to the oceans, due to precipitation throughout the basin, but an arid-region river is more likely to be a ‘losing (giving) stream’ once it leaves its relatively wet headwaters.

A state-of-the-science study by the Western Water Assessment (based at the University of Colorado), compiling work from many river scientists, reported that 85-90 percent of the Colorado River’s total water supply is runoff from the mountain headwaters of the Colorado River.  The mountains force air upward into cooler atmospheric levels, where any moisture in the air condenses and falls as precipitation, mostly above 8,000 feet in elevation. There would be no Colorado River were it not for the mountain ranges rising to 14,000 feet in the Southern Rockies – which constitute less that 15 percent of the Basin’s 250,000 square miles. The river’s desert reaches receive very little dependable precipitation – a lot of which comes in violent summer storms powerful enough to break through the ‘heat shield’ that creates the virga – the afternoon would-be storms when rain is seen trailing out of clouds, but being vaporized before reaching ground by the rising desert heat.

The Colorado River, despite its mountain origins, is a desert river. Below the 7,000-foot elevation the river’s tributary streams flow onto (and deeply into) the high deserts of the Colorado Plateau, then out of those canyons and into the subtropical Sonora and Mojave Deserts. Desert rivers, as a rule, are gaining streams only in their headwaters highlands; once in the deserts, they are losing (giving) streams that begin to disappear, through evaporation, plant transpiration, and ‘giving’ to low water tables – and now, of course, to humans diverting the river to irrigate rich but dry desert lands, or to water great desert cities: human practices that go back 6,000 years to the ‘Fertile Crescent’ of the Tigris and Euphrates Rivers and the floodplains of the Nile.

The Colorado River, despite its mountain origins, is a desert river. Below the 7,000-foot elevation the river’s tributary streams flow onto (and deeply into) the high deserts of the Colorado Plateau, then out of those canyons and into the subtropical Sonora and Mojave Deserts. Desert rivers, as a rule, are gaining streams only in their headwaters highlands; once in the deserts, they are losing (giving) streams that begin to disappear, through evaporation, plant transpiration, and ‘giving’ to low water tables – and now, of course, to humans diverting the river to irrigate rich but dry desert lands, or to water great desert cities: human practices that go back 6,000 years to the ‘Fertile Crescent’ of the Tigris and Euphrates Rivers and the floodplains of the Nile.

The Colorado River, as it ran before we went to work on it, still carried enough water so there would be some left after its passage through the deserts, to ‘waste’ into the Gulf of California – most of in a 2-3 month flood as the snow melted, then dropping to a trickle in the delta that probably went intermittent in drier periods. But the Great Basin north of the Colorado River region has good current examples of what happens more or less naturally with desert rivers.

Forty streams and rivers flow into the Great Basin from the Sierras, the Wasatch, the Colorado and Columbia Plateaus, and the smaller Nevada ranges within its basin-and-range landscape, and most of those streams just disappear there. Some of them are substantial like the Truckee and Humboldt Rivers as they emerge from the mountains, and flow into salty fluctuating lakes similar to but much smaller than the Great Salt Lake (also in the Great Basin). But most of those streams disappear in shallow silty playas that are dry most of the year, or they just dribble off into the riparian scrub growth they nurture in passing.

Evaporation and plant transpiration from those ‘dying’ Great Basin desert rivers is probably responsible for some of the precipitation that falls on the Southern Rockies and creates the Colorado River. As the dried-out westerlies pass over the Sierras where they’ve dumped their load of Pacific moisture – a lot of it on the Sierras’ east slopes (Tahoe Lake regularly gets 8-20 feet of snow), the dried air warms up as it flows down the mountains and begins picking up vapor evaporated from the 40 Great Basin streams and rivers, carrying it on to the Rockies where it is again condensed to precipitation.

Colorado River water is thus at the end of a line of freshwater transformations beginning with water vapor from the Pacific Ocean, condensed to rain over California’s coastal mountains, running off as liquid water to the Central Valley, then to vapor again under the hot sun, picked by the westerlies, then condensed to serious rain or snow over the high Sierras, then back to water running off the Sierras, then evaporated again in the Great Basin and again picked up by the westerlies, then condensed again to snow as it is cooled over the Southern Rockies, then melted as runoff and groundwater for the Colorado River.

The freshwater dance: less than three percent of the planet’s water is in the freshwater cycle at any time, but all land-based life depends on that fraction, mostly in its liquid state. One notices, however, that the sun and wind that create it over the ocean and move it onto land work hard to return it to its vaporous state – and what we are doing to our atmosphere is making it easier for the vaporizing forces, and more difficult to keep enough liquid water for all life everywhere.

When it comes to contemplating the management and operation of a desert river, it’s useful to begin by trying to ignore all of the artificial boundaries drawn over the river basin, especially the state boundaries which (except for where the river divides California from Arizona) bear absolutely no resemblance to or reflection of any real geography. Dividing unsettled lands into large ‘territories,’ bounded by straight lines useful only in oceanic navigation, is an imperial ploy used to create weak political and economic states with a developed dependence on the powers that drew the lines – in our case, setting up resource supply territories for the ever-expanding industrial juggernaut ‘back east.’

If you can forget the state lines and look at nature’s usually blurrier or fuzzier lines – you don’t need to be hydrologist to see that a desert river divides naturally into two regions: a water-production region in the mountains and other uplands that receive most of the river-creating precipitation, and a water-consumption region, the deserts where the river’s water gradually disappears into atmospheric vapor, groundwater, or riparian life – now including extensive human activities taking some of the water a long way from the natural river channel.

Obviously the two regions require different management strategies, in a time of water-stress. In the Colorado River’s ‘water-consumption’ region, with humans now the largest consuming entity, the management challenge is in the broad range of activities that can be called ‘conservation’: implementing systemic changes like requiring low-flow fixtures in all construction or remodeling; determining the best balance of water uses and providing the carrots and sticks to work toward those balances; doing what can be done to capture whatever precipitation does fall rather than treating it as ‘storm runoff’; where possible ‘hiding’ stored water away from the sun through recharging underground aquifers; developing internal and inter-community water reuse and sharing systems for the metropolitan sprawls – et cetera.

A lot of work is already being done in these ventures – mostly initiated by the cities themselves, or by large irrigation entities – sometimes working together with the cities. Such measures are expensive – some of them very expensive, like reuse systems requiring substantial disruptive replumbing, but they do ‘increase the water supply’ to the extent that water not needed in one place can fill a shortage somewhere else.

But an entirely different set of management challenges await up in the ‘water-production’ region – the 15 percent of the basin that produces 85-90 percent of its water – and not a lot is being done about those challenges, so far as I can tell, at least not in a conscious and deliberate way. Most of the water-production region is public land, and most of it is administered by the U.S. Forest Service which has a lot of other challenges on its plate.

But there is a factoid from the aforementioned Western Water Assessment study of Colorado River science that intrigues: they say that as much as 170 million ace-feet of precipitation falls on the Colorado River Basin, the majority of it in the mountain headwaters tributaries – yet only about 10 percent of that shows up in the river. What happens to the rest of it?

That’s what we will look at in the next post.