Wet Slope, Dry Slope
It’s 2040. The population of the Front Range mega-region of Colorado, which now stretches almost uninterrupted from old Pueblo to Laramie, is over 6.3 million. Similar growth has occurred in the “lower Colorado basin” states of Nevada, Arizona, and southern California. This is the fourth summer of Cici, the first drought ever to be named like a hurricane. It’s believed, though nobody quite knows, that the name Cici derives from the initials of Climate Change.
Cici covers the Four Corners states and extends southwest to Baja California. No rain at all has fallen on Las Vegas in 26 months. And the Front Range is in chaos because the lower basin has just issued a Compact Call. The diversions of water from the Colorado River to the cities of the Front Range and the farms of the Eastern Plains are about to be curtailed. In the cities and suburbs of the Front Range, the panics and the water riots are beginning.
OK, let’s get back to reality. This is not a dystopian novel (though there are a few out there that begin this way). This is 2017 and rampant growth on the Front Range is continuing to drain away the water from the West (or Wet) slope of the Rockies. We’re seeing more energetic weather patterns that a majority of Americans are finally saying must be harbingers of climate change. One of the consequences of that is that we are all going to need to understand water law.
The Compact
What is a Compact Call? The Compact of 1922 is an agreement forged among the seven states of the Colorado River Basin. In addition to the lower basin states named above, the upper basin states include Colorado, Utah, Wyoming, and New Mexico. The Compact divides rights to the waters of the Colorado among the seven Compact states. The major provision of the Compact is that the three Lower Basin states must receive 7.5 million acre-feet of water, measured at the entrance to the Grand Canyon. The upper basin states divide the water not promised to the lower basin on a percentage basis.
We all know that the population centers of Colorado’s Front Range lie in the “rain shadow” of the Rocky Mountains. Average precipitation on the Western Slope of the Rockies is about 40 inches per year, but east of the Continental Divide, the average is only 12 to 20 inches. 75% of the rain and snow that falls on Colorado falls west of the Divide. 80% of the population of Colorado lives east of the Divide along the Front Range. The problem of providing water to the roughly 4 million residents of the Front Range megaregion is largely solved by diverting water from the Western Slope, mostly from the Colorado River basin. Water from these “transbasin diversions” passes under the Continental Divide into an East Slope river basin.
Creating Water Rights
In Colorado, a water right is created when water is diverted from its natural or previous course of flow for a “beneficial use.” The two most obvious beneficial uses are municipal consumption, and agriculture. There are other types of beneficial use, too, but these are the main ones. Of course, once established, water rights may be bought and sold.
A water right dates from the time of the diversion. Because the volume of water flowing in a particular channel is not constant, water rights can come into conflict. Suppose that Farmer Brown began diverting water from the Winding River to water his crops. He has taken 20 acre-feet per year since 1945. In 1980, Farmer Green began diverting water 20 miles upstream from Farmer Brown. He diverts 30 acre-feet per year. Because there has historically been plenty of water in the river for both farms, the two water rights are not in conflict.
Now comes the drought year 2000. This year, the flow in the Winding River past the Green and Brown farms drops below the level required to satisfy the needs of both farms. Even though there is enough water flowing past the Green farm, which is upstream of the Brown farm, it is Farmer Green who must reduce his consumption, because his water right (1980) is junior to Farmer Brown’s water right (1945).
Hierarchy of Benefits
In our simplified version of Colorado water law, there’s not a lot to say about this. Beneficial use of water for people — such as municipal use — is more important than agricultural use. If there’s only enough water for the city taps, then the irrigation ditches must run dry, even if the irrigation right is senior to the city’s right. City consumption includes domestic uses such as watering lawns and washing cars, as well as drinking and washing. It is likely that this aspect of the theory of beneficial use will be tested in the next period of extreme shortage. There are precedents for state law setting limits on water rights.
Back to the Future
Now we have the tools to understand how super-drought CiCi is causing water wars in 2040. Essentially all the water rights that divert Colorado Basin water to the East Slope (for the most part, to the Platte River Basin) are junior to the Compact. Eastern slope agriculture in the north subsists on water from rainfall on the Eastern Plans, and from water recovered after use by the cities. Most of the latter comes from the Colorado-Platte diversions. [There is another group of diversions in southern Colorado, into the Arkansas river basin. That water supports Pueblo and the agricultural regions of La Junta, Lamar, and Rocky Ford.]
Western slope agriculture has been surviving on the heavier West Slope rainfall, and water from secondary river basins not tributary to the Colorado. But the Compact guarantee of 7.5 million acre-feet of water to California, Nevada, and Arizona looms, and that water is almost entirely consumed by great arid-climate cities like Las Angeles, Las Vegas, and Phoenix. And all the Eastern-slope diversions are junior to the Compact.
When the Colorado-Platte diversions, all of which are far upstream of the Colorado’s entrance to the Grand Canyon, cause the flow into the Grand Canyon to fall below 7.5 million acre-feet, that triggers a compact call. Because the East-Slope diversions are junior to the Compact, the law calls for curtailing the diversions. There will be attempts to preserve the necessary flows to the Front Range by purchasing the remaining agricultural rights of the Western agricultural regions in a massive buy-and-dry scheme. But those rights are some of the oldest in Colorado, dating to the 1800s and far senior to the Compact. The resulting litigation, one source estimates, could last 20 years.
We should all hope that Cici is shorter than that.
