Flawed Flow Estimates by 1921 Federal Govt. Caused River Water Over-Allotment

_{Whiskey is for drinkin’ & water is for fightin’}~_{Mark Twain}

by Bruce Heath

The dryness of the land west of the 100th Meridian has been known for a considerable number of years. As early as 1540, Francisco Vazquez de Coronado, on his 4,000 mile odyssey through land that would become six western states, in search of the seven cities of Gold reported water was difficult to find. The most frequent physical malady reported in the journals of Lewis & Clark was the men’s sore feet caused by cactus tines puncturing their moccasins. In 1820, Stephen Long’s expedition traveling through what would become the states of Nebraska, Colorado, Oklahoma and Arkansas noted, “ I do not hesitate in giving the opinion that the land is almost wholly unfit for cultivation, and of course uninhabitable by people depending upon agriculture for their subsistence.” In reference to these conditions, he then labeled the region The Great American Desert.
In 1878, John Wesley Powell sent Congress a Report on the Lands of the Arid Regions of the USA. By careful observation, Powell determined the vast amount of the territory west of the 100th meridian received less the 20” of precipitation annually. He stated that only 2% of the land was suitable for agriculture and that that land needed to be near a water source. He suggested an approach for the government to distribute land to settlers and how to organize water usage because its existence was not in sufficient amounts needed to irrigate large swaths of land. The federal government, railroad companies and land speculators all needed western settlers to achieve the economic growth they desired. Negative publicity about their “ promised land” was not acceptable. This group rejected Powell’s approach in favor of the theory put forth by Professor Cyrus Thomas. His idea was agricultural development would change the climate and cause higher rates of precipitation. He coined the phrase, “ rain will follow the plow.” The famed author Wallace Stegner has described the American West as the geography of hope. Hopeful settlers filled with belief in Thomas’s theory showed up in increasing numbers. For the following 60 years, cities, farmers and ranchers dealt with the inconvenient fact that the territory west of the 100th Meridian received less that 20” of precipitation a year. It wasn’t until the dust bowl years of the 1930s, after brutal hardship and suffering, that Powell’s recommendations were reconsidered.
For those in Hinsdale County of a certain age, who knew the settling generations, there was an oft repeated joke told by them. Two cowboys on horseback are riding along the Lake Fork of the Gunnison river. One said to the other, “ This land is starting to grow on me. I am really taking a liking to it. All this place needs is good people and water.” His riding partner thought about it for awhile and then said, “ Just remember people say the same thing about Hell.”
By 1900, it became known that portions of Arizona and southern California were capable of significant agricultural production if sufficient irrigation water could be brought to the crops. This would be a major catalyst for forming the Colorado River Compact in 1922. The river’s water source was recharged annually by snow melt from the Rocky Mountains. The purpose of the compact was to provide for an equitable division and apportionment of the river water for municipalities and agriculture use among seven western states located in two basins. The Chair of the Commission who would decide this was the Secretary of Commerce Herbert Hoover.
The challenge was to determine how much water was available to be distributed. The middle section of the Colorado River Basin was one of the most remote and inaccessible regions in the nation at the time. In particular, the canyon region from the mouth of Green River in Utah to the Grand Wash in Arizona, covering a water course of approximately 520 miles, was accessible to wheeled vehicles at only three points. Because of the inaccessibility, no stream gauges were established at Lees Ferry until 1921.
An article providing the detail of how the river flow estimates were determined can be found on EOS.org Fixing the Flawed Colorado River Compact. Portions of what follows come from this article. The federal government used a methodology that in retrospect can be labeled as non scientific and politically driven. Their estimate was an assumption that the river’s average discharge at Lees Ferry was 16.4 million acre-feet per year. Based on this estimated flow, the commission then allocated a combined total of 15 million acre-feet per year which would leave the remaining water to meet the needs of future development. It’s clear today that the commission’s 16.4-million-acre-feet-per-year estimate was based on errors about past flow amounts, inaccurate water evaporation assumptions and grossly optimistic future precipitation considerations. They also ignored the more conservative science and more reliable hydrology data available at the time.
Actually, the best data available came from a US Geological Survey employee named Eugene LaRue. LaRue calculated the average discharge at Lees Ferry between 1895 and 1920 to be 15.0 million acre-feet per year using records from actual stream gauges and tributary contributions up and downstream from Lees Ferry. LaRue submitted his findings to Hoover who replied with a polite thank you note and then ignored them. LaRue’s findings did not support the political needs associated with proposed water distributions. The different approaches of LaRue and the one used by the federal government led to a disparity in their discharge estimates of approximately 1.4 million acre-feet per year. Future measurements and tree ring analysis would prove LaRue’s calculated flows of 15m acre feet to be valid. So from the compact’s inception, the government distributions were based on an exceedingly wet previous 20 years, non scientific calculations of historic flows and overfly optimistic future flow estimates caused the river to become over allocated.
With the Compact in place, the era of dam building began in 1931 with the Hoover Dam and neared completion in 1963 with the Glen Canyon Dam. The premise was simple. The annual river flows were variable because the snow pack for each year could be widely different in amounts. Reservoirs assured, even in low runoff years, the availability of stored water to be reliably released to meet downstream legal usage distributions.
In the 1980s, even a keen observer would not have been able to know that 1983 would bring record high water reservoir levels and then that 1984 would be the beginning of increasingly lower snow pack years. Going forward from the late 1980s, in spite of lower inflows to Lake Powell, the storage and usage premise still prevailed. Downstream users still took their legal allocations from the stored water and they believed that, based on past history, eventually higher snow melt runoff in future years would restore what had been taken. Besides that, Lake Powell was at 76% of capacity in the summer of 1995 so there was plenty of water in reserve.
Then as the saying goes…stuff happens. Starting in the year 2000, the region utilizing Colorado River river water began experiencing what would become a 24-year-long mega drought that is still ongoing. This span would be the worst consecutive years of severe drought in the last 1200 years. Streamflows were reduced to 12.4M acre feet annually. The lower basin users continued to take their legal allocations from stored water until 2007. Then it became obvious that inflows were not replenishing allocated outflows. Lake Powell capacity had dropped to 60% of full pool capacity and thus usage had to be reduced. The mega drought continued its relentless onslaught, and in 2021-22, the levels of Lake Powell reached all time lows at 30% of full pool capacity. The usage reductions had not been enough. The breach of the critical water elevation level of 3525′ alerted the federal government that the ability of the Glen Canyon Dam to produce reliable hydro generated electricity for 5 million users was in jeopardy. This triggered emergency water releases from the Flaming Gorge and the Curecanti reservoirs on the Gunnison River. Again, users had to further reduce their usage.

It has now been determined that the average flow between 1906 and 2024 had been 14.6M acre feet annually proving the 1922 government flow estimate of 16.4M feet to be wrong. Worse, during this mega drought the average has actually…._{read more.}