HISTORY156 - Upper Colorado River Basin

Earlier this month Pat and I took Canyon Spirit’s luxury scenic train trip between Salt Lake City, Utah and Denver, Colorado.  Besides thoroughly enjoying the vista car views, gourmet food, and outstanding service, we were impressed with two other aspects of the trip that are resulting in two blog topics. 

The train route from Salt Lake City, Utah to Denver, Colorado.

  

The first aspect that really caught my attention was passing through the very deep, very narrow Glenwood Canyon, alongside the Colorado River, beginning at Glenwood Springs, and appreciating the incredible engineering and construction effort it must have taken to construct the track bed through the canyon.  Moreover, traversing the same river bed in the canyon was Interstate 70, implying another incredible feat of engineering and construction.  Documenting the history of Glenwood Canyon, including how the railroad route and interstate highway were constructed, will be the subject of my blog that follows this one.

The second aspect of the trip that impressed me was the Colorado River itself.  For over 200 miles, the train track follows the river bed of the Colorado River, from just north of Moab, Utah to just beyond Glenwood Springs, Colorado (at the western end of Glenwood Canyon). 

The Colorado River is the principal river in the Southwestern United States. It extends southwest 1450 miles from its source high in high in Rocky Mountains in northern Colorado, to Lee’s Ferry, just below Lake Powell, in northern Arizona, westward through the Grand Canyon, and then south to the Gulf of California - a journey through seven U.S. states and two Mexican states.    

The course of the Colorado River from northern Colorado to the Gulf of California.  Also shown are principal tributaries of the Colorado River.

 

The Colorado River drainage basin encompasses approximately 246,000 square miles. This drainage basin is the total land area where all participation (rain, snowmelt) drains downhill to the Colorado River from its tributaries.  For example, the Green River, which starts in southwest Wyoming, flows south and drains into the Colorado River in southeastern Utah.  The figure below shows two Colorado River draining areas called the Upper Basin and the Lower Basin - conveniently defined for water management purposes - with the boundary between them at Lee’s Ferry.

The Colorado River and the Upper and Lower Drainage Basins.

 

Three and a half years ago, I wrote about the Colorado River (see  https://bobringreflections.blogspot.com/2023/05/history73-colorado-river-is-in-crisis.html), but I emphasized the Lower Colorado River Basin, with Hoover Dam and Lake Mead, and water management efforts that directly affect Tucson, Arizona where I live.  So, this seemed like an appropriate time to write about the history of the Upper Colorado River Basin and update water management planning for the entire river.

After an introduction to the Upper Colorado River Basin, I will discuss indigenous peoples, the Spanish and Mexican era of exploration and mapping, the early American era of resource booms, the foundation of water law on the river, the climate crisis and the “aridification” era, the long-term, permanent process of a region transitioning to an increasingly dry and water-scarce climate).  I will finish with current Colorado River water allocation efforts.

As usual, I will list my principal sources at the end.

Introduction

The Colorado River and its tributaries are a vital source of water for 40 million people.  An extensive system of dams, reservoirs, and aqueducts divert its flow for agricultural irrigation and urban water supply.  Its large flow and steep gradient are used to generate hydroelectricity for much of the Colorado basin.  The river is also important for fish and wildlife, and recreational uses.

The Colorado River in the Upper Basin flows approximately 550 miles from its headwaters high in the Rocky Mountains down to Lee’s Ferry, just below Lake Powell and Glen Canyon Dam.  The Upper Colorado River Basin is comprised of parts of four states: Colorado, New Mexico, Utah and Wyoming. 

Near the source of the Colorado River, deep in the Rocky Mountains.

 

The Colorado River officially begins at La Poudre Pass Lake, located at an elevation of 10,184 feet along the Continental Divide in Rocky Mountain National Park.  The river travels through a dramatic sequence of high alpine terrain, broad agricultural valleys, and deep sandstone canyons.  Major tributaries include the Green River, flowing from the north, and the San Juan River flowing from the east (see map below).

The upper part of the Colorado River flows 550 miles from high in the Rocky Mountain to just below Lake Powell.

 

Collectively, the Upper Basin States contribute the vast majority of the water coming in to the Colorado River Basin, primarily through winter snowpack and precipitation.  But with the impacts of climate change altering the amount of snowpack, timing of the spring runoff water supply, and uncertain precipitation, the Colorado River water available for distribution to states is increasingly strained.

 

Indigenous Peoples

The history of Indigenous peoples in the Upper Colorado River Basin spans over 12,000 years, moving from ancestral nomadic and agrarian societies to a modern struggle for water equity.  Today, the region's history is tied to six federally recognized Upper Basin Tribes: the Southern Ute Indian Tribe, the Mountain Ute Tribe, the Ute Indian Tribe of the Uintah and Ouray Reservation, the Jicarilla Apache Nation, the Navajo Nation, and the Paiute Indian Tribe of Utah.

Ancient Eras and Deep Roots:

·        Ancestral Cultures: Long before modern tribal boundaries, the Colorado River and its tributaries were sustained by the Ancestral Puebloans and Fremont cultures. They developed sophisticated irrigation, farming, and crafting techniques well-suited to the arid landscape.

·        The Ute Nations: The Ute people are among the oldest continuous residents of the Upper Basin, inhabiting vast swaths of present-day Colorado and Utah.  Originally traveling in seasonal family groups to hunt and gather, their lifestyle transformed dramatically in the 17^th century after acquiring horses from the Spanish, turning them into highly mobile and formidable warriors.

·        The Diné (Navajo) and Apache: The Navajo Nation utilized the river's upper tributaries for centuries, establishing farms for corn and squash and gathering resources along the riverbanks. The Jicarilla Apache held traditional lands extending into the southern reaches of the Upper Basin, utilizing the river systems for survival and trade.

Colonial Displacement: In the mid-19^th century, the influx of American fur trappers, miners, and settlers pressured Upper Basin tribes off their lands.  Through a series of forced treaties, the tribes were relocated to compressed reservations. 

 

Spanish and Mexican Eras

Spanish and Mexican history in the Upper Colorado River Basin is defined by rugged exploration, trade alliances, and the pursuit of crucial overland routes.  While the lower stretches of the Colorado River saw 16^th-century Spanish explorers, the Colorado River remained largely controlled by Native nations (primarily the Utes) and was left uncharted by Europeans for over two centuries.

Early Spanish Exploration (1760s): For generations, the Spanish colony of New Mexico remained isolated from lucrative silver mines further south.  Intrigued by rumors of vast silver deposits in the San Juan Mountains, and legends of a wealthy, unexplored northern land, Spanish officials finally pushed northward into the Upper Basin:

·        The Rivera Expedition (1765): Juan Maria Antonio Rivera led a small party from Santa Fe into southwestern Colorado.  Charged by the New Mexican Governor to locate the Colorado River and assess Indigenous settlements, Rivera’s group became some of the first Europeans to document the upper tributaries of the Colorado River system.

·        The Domínguez-Escalante Expedition (1776): The most significant Spanish exploration of the Upper Basin took place in the summer of 1776.  As American colonists on the East Coast were declaring independence from Great Britain, Franciscan priests Atanasio Domínguez and Silvestre Vélez de Escalante departed Santa Fe with a small multicultural crew.  The objective was to map a reliable, overland northern route connecting Santa Fe to the newly established Roman Catholic missions in Monterey, California.  Guided by companions, the expedition traveled through western Colorado, crossing major Colorado River tributaries like the Green, Dolores, Gunnison, and Uncompahgre rivers.  But, facing early winter snows, harsh terrain, and the loss of their guides, the friars decided to abandon the trek to California.  They turned south and endured a treacherous crossing of the Colorado River (at a site later known as the Crossing of the Fathers) before safely returning to Santa Fe in 1777.  Though they failed to reach California, the expedition’s mapmaker, Bernardo Miera y Pacheco, drafted highly detailed regional maps and documents that became the literal template for future trade in the American West.

Route map for the Domínguez-Escalante Expedition (1776).

 

The Mexican Era and the Old Spanish Trail (1821 - 1848): Following the Mexican War of Independence in 1821, Spain's northern territory became part of the First Mexican Republic.  Under Mexican rule, the Upper Colorado River Basin transformed from an area of pure exploration into a bustling commercial highway.

·         Blazing the Old Spanish Trail: Building directly upon the routes mapped by Rivera, Domínguez, and Escalante, traders successfully linked Santa Fe to Los Angeles via the Old Spanish Trail.

·         The Blanket-for-Horse Trade: Every winter, Mexican trading parties traveled west along the trail packed with hand-woven New Mexican woolen blankets. Upon reaching California, they traded these goods for thousands of highly prized California horses and mules, driving the livestock back across the Colorado River before spring snowmelts made the rivers impassable.

·         Trappers and Modern Borders: This era also saw Mexican cities like Taos serve as vital supply hubs for American and French-Canadian fur trappers.  While some trappers operated illegally in Mexican territory, others chose to become naturalized Mexican citizens to safely build outposts.

The Transition to American Territory: The Mexican era along the Colorado River abruptly concluded with the Mexican-American War (1846-1848).  With the signing of the Treaty of Guadalupe Hidalgo in 1848, Mexico ceded its massive northern territory to the United States.  Overnight, the vast Upper Colorado River Basin became American soil.

 

Early American Era

Early American history along the Colorado River in the Upper Basin is defined by 19^th-century trapper exploration, scientific mapping, and resource booms.

Fur Trappers and Mountain Men (1820s - 1840s): Following the Treaty of Guadalupe Hidalgo in 1848, the region formally became United States territory.  However, the earliest Euro-Americans to physically penetrate the upper basin were independent fur trappers searching for beaver pelts.

·        Trappers like Jedediah Smith, William Ashley, and Kit Carson navigated the rugged terrain around the Green River and source region of the Colorado River deep within the Rocky Mountains.  They established the famous Fur Rendezvous system, treating the upper river basins as seasonal economic hubs rather than permanent settlements.

The Era of Great Surveys (1860s -1870s): By the mid-19^th century, the Colorado River in the Upper Basin was one of the last prominent "blank spaces" on American maps.  The federal government and ambitious naturalists launched daring expeditions to chart the river's path and assess its commercial potential.

·        The "Breckenridge Navy" (1868): In a little-known precursor to more famous journeys, Captain Sam Adams attempted to run the Colorado River starting near Breckenridge, Colorado.  He boldly named what we know today as Glenwood Canyon "Cedar Canyon."  Though his wooden rafts were completely demolished by the rowdy Class IV and V rapids near Dotsero, he was the first Anglo-American to attempt a descent of the upper river.

·        The Powell Expeditions (1869 & 1871): Civil War veteran and geologist John Wesley Powell launched his historic scientific investigations from Green River Station, Wyoming Territory.  Powell’s team mapped the convergence of the Green and Colorado rivers in Utah, and successfully navigated the treacherous canyons downstream.  Powell famously warned the U.S. government in his 1878 report that the arid climate surrounding the basin would severely limit conventional agriculture - a warning that was ultimately pushed aside by eager developers.

Map of the route of John Wesley Powell expedition of 1869.

 

Mining and Permanent Settlements: The character of the Upper Basin changed permanently in the 1860s and 1870s when gold and silver strikes drew tens of thousands of prospectors into the Western Slope (west of the continental divide) of the Rocky Mountains.

·        Colorado Silver and Coal Booms (1869 - 1893): The remote mining camp of Aspen and Leadville rapidly exploded into the nation's most productive silver districts.  To the west lay the massive coal fields in the Colorado River Valley.  Connecting these silver and coal vital resources to Denver and markets east of the Rocky Mountains promised astronomical wealth to whichever railroad could conquer the rugged terrain first.

·        As mining camps ballooned into permanent towns along the upper tributaries, settlers began looking at the river not as a highway for travel, but as a crucial source of irrigation and water diversion.  This late-19^th-century rush laid the groundwork for the river's first massive transbasin diversion project - the Grand Ditch in 1892 - which began piping Colorado River water across the Continental Divide to the booming agricultural fields of Eastern Colorado, setting off a century of legal and environmental battles over the river's flow.

Note:  I will discuss the history of railroads crossing the Rocky Mountains and the related history of the Upper Colorado Basin in my next blog.  The balance of this blog will concentrate on water conservation efforts along the Colorado River.

 

Foundation of Water Law (1900 - 1948)

As rapid agricultural growth exploded in the Lower Basin (particularly California's Imperial Valley), Upper Basin states grew concerned that California would claim the entire river under the Western doctrine of "prior appropriation" ("first in time, first in right").

·        The 1922 Colorado River Compact: To protect their future growth, Upper Basin states negotiated the foundational 1922 Colorado River Compact.  It split the watershed at Lee Ferry, Arizona, allocating 7.5 million acre-feet (maf) of water annually to both the Upper and Lower Basins.

o   Upper Basin: Colorado, New Mexico, Utah, and Wyoming.

o   Lower Basin: Arizona, California, and Nevada.

Upper Basin states could not deplete the 10-year rolling average flow at Lee Ferry below 75 million acre-feet.  Agricultural and domestic water uses took legal precedence over power generation and navigation.

When the historic Colorado River Compact of 1922 divided the river's flow between Upper and Lower Basin states, all 30 Indigenous Native American tribes were excluded from the negotiations.   Despite holding the most senior water rights in the basin, tribes were denied a seat at the table and left without the federal infrastructure needed to access their water.

 

President Hoover signing Colorado River Compact of 1922. 

 

·         The Mathematical Error: The compact negotiators based their allocations on data from an unusually wet period, assuming the river averaged 17.5 to 18 maf per year.  In reality, the long-term average was much lower, creating a structural water deficit that persists today.

·         Mexican Allocation: A subsequent 1944 treaty added an annual delivery of 1.5 MAF to Mexico, increasing total promised allocations beyond the river's actual historical supply.

·         Upper Colorado River Basin Compact (1948): To solidify their internal sharing, the four Upper Basin states signed their own compact, allocating the Upper Basin's share by percentages to account for fluctuating river levels: Colorado (51.75%), Utah (23%), Wyoming (14%), and New Mexico (11.25%).

 

 

Era of "Big Dam" Engineering (1950s - 1999)

With legal allocations in place, the mid-20^th century saw the federal government step in to build massive water storage infrastructure to control the volatile river.  While the Lower Basin boomed with projects like the Hoover Dam in the 1930s, the Upper Basin developed much more slowly.

·        Colorado River Storage Project Act (1956): Congress approved a sweeping plan to build massive reservoirs across the Upper Basin.  The primary purpose was to store water during wet years so the Upper Basin could meet its legal obligation to deliver a rolling average of 7.5 maf per year to the Lower Basin.

·        The Rise of Glen Canyon Dam: Completed in 1963, Glen Canyon Dam flooded a majestic red-rock canyon to create Lake Powell, the primary water savings bank for the Upper Basin.  Other major projects built during this era included the Flaming Gorge Dam (Wyoming/Utah) and the Aspinall Unit (Colorado).

Glen Canyon Dam forming Lake Powell.

 

·        Trans-Mountain Diversions: Extensive tunnel networks (such as the Colorado-Big Thompson Project) were expanded to pipe water from the Upper Basin's Western Slope through the Continental Divide to fuel the population booms of Colorado's Front Range (Denver).

 

Climate Crisis and Aridification (2000s - Present)

By the turn of the 21^st century, the structural flaws of the 1922 Compact caught up with the region, amplified by climate change.

·        The Millennium Drought: Beginning in 2000, the basin entered a historic, multi-decade megadrought - the driest period in over 1,200 years.  Lake Powell plummeted to unprecedented lows, threatening the Upper Basin's ability to generate hydropower and fulfill downstream delivery obligations.

·        Drought Contingency Plans (2019): Realizing the system was close to crashing, the Upper Basin states signed emergency agreements to coordinate reservoir releases and incentivize water conservation.

After a century of being marginalized in river management, the six federally-recognized Upper Basin tribes achieved a historic breakthrough.  On April 22, 2024, tribal leaders signed a permanent Memorandum of Understanding with the Upper Colorado River Commission.  This agreement formalizes mandatory, bi-monthly meetings, ensuring Upper Basin tribes have a direct voice in dictating post-2026 river operations and shortage guidelines.

 

Current Colorado Water Allocation Efforts

The U.S. Department of the Interior finalized a new, two-year operating framework in August 2026 that enforces historic mandatory water cuts exclusively on Lower Basin states for 2027 and 2028.  Adopted by the Bureau of Reclamation to address critically low reservoir levels at Lake Mead and Lake Powell, the plan has sparked intense legal friction.  While intended to serve as a short-term stabilizing "bridge" through 2028, the framework has pushed Arizona and Nevada to take legal action against the federal government.

Mandatory Reductions for 2027 - 2028: The framework mandates a collective reduction of 1.25 million acre-feet annually for the Lower Basin states, alongside an additional target of 700,000 acre-feet in voluntary conservation over the two-year period.

State	Annual Mandatory Reduction	Impact Context
Arizona	760,000 acre-feet	Absorbs roughly 30% of its total river allocation; Central Arizona Project (CAP) deliveries face a 50% cut.
California	440,000 acre-feet	Demands heavy short-term cuts, forcing regional agricultural and municipal adjustments.
Nevada	50,000 acre-feet	Represents one-sixth of the state's total annual river entitlement.

 

The Upper vs. Lower Basin Conflict & Lawsuits: The federal plan does not mandate any water cuts for the four Upper Basin states (Colorado, Utah, Wyoming, and New Mexico).  Instead, the Upper Basin is developing a separate, smaller voluntary conservation plan funded by the federal government.

·         The Upper Basin Perspective: State officials argue that Upper Basin water users already experience "mandatory cuts" directly from Mother Nature via fluctuating snowpack and diminished local stream flows.

·         The Lower Basin Backlash: Lower Basin states argue it is unlawful to leave downstream users to absorb the entire structural deficit while upstream reservoirs are protected.

·         Active Litigation: Nevada filed a lawsuit shortly after the August 2026 announcement.  In October 2026, Governor Katie Hobbs and the Arizona Department of Water Resources officially moved to join Nevada's lawsuit to challenge the federal framework.  Major municipal entities, including the City of Phoenix and the CAP governing board, have also authorized legal counsel for potential intervention.

Long-Term Post-2026 Operations: This 2027 - 2028 framework serves as an interim patch because the river's foundational operating guidelines expire at the end of 2026.  Simultaneously, the Bureau of Reclamation is analyzing a January 2026 Draft Environmental Impact Statement that proposes five distinct alternatives for long-term operations.  These proposals contemplate permanent annual delivery cuts ranging from 1.48 to 4.0 million acre-feet per year, which the seven basin states must negotiate as they try to craft a permanent solution.

Emerging from Glenwood Canyon on our Canyon Spirit train trip.

 

 

For 200 miles we followed the Colorado River through deserts, red rock formations, awesome canyons, and river-side ranches - at peak fall-color time: an experience to be treasured and long remembered.

 

 

Sources

My principal sources include: “Canyon Spirt: An elevated rail journey through the American Southwest,” canyonspirit.com; “Course of the Colorado River,” Wikipedia.com; “Upper Basin of the Colorado River,” americanrivers.com; “Where does Lake Powell Get Its Water?”; lakepowellwaterlevel.com; plus, numerous other online sources, including answers to many queries using Google in AI-Mode.