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Colorado Water Law for Non-Lawyers
By P. Andrew Jones, Tom Cech
University Press of ColoradoCopyright © 2009 the University Press of Colorado
All rights reserved.
Colorado Climate, Geology, and Hydrology
CLIMATE AND TOPOGRAPHY
The nature of a society is determined, at least in part, by the attributes of the natural setting in which it develops. To understand the story of Colorado water law, one must first explore the windswept peaks, cathedral forests, and sweeping plains that form the state's landscape. One must meet a mountain stream swollen with snowmelt in a high meadow and follow it down the mountain, through the foothills, and across the broad plain to the horizon. One must look beneath the surface of the earth at the vast, silent formations of rock and sediment, formed in ages past, now holding vast amounts of water suspended in pores and cracks within the rocks. This chapter looks at the constraints and opportunities presented by Colorado's climate, topography, hydrology, and geology.
Colorado is a very large state — the eighth largest of the fifty U.S. states — with 104,000 square miles within its borders. Many nonresidents have a preconceived vision of Colorado as composed of wall-to-wall mountains, sparkling rivers, and snow-covered ski resorts from Julesburg to Rifle. That vision is abruptly altered as one drives along Interstate 76 in northeastern Colorado, passing vistas of sagebrush, prickly pear cactus, and unending treeless prairie. Approximately 40 percent of Colorado's land area is located in the relatively flat Eastern High Plains. The remaining landscape is almost equally divided between the Central Mountains and the Western Plateaus. Mountains, plains, mesas, and plateaus all combine to make up Colorado (Figure 1.1).
Colorado's climate is one of extremes. For a sportsperson, a good spring day could involve a round of golf in the morning and downhill skiing in the afternoon — both at world-class resorts. What makes this possible is Colorado's diverse climate, which is shaped by its unique location and topography. According to the Ground Water Atlas of Colorado, five major factors combine to produce different, localized climates in the state: (1) latitude, (2) distance from large bodies of water, (3) elevation, (4) topography, and (5) winter storm track position. Average seasonal temperature and precipitation vary tremendously across Colorado. The mile-high topography varies from a low elevation of 3,315 feet, where the Arikaree River flows out of eastern Colorado into northwestern Kansas, to a high of 14,433 feet on the peak of Mt. Elbert (almost 3 miles above sea level). Average elevation is 6,800 feet above sea level and includes fifty-three mountains with elevations of 14,000 feet or more. Colorado has more mountains with peaks in excess of 14,000 feet than all other states combined. Mile high indeed!
Colorado is one of only three states (Wyoming and Utah are the other two) that generally follow lines of latitude and longitude for all its borders. State lines extend from 37 degrees N to 41 degrees N and from 102 degrees W to 109 degrees W.
Although towering mountains are poised to grab passing moisture from the atmosphere, Colorado's average annual precipitation is only seventeen inches. This is somewhat misleading, however, because elevation and topography create great regional extremes across the state. For example, the San Luis Valley in south-central Colorado is a high mountain desert that receives about seven inches of average annual precipitation, while the nearby San Juan Mountains receive over forty inches of precipitation each year. Extreme variability in rain and snowfall — with occasional droughts thrown in — presents serious challenges to water managers and users and has created the setting for Colorado's unique and expansive water law system. Figure 1.2 shows the average annual precipitation across Colorado.
Colorado can be divided into three general areas, from east to west: Eastern High Plains, Central Mountains, and Western Plateaus (Figure 1.3).
Eastern High Plains
The Eastern High Plains of Colorado are vast and sometimes brutal. Large regions of rolling grassland extend westward from Kansas and Nebraska, rising gently about 1,000 feet in elevation to meet the foothills of the Rocky Mountains in the central portion of the state.
Precipitation on the semiarid Eastern High Plains averages between 12–16 inches per year. Much of it occurs in a few scattered, violent summer thunderstorms or dangerous spring blizzards. In repayment for this violent weather, the region has abundant sunshine, low relative humidity, wide-ranging daily temperature variations (including relatively cool summer evenings), some wind, and dry spells that last for weeks and sometimes months at a time. Colorado's Eastern High Plains embrace a raw beauty that is timeless.
Two of eastern Colorado's major river systems, the South Platte and the Arkansas, originate as coldwater streams high in the Rocky Mountains. From an alpine terrain of spruce and pine, melted snow trickles toward the expanding urban Front Range cities. The Arkansas River proceeds east past Pueblo, while the South Platte River carves a path through Denver. Indirectly, even lazily at times, these two rivers continue for 200 miles across the Eastern High Plains toward the flatlands of Kansas and Nebraska.
STEPHEN HARRIMAN LONG
Major Stephen Harriman Long (Figure 1.4) was selected by President James Monroe to lead the 1820 expedition to explore areas acquired in the 1803 Louisiana Purchase. Major Long was born in 1784 in Hopkinton, New Hampshire, the youngest of thirteen children. He was a graduate of Dartmouth College and taught for two years at the U.S. Military Academy before exploring the future state of Colorado.
Major Long's expedition was instructed to locate the headwaters of the South Platte, Arkansas, and Red rivers. He followed the Platte River (the same route taken by Interstate 80 across Nebraska today) and then the South Platte River (generally following the future route of Interstate 76 in northeastern Colorado). Long's twenty-man expedition included a geologist, a zoologist, a botanist, a mineralogist, a surgeon named Edwin James, and artists Samuel Seymour and Titian Peale (who was also a naturalist).
This was a military expedition of the Corps of Topographical Engineers. It reached Colorado's Front Range in July 1820 and traveled to and named Long's Peak. The group then traveled upstream along the South Platte River through the future location of Denver, then down to the Arkansas River watershed. Three members of the expedition, including Dr. Edwin James, climbed Pikes Peak. Later, Long's group was unable to find the Red River, ran into hostile Kiowa-Apache Indians, and eventually had to eat their horses to survive.
Fairly recently, the 1819 wintering site of the Long Expedition may have been located on river-bottom farmland north of Omaha, Nebraska, near the mouth of the Platte River. Only one of the specimens collected by the expedition remains today — a greater prairie chicken at the Academy of Natural Sciences in Philadelphia. Fortunately, a two-volume, 1,000-page report issued by the government is also on display at the academy.
The region's elevation begins at around 5,000 feet along the Front Range foothills and gradually declines to about 3,400 feet above sea level at the Kansas border near Holly and at Julesburg near the Nebraska border. Large areas of rolling flatland dominate the region — which caused the expedition of Stephen Harriman Long to call it the Great American Desert. Long's cartographer wrote this desolate description on a map published in 1823, perhaps for two reasons: (1) to describe the dry nature of the Eastern High Plains, a "barren and uncongenial district"; and (2) to discourage the interest of foreign governments in the area.
Colorado pioneers followed Long's route in the mid-1800s and commented on the dry condition of the South Platte River during July and August. Winter snows melted in the late spring and filled the South Platte with high flows. Remarkably, a few weeks later the riverbed was dry. This is the historical nature of the South Platte River, as well as the Arkansas River.
Historically as well as today, river flows of the South Platte and Arkansas are greatly affected by summer rainstorms and springtime mountain snowmelt. Approximately 70–80 percent of the region's annual precipitation occurs during the growing season of April through September. However, precipitation extremes can vary wildly. Average annual precipitation for this region varies between 12–16 inches, but during May 1935, for example, nearly 24 inches of rain fell along the Republican River in northeastern Colorado. Extended droughts in the 1930s, mid-1950s, 1970s, and 2002–2003 are stark reminders of the fickle nature of precipitation on the Eastern High Plains.
The Central Mountains of Colorado are the backbone of North America. These majestic peaks form the Continental Divide, which towers across Colorado from the Steamboat Springs area in the northern part of the state to Pagosa Springs and beyond to the south. The Continental Divide is the highest terrain between the Atlantic and Pacific oceans and separates the direction of flowing water in the state. Precipitation that falls on the Eastern Slope of the Rocky Mountains in Colorado ultimately flows toward the Gulf of Mexico and the Atlantic Ocean. By contrast, precipitation that falls on the Western Slope of the Rockies flows to the Colorado River, the Sea of Cortez, and the Pacific Ocean.
THE COLORADO RIVER
The Colorado River is one of the most aggressively utilized rivers in the world. The Colorado River begins at the Continental Divide in Rocky Mountain National Park. By the time the river reaches its last seventy-five miles and the Sea of Cortez (also called the Gulf of California) and the Pacific Ocean, all of its flows have been diverted, consumed, or evaporated. The once mighty Colorado River rarely flows through the Mexican states of Sonora and Baja California; all that remains in these regions is a remnant system of wetlands and brackish mudflats.
The elevation of the Continental Divide in Colorado is responsible for much of the state's climatic extremes and changeable weather. Why? Orographic lifting is the reason, as it creates far more precipitation on the Western Slope of the Continental Divide than on the Eastern Slope. This phenomenon is created when moist Pacific air masses are driven across the Western Slope and blown over the peaks of the Continental Divide. This uplifting of air causes moisture to be released on the windward, or Western Slope, side, leaving much less moisture to reach the leeward, or downwind, eastern side of the Continental Divide. The Central Mountains and Western Slope of Colorado can receive nearly three times as much river water supplies as their Front Range and Eastern High Plains neighbors.
These same mountains are also thunderstorm-generating machines during the summer months, particularly July and August. Quite often, storms will track out onto the much drier Eastern High Plains, with welcome summer rains. Sometimes, these summer storms turn severe, creating hail, high winds, and torrential downpours that can lead to flash flooding.
Colorado's major mountain ranges include the Front Range, Sangre de Cristo Mountains, Park Range, Sawatch Range, and San Juan Mountains. As mentioned, Mt. Elbert, located in the Sawatch Range, is the highest peak in the state, with an elevation of 14,433 feet above sea level. All of Colorado's major rivers — the Colorado, Arkansas, Rio Grande, South Platte, and White/Yampa — originate high in the Central Mountains.
SNOW DEPTH MEASUREMENTS
Snow depth measurements are extremely important in forecasting Colorado's future water supplies. Snow surveys began around 1906 in the western United States when Dr. James Church, a Latin, German, and fine arts professor at the University of Nevada, laid out the first snow course. (A snow course is a permanent site where monthly snow depth measurements are taken during the winter and spring.) Dr. Church also invented sampling procedures, such as a butter sampler used to drill a snow core sample. By weighing the sample, he could determine the water content of snowpack in an area.
In Colorado, the Natural Resources Conservation Service (NRCS) Snow Survey Program provides mountain snowpack data and stream flow forecasts. An automated radio snowpack telemetry network, called SNOTEL, provides NRCS offices and other users with daily information on snow depths and water content along set snow courses. The courses are usually 1,000 feet long and are generally located in small mountain meadows shielded from wind. Go to http://www.co.nrcs.usda.gov/snow/ for current Colorado snowpack data and stream flow forecasts.
Mountain snow typically begins in October and November, but some of the heaviest snows occur in March and April, with average annual snowfall ranging from 6 to 35 feet. Average annual precipitation ranges from 30 to over 60 inches in the mountains. Much of Colorado's water arrives as snow and provides summertime water supplies for lower-elevation water users.
Colorado's Western Plateaus constitute a region of plateaus, mesas, mountains, and canyons. Elevations vary significantly from east to west and help create a climate of warmer temperatures as one approaches the eastern border of Utah. Winters can be cold, with temperatures dipping to below zero Fahrenheit, although many Western Plateau valleys have milder climates and receive ample sunshine year-round. This region has several major features including the White River Basin, Roan Plateau, Piceance Basin, Grand Mesa, Colorado National Monument, Uncompahgre Plateau, Paradox Basin, and San Juan Basin. The area around Grand Junction, the largest city on the Western Slope, has grown into an extensive orchard region, with plentiful peaches, apricots, wine grapes, and sweet corn. Summertime temperatures can exceed 100°F, with colder readings at higher elevations. Annual precipitation averages eight to fourteen inches in the western valleys, although it is much greater at higher elevations.
The Western Plateaus are generally drained by the Colorado River and its tributaries. The San Juan Mountains are located in southwestern Colorado, and they can experience some of the highest wintertime snowfall totals in the state. The Grand Mesa is a large flat-topped mountain located north of the San Juan Mountains, near Grand Junction, and is the largest flat-top mountain in the world (elevation over 10,000 feet). The northwestern corner of Colorado is predominantly rangeland and is sparsely populated except for the communities of Craig, Meeker, and Rangely.
COLORADO'S SURFACE WATER HYDROLOGY
All Streams flow into the sea, yet the sea is never full. To the place the streams come from, there they return again.
— ECCLESIASTES 1
As mentioned, Colorado is generally divided into five major river systems — the South Platte, Arkansas, Colorado, Rio Grande, and White/Yampa. All of these major river systems have their headwaters in the Rocky Mountains. Figure 1.5 shows the location of these drainage basins. All rivers west of the Continental Divide flow into the Colorado River and ultimately end in the Sonoran Desert near the Gulf of California. The major tributaries of the Colorado River on the Western Slope are the Yampa, White, Gunnison, Dolores, and San Juan rivers. The major rivers east of the Continental Divide are the North and South Platte, Arkansas, and Rio Grande. All drainages east of the Continental Divide flow eventually toward the Gulf of Mexico.
Over 80 percent of Colorado's population resides east of the Rocky Mountains, while 80 percent of the state's water supply is west of the Continental Divide. This paradox creates an economic incentive to divert water from the Western Slope to the Eastern Slope (Figure 1.6).
Major River Systems of Colorado
South Platte River
And finally there is the [South Platte] river, a sad, bewildering nothing of a river. It carries no great amount of water, and when it has some it is uncertain where it wants to take it. No ship can navigate it, nor even a canoe, with reasonable assurance. It is the butt of more jokes than any other river on earth, and the greatest joke is to call it a river at all. It's a sand bottom, a wandering afterthought, a useless irritation, a frustration, and when you've said all that, it suddenly rises up, spreads out a mile wide, engulfs your crops and lays waste [to] your farms.
— JAMES MICHENER, CENTENNIAL
Excerpted from Colorado Water Law for Non-Lawyers by P. Andrew Jones, Tom Cech. Copyright © 2009 the University Press of Colorado. Excerpted by permission of University Press of Colorado.
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