Colorado is a headwater state, meaning all of its rivers begin in the Rocky Mountains and flow out of the state. The exceptions to this are the Green and Little Snake Rivers, which flow into the northwest corner of the state, albeit only for very brief stretches (Water Education Colorado [WEC], 2005). Four regional watersheds originate high in the mountains in Colorado: the Arkansas, Colorado, South Platte (Missouri) and Rio Grande River Basins (Colorado Watershed Assembly, n.d.).

Map of Colorado's four major watersheds.
Four Major Watersheds of Colorado.
Map of Colorado's seven major river basins.
Seven major river basins within Colorado. CGS (2003).

Within those major watersheds, there are seven major river basins designated as water divisions by the State of Colorado (per the Water Right Determination and Administration Act of 1969):

  • The South Platte Basin is located in northeastern Colorado and covers approximately 27,660 square miles (26.4% of the total area of the state) within the state (Colorado Water Conservation Board [CWCB] & Colorado Division of Water Resources [DWR], 2005g).
  • The headwaters of the South Platte River are formed by a number of smaller rivers (north, middle and south forks) located in the mountains southwest of the Denver Metro area at approximately 11,500 feet elevation. The river flows north and east out of the mountains, through the metropolitan area and up into the High Plains at approximately 3,400 feet before flowing into Nebraska and meeting its confluence with the North Platte (WEC, 2005; CWCB, 2006h).
  • Major tributaries to the South Platte River include the North, Middle, and South Forks of the South Platte River (upstream of Chatfield Reservoir), the Big Thompson and Cache la Poudre Rivers, and Bear, Boulder, Clear, St. Vrain, Plum, Cherry, Sand, Box Elder, Kiowa, Bijou, Badger, Beaver, Tarryall and Wildcat Creeks (WEC, 2005; CWCB, 2006a). Although he Republican River is found within the basin, it is actually a tributary of the Kansas River (CWCB, 2002c).
  • Major reservoirs in the South Platte Basin include Horsetooth, Eleven Mile Canyon, Cheesman and Riverside Reservoirs, as well as Carter Lake and North Sterling (CWCB, 2006h).
  • All or parts of 23 counties (Larimer, Weld, Logan, Sedgwick, Phillips, Yuma, Washington, Morgan, Boulder, Gilpin, Clear Creek, Park, Teller, Jefferson, Denver, Adams, Arapahoe, Douglas, Elbert, El Paso, Lincoln, Kit Carson and Cheyenne) are found within the basin.
  • Denver, Aurora and Lakewood are the largest cities in the basin. Denver is located in Denver Country, Lakewood in Jefferson Country, and Aurora spans across Arapahoe and Adams Counties, and slightly into Douglas County (CWCB, 2006h).
  • Approximately one third of the land in the basin is publicly owned, with the majority consisting of forest areas in the mountains. Western portions of the basin and its montane and subalpine areas are primarily forested, while the High Plains region is mainly planted/cultivated land and grassland, which includes the Pawnee Natural Grassland (CWCB, 2006h).
  • The South Platte River Basin is administered by the DWR as Water Division 1, and it is further broken down into 16 water districts (District 1: South Platte: Greeley to Balzac; District 2: South Platte: Denver Gage to Greeley; District 3: Cache La Poudre River; District 4: Big Thompson River; District 5: St. Vrain Creek; District 6: Boulder Creek; District 7: Clear Creek; District 8: South Platte Cheesman to Denver Gage; District 9: Bear Creek; District 23: Upper South Platte; District 48: Laramie River; District 49: Republican River; District 64: South Platte: Balzac to Stateline; District 65: Arikaree River; District 76: Sand Creek; District 80: North Fork of South Platte) for more precise, localized management and administration (DWR, n.d.a).
  • Located in southeast Colorado and covering an area of 28,268 square miles (27% of the total area of the state), the Arkansas Basin is Colorado’s largest river basin (CWCB & DWR, 2005a).
  • The headwaters of the Arkansas River begin in the central mountains near the city of Leadville at more than 14,000 feet elevation, and the river meanders south and east to 3,340 feet before flowing into Kansas (CWCB, 2006b).
  • Major tributaries to the Arkansas include Cottonwood Creek, Chalk Creek, South Arkansas River, Grape Creek, Smith Canyon Creek, Rule Creek, Rush Creek, Adobe Creek, Timpas Creek, Cucharas River, Fountain Creek, St. Charles River, Huerfano River, Apishapa River, Horse Creek, Purgatoire River, Big Sandy Creek and Twin Buttes Creek (CWCB & DWR, 2011).
  • Major reservoirs in the basin’s boundaries include Pueblo Reservoir, John Martin Reservoir, Pueblo Reservoir, Great Plains Reservoir System, Twin Lakes, Turquoise Reservoir and Trinidad Reservoir (CWCB, 2006b).
  • All or parts of 21 counties (Baca, Bent, Chaffee, Cheyenne, Costilla, Crowley, Custer, Elbert, El Paso, Fremont, Huerfano, Kiowa, Lake, Las Animas, Lincoln, Otero, Park, Prowers, Pueblo, Saguache and Teller) are found within the basin.
  • Colorado Springs and Pueblo are the largest cities in the basin, located in El Paso and Pueblo Counties, respectively (CWCB, 2006b; CWCB & DWR, 2011).
  • Grassland (67%) and forest (13%) are the predominant land use types in the Arkansas Basin , with grassland areas being concentrated in the central portion of the basin and forested land mainly in the western portions (CWCB, 2006b).
  • The Arkansas River Basin is administered by the Colorado DWR as Water Division 2, and is further broken down into 13 water districts (District 10: Fountain Creek; District 11: Arkansas: Headwaters to Salida; District 12: Arkansas: Salida to Portland; District 13: Wet Mountain Valley; District 14: Arkansas: Portland to Fowler; District 15: Saint Charles; District 16: Cucharas River; District 17: Arkansas: Fowler to Las Animas; District 18: Apishapa River; District 19: Purgatoire River; District 66: Cimarron River Basin; District 67: Arkansas: Las Animas to Stateline; District 79: Huerfano River) for more precise, localized administration and management (DWR, n.d.a).
  • Located in the south central portion of the state, the Rio Grande Basin covers 7,543 square miles (7.2% of the total area of the state) within Colorado (CWCB & DWR, 2005d).
  • The headwaters of the Rio Grande River begin in the eastern San Juan Mountains near the Town of Creede at approximately 12,000 feet elevation, and the river flows east into the San Luis Valley (averaging 7,500 feet) before heading directly south into New Mexico (CFWE, 2005). In the northern region of the San Luis Valley lies an internal drainage basin called the Closed Basin which does not provide any surface flows to the Rio Grande.
  • Major tributaries to the Rio Grande River include the Alamosa and Conejos Rivers and the La Jara and Trinchera Creeks (CWCB, 2002b).
  • Major reservoirs in the basin include Sanchez, Platoro, Rio Grande, Santa Maria, Continental and Mountain Home Reservoirs (CWCB, 2006g).
  • All or parts of ten counties (Alamosa, Archuleta, Conejos, Costilla, Hinsdale, Mineral, Rio Grande and Saguache) are found within the basin.
  • Alamosa and Monte Vista are the largest cities in the basin, located in Alamosa and Rio Grande Counties, respectively (CWCB, 2006g).
  • The majority of the San Luis Valley is privately owned. In the central portion of the basin, more than 600,000 acres of irrigated land is used for agricultural operations. Non-irrigated land in the valley is mostly classified as shrubland (24 %) and grassland (31%). The San Juan and the Sangre de Cristo mountain ranges are largely forested (CWCB, 2006g).
  • The Rio Grande Basin is administered by the Colorado DWR as Water Division 3, and it is further broken down into 8 water districts (District 20: Rio Grande; District 21: Alamosa La Jara; District 22: Conejos Creek; District 24: Culebra Creek; District 25: San Luis Creek; District 26: Saguache Creek; District 27: Carnero Creek; District 35: Trinchera Creek) for more precise, localized administration and management (DWR, n.d.c).
  • Extending from the Continental Divide to the confluence of the Gunnison and Colorado Rivers in western Colorado, the Gunnison Basin covers over 8,000 square miles (8% of the total area of the state) within the state (CWCB & DWR, 2005c).
  • The Gunnison River begins at the confluence of the East and Taylor Rivers just outside of the Town of Gunnison at an elevation of over 13,000 feet elevation. The Gunnison travels west towards Grand Junction and ends at approximately 4,600 feet elevation at the confluence with the Colorado (CWCB, 2004a).
  • Principal tributaries of the Gunnison River include the Uncompahgre, North Fork Gunnison, Lake Fork Gunnison, East and Taylor Rivers, as well as the Ohio, Tomichi and Cochetopa Creeks (Topper et al., 2003).
  • Major reservoirs in the basin include Blue Mesa, Morrow Point, Taylor Park, Ridgeway, Crystal and Paonia Reservoirs (CWCB, 2006e).
  • All or parts of seven counties (Delta, Gunnison, Hinsdale, Mesa, Montrose, Ouray and Saguache) are found within the basin.
  • Montrose, Delta and Gunnison are the largest cities in the basin, located in Montrose, Delta and Gunnison Counties, respectively (CWCB, 2006e).
  • Forest is the predominate land use (about 52%) and distributed throughout the basin. Approximately 5% is classified as planted/cultivated land and is concentrated in the Uncompahgre Valley between Montrose and Delta, with additional concentrations near Gunnison and Hotchkiss (CWCB, 2006e).
  • The Gunnison River Basin is administered by the Colorado DWR as Water Division 4, and it is further broken down into 11 water districts (District 28: Tomichi Creek; District 40: North Fork/Tributaries; District 41: Lower Uncompahgre River; District 42: Lower Gunnison River; District 59: East River Basin; District 60: San Miguel River Basin; District 61: Paradox Creek; District 62: Upper Gunnison River; District 63: Dolores River Basin; District 68: Upper Uncompahgre River; District 73: Little Dolores River) for more precise, localized administration and management (DWR, n.d.d).
  • In the west-central portion of the state the Colorado Basin covers 9,830 square miles (9.4% of the total area of the state) within Colorado (CWCB & DWR, 2005b).
  • The headwaters of the Colorado River begin high in the central Rockies at approximately 12,800 feet elevation, and the river gradually descends west and south into rugged canyons and plateaus to about 4,325 feet before exiting the state into Utah.
  • Major tributaries to the Colorado River include the Fraser River, Williams Fork River, Muddy Creek, Blue River, Eagle River, Roaring Fork River, Rifle Creek and Plateau Creek (CWCB & DWR, 2007).
  • Major reservoirs in the basin include Granby Reservoir, Dillon Reservoir, Green Mountain Reservoir, Ruedi Reservoir, Williams Fork Reservoir and Wolford Mountain Reservoir (CWCB, 2006c).
  • All or parts of eight counties (Eagle, Garfield, Grand, Gunnison, Mesa, Pitkin, Routt and Summit) are found within the basin.
  • Grand Junction and Glenwood Springs are the largest cities in the basin, located in Mesa and Garfield Counties, respectively (CWCB, 2006c; CWCB & DWR, 2007).
  • Rangeland and forest are the predominant land uses in the Colorado Basin (85%), with forested land present throughout many parts of the basin. A substantial portion of the basin is comprised of federally owned land, with livestock, grazing, recreation and timber harvesting as the predominant uses on those lands (CWCB, 2006c).
  • The Colorado River Basin is administered by the Colorado DWR as Water Division 5, and it is further broken down into 11 water districts (District 36: Blue River Basin; District 37: Eagle River Basin; District 38: Roaring Fork River Basin; District 39: Rifle/Elk/Parachute Creeks; District 45: Divide Creek; District 50: Muddy/Troublesome Creeks; District 51: Upper Colorado/Fraser Rivers; District 52: Piney/Cottonwood Creeks; District 53: Tributaries North of Colorado River; District 70: Roan Creek Basin; District 72: Lower Colorado River) for more precise, localized administration and management (DWR, n.d.b).
  • The Yampa/White Basin is located in the northwest corner of Colorado and covers approximately 10,500 square miles (10% of the total area of the state) within the state (CWCB & DWR, 2005h). The North Platte Basin is located in north central Colorado and covers roughly 2,050 square miles (about 2% of the total area of the state) within the state (CWCB, 2006f).
  • The headwaters of the Yampa and White Rivers both originate in the Flatt Top Mountains between approximately 11,000 to 12,000 feet elevation and flow west towards the Utah border to approximately 5,500 feet (CWCB, 2004b; CWCB, 2009). The headwaters of the North Platte River begin in the four surrounding mountain ranges of the basin (Medicine Bow, Never Summers, Rabbit Ears and Park Range) in Jackson County at approximately 11,000 feet elevation (Benke & Cushing, 2011). The river meanders out of the mountains into the broad valley of North Park northward into Wyoming.
  • Both the Yampa and White Rivers are tributaries to the Green River. Major tributaries to the Yampa River include the Bear, Elk, Williams Fork and Little Snake Rivers, and the Chimney, Walton, Fish, Trout, Elkhead and Fortification Creeks (CWCB, 2004b). Major tributaries to the White River include Douglas, Yellow and Piceance Creeks, and the North and South Forks of the White River (Topper et al., 2003). The North Platte Basin consists of the North Platte River, as well as two tributaries, the Laramie River and Sand Creek, which join the North Platte in Wyoming. (CWCB, 2002a). The main tributaries to the North Platte within Colorado include the Canadian, Michigan, Illinois and North Fork of the North Platte, as well as the Big and Little Grizzly Creeks (CWCB, 2010).
  • Major reservoirs in the Yampa/White Basin include Stagecoach, Willow Creek (Steamboat Lake), Taylor Draw, Elkhead Creek, Yamcolo and Big Beaver (Lake Avery) Reservoirs (CWCB, 2006i). Major reservoirs in the North Platte Basin include Lake John, MacFarlane, Walden, Meadow Creek, Laune and Pole Mountain Reservoirs (CWCB, 2006f).
  • All of parts of five counties (Moffat, Routt, Jackson, Rio Blanco and Garfield) are located within the Yampa/White Basin. All of Jackson County and a small portion of Larimer County are found within the North Platte Basin (CWCB, 2006f).
  • Steamboat Springs and Craig are the largest cities in the Yampa/White Basin, located in Routt and Moffat Counties, respectively (CWCB, 2006i). Walden is the largest city in the North Platte Basin, centrally located in Jackson County (CWCB, 2006f).
  • A majority of the land in the Yampa/White Basin is federally owned, with livestock, grazing and recreation being the predominant land uses (CWCB, 2006i). Land use in the North Platte Basin includes forest (46%) located on the edges of the basin boundaries, shrubland (24%) concentrated in the central portion of the basin and grassland (17%) near the basin edges below the forested areas. Agricultural areas generally are concentrated in the central basin, but also follow the basin s streams and rivers (CWCB, 2006f).
  • While the North Platte is part of the Platte river system, for administration purposes, it is included with the Yampa and White as Division 6 administered by the DWR. Division 6 is further broken down in to eight water districts (District 43: White River Basin; District 44: Lower Yampa River; District 47: North Platte River Basin; District 54: Slater/Timberlake Creeks; District 55: Little Snake River; District 56: Green River Basin; District 57: Middle Yampa River; District 58: Upper Yampa River) for more precise, localized management and administration (DWR, n.d.f).
  • Also referred to as the Southwest Basin, the Dolores Basin/San Juan Basin is located in the southwestern corner of Colorado covering an area of approximately 10,169 square miles (9.7% of the total area of the state) within the state (CWCB & DWR, 2005e).
  • The headwaters of both the San Juan and Dolores Rivers begin high in the San Juan Mountains at elevations between 13,000 and 14,000 feet. The San Juan River originates just north of Pagosa Springs and flows southwest to 4,800 feet before moving into New Mexico, and then Utah before joining the Colorado River. Located north of the San Juan River and just south of the Town of Telluride, the Dolores River flows southwest to McPhee Reservoir where the river then begins to flow northwest to 4,100 feet elevation as it enters Utah to join the Colorado River (CWCB, 2005f).
  • Major tributaries to the Dolores River include the West Fork of the Dolores and the San Miguel Rivers, as well as Lost Canyon, Disappointment and West Paradox Creeks. The major tributaries to the San Juan River include the Navajo, Piedra, Los Pinos, Animas, Florida, La Plata, Rio Blanco and Mancos Rivers, as well as McElmo Creek (CWCB, 2005f; CWCB & DWR, 2006d).
  • Major reservoirs in the Dolores/San Juan Basin include the McPhee, Vallecito, Lemon, Cascade, Groundhog and Narraguinnep Reservoirs (CWCB, 2006d).
  • All or parts of eight counties (Archuleta, Dolores, Hinsdale, La Plata, Mineral, Montezuma, San Juan and San Miguel) are found within the basin.
  • Durango and Cortez are the largest cities in the basin, located in La Plata and Montezuma Counties, respectively (CWCB & DWR, 2005e).
  • Although three quarters of the basin consists of forest and shrubland, land use in the region is highly variable and often reflects a conflict between historic and modern uses. Agriculture and ranching predominate in the lower elevations of Dolores, San Miguel and Montrose Counties as they have for many generations. Due to the many fishing and rafting opportunities along the Animas, Piedra, Dolores and San Miguel Rivers, tourism and recreation have become more prevalent in the region. Montezuma and La Plata Counties are dominated by agriculture, grassland and forested land use types (CWCB, 2006d).
  • The Dolores/San Juan Basin is administered by the DWR as Water Division 7, and it is further broken down into 11 water districts (District 29: San Juan River Basin; District 30: Animas River Basin; District 31: Los Pinos River Basin; District 32: McElmo Creek Basin; District 33: La Plata River Basin; District 34: Mancos River Basin; District 46: Navajo Reservoir; District 69: Disappointment Creek Basin; District 71: West Dolores Creek/Tributaries; District 77: Navajo River Basin; District 78: Piedra River Basin) for more precise, localized management and administration (DWR, n.d.g).
Map depicting the typical surface water hydrology of Colorado in wet and dry years.
Colorado Surface Water Hydrology. CWCB (2017).

Benke, A.C., & Cushing, C.E. (Eds.). (2011). Missouri River Basin. In Rivers of North America. Burlington, MA: Elsevier Academic Press.

Colorado Division of Water Resources [DWR]. (n.d.a). Division 1 (Greeley): South Platte River Basin. Division Offices.

—–. (n.d.b). Division 2 (Pueblo): Arkansas River Basin. Division Offices.

—–. (n.d.c). Division 3 (Alamosa): Rio Grande River Basin. Division Offices.

—–. (n.d.d). Division 4 (Montrose): Gunnison River Basin. Division Offices.

—–. (n.d.e). Division 5 (Glenwood Springs): Colorado River Basin. Division Offices.

—–. (n.d.f). Division 6 (Steamboat Springs): Yampa, White, and North Platte River Basins. Division Offices.

—–. (n.d.g). Division 7 (Durango): San Juan and Dolores River Basins. Division Offices.

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—–. (2002b). Rio Grande River Basin Facts.

—–. (2002c). South Platte/Republican River Basin Facts.

—–. (2004a). Gunnison River Basin Information. Colorado’s Decision Support Systems.

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—–. (2006d). Statewide Supply Initiative Fact Sheet: Dolores/San Juan/San Miguel Basin.

—–. (2006e). Statewide Supply Initiative Fact Sheet: Gunnison Basin.

—–. (2006f). Statewide Supply Initiative Fact Sheet: North Platte Basin.

—–. (2006g). Statewide Supply Initiative Fact Sheet: Rio Grande Basin.

—–. (2006h). Statewide Supply Initiative Fact Sheet: South Platte Basin.

—–. (2006i). Statewide Supply Initiative Fact Sheet: Yampa/White/Green Basin.

—–. (2009) White River Basin Information. Colorado’s Decision Support Systems.

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CWCB & DWR. (2005a). Arkansas River Basin. Colorado’s Decision Support Systems.

—–. (2005b). Colorado River Basin. Colorado’s Decision Support Systems

—–. (2005c). Gunnison River Basin. Colorado’s Decision Support Systems.

—–. (2005d). Rio Grande River Basin. Colorado’s Decision Support Systems.

—–. (2005e). San Juan/Dolores River Basin. Colorado’s Decision Support Systems.

—–. (2005f). San Juan and Dolores River Basin Information. Colorado’s Decision Support Systems.

—–. (2005g). South Platte River Basin. Colorado’s Decision Support Systems.

—–. (2005h). Yampa/White River Basin. Colorado’s Decision Support Systems.

—–. (2007). Upper Colorado River Basin Information. Colorado’s Decision Support Systems.

—–. (2011). Arkansas River Decision Support System Feasibility Study. Prepared by Brown & Caldwell.

Topper, R., Spray, K. L., Bellis, W. H., Hamilton, J. L., & Barkmann, P. E. (2003). Chapter 5: Major Alluvial Aquifers. In Groundwater atlas of Colorado. (Colorado Geological Survey Special Publication 53). Denver, CO: Colorado Geological Survey.

Water Education Colorado [WEC]. (2005). Citizen’s guide to where your water comes from.