Just The Facts

Land, Water, and Agriculture in the Colorado River Basin: Sources and Methods

Annual Colorado River Water Allocations

Sheikh, P. A., and Stern, C. V. 2019. "Management of the Colorado River: Water allocation, drought, and the federal role." Renewable Resources Journal, 33(4), 8–15.

Colorado River Facts

Length of the Colorado River: The most cited number is 1,450 miles (Britannica. "Colorado River").  However, using ArcGIS Pro, the geodesic length using NAD 1983 UTM Zone 11N was calculated as 1,426.68 miles which can be rounded up to 1,450 miles. 

Colorado River Basin and Areas Served Area: The area of the CRB and AS were calculated using the Calculate Geometry tool and the basin outlines from the Colorado River Basin Hydrologic Boundaries with Areas served by Colorado River feature layer on the Colorado River Basin GIS Open Data Portal. The AS areas are originally from the USBR. Note also that the CRB outline excludes HUC 150801, 150802, 150803, but includes 181002 and the Mexican HUC which includes Laguna Salada.

Historical Average Annual Flow Volume:
A., W. C., M., M. D., M., M. G., W., S. D., and R., C. E. 2010. "A 1,200-year perspective of 21st-century drought in southwestern North America." Proceedings of the National Academy of Sciences 107(50): 21283–21288. 

Streamflow Contributions of Upper Basin and Groundwater:
McCabe, G. J., and Wolock, D. M. 2007. "Warming may create substantial water supply shortages in the Colorado River basin." Geophysical Research Letters 34(22): 1–5.

Rumsey, C. A., Miller, M. P., Susong, D. D., Tillman, F. D., and Anning, D. W. 2015. "Regional-scale estimates of baseflow and factors influencing baseflow in the Upper Colorado River Basin." Journal of Hydrology: Regional Studies 4(PB): 91–107. 

Basin Facts

Highest Point: Clipped a feature layer of Colorado peaks above 14,000 feet to the CRB and AS outline and ordered by highest elevation.

Lowest Point: Encyclopedia Britannica entry for Colorado River “... The Colorado then cut a channel into the lower gulf. The upper waters, cut off from the sea, gradually evaporated, forming a large area of desert land extending to about 235 feet below sea level…”  (Britannica. "Sea Level").  

Population: The boundary of the CRB and AS was uploaded to the application PopGRID, WorldPOP 2020 and GPWv4 2020 estimates were averaged to provide population estimates for the CRB and AS

Federal and State Lands in CRB and AS: from the National Surface Management feature layer was clipped to the CRB and AS boundary. 

Tribal Land Ownership: Estimated using the American Indian, Alaska native, and Native Hawaiian (AIANNH) feature layer clipped to the CRB and AS boundary.

Developed Land: Estimated using the 2020 Cropland Data layer clipped to the CRB and AS, combined low, medium, and high intensity, but does not include ‘Developed Open Space” category.

Tribal Water Facts

Roller, Z., Gasteyer, S., Nelson, N., Lau, W., Shingne, M. C., Gardner, A., Frankel, M., Allen, S., Butler, K., and App, B. 2019. "Closing the Water Access Gap in the United States: A National Action Plan." 

Tanana, H., Garcia, J., Olaya, A., Colwyn, C., Larsen, H., Williams, R., and King, J. 2021. "Universal Access to Clean Water for Tribes in the Colorado River Basin."

Water & Tribes Initiative. 2019. "The Enduring Role of Tribes in the Colorado River Basin: Policy Brief #1." 

Water & Tribes Initiative. 2021. "The Status of Tribal Water Rights in the Colorado River Basin: Policy Brief #4." Page 8.

Agricultural Facts

Approximatly 70% of Colorado River water is used for agriculture:
Cohen, M., Christian-Smith, J., and Berggren, J. 2013. "Water To Supply The land: Irrigated Agriculture in the Colorado River Basin." Oakland, CA: Pacific Institute, 93 pp. 

Crop cultivation/fallow acreage CRB and AS: crop cultivated estimates from the National Cropland Data Layer 2020 clipped to the CRB and AS.

15% of nations crops and 13% of nations livestock raised in CRB and AS:
U.S. Bureau of Reclaimation. 2012. "Colorado River Basin Water Supply and Demand Study - Executive Summary." Reclamation: Managing Water in the West. (December).

Percent of cropland and water use for cattle and horses:
Cohen, M., Christian-Smith, J., & Berggren, J. (2013). "Water To Supply The land: Irrigated Agriculture in the Colorado River Basin." Oakland, CA: Pacific Institute, 93 pp.

Alfalfa Coverage: Estimated from the 2020 Cropland Data Layer clipped to the CRB and AS.

Irrigated Pasture and forge crops consume 5 maf water each year:
Cohen, M., Christian-Smith, J., and Berggren, J. (2013). "Water To Supply The land: Irrigated Agriculture in the Colorado River Basin." Oakland, CA: Pacific Institute, 93 pp.

Arizona agricultural GDP:
University of Arizona, Division of Agriculture. "The Economic Contributions and Impacts of U.S. Food, Fiber, and Forest Industries". 

U.S. Department of Agriculture. "NASS 2020 State Agriculture Overview for Arizona".

Arizona Department of Agriculture. "Arizona Agriculture is Growing".

Water Storage Facts

37 large reservoirs in the Colorado River system: What we term ‘Large’ reservoirs are those with dams taller than 250 feet or reservoirs which hold 50,000 acre feet of water. List of dams from Wikipedia article List of dams in the Colorado River system.

Lake Powell water level from Lake Powell Water Database (water-data.com)

Glen Canyon Dam/Lake Powell facts from Wikipedia

Lake Mead water level from Lake Mean Water Level History (uslakes.info)

Hoover Dam/Lake Mead facts from Wikipedia