All Glossary Terms
Acre-foot
Non-SI unit of volume equal to about 1,233 cubic meters of water or 325,850 gallons. As the name suggests, an acre-foot is defined as the volume of one acre of surface area to a depth of one foot. Source: Acre-foot - Wikipedia.
Anthropogenic warming (or anthropogenic climate change)
Combines the terms climate change and anthropogenic. Anthropogenic climate change refers to warming of the planet that can be attributed to human activities. Source: IPCC, 2018. See also Climate change.
Climate models
Also known as general circulation models (GCMs), these use mathematical equations to determine how energy and matter interact in different parts of the ocean, atmosphere, and land. Based on well-documented physical processes, they simulate the transfer of energy and materials through the climate system. Source: Climate Models | NOAA Climate.gov.
Colorado River Compact of 1922
An agreement among the seven Southwest U.S. states that fall within the Colorado River drainage basin. The pact governs the allocation of the river’s water rights. Originally proposed by attorney Delph Carpenter, the agreement was signed at a meeting at Bishop’s Lodge, near Santa Fe, by representatives of the seven states the Colorado River and its tributaries pass through on the way to Mexico. Arizona did not formally ratify the compact until 1944. Sources: Colorado River Compact - Wikipedia; Danver, 2013.
Evapotranspiration (ET)
The combined processes by which water moves from Earth’s surface into the atmosphere. It covers both water evaporation (movement of water to the air directly from soil, canopies, and water bodies) and transpiration (movement of water from the soil, through roots and bodies of vegetation, to leaves, and then into the air). Source: Evapotranspiration - Wikipedia.
Law of the River
Refers collectively to the numerous compacts, federal laws, court decisions and decrees, contracts, and regulatory guidelines that apportion the water and regulate the use and management of the Colorado River among the seven Basin states and Mexico. Source: Law of the River| Lower Colorado Region | Bureau of Reclamation (usbr.gov).
Lees Ferry, Arizona
A site on the Colorado River in Coconino County, located about 7.5 miles southwest of Page, AZ, and 9 miles downstream of Glen Canyon Dam. Near the junction of the Paria River and the Colorado River, it is the traditional dividing line between the Upper and Lower Basins. Lees Ferry is named for John Doyle Lee, who operated a ferry there in the mid-nineteenth century. Source: Lees Ferry - Wikipedia.
Millennium drought
Also known as the twenty-first century drought, or the southwestern North American megadrought. The millennium drought in southwestern North America began in the year 2000 and is ongoing as of 2023. Based on historical reconstructions of Colorado River streamflow, the millennium drought represents the driest 22-year period since at least 800CE. Sources: Williams et al., 2022; Xiao et al., 2018.
Streamflow
The movement of water in streams, rivers, and other channels; a major element of the water cycle. Also referred to as channel runoff. Source: Streamflow - Wikipedia.
Water year
Defined by the U.S. Geological Survey as the 12-month period from October 1st through September 30th and designated by the calendar year in which it ends, which includes 9 of the 12 months. Commonly used by USGS and other scientific agencies in reports that deal with surface water supply. See USGS--Water Resources of the United States.