All Glossary Terms
Accessory dwelling units (ADUs) (or secondary suites)
Self-contained apartments, cottages, or small residential units, that are located on a property that has a separate main, single-family home, duplex, or other residential units. Source: Secondary suite - Wikipedia.
Adjacent Areas Served (AAS)
Short for adjacent areas served by Colorado River water. It refers to locales outside the hydrologic basin of the Colorado River, where its waters are exported via transbasin diversions. Most of the population that relies on Colorado River water lives in large cities in the Adjacent Areas Served, such as Denver, Los Angeles, and San Diego. The Adjacent Areas Served, as defined in this report, generally correspond with the “adjacent areas that receive Colorado River water” as defined by the U.S. Bureau of Reclamation (2012), with two notable differences. One is the watershed of the Salton Sea, a portion of which is classified as an adjacent area by the Bureau of Reclamation because it receives Colorado River water via the All-American Canal and Colorado River Aqueduct but no longer contributes tributary flow to the river. However, before Hoover Dam was built, the Colorado River would sometimes migrate from its current channel and into the Salton Sink (see, e.g., Ross 2020). Because of that connection, we include it within the hydrologic CRB area, rather than in Adjacent Areas Served. See U.S. Bureau of Reclamation, 2012, p. ES-3. The second exception is the area in northwestern Mexico encompassing the cities of Tijuana and Ensenada. Colorado River water is exported to Tijuana via the Colorado River-Tijuana aqueduct. For our purposes this counts as an AAS, but since it is a Mexican infrastructure project, it is not included in Bureau of Reclamation service area maps. The city of Ensenada is included in this area because Tijuana sends Colorado River water there via a pipeline that was originally constructed to pump water in the opposite direction. Although in our map this area may appear contiguous with the Southern California AAS that includes San Diego and Los Angeles, it is not part of the same service area on account of the international border.
Colorado River Basin (CRB)
The area drained by the Colorado River and its tributaries; a hydrologic boundary including the combined areas of the Upper Colorado and the Lower Colorado Basins. When we use the term Colorado River Basin in this study, we refer to an area that differs slightly from the HUC-02 Region shapefiles in the USGS National Hydrography Dataset (see entry for Hydrologic Unit Code). We exclude some watersheds whose tributaries do not flow directly into the Colorado River, including the Great Divide Closed Basin (HUC ID: 140402) and several basins along the Arizona-Mexico border that flow directly into the Sea of Cortez (e.g., Río Sonoita and Río Concepción). We also include a few areas that are not in the HUC-02 Region footprints of the Upper or Lower Colorado within the National Hydrography Dataset, most notably the areas around the Salton Sea and Laguna Salada in Mexico. The Colorado River, like all rivers, shifts over time. Before Hoover Dam closed, the Lower Colorado would migrate wildly and often swung westward to feed directly into the Salton Basin, hence we include that area as part of the Colorado River Basin rather than within the Adjacent Areas Served. For more, explore the Babbitt Center’s map of the Colorado River Basin.
Colorado River Basin and Adjacent Areas Served (CRBAAS)
This is the combined area of the hydrologic Colorado River Basin boundary (see CRB definition for exceptions) and the Adjacent Areas Served via transbasin diversions (see AAS definition). The CRBAAS had an estimated population of 43 million people in 2021.
Consumptive water use
When water is removed from available supplies without return to a water resource system. In the case of irrigation, consumptive use is the amount of water that does not flow off the field and returns to the canal or water body for re-use. Source: Consumptive water use - Wikipedia.
Front Range Urban Corridor
Often shortened to just “Front Range” this refers to an oblong region with a population of more than five million, located along the eastern face of the Southern Rocky Mountains. It encompasses 18 counties in Colorado and Wyoming and is named after the mountain range that defines the corridor’s western boundary. Source: Front Range urban corridor - Wikipedia.
Groundwater recharge
A hydrologic process, where water moves downward from surface water to groundwater. Recharge is the primary way that water enters an aquifer. This process usually occurs in the vadose zone below plant roots. Source: Groundwater recharge - Wikipedia.
Hydrologic (ecosystem) services
The benefits ecosystems provide to people are known as ecosystem services, and hydrologic services are the subset of terrestrial ecosystem services related to water. These may include transpiration, filtration, fog intersection, and other impacts on water quality, quantity, timing, and location. Source: Brauman et al., 2015.
Hydrologic Unit Code (HUC)
The United States is divided and sub-divided into successively smaller hydrologic units which are classified into four levels: regions, subregions, accounting units, and cataloging units. The hydrologic units are arranged or nested within each other, from the largest geographic area (regions) to the smallest geographic area (cataloging units). Each hydrologic unit is identified by a unique hydrologic unit code (HUC) consisting of two to eight digits based on the four levels of classification in the hydrologic unit system. Source: USGS Water Resources: About USGS Water Resources.
Indicator
A summary measure that provides information on the state of, or change in, the system being measured. Sometimes used interchangeably with metric, as in this report. See also Metric. Source: Fiksel et al. (2012).
Metric
The measured value(s) used to assess specific indicators. It defines the units and how the indicator is being measured. Sometimes used interchangeably with indicator. Source: Fiksel et al., 2012.
Multifamily residential zoning
A classification of housing where multiple separate housing units for residential inhabitants are contained within one building or several buildings within one complex. Units can be next to each other (side-by-side units) or stacked on top of each other (top and bottom units). A common form is an apartment building. Many intentional communities incorporate multifamily residences, such as in cohousing projects. Sometimes units in a multifamily residential building are condominiums, where typically the units are owned individually rather than leased from a single apartment building owner. Source: Multifamily residential - Wikipedia.
National Land Cover Database (NLCD)
The NLCD includes spatial reference and descriptive data for the land surface, such as thematic class (for example, urban, agriculture, and forest), percent impervious surface, and percent tree canopy cover. The database provides cyclical updates of United States land cover and associated changes. Systematically aligned over time, the database makes it possible to understand both current and historical land cover and land cover change and enables monitoring and trend assessments. Sources: The National Land Cover Database Factsheet; Land Cover | Multi-Resolution Land Characteristics (MRLC) Consortium.
Single-family residential zoning
A type of planning restriction applied to certain residential zones in the United States and Canada that limits development by allowing only single-family detached homes. It prevents townhomes, duplexes, and multifamily housing (apartments) from being built on any plot of land that has this zoning designation. It is a form of exclusionary zoning, created to keep minorities out of white neighborhoods. It both increases the cost of housing units and decreases the supply. Source: Single-family zoning - Wikipedia.
Wildland-Urban Interface (WUI)
The zone of transition between unoccupied land and human development. It is the line or area where structures and other human development meet or intermingle with undeveloped wildland or vegetative fuels. Source: What is the WUI? (fema.gov).