All Glossary Terms
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.
Community resilience (National Risk Index)
The ability of a community “to prepare for anticipated natural hazards, adapt to changing conditions, and withstand and recover rapidly from disruptions (NIST, 2020).” As a consequence-reduction risk component of the National Risk Index, a community resilience score and rating represent a community’s resilience compared to that of all other communities at the same administrative level (e.g., county, census tract). A community resilience score is inversely proportional to a community’s risk. A higher community resilience score results in a lower Risk Index score. Source: FEMA, 2023.
Composite risk score (National Risk Index)
Measures the relative risk to a community based on 18 natural hazards. Source: Determining Risk | National Risk Index (fema.gov). See also: National Risk Index.
Expected Annual Loss (EAL)
An indicator that measures the statistically anticipated dollar value of economic losses (e.g., to agriculture, buildings, and population) each year for a given area due to natural hazards. EAL is composed of hazard-specific frequency estimates, exposure estimates, and historical loss ratios. It is one of the three component indices of the National Risk Index. Source: Expected Annual Loss | National Risk Index (fema.gov).
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.
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.
National Risk Index (NRI)
According to FEMA, the National Risk Index "...analyzes 18 natural hazard types, in addition to a community’s social vulnerability, community resilience, to provide a more holistic view of risk. It is a great alternative for communities that do not have access to mapping services, since it uses authoritative data from a variety of contributors." The NRI is derived from component indices for Community Resilience, Social Vulnerability, and economic Expected Annual Losses. Source: National Risk Index for Natural Hazards | FEMA.gov.
Risk (community)
Defined by the Federal Emergency Management Administration (FEMA) as the potential for experiencing negative impacts of a natural hazard.
Social vulnerability (National Risk Index)
A general concept that is defined specifically in the FEMA National Risk Index as "...the susceptibility of social groups to the adverse impacts of natural hazards, including disproportionate death, injury, loss, or disruption of livelihood. Social Vulnerability is a consequence-enhancing risk component of the National Risk Index. A Social Vulnerability score and rating represent the relative level of a community’s social vulnerability compared to all communities at the same level. A community’s Social Vulnerability score is proportional to a community’s risk. A higher Social Vulnerability score results in a higher risk score.” The National Risk Index currently uses the CDC/ATSDR Social Vulnerability Index. Source: Social Vulnerability | National Risk Index (fema.gov).