- Growing, or living in, or frequenting water.

Aquifer - One or more geological formations containing enough saturated porous and permeable material to transmit water through a spring or well.

Biodiversity - A multiplicity of species in a given area, representing various interdependent life forms. Biodiversity usually refers to native species only.

Biological stress - Any activity that puts pressures on living things and threatens to reduce their numbers or range. Although most biological stresses are human-caused, natural activities such as earthquakes or drought are also biological stressors.

Candidate species - A species that is possibly declining and that is being considered for threatened or endangered status.

Cienega - A perennially wet area supported by a spring or other water source, also called "wetland," "marsh," or "swamp."

Conservation easement - A legally binding agreement not to develop part of a property, but to leave it "natural" permanently or for some designated very long period of time. The property still belongs to the landowner, but restrictions are placed both on the current landowner and on subsequent landowners.

Constructed wetland - A wetland created by humans, usually supported by wastewater.

Cultural landscape - A landscape created by people and their culture, simultaneously the product of nature and of human interaction with nature.

Desert Grassland - Desert grassland is a vegetation type in semi-arid climates that is widspread at 3500 to 5500 feet in elevation. The dominant vegetation are usually bunch grasses or if disturbed, various shrubs. Grasslands develope on bajadas and in valley bottoms where clay-rich soils prevent water from draining.

Desert Scrub Community - The desert scrub community is characterized by plants such as saguaros, prickly pear cactus, ocotillo, paloverde, and cholla. This landscape is typical of the desert surrounding Tucson.

Distributary flow - Flow that occurs on the surface in ill-defined, changing channels.
Effluent-dominated riparian area - A stream with perennial flow supported mostly by wastewater from a municipal wastewater treatment plan.

Ecosystem - An Ecosystem encompasses the living biological community-assemblage of species living in a certain area and interacting with each other, and the surrounding physical environment (soil, water, climate, atmosphere).

EIS - Environmental Impact Statement. A study required under the National Environmental Policy Act before certain federally sponsored actions can be taken.

Effluent - Wastewater that has been treated in a wastewater treatment plant.

Endangered Species Act - A federal law that is designed to protect species that are in danger of becoming extinct.

Endangered Species - Section 3 of the Endangered Species Act of 1973 defines "endangered species" to mean any species which is "in danger of extinction throughout all or a significant portion of its range."

EPA - Environmental Protection Agency. Federal agency that regulates water and air quality.

Ephemeral stream - A stream that only flows right after a rain. These streams may only flow for a short time in any year, yet they support more vegetation than surrounding drier areas.

Exotic species - A species that has evolved in a location other than the local area and moved by humans to a place where it would not naturally have arrived, usually a species brought by humans from another continent. The terms "introduced" and "non-native" mean the same thing.

Extinction - Complete disappearance of a species from existence anywhere.

Extirpation - Loss of a species from a specific area, although the species still lives elsewhere.

Floodplain - The part of a stream through or over which water may flow at some time.

Groundwater - Water under the surface of the ground away from streams.

Habitat - The total environment in which species live, including vegetation, animals, water supply, soils, and air. Generally, each species of plant and animal has a limited range of environmental conditions in which it can survive. Every plant and animal has a habitat.

Habitat Conservation Plan - A legally binding plan, agreed to by the U.S. Fish and Wildlife Service, to protect a specified area as habitat for a threatened or endangered species.

Hydroriparian area - A riparian area with a steady water supply that supports vegetation that needs more water than the surrounding desert.

Intermittent stream - A stream that flows part of the time because of a connection with groundwater or because of season snow melt.

Invasive species - Species, usually exotic, that take over an area, crowding out native species.
Listed species - See "candidate species."

Keystone Species - Species who enrich ecosystem function in a unique and significant manner through their activities, and the effect is disproportionate to their numerical abundance. Their removal initiates changes in ecosystem structure and often loss of diversity. These keystones may be habitat modifiers (ie. cottonwoods, rushes and ironwood), keystone predators (ie. puma and coyote) or keystone herbivores (ie. prairie dog and beaver).

Mesquite Bosque - A mesquite bosque (Spanish for forest) is a large forest of mesquite trees occurring along major water courses and their tributaries. Bosques provide cover and habitat for many types of animals, including javelina, mule deer, and many species of rodents. White-winged doves, as well as other species of birds, depend on mesquite bosues for breeding and roosting. Bosques have been in decline due to goundwater pumping and tamarisk invasions.

Mesoriparian area - A riparian area with an intermittent water supply that supports vegetation that needs more water than the surrounding desert, but not vegetation that requires constant water.

Multispecies habitat conservation plan - A habitat conservation plan that protects habitat for more than one threatened or endangered species.

Native species - A species that has evolved locally over a long period of time.

Overbank storage - The area next to a stream where floodwaters can spread out to recharge the water supply and slow down flood waters.

Perennial stream - A stream that flows all the time because of a steady water supply.

Pest Species - Invasive or native species who adversely affect habitat functions, and directly compete with threatened natives. They may dramatically transform entire habitats over a 5-25 year scale or indicate prior habitat degradation. Some of these species cause economic losses to farmers, ranchers and protected areas.

Piedmont - Foothills, the area between a mountain and a valley.

Priority Vulnerable Species: includes 56 plant, animal, and invertebrate species that are being considered and analyzed as potentially covered species under the multi-species habitat conservation plan. These species were chosen through a process of scientific review of over 100 species that are already listed as Threatened or Endangered or recognized by the federal government as imperiled, extirpated species, and a much larger number of species that are in decline, and potentially on the way toward ESA listing.

Recharge - Addition of water to the aquifer by natural or artificial means.

Rehabilitation - The act of revegetating an area or otherwise repairing a damaged environment.

Restoration - The act of returning an environment to conditions which it naturally had at some time in the past.

Riparian Area - An area associated with a stream that includes vegetation, wildlife, and other natural features of the habitat. The word 'riparian' originates from a Latin word meaning, "along the river." In our area of the world, this includes areas associated with arroyos, seeps, ponds, and any place with more water than the surrounding area. The riparian area includes the entire community of the watercourse including its wildlife, vegetation, soils and water.

Shallow groundwater - Groundwater that close enough to the surface to support riparian vegetation.

Species of Concern: these are species which the USFWS is reviewing for consideration as Candidates for lising under the ESA. Additional information is needed in order to propose as threatened or endangered.

Surface water - Water that flows on the surface of the ground or is directly underneath a lake or stream.

Threatened and endangered species - Species that have declined so drastically that the U.S. Fish and Wildlife Service has determined that federal action is necessary to protect them. Threatened species are considered slightly more at risk than endangered species, but both are usually treated with similar caution.

Umbrella Species - Species who generally cover large areas in their daily or seasonal movements. They serve as "mobile links" at the landscape scale, through predation, seed dispersal or pollination. Protecting enough habitat and connectivity to assure viable population of these organisms benefits many other species more restricted in their range.

Vulnerable species - Species that are in danger of declining in an area, including threatened and endangered species as well as other species that may be vulnerable, but not listed by the U.S. Fish and Wildlife Service.

Water table - The top level of the aquifer, the highest point in the aquifer from water can economically be obtained.

Wetland - See "cienega."

Wildlife corridor - A area which allows animals to move with relative safety from one region to another.

Xeroriparian area - A riparian area that has only ephemeral flow, but has more vegetation than the surrounding desert.

Woodland - An area covered with woody vegetation.