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Facultative Bacteria — Bacteria that can live under Aerobic or Anaerobic conditions.

Failure — The collapse or slippage of a large mass of bank material into a stream.

Fall Overturn — A physical phenomenon that may take place in a body of water during early autumn. The sequence of events leading to fall overturn include: [1] The cooling of surface waters;
[2] A density change in surface waters producing convection currents from top to bottom;
[3] The circulation of the total water volume by wind action; and
[4] Eventual vertical temperature equality. The overturn results in a uniformity of the physical and chemical properties of the entire water body.

Fan-Head Trench — A relatively deep drainageway originating in a mountain valley and cut into the apex of, and commonly across an alluvial fan. It may empty into an interfan-valley drainage, debouch onto the fan piedmont, or cross the fan piedmont.

Fanglomerate — Heterogeneous materials that were originally deposited in an Alluvial Fan but since deposition have been cemented into solid rock.

Fecal Coliform Bacteria — A group of bacteria normally present in large numbers in the intestinal tracts of humans and other warm-blooded animals. Specifically, the group includes all of the rod-shaped bacteria that are nonsporeforming, Gram-Negative, lactose-fermenting in 24 hours at 44.5EC, and which can grow with or without oxygen. In the laboratory, they are defined as all organisms that produce produce blue colonies with specified time frames. The presence of this type of bacteria in water, beverages, or food is usually taken to indicate that the material is contaminated with solid human waste. Bacteria included in this classification represent a subgroup of the larger group termed Coliform. Their concentrations are expressed as number of colonies per 100 mL of sample.

Filamentous Algae — Aggregations of one-celled plants that grow in long strings or mats in water and are either attached or free floating and tend to plug canals, weirs, and other structures, but also provide habitat of invertebrate animals.

Finding of No Significant Impact (FONSI) — A document prepared by a federal agency showing why a proposed action would not have a significant impact on the environment and thus would not require the preparation of an Environmental Impact Statement (EIS). A FONSI is based on the results of an Environmental Assessment (EA).

(United States) Fish and Wildlife Service (USFWS) — Part of the U.S. Department of the Interior, the early beginnings of the Fish and Wildlife Service go back to 1871 when the federal government established the Commissioner of Fisheries. In 1896, the Division of Biological Survey was established within the Department of Agriculture. In 1939, these functions were transferred to the Department of the Interior. Then in 1940, these functions were formally consolidated and redesignated as the Fish and Wildlife Service. Further reorganization came in 1956 when the Fish and Wildlife Act created the Bureau of Sport Fisheries and Wildlife. An amendment to this act in 1974 designated the Bureau as the U.S. Fish and Wildlife Service. Today the USFWS consists of a
headquarters in Washington, D.C., eight regional offices, and over 700 field units and installations. Included are more than 470 National Wildlife Refuges, comprising more than 90 million acres, 57 fish and wildlife research laboratories and field units, 43 cooperative research units at universities across the country, nearly 135 national fish hatcheries and fishery assistance stations, and a nationwide network of law enforcement agents and biologists. The functions of the USFWS primarily includes the following:
[1] Acquires, protects and manages unique ecosystems necessary to sustain fish and wildlife, such as migratory birds and endangered species;
[2] As specified in the Endangered Species Act (ESA) (1973), as amended, and in conjunction with the National Marine Fisheries Service (NMFS), determines critical habitat and develops recovery plans for protected endangered and threatened species of plants and animals;
[3] Operates fish hatcheries to support research, develop new techniques and fulfill the public demand for recreational fishing;
[4] Operates wildlife refuges to provide, restore, and manage a national network of lands and waters sufficient in size, diversity and location to meet society’s needs for areas where the widest possible spectrum of benefits associated with wildlife and wildlands is enhanced and made available;
[5] Conducts fundamental research on fish, wildlife and their habitats to provide better management and produce healthier and more vigorous animals; also protects fish and wildlife from dislocation or destruction of their habitats;
[6] Renders financial and professional assistance to states, through federal aid programs, for the
enhancement and restoration of fish and wildlife resources;
[7] Establishes and enforces regulations for the protection of migratory birds, marine mammals, fish and other non-endangered wildlife from illegal taking, transportation or sale within the United States or from foreign countries; and
[8] Communicates information essential for public awareness and understanding of the importance of fish and wildlife resources, and changes reflecting environmental degradation that ultimately will affect the welfare of human beings.

Fish Credit Water — Generally, water reserved in upstream reservoirs for release for downstream fisheries purposes. Often provisions will be made such that other forms of water credits, e.g., Drought Reserve Water, will convert to fish credit water if snowpack water content or runoff is deemed sufficient by a stipulated date.

Fishway — A passageway designed to enable fish to ascend a dam, cataract, or velocity barrier. Also referred to as a Fish Ladder.

Floc — Generally, a very fine, fluffy mass formed by the aggregation of fine suspended particles, as in a precipitate. In terms of water quality, clumped solids or precipitates formed in sewage by biological or chemical activity.

Flocculate — To aggregate or clump together individual, tiny particles into small clumps or clusters.

Flocculation — (Water Quality) In water and wastewater treatment, the agglomeration or clustering of colloidal and finely divided suspended matter after coagulation by gentle stirring by either mechanical or hydraulic means such that they can be separated from water or sewage.

Flume — (1) A narrow gorge, usually with a stream flowing through it. (2) An open artificial channel or chute carrying a stream of water, as for furnishing power, conveying logs, or as a measuring device.

Fluve — A linear depression, rill, gully, arroyo, canyon, valley, etc., of any size, along which flows at some time, a drainageway.

Fluvial — Of or pertaining to rivers and streams; growing or living in streams or ponds; produced by the action of a river, stream or flood flow, as in a fluvial plain.

Fluvial Geomorphology (Geomorphologist) — The science concerned specifically with the influences of water and rivers on the erosional cycle of land deposition and degradation over time. While hydrology concentrates on the description, measurement, and analysis of precipitation and the flow of water on the earth’s surface and underground, fluvial geomorphology concentrates on understanding the processes that govern the influence of water
on the landscape over time.

Forb —
(1) Any Herbaceous flowering plant, other than a grass; especially one growing under range conditions.
(2) An herbaceous plant other than a Graminoid.

Forebay — The water behind a dam. A reservoir or pond situated at the intake of a pumping plant or power plant to stabilize water levels; also a storage basin for regulating water for percolation into ground water basins. Compare with Afterbay.

Foreshore —
(1) The part of a shore that lies between high and low watermarks.
(2) The part of a shore between the water and occupied or cultivated land.

Fossil Water — Limited subterranean water deposits laid down in past ages but drawn on by modern man.

Fractured Bedrock Aquifer — An aquifer composed of solid rock, but where most water flows through cracks and fractures in the rock instead of through pore spaces. Flow through fractured rock is typically relatively fast.

Freeboard —
(1) The vertical distance between a design maximum water level and the top of a structure such as a channel, dike, floodwall, dam, or other control surface. The freeboard is a safety factor intended to accommodate the possible effect of unpredictable obstructions, such as ice accumulation and debris blockage, that could increase stages above the design water surface.
(2) (FEMA) A factor of safety expressed in feet above a design flood level for flood protective or control works. Freeboard is intended to allow for all of the uncertainties in analysis, design and construction which cannot be fully or readily considered in an analytical fashion.

Fry — Immature life stage of fish. Emergent fry leave the salmonid redd (nest) and become free-swimming. Salmonid fry may rear in freshwater for one to three (occasionally more) years.

Full Cost (USBR) — A water rate defined by Congress in the Reclamation Reform Act of 1982 intended to represent the federal government’s actual cost in providing project water to irrigators. The full-cost rate for each project or district is calculated by amortizing the expenditures for construction properly allocable to irrigation facilities in service, including all operation and maintenance deficits funded, less payments, over such periods as may be
required under federal reclamation law or applicable contract provisions. Interest on all charges accrues from October 12, 1982, on costs outstanding at that date or from the date incurred of costs arising subsequent to October 12, 1982. The term Full-Cost Rate means the full-cost charge plus actual operation, maintenance, and replacement costs.

Full-Cost Rate (USBR) — An annual rate as determined by the U.S. Secretary of the Interior that shall amortize construction expenditures that are properly allocable to irrigation facilities in service, including all operation and maintenance deficits funded, less payments, over such periods as may be required by reclamation law or applicable contract provisions, with interest on both accruing from October 12, 1982, on costs outstanding at that date, or from the date incurred in the cast of costs arising subsequent to October 12, 1982.

Furrow Stream — The size of water flow released into the furrow; the size of the stream is adjusted to prevent erosion, limited in amount to the capacity of the furrow, and as needed for the intake rates of the soil involved.