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Diss4lved Oxygen (D.O.) Oxygen that is <br />dissolved in waier. Fish and other water <br />organisms nePd �xygen for respiration to <br />survive. Repletion of oxygen from water can <br />occur as a result of chemica! and bialogical <br />processes, including decornpasition of <br />organic matter. <br />Downcutting The process by which a river <br />or stream erodes and lowers its bed, <br />eventually resulting in the 6ormation of a <br />valley or ravine. <br />Drift (glacial) Rock material, such as <br />boulders, gravel, sand, silt, or clay, removed <br />from one area and deposited in another by <br />glaciers_ Drift includes materia[ deposited <br />directly by glacial ice, such as till, as wefl as <br />material deposited indirectly, such as <br />outwash. <br />Ecosys#em The interacting group of <br />physical elements {suc� as soils, water, <br />etc.), plants, animals, and human <br />communities that inhabit a particular place. <br />Emergent Describes a pla�t capable of <br />surviving indefinitely with its root system and <br />lower stem in water and its upper stem <br />above water (e.g., cattails). <br />Empirical Baseci on experiment and <br />obserr�ation; used to describe water quality <br />models which are developed from measured <br />data. <br />End moraine A typically hilly landform <br />composed of material deposited at the <br />margin of a gfacier. <br />Ephemera! habitat A temporary habitat <br />created by low intensity, short-lived <br />fiuctua#ions in environmentai factors. <br />Epilimnion: Upper warm layer of a lake <br />during thermal stratification. <br />Esker A long, often serpentine hili or ridge <br />composed of sand and gravel deposited by <br />meEtwater s#reams flowing in a channel in a <br />decaying ice sheet. <br />Eutrophication A natural process caused <br />by the gracival accumulation of nutrients and <br />consequent increased bioiogical production, <br />and resulting in the slow filling in of a basin <br />with accumulated sediments, si�t, and <br />organic matter. Mar�'s activities can <br />increase #he rate at which eutrophication <br />occurs. <br />Eutrophic Lake: A nutrient rich lake; <br />usually shallow, green due to excessive <br />algae growth and with limited oxygen ir� the <br />bottam layer of water. <br />Exotic species A species that has been <br />introcfuced to an area by humans or that is <br />present in the area as a result of human- <br />caused changes. (same as non native <br />species.) <br />Export Coefficien# An estimate of the <br />expected annual amount of a nutrient <br />carried from its source to a lake. <br />Fen a wetland community compased of <br />sedges, grasses, forbs, and sometimes <br />shrubs, that deveiops on peat in shallow <br />basins. <br />Floaiing-leaved plants Aquatic plants that <br />root on lake, pond, or river bottoms and <br />have ieaves that float on the water surface <br />at the end of long, flexible stems ( e.g., <br />water-lilies}. <br />Floodplain A flat area adjacent to a stream <br />or river channel, created by erosion and <br />deposition of sediment during regular <br />flooding. S'rgns of'flooding include debris <br />caught in trees and ice scars at the bases oi <br />trees. <br />Flushing Rate The number of times per <br />year that a volume of water equa! #o the <br />lake's volume flows through the lake. <br />Forb A generai term for broad-leaved, <br />herbaceous plants. <br />Forest A plant community with a nearEy <br />continuous to continuous canopy (7p to <br />1fl0% cover) of mature trees. <br />Forest-grown tree A tree that matured <br />within a closed-canopy forest. Forest-grown <br />trees tenci to have narrow crawns and tall, <br />straight trunks with few lower iimbs. <br />Graminvid An herbaceous plant with linear, <br />"grasslike" leaves #hat typically are oriented <br />verticaliy. Graminoids include grasses, <br />sedges, and rushes. <br />Greenway or Greenway Corridor A linear <br />open space area, usually composed of <br />natural vegetation, or vegetation that is more <br />natural than surrounding iand uses. May <br />include paths or recreational trails. <br />Ground fayer A vegetation layer, mostly <br />less that 3 feet tall, af grasses, forbs, and <br />woody plants. <br />Ground moraine A broad anci level or <br />gently undu{at9ng landform composed of <br />material that was deposited undemea#h and <br />sometimes at the margin of a glacier as the <br />ice sheet melted; also referred to as a till <br />plain. <br />� Many of the definitions used In this section are <br />borrowed from Minnesota'S St. Croix River ValEev and <br />Anoka 5andpiain, Worcha et al, Minnesota DNR, 1935. <br />Glossary <br />2 <br />