7. PRSR 04-11-2007 - Laserfiche WebLink

Home Browse Search

Detention Pond A pond designed to catch and temporarily store runoff before discharging the water downstream. The volume of the pool of standing water in the pond is important in determining how effective the pond will be in treating the incoming stormwater. Dissolved Oxygen (D.O.) Oxygen that is dissolved in water. Fish and other water organisms need oxygen for respiration to survive. Depletion of oxygen from water can occur as a result of chemical and biological processes, including decomposition of organic matter. Downcutting The process by which a river or stream erodes and lowers its bed, eventually resulting in the formation of a valley or ravine. Drift (glacial) Rock material, such as boulders, gravel, sand, silt, or clay, removed from one area and deposited in another by glaciers. Drift includes material deposited directly by glacial ice, such as till, as well as material deposited indirectly, such as outwash. Ecosystem The interacting group of physical elements (such as soils, water, etc.), plants, animals, and human communities that inhabit a particular place. Emergent Describes a plant capable of surviving indefinitely with its root system and lower stem in water and its upper stem above water (e.g., cattails). Empirical Based on experiment and observation; used to describe water quality models which are developed from measured data. End moraine A typically hilly landform composed of material deposited at the margin of a glacier. Ephemeral habitat A temporary habitat created by low intensity, short-lived fluctuations in environmental factors. Epilimnion: Upper warm layer of a lake during thermal stratification. Esker Along, often serpentine hill or ridge composed of sand and gravel deposited by meltwater streams flowing in a channel in a decaying ice sheet. Eutrophication A natural process caused by the gradual accumulation of nutrients and consequent increased biological production, and resulting in the slow filling in of a basin with accumulated sediments, silt, and organic matter. Man's activities can increase the rate at which eutrophication occurs. Eutrophic Lake: A nutrient rich lake; usually shallow, green due to excessive algae growth and with limited oxygen in the bottom layer of water. Exotic species A species that has been introduced to an area by humans or that is present in the area as a result of human-caused changes. (same as non native species.) Export Coefficient An estimate of the expected annual amount of a nutrient carried from its source to a lake. Fen a wetland community composed of sedges, grasses, fortis, and sometimes shrubs, that develops on peat in shallow basins. Floating-leaved plants Aquatic plants that root on lake, pond, or river bottoms and have leaves that float on the water surface at the end of long, flexible stems (e.g., water-lilies). Floodplain A flat area adjacent to a stream or river channel, created by erosion and deposition of sediment during regular flooding. Signs of Zflooding include debris caught in trees and ice scars at the bases of trees. Flushing Rate The number of times per year that a volume of water equal to the lake's volume flows through the lake. Forb A general term for broad-leaved, herbaceous plants. Forest A plant community with a nearly continuous to continuous canopy (70 to 100% cover) of mature trees. Forest-grown tree A tree that matured within aclosed-canopy forest. Forest-grown trees tend to have narrow crowns and tall, straight trunks with few lower limbs. z Many of the definitions used in this section are borrowed from Minnesota's St Croix River Valley and Anoka Sandolain, Worcha et al, Minnesota DNR, 1995. Top of the World Park Addition Natural Area Management Plan 2