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Cowardin Water Regime Modifiers <br /> The purpose of water regime modifiers is to provide a better description of the variations in <br /> hydrology that occur in wetlands on a seasonal and annual basis. These descriptions are general in <br /> nature because wetland hydrology is extraordinarily dynamic. Hydrology is the most variable <br /> component of wetlands and can vary substantially within a single basin weekly,monthly,seasonally, <br /> annually and over decades.Extraordinarily wet or dry periods,whether short or prolonged,do have <br /> dramatic effects on the presence or absence of water in any given wetland.Whether a wetland has <br /> naturally occurring hydrology or whether it is partially or completely drained affects its behavior as a <br /> component of the landscape,its appearance,the vegetation that inhabits it,and the effectiveness of <br /> the functions that it performs. Wetlands may also have artificially induced hydrology due to <br /> stormwater inputs or interconnections to other-wetlands via ditch or file drain systems. Careful <br /> consideration of each wetland within the overall context of the landscape is necessary to understand <br /> which water regime best fits along with the special modifiers that describe alterations to wetlands. <br /> One special modifier class that is missing is the"Stormwater Pond"category.This is a commonly <br /> occurring condition in urban landscapes and should be added. Stormwater Ponds may have been <br /> specifically constructed for that purpose or,in the past,previously existing wetlands were used to <br /> treat stormwater and now function as Stormwater Ponds rather than"natural"wetlands. <br /> Descriptions of the modifiers are taken from Cowardin et al(1979,pgs 21—22)and from Santos and <br /> Gauster(1993,pgs 30—32). <br /> Descriptions within the parentheses are terms used on the NWI key and the longer description is the <br /> one used by Cowardin et al. (1979). Where a parenthetical term.is excluded,the two terms are the <br /> same. <br /> Modifier"A" <br /> Temporarily Flooded(Temporary <br /> Surface water is present for brief periods during the growing season but the water table usually is <br /> well below the soil surface for most of the season.Temporarily flooded wetlands usually have plants <br /> that are characteristic of both uplands and wetlands.This modifier description is most appropriately <br /> assigned to Type 1 and 1 L wetlands but clearly does not fit the Type 7 Hardwood Swamp wetland <br /> type. Table 4 (Cowardin et al 1979, pg 28) is inconsistent by including this regime in the Type 7 <br /> category. <br /> Modfiier"B" <br /> Saturated <br /> Soil saturation occurs to the surface for extended periods during the growing season but surface <br /> water is seldom present or evident. Many sedge and rush wetlands fit into this category. This <br /> modifier also aptly fits the water regime that occurs in the hardwood swamps that are present in parts <br /> of Minnesota in hardwood swamps such as black ash swamps and in coniferous swamps such as <br /> white cedar,tamarack, and black spruce swamps. This modifier also describes Type 2 wetlands as <br /> described above and includes fens and sedge/rush dominated wetlands. <br />