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Results and Discussion General Comments. The Corps of Engineers Wetland Delineation Manual IUSCOE 198'x, provides guidelines and methods for identifying, delineating and mapping wetlands for this study. The Manual establishes three criteria to distinguish ~.•etlands from upland areas: wetland vegetation, hydric soils and appropriate hydrology. These three criteria can be readily used to identify natural wetlands. Special circumstances apply when the Manual is applied to man created ~retlands or to wetlands that have developed in response to human activities. The manual lists several types of man-induced wetlands including: irrigated wetlands, wetlands resulting from impoundments (reservoir shorelines) and wetlands resulting from stream channel realignment. The Manual (page 91) states that "In virtually all cases, man-induced wetlands involve a significant change in the hydrologic regime, which may either increase or decrease the wetness of the area:' Since it may require long periods of time (hundreds of years) for hydric soils to develop under these altered hvdrologic regimes, the Manual specifies that the wetland determination be based on only two criteria: hydrophytic vegetation and appropriate hydrology. Sites that support hydrophytic vegetation and have appropriate hydrology would be considered to be wetlands, even though they are man-induced and lack hydric soils. However, only some of these wetlands may be subject to regulation under Section 404 of the Clean Water Act and others would be non-jurisdictional. An important cautionary note is included in the Manual, specifically with regard to man-induced wetlands: "If h~droph~tic vegetation is being maintained only because of man-induced wetland lr~drology drat would no longer exist if the actiaih~ (e.g. irrigation) were to be terninated, the urea should not be considered n wetland." (See Manual at p. 92). On the Duckworth site, most of the wetlands occur as a result of human activities, and in the absence of these activities, the areal extent of wetlands would be greatly reduced (i.e., most of the hydrophytic vegetation is being maintained because of man-induced hydrology and would no longer exist if irrigation on the site were terminated). Prior to European settlement, Idaho Creek was likely an intermittent stream that was probably tributary to Boulder Creek (or possibly St. Vrain Creek). As water diversion/manipulation systems were developed in conjunction with settlement of the region, water was diverted from Boulder Creek into a realigned Idaho Creek, which was then ultimately connected to the Last Chance Ditrh via a series of downstream irrigation and diversion ditches. Idaho Creek has been converted to a managed/ manipulated irrigation ditch, portions of which have been periodically re-located and excavated in upland areas. Most of this realignment activity has occurred upstream of the Duckworth site, however there is some evidence to suggest that channelization of the stream has also occurred on the Duckworth site. -2-