WSP00190

• File Number: 8407
• Description: Platte River Basin - River Basin General Publications
• State: CO
• Basin: South Platte
• Water Division: 1
• Date: 6/2/1999
• Author: URS Greiner Woodward
• Title: Documentation of Existing Conditions in the Central Platte Valley - Delivery Order Number 86
• Water Supply Pro - Doc Type: Report/Study

SECTIONTWO

Environmental Selling

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cattail and brush marshes, wetland swales, ponds and sloughs, and lowland savannas are all
aspects of wet meadows...The common thread among these diverse types of wet meadows is a
high groundwater table, a surrounding matrix of prairie, and the presence of scattered wetlands,
poor drainage, and nutrient-rich soils."

The term "wet meadow" is more widely used in the central and western U.S. to describe
herbaceous meadows on mineral soils of seasonally flooded or saturated flats, which are usually
dry for a portion of the growing season (Windell et al. 1986; Hansen et al. 1995; Stewart and
KantrUd 1971, 1972). Stewart and Kantrud described the wet meadow zone as intermediate
between wetland-low prairie and shallow marsh. Under the National Wetlands Inventory (NWl),
wet meadows would typically be mapped as PEMA (palustrine, emergent, temporarily flooded)
(Cowardin et al. 1979). NWI would not map Stewart and Kantrud's wetland-low prairie zone as
wetland and would identify shallow marsh as PEMC (palustrine, emergent, seasonally flooded)
or PEMF (palustrine, emergent, semi-permanently flooded). Wet meadows in this usage are a
type of wetland, which is "an ecosystem that depends on constant or recurrent, shallow
inundation or saturation at or near the surface of the substrate" (National Research Council
1995).

The term "wet meadow" has been used to refer to both non-wetland bottomland grassland and to
wetlands ranging from true wet meadows to ponds and sloughs. This may be due in part to
evidence that wetlands were far more prevalent in the bottomlands prior to agricultural
development and water diversions. However, since many of these areas are not currently
wetlands and the term "wet meadow" has been applied both to wetlands and to non-wetlands in
bottomland areas along the Platte River, the following section will use the term "bottomland
grassland" except where it is clear that the literature being discussed refers only to wet meadows
as a type of wetland.

2.7.2 Location and Distribution

Mapping of bottomland grasslands ("wet meadows") was included as part of the WELUT
database (Cw.J.~cr ct ai. 19&5) end iz being l.'1cluded ;n the: current BOR study. These areas were
defined as grasslands with emergents or open water within the floodplain. The WELUT database
did not include wet meadows or bottomland grassland outside of the Platte River floodplain;
these areas were counted as upland grassland (Sidle et al. 1989).

The National Wetlands Inventory has also mapped wetlands on all of the U.S. Geological Survey
(USGS) quads in the study area. The currently available maps were prepared in 1987 based on
May, July, or September 1981 aerial photography (NWI 1987). Although these maps are not up
to date and may not be accurate, they are useful for identifying general areas of wet meadows and
bottomland grasslands.

Bottomland grasslands and wet meadows occur throughout the study area but are much more
prevalent in the eastern portion of the study area. Currier et al. (1985) reported that about 75
percent of the bottomland grasslands and wet meadows in the WELUT study area (Segments I to
11) occurs in Bridge Segments I, 2, 3,4, and 7. The largest area is on Mormon Island in
Segment 3, most of which (about 2,000 acres) is mapped as wet meadow (about 90 percent

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