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. . wetland habitats typically support more than 70% of all species in the basin. . land Use The basin's population exceeds 2.5 persons/km2 and principle land uses include grazing, recreation and mining. Major population centers on the Colorado Plateau include Rock Springs lwyoming); Grand Junction, Montrose, Cortez, and Durango Colorado); Price, Moab, Kanab, and St. George (Utah); Farmington New Mexico); and Page, Flagstaff, Tuba City, and Kingman Arizona), as shown in Fig. 2. Figure 3 shows that approximately 0% of the Upper Colorado River Basin is administered by U.S. government agencies, including the Bureau of land Management, National Forest Service, and National Park Service, and 15% is administered by Indian tribes. Wetland Classification Of the many schemes proposed, the wetland classification scheme of Cowardin et al. (1979) is one of the more useful approaches for categorizing the wetland habitats of the Colorado Plateau (Table 1). This wetland classification is based on a hierarchical taxonomy of habitat systems, subsystems, classes, and subclasses. Modifiers are based on water pH and salinity, soil, and anthropogenic modification. Systems are the "complex of wetlands and deepwater habitats that share the influence of similar hydrologic, geomorphologic, chemical, or biological factors (p 4)". Freshwater systems include riverine (fluvial), lacustrine (1akes), and palustrine (marshlands; Fig. 4A, 4B, and 4C, respectively). Colorado Plateau riverine systems include "all wetland and deepwater habitats contained within a channel (except)...wetlands dominated by trees, shrubs, persistent emergents, emergent mosses, or lichens". lacustrine systems include wetland and deepwater habitats which are: (1) situated in a topographic depression or a dammed river channel; (2) lacking trees, shrubs, persistent emergents, emergent mosses or lichens with greater than 30% areal coverage; and (3) total area exceeds 8 ha; or "if an active wave-formed or bedrock shoreline feature makes up all or part of the boundary, or if the water depth in the deepest part of the basin exceeds 2 m at low water" (p. 11). Palustrine systems relevant to the plateau include "all wetlands dominated by trees, shrubs, persistent emergents, emergent mosses or lichens" or if without vegetation, those habitats having an: (1) area less than 8 ha (20 acres); (2) active wave-formed or bedrock shoreline features lacking; (3) water depth in the deepest part of the basin less than 2 m at low water (p. 12)." Cowardin et al.'s (1979) regional classification scheme is comprised of domains, divisions, provinces and sections and is based on Bailey (1976; Table 2). . . . . . . . 2 .