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PART 2: BACKGROUND . Geographic, Hydrologic, and Biological Setting Page 17 Utah's major streams and rivers are identified in Figure 2-1. One or more of the three species are found in the Green River and its tributaries such as the Duchesne in the Division's Northeastern Region; the Price, San Rafael, Escalante, Dolores, and San Juan rivers and Muddy Creek in the Division's Southeastern Region; the Escalante, Fremont, and Virgin rivers in the Division's ~ Southern Region; and the Weber, Ogden, and Bear rivers in the Division's Northern Region. Each of the three species is also found in the mainstem Colorado River, though roundtail chub is currently considered rare in most mainstem locations. Only flannelmouth sucker are found in the Virgin River Basin, which is located within the Lower Colorado River Basin. Only bluehead sucker are found in the Bonneville Basin. Occurrences in these locations are historical only ~ except for the Weber River where they are considered quite rare. Geographic, hydrologic, and biological characteristics of these basins are briefly described in the following sections as well as in the Range-wide Conservation Agreement and Strategy. Altered hydrologic systems ~ Historically, flows, temperatures, and sediment loads of these systems varied widely on both infra- and inter-annual time scales in relation to wet and dry climatic regimes. These variable characteristics remain today only in the remote locations such as the Escalante and Paria rivers that lack water development structures such as power, storage, and diversion dams. ~ Today, water development in high desert tributary streams in Utah is extensive (Cavalli 1999; Walker and Hudson 2004) (see Figure 2-2) and has likely lead to severe habitat fragmentation, disruption of native fish metapopulation dynamics, and has led to population declines due to extreme habitat degradation. While negative effects of dams on mainstem native fish communities are well documented (Berry 1988, Berry and Pimentel 1985, Childs and Clarkson 1996, Clarkson and Childs 2000, Collier et al. 1996, Haines et al. 1998, Kaeding and Osmundson 1988, Robinson et al. 1998a, Robinson et al. 1998b), lack of water in high desert tributary drainages resulting from water development for municipal, agricultural, and industrial purposes is perhaps the most severe threat to persistence of three species populations in Utah (Cavalli 1999, Walker and Hudson 2004). A large number of studies have linked habitat fragmentation or the fragmented distribution of species to declines in population size and/or increases in ~ extinction risk (Cox et al. 2004, Davies et al. 2000, Fagan et al. 2005, Jager et al. 2001, Knapp et al. 2003, Morita and Yamamoto 2002, Robinson et al. 1995). Currently, the presence of diversions and dams limits fish movement either by creating an obstruction to passage between reaches or by dewatering tributary reaches entirely. Impacts of disrupted movement on the three species, particularly flannelmouth sucker and roundtail chub, include inability to escape the ~ harsh environmental conditions brought on by dewatering itself (loss of water, high temperatures, low oxygen; Walker and Hudson 2004) and blocked seasonal movements to habitats important to various life stages of the species (Chart 1987, McKinney et al. 1999). Like many states in the west, all surface flows are diverted at some point, and in the state of ` Utah, these surface water diversions are plentiful. Figure 2-2 shows all point-to-point and surface water diversions within 10 feet of streams or springs within the range of the three species. This map does not display the entire extent of diversions within the state. The Utah Division of Water Rights' GIS data show over 12,000 total point-to-point and surface diversions within the Weber