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River restoration in the Intermountain West — what can we really hope to achieve?
Jack Schmidt, Utah State University, Logan, UT
The Basin and Range, Colorado Plateau, and Interior Mountains and Volcanic Plateaus of the Pacific Northwest are characterized by 3 types of streams. The stream flow of inter-regional rivers is primarily derived from the high mountains that are the rim of the region. These rivers that cross or terminate in the region -- such as the Rio Grande, Colorado, Bear, Provo, Weber, Truckee, Carson, Walker, and Owens – have large annual stream flows, sustain significant riparian and aquatic ecosystems, and are extensively developed for off-channel consumptive uses. These rivers are the subject of large-scale restoration efforts. More than $40 million/year is now spent in the United States in efforts to rehabilitate parts of the Colorado River system. Similar scale efforts are underway in parts of the Provo and Truckee Rivers and are being planned for the Walker River. In all cases, restoration efforts do not challenge existing water use patterns. Despite application of state-of-the-science to many of these program, it is unclear whether any of the efforts presently underway to restore the largest rivers of the region will be successful. Each of these great rivers is prisoner to its distinctive geography of water and sediment sources in relation to the locations of major urban and agricultural centers, and to the uncertainty of how water- and energy-short societies will respond to population growth in a changing climate.
A second category of streams are regional rivers -- ones that arise within the region and include the Puerco, San Rafael, Virgin,
and Humbolt. The third category of streams is everything else -- the small perennial streams and countless ephemeral and intermittent streams that
drain most of the interior basins of the Great Basin and the small watersheds further
to the east. Restoration of the second category is challenged by smaller budgets,
extensive human uses for diversions and direct land use activities, and the shear
scale of the number of these streams and unclear priorities of deciding which rivers
to restore. In the case of the smallest of these streams and minimal budgets, passive
restoration approaches may allow ecosystem recovery with only modest investment. In
fact, there may be an inverse relationship between the amount of annual stream flow
and their restoration potential.