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2 Review of the Draft Levee Removal Strategic Plan for the Upper Colorado River Basin Recovery Implementation Program By Larry W. Hesse River Ecosystems, Inc. 3 November 1995 Comments on Background (page 2,3): A levees primary role is to prevent seasonal floodwater from inundating portions of the floodplain. Typically these floodplain lands would be overgrown with a community of adapted macrophytes. Moreover, the period of inundation would have been relatively short since the flood pulse in the Colorado was relatively short. In addition, the exceedence of bankfull discharge would have meant maximum turbidity for the year. For these reasons I would question that areas of the floodplain, inundated each spring would have higher temperatures or light intensities than main channel water, since the water inundating the floodplain, pre-dam, would have quickly cycled on and off of the floodplain. It is conceivable that as the main channel flows receded back into the high banks, that water remaining in oxbows or small depressions may then develop some permanency which might have the described characteristics, including the production of phytoplankton. But it is my guess that the benefit you want to derive from levee removal is the annual flood pulse inundation of massive amounts of terrestrial plant material by flood waters which will be turbid, and about the same temperature as the main channel. Primary prOduction is most likely allochthonous by nature, and the initial benefits would be in a greatly expanded secondary production. Even if pre-dam floodplain depressions such as oxbow lakes existed to nurse large populations of larval suckers and squawfish, these areas today will contribute to the survival of non-natives, such as centrarchids and cyprinids. That is not what you want from the areas protected by levees. There is no question that floodplain land that has not been inundated in recent times because of levees, will contribute significantly to the energy cycle of the river ecosystem; however, inundation should be aimed at areas that will readily cycle water which means that the floodplain will have a flow across it not just develop standing water. The native species are much better designed to tolerate velocity than some of the nonnatives of concern.