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0024u8 2 The duration of the BHBF may be determined in real time by sediment and drift researchers stationed at three sites: in Marble Canyon, upstream from the mouth of the Little Colorado River and near Phantom Ranch. Sediment deposition rates and Secchi depth analyses or other appropriate sediment or turbidity tests, may be used to evaluate when a reduction in sediment and drift transport occurs. Concurrence on these measurements among the field researchers will signal the conclusion of the experiment. Ongoing monitoring efforts will be incorporated to minimize the research costs associated with this BHBF. Research and monitoring activities will be coordinated and logistically supported by GCMRC, pending discussions by the TWG and AMWG, and approval of proposals. Given the short time frame surrounding planning and implementation of research activities for this BHBF, GCMRC will not pursue a competitive funding approach to accomplish research and monitoring tasks, but will use a variety of mechanisms, including modification of existing contracts and in- house expertise. Results of the monitoring and research activities conducted in 1996 are the basis for developing the hydrograph proposed for this BHBF. The subset of monitoring and research activities presented here will ensure sufficient information to assess the effects of this hydrograph. In addition, each project undertaken here will also include a review and analysis of other alternative flow regime impacts (high or low, constant or fluctuating) on each resource category. This information will be used by the Center in an existing science review of impacts of differing flow regimes on resources. This assessment will be used to plan subsequent future research on impacts from differing flow regimes. The following research and monitoring studie~ are suggested as appropriate for this event, pending discussions by the TWG and AMWG. . .' .1) Fixed wing aerial photography during the BHBF, and associated analyses, will provide a precise, system-wide documentation of stage level. Protocol comparison between the traditional Reclamation videography and multi-spectral videography prior to and after the BHBF, and associated analyses, will permit evaluation of existing data and potential new remote sensing analyses: 2) Changes in the limnological structure of Lake Powell will be assessed by measurements upstream, in and downstream from the dam before, during and after the BHBF. 3) Flow and/or sediment concentration and storage data will be provided by monitoring of mainstream (including a temporary gage in near mile 40) and tributary (Paria and Little Colorado riyers) stream gage; and by monitoring of established mairistream cross-sections. . . 4) A subset or all of the 34 sand bars under Intensive study since 1990 wiiJ be monitored before and after the BHBF, and grain size and stratigraphy will be measured following the BHBF. .