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Potential for Flooding at Delta, Colorado May Forecasted Runoff Actual Runoff. Flooding Potential Compared to Historic Operation Wet equal to or greater than increased (Upper 10% category) forecast Moderately Wet to Wet equal to or greater than increased (Upper 10% - 30% category) forecast Average Wet to Moderately Wet moderately wet or greater increased (Upper 30% - 50% category) than forecast In other types of runoff situations, flooding at Delta does not appear to be an issue or potential issue when attempting to meet NPS peaks. From another perspective, downstream flooding becomes a concern at 12,000 cfs as the possibility always exists of a surge in unregulated tributaries that could quickly increase flows over 12,000 cfs. Under baseline conditions, 12,000 cfs is reached 21 percent of the time; under NPS desired flow model runs, this increases to 29-38 percent of the time, depending on the model run. Upstream flooding due to ice jams above Blue Mesa would not be affected by any of the model runs because the hydrology model criteria was developed to meet the winter target reservoir elevation that reduces ice jams. Compact Development The State of Colorado is entitled to waters from the Colorado River and its tributaries based on several compacts, including the 1922 Colorado River Compact and the 1948 Upper Colorado River Basin Compact. Colorado is entitled to at least 450,000 acre-feet of future development from the Colorado Basin. As noted earlier, one of the purposes of the Aspinall Unit is to allow Colorado to use its apportionment of water under the compacts. The Gunnison River, as the largest tributary to the Colorado, is a strong potential source for this future water development. The effect of the reserved water right on future Colorado water uses has not been analyzed. Blue Mesa Reservoir holds the state of Colorado's largest uncommitted water supply. In general, model runs that reduce the frequency of filling Blue Mesa will reduce the potential for Colorado to develop water supplies. In dry to average water years, operating to meet the NPS desired flows can result in Blue Mesa storing 30,000 to 100,000 acre-feet less than with the base run. The larger impacts occur when the actual April to July inflow to Blue Mesa Reservoir is significantly less than the April Is` forecast. It may be possible to decrease these impacts by changing operating criteria during April and early May in these types of years to reduce the risk to Blue Mesa storage. In effect, by releasing water to meet NPS desired spring peaks, Reclamation assumes the risk of lower storage when actual inflows are other than forecasted. Thus, the NPS desired flows may have a yet to be 13