San Juan River/Delores Division 7 Durango RICD 06CW09 Boating Park Hydrology Study

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1 ' any junior upstream water rights that may be depleting the flow of the river. Such call will not affect upstream senior water rights. ' Average Streamflow Calculations At the Boating Park location, the Animas River streamflow averaged approximately 581,000 acre -feet per year during the 1928 through 2004 study period. The RICD appropriation (limited to 12 hours per day) would command an average of ' 159,000 acre -feet per year, which is 27 percent of the available streamflow. Approximately 422,000 acre -feet per year will be surplus to the Boating Park demand. ' Table 4 summarizes the average available streamflow throughout the year. ' The amount of water commanded by the Boating Park would increase to the extent that there are competitive events, when the RICD claims will increase to 18 hours per day. Accordingly, the amount of surplus streamflow will be reduced to the same extent. IExceedance Probability We have produced exceedance plots of the Animas River streamflow at the tBoating Park location. The streamflow exceedance plots are based on the Log Pearson Type III statistical distribution and are enclosed in Appendix B. Using the exceedance plots, the flow percentiles for the RICD claims have been calculated. The flow percentiles are the percentage of years during which the average daily streamflow would Ibe less than the RICD right, based on the statistical distribution. The flow percentiles are summarized in Table 5. As shown in these tables, the maximum claimed flows (Structures 5 and 9) are at the 24th percentile average rate. In ' other words, the average daily streamflow (during each period in which the RICD is claimed) would be less than the RICD appropriation 24 percent of the years. The ' streamflow on individual days may be more or less than the RICD appropriation, so a call might be placed more frequently than indicated by the percentiles. 14