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to which releases are routed. This information permitted assessment of the flood risk downstream and the risk to the structural integrity of Oroville Dam. Challenges in reservoir operation analysis for Oroville Dam included: (1) the need for quick turnaround to set guidelines during construction and provide information critical for decision making about recovery; (2) the need for statistical analysis from which reservoir inflow probability information could be derived; (3) the lack of certainty about seasonal and sub-seasonal inflows to the reservoir due to uncertainty about weather; (4) the risk of misunderstanding or misinterpreting model results as critical decisions were made; and (5) the requirement for concurrence by USACE, FERC, and DSOD with changes in Lake Oroville operations. Solutions included: (1) the use of cloud computing, with parallel model runs on multiple servers in the Amazon cloud, and multiple modelers to configure and execute model runs and synthesize results; (2) parallel statistical analysis of reservoir inflow data by hydrologic engineering experts, as described below; (3) analysis with ensemble forecasts, historical period of record, and statistically- based hydrographs; (4) careful communication to decision makers of results by DWR and consultant experts; and (5) continuous collaboration and coordination with reviewers and regulators through in-person meetings, a series of webinars, and technical memorandums for which review and comments were solicited. The outcome of the reservoir operation analyses was a series of interim operation plans approved by regulators and implemented by DWR. Operation following those plans has been successful thus far, with the initial phase of construction completed in November 2017. 5. HYDROLOGIC ENGINEERING ANALYSIS DURING RECOVERY Hydrologic engineering analysis during recovery provided information for sizing the restored FCO Spillway chute and for developing the operation plans described above. The analyses included the following:  Reassessment of the PMF, a design event that fixes the capacity of the spillways and the operational relationship between release capability and reservoir storage.  Assessment of hydrologic hazard in terms of statistically likely seasonal inflows to the reservoir. Results of this analysis informed decision makers about the schedule of construction and about operation before, during, and following various phases of the construction. DWR had scheduled the PMF re-analysis for Oroville Dam prior to the February 2017 incident as a part of normal relicensing activities. The PMF update was to account for: (a) enhanced understanding of atmospheric conditions that lead to the probable maximum precipitation (PMP) — the precipitation event that 131