Page - 128 - in Book of Full Papers - Symposium Hydro Engineering

been at or exceeded 4248 m3/s (150,000 ft3/s twice, in February 1986 and January 1997. Fig. 3 shows the FCO Spillway chute, looking downslope, in February 1986. As predicted during design, flow along the chute appears to be aerated through the development of a boundary layer as well as through the piers of the Flood Control Outlet. DWR maintenance records show no significant cavitation damage through the project history [5]. Any damage patterns were random, not clearly related to a particular flow condition in the FCO Spillway chute. Prior to the event of 2017, the Emergency Spillway had never been used, so no record of historical performance existed for that facility. Fig. 3 Photograph of FCO Spillway chute during release of 4248 m3/s (February 21, 1986) 3. HYDRAULIC ENGINEERING, HYDROLOGIC ENGINEERING, AND RESERVOIR OPERATION ANALYSES DURING 2017 INCIDENT During the 2017 incident, hydrologic and hydraulic engineering and reservoir operation analyses provided information to support decision making by DWR management. Lake Oroville inflow forecasts were made every six hours by DWR staff and the United States National Weather Service (NWS), using conceptual models of watershed hydrology. As snow had accumulated in much of the contributing Feather River Basin watershed, these forecasts included assessments of both runoff from rainfall at lower elevations and snowmelt at higher elevations. 128