Firm yields are presented based alternatively on each reservoir operating individually and with multiple reservoir system operations. System firm yields are shown excluding and including local flows which enter the river below the dams. The firm yields are based on 2010 sediment conditions. System firm yields are computed based on the ten reservoirs making coordinated releases for a diversion at the Richmond gage. Thus, senior water rights significantly decrease firm yields, and system operations significantly increase firm yields.
Larger yields have lesser reliabilities.
However, yield levels significantly larger than firm yield result in shortages only a relatively small percent of the time. A number of factors affecting reservoir yield are addressed in this report. The stochastic nature of streamflow, loss of capacity due to sedimentation, multiple reservoir interactions, and multiple users are particularly important fundamental aspects of a water supply and use system which must be considered in yield studies. Consideration of senior water rights significantly decreases estimated reservoir yield. Coordinated system operation of multiple reservoirs significantly increases yield.