A leaky reservoir model for ephemeral flow recession

The flood wave in ephemeral streams can often be portrayed accurately by assuming ‘instantaneous ’ rise to peak flood stage (depth) and specifying a recession curve. Here recession is modeled as a conceptual analog of discharge from a single leaky reservoir. Physically, the reservoir may be considered to approximate that portion of the ephemeral stream channel that is flowing at the onset of recession. The discharging reservoir is described by a continuity equation and by discharge‐stage (stream rating) and storage‐stage (reservoir configuration) relations. No input is routed through the reservoir; at the onset of recession the reservoir has water in storage. A good fit to observed curves is obtained by calibrating two parameters, reservoir leakage rate and initial storage (reservoir shape). The agreement is most sensitive to changes in initial storage. The best fit parameter values are physically plausible.