where C is an empirical parameter and the subscript \(i\)indicates the time step. The parameter C was originally proposed as an empirical coefficient. Essentially, C accounts for time scale effects by applying a Budyko-type equation to a monthly time scale, i.e., secondary influences of dynamics in soil water storage rather than P and PET on catchment E .
Monthly runoff (\(Q_{i}\)) in TWBM is estimated from catchment water content (\(S_{i}\)) as: