The outflow hydrograph at the downstream end is calculated using the following formula.
(24)
where: (25)
(26)
(27)
(28)
(29)
where:
Q = discharge
K = travel time in seconds
x = weighting factor, 0 <= x <= 0.5
∆x = subreach length
∆t = time interval
q = lateral flow
c = wave celerity
The parameters of K and x are expressed as follows (Cunge, 1969 and Ponce, 1978): (30)
(31)
where:
B = top width
S = the channel slope.