Hydrology and Runoff

In the derivation of a unit hydrograph, the convolution equation for direct runoff ordinate $Q_n$ at time step $n$ from rainfall excess pulses $P_m$ and unit hydrograph ordinates $U_k$ is:

Options:

• (A) $Q_n = \sum_{m=1}^n P_m U_{n - m + 1}$
• (B) $Q_n = \sum P_m / U_m$
• (C) $Q_n = P_n \times U_n$
• (D) $Q_n = \sqrt{P_n U_n}$