This paper asserts that the traditional method for reservoir routing is unnecessarily complicated. It requires the solution of a transcendental equation at each time step. Reservoir routing is actually simply the numerical solution of a differential equation. Any standard method can be used, and all are simpler than the traditional method. The paper also shows that the alternative form of the governing equation in terms of the reservoir surface elevation has some advantages over the usual form involving storage volume. The presentation incorporates the case where reservoir outflow may be varied by control of valves or spillway gates. Numerical methods for reservoir routing are examined and compared, and it is concluded that simple standard methods for solving differential equations are to be preferred to the traditional method for flood routing, and should replace it.