In the Muskingum channel routing method, what specific physical process does the 'x' parameter represent or account for, which distinguishes it from simpler routing methods?

In the Muskingum channel routing method, the 'x' parameter specifically represents the weighting factor that accounts for the relative influence of inflow and outflow on the total storage within a channel reach during unsteady flow conditions. This effectively distinguishes between two primary forms of storage: prism storage and wedge storage. Prism storage is the volume of water that would exist in the channel if the flow were uniform and steady, primarily dependent on the outflow from the reach. Wedge storage is the additional, dynamic volume of water (positive or negative) that accumulates or depletes during ....