Hysteresis

Hysteresis is a phenomenon in which the response of a physical system to an external influence depends not only on the present magnitude of that influence, but also on the previous history of the system. Expressed mathematically, the response to the external influence is a doubled-valued function; one value applies when the influence is increasing, the other applies when the influence is decreasing. It is derived from the Greek word “husteros” which means slow, lagging behind or delayed.

In hydrology, the river discharge, soil moisture tension, solute concentration, and suspended sediment concentrations experience the hysteresis phenomenon. Hysteresis in river discharge occurs during unsteady flow when the water surface slope changes due to either rapidly rising or rapidly falling water levels in a channel control reach. Hysteresis is most pronounced in flat sloped streams. On rising stages, the water surface slope is significantly steeper than for steady flow conditions, resulting in...