Flow routing with unknown rating curves using a state-space reservoir-cascade-type formulation

A discrete version of the Kalinin-Milyukov-Nash-cascade is formulated for operational forecasting of stream stages when no information of rating curves is available. Model performance is slightly reduced in comparison to flow routing results using accurate, single-valued stage-discharge relationships. However, when only inaccurate rating curves are available, the present approach may yield superior forecasts. Since in practice the accuracy of the employed rating curves, used to convert stage measurements into discharge values for flow routing, may be somewhat uncertain, application of the present technique is recommended for rating-curve falsification. The method allows for stage predictions using physically based flow routing in rivers where flow rates are unknown or the available rating curves are inaccurate. The technique can also be used without modification for streams with tributaries.