Muskinum Channel Routing using reach storage as an operating variable

The study presents a flood routing method using the Muskingum storage as an operating variable, and develops a routing equation which estimates the reach storage using the current time inflow, and the inflow and reach storage of the immediately previous time level. Using the estimated storage, the discharge at the outlet of the Muskingum reach is estimated based on the Muskingum storage equation. The parameters of the Muskingum method used for the determination of coefficients of the storage routing equation were estimated using the relationships given by Perumal and Price (2013) while developing the Variable parameter McCarthy-Muskingum (VPMM) method. The suitability of the proposed routing method is studied using the input data and the channel configurations which were employed for the development of the VPMM method by Perumal and Price (2013). The results of the outflow hydrographs obtained using the proposed routing method compare very well with the outflow hydrographs obtained using the VPMM method. The practical application of the proposed method requires the accounting of lateral flow while routing the inflow hydrograph in a river reach. Assuming the lateral flow is uniformly distributed along the river reach in proportion to the inflow hydrograph, the routing equation was accordingly modified to take into account the lateral flow. The applicability of this routing equation is tested by routing in the upper reach between Rottweil and Oberndorf of the Necker river in Germany. The geometric parameters of the channel reach which have not been measured were estimated using the ROPE algorithm. The routing results compare very well with the observed hydrographs at the Oberndorf gauging station and demonstrates the appropriateness of the proposed routing scheme using reach storage as one of the operating variables and by duly accounting for the lateral flow in the routing reach.