Improvement of hydrologic simulation by utilizing observed discharge as an indirect input : (Computed Hydrograph Adjustment Technique-- CHAT)

A computerized technique is presented whereby the output of a continuous conceptual hydrologic model is adjusted in real time to agree with the observations of discharge. Since the discharge generated by the model in response to a moisture input is dependent upon the current values of the state variables of the model, the procedure also adjusts the state variables to correspond to the output. The technique is applicable to outflow from headwater catchments during runoff events that result from liquid precipitation. Its approach is to make adjustments, iteratively and simultaneously, to the precipitation and the shape of the unit graph until the model produces a simulation that agrees, within reasonable limits, with the discharge observations. Examples of the performance of the procedure under a variety of hydrologic conditions are included. Walter T. Sittner and Kay M. Krouse. Assigned SUS document no. 119 in the Susitna Aquatic Impact Assessment Project bibliography. This report was used as supporting documentation in research by the Susitna Hydroelectric Project. Includes bibliographical references (page 125). 1979 NWS (National Weather Service) Library Public Domain 1931