Hydrological Rainfall-runoff Model Research Articles

A simplified hydrological rainfall-runoff model — Reply

A simplified hydrological rainfall-runoff model — Reply

A simplified hydrological rainfall-runoff model — Comment

A simplified hydrological rainfall-runoff model — Comment

A simplified hydrological rainfall-runoff model

The rainfall-runoff process is investigated for relatively small catchment areas (<100 km 2) and for heavy rainfalls. It is assumed that: (1) the rainfall excess nearly equals the effective rainfall; and (2) the rainfall intensity function depends on time alone and is single-peaked. The catchment area is approximated by two rectangular planes of not necessarily equal width but with constant bottom slopes and constant roughness factors. A small stream runs where the two planes intersect each other. Both the overland and the stream flow are assumed to be fully turbulent; they are modelled using the Manning-Strickler formula. Kinematic wave theory serves as the mathematical model to compute the hydrographs at an arbitrary location in terms of the prescribed, basic parameters. The solutions are displayed graphically, which allows direct determination of the solution sought. Variations in the average bottom slope and the average friction coefficient are found to have little influence on the resulting hydrograph. Rough estimates of these parameters suffice to obtain fair results. The model is tested by comparing observations collected in western Switzerland with present predictions. Agreement between the computed and the observed hydrographs is fair, given the simplicity of the described hydrological model. A step-by-step procedure with examples illustrate the method in detail.

Accuracy of reservoir inflow forecasts based on radar rainfall measurements

For efficient application of optimum operating procedures to flood protection reservoirs it is essential to forecast on line, i.e., during a storm, the relevant inflow hydrographs. This can be achieved with the aid of a weather radar linked to a computer in which the optimum reservoir operating program is stored as well as a program of a hydrologic rainfall‐runoff model producing the reservoir inflow hydrographs from radar‐measured rainfall data. These inflow hydrographs may be evaluated on the computer during each storm event and can be updated every 5 min, if necessary. The accuracy of these computed hydrographs was tested against the recordings of two river gages installed in catchments close to a weather radar at Hohenpeissenberg in Upper Bavaria. By using a linearly distributed mathematical catchment model it was shown that for the two rivers the synthetic hydrographs computed from radar‐measured rainfall were more accurate than those obtained from continuous measurements of the official point rain gage network of the German Weather Service (one recording gage in 500 km2) and that they were of the same accuracy as those obtained from a special very dense rain gage network (one recording gage in 25 km2) set up for research purposes in the same area.