Analysis Of Hydrologic Characteristics From Runoff Data - A Hydrologic Inverse Problem

Abstract

In this paper, the characteristics of hydrologic basins as well as rainfall are derived only from daily runoff data. This is a sort of inverse hydrologic problem. First, time series of daily runoffs are separated into components of surface flow, inter-flow and groundwater flow by numerical filters whose cut-off infrequencies are deter-mined from the order of magnitude comparison ofAR (autoregressive) coefficients of runoff data and confirmed by the coherence gap in rainfall-runoff data. By assuming the daily rainfall to be of white noise, the time series of each component thus separated are fitted to the AR model from which the hydrologic impulse response characteristics (unit hydrographs for each subsystem) are determined. Time series of the daily rainfall are inversely generated from the original time series of the daily runoff and the coefficients of AR model determined as above. The estimated time series of rainfalls agree relatively well with the real, but screened, rainfall data. Finally, a nonlinear separation law of effective rainfall into several rainfall components is estimated.