Probabilistic approach to modelling of recession curves

Recession curves of daily streamflow hydrographs are analysed by a probabilistic approach. Flow of a day on a recession curve is calculated by multiplying the previous day's flow with a value of K smaller than one; K, defined as the ratio of the flows of successive days on the recession curve, was determined from observed daily flow time series. The range of K is divided into three class intervals. A procedure using the concept of gradually increasing values of K is adopted. For this, transition probabilities and average values of K are determined for each class interval and each month of the year. A recession curve can be generated, once the peak flow is known, by the probabilistic approach. The procedure allows nonlinear, seasonal and stochastic effects in flow recession of a river to be considered.