A Daily Intermittent Streamflow Simulator


Abstract: Stochastic models are required in order to generate synthetic values of flows statistically similar to observed ones for use in simulation studies of water related structures. Such models are extremely important for the generation of flows of streams with short record length. This study presents a model for the generation of daily flows of an intermittent stream. The model is based on Markov chains and has four steps: (i) determination of the days on which flow occurs, (ii) determination of the days on which a flow increment occurs, (iii) determination of the flow increment, and (iv) calculation of the flow decrement on days when the flow is reduced. In the first two steps, two 2-state Markov chains are used for determination of the state of the stream. In the third step of the model, it is assumed that increments occurring on the ascension curve of the hydrograph are gamma distributed. In the fourth step of the model, the recession curve of the hydrograph is calculated by an exponential decay function with two different coefficients. Parameters required for the model are estimated from daily flows for each month of the year. The model is applied to a daily series of 35 years' length. At the end of the study it was seen that the model preserves the short-term characteristics of flow values in addition to the long-term characteristics.

Keywords: Intermittent streams, daily flow, Markov chain, gamma distribution.

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