REGIONAL STOCHASTIC MODELS OF ANNUAL STREAMFLOW FOR WEST BASINS OF IRAN (KARKHEH, DEZ AND KAROON)

Inference from individual stream flow records can be extremely misleading, even for large samples. One is often tempted to trust information available from a stream flow record rather than to exploit regional average statistics of those records. This study has sought to understand the spatial and temporal characteristics of historical annual stream flow in the western watersheds of Iran (i.e., Karkhe, Dez and Karoun). The first goal of the study is to explore the regional and stochastic structure of annual flow records with an emphasis on characterizing the variability and persistence of flow records used in the regional stochastic stream flow models. The second goal is to develop regional hydroclimatological models of annual stream flow which relate mean annual stream flow to climatic and geomorphic characteristics. To achieve the first goal, parameters of regional autoregressive model of AR(1)-LN for each watershed were estimated from time series of annual stream flow at 84 gauging stations with record length of 17 years or more out of 213 total hydrometric Stations. Based on the same time-series, regional hydrologic regression equations were developed for each watershed.