Analysis of Rainfall and Discharge Trend in Kashafrood Watershed

The human activates and change of the land use has made changes in the peak and base flow discharge of the rivers. Also increasing the global average temperature has made anomalies in meteorological and hydrological variables such as precipitation and evapotranspiration. For better management of water resources, the data of river flow rate changes and their creating elements of such changes are required. Therefore the review of these anomalies as the trend determination in time series of hydrological and meteorological variables in different areas and their relation with each other can have an especial importance. In recent years, a great deal of studies have been made for the possible impacts of climatic changes on the river flow, which most of them have studied the changes of long term climatic averages and hydrological characteristics. Generally these changes have been studied in two cases. Firstly, the analysis of registered and available statistics of precipitation and river flow and the other is the impacts of different scenarios of climatic changes on the river flow by hydrological models. The most common method for analysis of hydrometeological time series is the review of the existence or non- existence of trend in them by using statistical tests. Generally the existence of trend in these series may be due to gradual natural changes and climatic changes or the impacts of human activities. Various methods have been presented up to now for analysis of time series trend which are dividable in to two groups of parametric and non parametric. Non-parametric methods have a more extensive use in comparing with parametric methods. The present research was performed to the aim of detecting the existence and amount of discharge trend and precipitation at Kashafrood watershed in 13 meteorology and hydrometric stations with statistical length of 1972-2006 at the north east part of Iran which is cnsidered as the areas with low precipitation in Iran.