Investigation of climate change occurring over watershed using stationary and trend analysis (Case study: Armand watershed)

In this study, the relationship between temporal variation of hydrological parameters and climate change was investigated using stationary and trend analysis. For this purpose, the precipitation and temperature (maximum, minimum and average) data of Shahrekord synoptic station and hydrometric data of Armand watershed in the period of 1971-2011 were used. Results showed that the minimum temperature of May, August, June and spring season had a significant decreasing trend. Also, a significant increasing trend was observed in the maximum temperature of September, March and autumn season time series. The average temperature of March has significant increasing trend. In the case of precipitation, the March and winter season experienced a decreasing significant trend. The stream flow time series of Armand River showed a strong decreasing trend and experienced a decline equal to 51.57 (m3/s)in the three past decades. In the hydrological point of view, the main reason is the increasing trend in maximum temperature of the autumn season and reduction of precipitation in winter season (the season with maximum precipitation). In order to evaluate the effect of trend on the stream flow of Armand River that is a reason of existence of climate change in this watershed, three stationary tests including ADF, DFGLS and KPSS were used. The stream flow time series were tested in Normal and standard forms. The results confirmed stationary in stream flow of Armand River at a 95% confidence level that indicating existence of variations in average and variance of stream flow time series.