Shift changes and heterogeneity analysis of hydro-climatic variables (A case study: Aji Chai Watershed)

Shift changes and heterogeneity analyses of hydro-climatic variables is very important in water resources planning and management. In order to shift changes and heterogeneity analyses of Tmin and Tmax, precipitation and discharge, 2, 7 and 7 stations was used over the 40 years (1972-2011), respectively. The results of annual Tmin and Tmax series showed that both of two stations had the significant increasing trend in 1 significance level. The results of precipitation showed no specific spatio-temporal trend in four last decades and identifying the exact pattern of changes was difficult in compared with other variables. Among 7 hydrometric stations, 5 stations showed the significant increasing trend. However, discharge had the most decreasing trend among the studding variables. Shift changes analyses of hydro-climatic variables by four heterogeneity tests, generally indicated the 50.5 percent of Tmax series, 62.5 percent of Tmin series, 26.25 percent of precipitation series and 45 percent of discharge series had heterogeneity in 95% confidence level in the studding stations. Studding shift changes in Tmin and Tmax series showed that all of the changes were positive/ or increasing. In compare with temperature series, shift changes of precipitation as same as its trend have no specific trend. In general, temporally all of the changes occurred in 1990s.