Trend analysis of water flow on Neka and Tajan rivers using parametric and non-parametric tests

River flow is an essential parameter in hydrology and water resources studies with mutual interaction with climate elements. So, studying the discharge change trend in the rivers is crucial for management programs and the design of irrigation and drainage systems. In the present study, river flow data measured at six hydrological stations at Neka (Ablu, Golverd, SefidChah) and Tajan (KordKhil, Rigcheshmeh, Soleimantangeh) rivers in Mazandaran Province have been studied by using Mann-Kendall test, age test, and regression analysis during the statistical period of 1976–2006. The MAKESENS 1.0 software was used to reveal annual and seasonal discharge change trends. Results of the present study showed that only two stations – Soleimantangeh and Rigcheshmeh – had decreasing trend at 5% significance level in yearly terms. In contrast, the regression analysis showed just significant trends at Soleimantangeh station. No crucial trends have been observed in the seasonal scale; in spring and autumn, most of the stations had a non-significant negative trend. By considering the methods used to evaluate trends in this study (Mann-Kendall test, age test, and regression analysis), it was observed that all the rivers had had decreasing and negative trends. The performance of parametric and non-parametric tests was similar in most cases.