Streamflow trends during recent decades at some near-natural catchments in Iran

• Published in: Hydrological sciences journal Vol. 67; no. 1; pp. 107 - 116
• Main Authors: Zhang, Qinghuan, Hosseini-Moghari, Seyed-Mohammad, Tang, Qiuhong, Wang, Zhihui
• Format: Journal Article
• Language: English
• Published: Abingdon Taylor & Francis 02.01.2022; Taylor & Francis Ltd
• Subjects: Annual precipitation; atmospheric precipitation; Catchments; Climate variations; Iran; light precipitation events; Mann-Kendall test; Mean temperatures; Precipitation; Sen's slope estimator; Stream discharge; Stream flow; Streamflow trends; Temperature; Temperature rise; Trends; Watersheds; Iran
• ISSN: 0262-6667; 2150-3435; 2150-3435
• DOI: 10.1080/02626667.2021.2011287

In this study, we assessed the impacts of climate variations on streamflow in 28 near-natural catchments in Iran. To this end, we analysed the trend of annual streamflow, precipitation, and temperatures using the Mann-Kendall test and Sen's slope between water years 1982 and 2011. We evaluated the frequency of precipitation in different classes, i.e. below 5, 5-10, 10-15, and above 15 mm/day. Our results indicate a decline in streamflow at 25 catchments, at a rate of −5.66 to −0.19 mm/year. The annual precipitation amount did not decrease significantly, while the frequency of light precipitation events (<5 mm/day) increased. About 60% of the upward trend was significant. Mean temperature increased at all studied catchments, at an average rate of 0.055°C/year. In short, our results indicate that increases in temperature and the frequency of light precipitation events are two leading factors in streamflow reduction across studied catchments.