Long-Term Trends and Seasonality Detection of the Observed Flow in Yangtze River Using Mann-Kendall and Sen’s Innovative Trend Method

Ali Ali,Kuriqi Kuriqi,Abubaker Abubaker,Kisi Kisi

doi:10.3390/w11091855

Ali Ali, Kuriqi Kuriqi + Show 2 more

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https://doi.org/10.3390/w11091855

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Abstract

Trend analysis of streamflow provides practical information for better management of water resources on the eve of climate change. Thus, the objective of this study is to evaluate the presence of possible trends in the annual, seasonal, maximum, and minimum flow of Yangtze River at Cuntan and Zhutuo stations in China for the period 1980 to 2015. The assessment was carried out using the Mann–Kendall trend test, and the innovative trend analysis, while Sen’s slope is used to estimate the magnitude of the changes. The results of the study revealed that there were increasing and decreasing trends at Cuntan and Zhutuo stations in different months. The mean annual flow was found to decrease at a rate of −26.76 m3/s and −17.37 m3/s at both stations. The minimum flow was found to significantly increase at a rate of 30.57 m3/s and 16.37 m3/s, at a 95% level of confidence. Maximum annual flows showed an increasing trend in both regions of the Yangtze River. On the seasonal scale, the results showed that stations are more sensitive to seasonal flow variability suggesting a probable flooding aggravation. The winter season showed an increasing flow trend, while summer showed a decreasing trend. The spring flow was found to have an increasing trend by the Mann–Kendall test at both stations, but in the Zhutuo Station, a decreasing trend was found by way of the innovative trend analysis method. However, the autumn flow indicated a decreasing trend over the region by the Mann–Kendall (MK) test at both stations while it had an increasing trend in Cuntan by the innovative trend analysis method. The result showed nonstationary increasing and decreasing flow trends over the region. Innovative trend analysis method has the advantage of detecting the sub-trends in the flow time series because of its ability to present the results in graphical format. The results of the study indicate that decreasing trends may create water scarcity if proper adaptation measures are not taken.

Highlights

The sharp increase in greenhouse gases emissions has resulted in a rise in temperature over many regions around the world [1,2,3]
The probability density function (PDF) of the null hypothesis is required to derive from calculating the test significance
This study assessed the presence of trends in the monthly and annual flows of Yangtze River

Summary

Introduction

The sharp increase in greenhouse gases emissions has resulted in a rise in temperature over many regions around the world [1,2,3]. The increasing temperature has induced various hydro-climatological hazards with lots of socio-economic consequences [4,5,6]. It has been observed that increasing temperature has altered the patterns of precipitation, which is one of the essential. The changing trends have direct impacts on the river flow, and river flows are found to be very sensitive with minor changes in the precipitation patterns [11,12,13]. It is imperative and necessary to evaluate the trends in the river flow for sustainable development in water resources and in the same time maintaining adequate environmental flows releases downstream of the hydraulic structures [16,17]

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