Climate Change Impact Assessment on Low Streamflows Using Cross-Entropy Methods in Iran’s Namak Lake Basin

Zahra Sheikh, Alireza Moghaddamnia*, Dawei Han

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

Abstract

Climate change impacts on low streamflows provide a comprehensive picture of the state of surface and groundwater resources, particularly in arid and semi-arid regions. The objective of this study is to assess the impacts of climate change on low streamflow variations by detecting long term spatiotemporal changes in recorded climatic variables such as rainfall and temperature, as well as their associations with low streamflow fluctuations. Seasonal variations in low streamflows (summer and winter) are examined at 18 hydrometric stations located in the Namak Lake Basin, Iran, between 1970 and 2015, using the nonparametric Modified-Mann-Kendall test and Sen’s Slope Estimator method. Seasonal low streamflow has demonstrated a clear diminishing significant trend (in more than 55% of the stations), while summer low streamflow has showed a more pronounced and drastic decreasing trend (at 82% significance at a p<0.01 probability level). Long-term changes in boreal seasonal and annual rainfall/temperature also reveal a dominant decreasing trend in winter and spring rainfall (in 82% and 58% of all stations, respectively) and a dominant increasing trend in all temperature time scales (in 90% of all stations). The effects of climate variations on low streamflow are quantified by applying Spearman's rank correlation and Cross-SampEn methods. The results reveal that the winter rainfall, annual and summer temperatures have the strongest association with seasonal low streamflows, especially in the entropy method. Although the relationships between low streamflows and temperature/rainfall are related to the different processes that generate streamflows, particularly in heterogeneous locations, the results indicate that rainfall has a stronger influence on low streamflows in this region than temperature does. In addition, the findings of the research indicate that low streamflows are more nonlinearly related to climatic parameters like temperature and rainfall, and the robustness of Cross-SampEn reflects the degree of asynchrony for complex, non-linear, and non-stationary time series.
Original languageEnglish
JournalClimate Research
Publication statusAccepted/In press - 21 Aug 2021

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