Abstract
This study evaluates the impact of climate change (CC) on runoff and hydrological drought trends in the Hablehroud river basin in central Iran. We used a daily time series of minimum temperature (Tmin), maximum temperature (Tmax), and precipitation (PCP) for the baseline period (1982–2005) analysis. For future projections, we used the output of 23 CMIP5 GCMs and two scenarios, RCP 4.5 and RCP 8.5; then, PCP, Tmin, and Tmax were projected in the future period (2025–2048). The GCMs were weighed based on the K-nearest neighbors algorithm. The results indicated a rising temperature in all months and increasing PCP in most months throughout the Hablehroud river basin's areas for the future period. The highest increase in the Tmin and Tmax in the south of the river basin under the RCP 8.5 scenario, respectively, was 1.87 °C and 1.80 °C. Furthermore, the highest reduction in the PCP was 54.88% in August under the RCP 4.5 scenario. The river flow was simulated by the IHACRES rainfall-runoff model. The annual runoff under the scenarios RCP 4.5 and RCP 8.5 declined by 11.44% and 13.13%, respectively. The basin runoff had a downward trend at the baseline period; however, it will have a downward trend in the RCP 4.5 scenario and an upward trend in the RCP 8.5 scenario for the future period. This study also analyzed drought by calculating the streamflow drought index for different time scales. Overall, the Hablehroud river basin will face short-term and medium-term hydrological drought in the future period.
Highlights
Climate change (CC) is not a process that is just related to our era, and the Earth has always been confronted with such changes in different geological periods based on the available evidence (The Core Writing Team IPCC, 2015)
The radial distance from the reference point (REF), indicating the observed values, is the pattern root-mean-square deviation (RMSD), and the radial distance from the origin indicates the standard deviation, whereas the correlation coefficient is shown by the angle (Taylor, 2001)
Analyzing the characteristics of the future streamflow, including the existence of a significant trend or homogeneity, and the occurrence of hydrological drought conditions to adopt an appropriate decision on the matters related to the Water Evaluation and Planning System of the basin is crucial
Summary
Climate change (CC) is not a process that is just related to our era, and the Earth has always been confronted with such changes in different geological periods based on the available evidence (The Core Writing Team IPCC, 2015). The nature and acceleration of CC in the last few years are the factors that make our era distinctive relative to the previous changes. Numerous publications have investigated the mutual impact of CC on runoff in recent years. Birkinshaw et al (2017) investigated the CC impacts on the Yangtze basin, which is among the most important rivers in China, under the Representative Concentration Pathway (RCP) 8.5 scenario during the period from 2041 to 2070, and their results represented variations of −3.6 percent to −14.8 percent in annual precipitation and variations of
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