Quantifying Climate Change Impacts on Hydrological Dynamics and Sedimentation Using GIS and SWAT+ Modelling

Abstract

Climate change significantly impacts natural hydrological systems worldwide, affecting water availability and sedimentation dynamics. The upper Indus Basin is one of the most crucial basins in South Asia, which is undergoing severe climatic variations, resulting in extreme flooding. This study examines the impact of climate change on the hydrological cycle, water availability, and sedimentation dynamics in the Shyok River basin in the Karakoram region. The study focuses on investigating the increasing outflows on a seasonal basis, as found in the previous studies, by utilising daily river discharge data between 2003 and 2014 at Yugo hydrographic station operated by WAPDA with geographic information systems (GIS), SWAT+ (Soil and Water Assessment Tool), remote sensing, and statistical techniques. To analyse climatic variables, using only available ground weather stations inside the basin, we have utilised the ERA 5 reanalysis dataset to evaluate seasonal precipitation and temperature trends. The significance of ERA5-derived climatic variables has been assessed using the Mann-Kendall test, Sen's slope analysis and the Coefficient of Determination R² from 2000 to 2020 on a monthly basis. Analysis of seasonal discharge data using SWAT+ reveals a decline in water flow from July to October and a general upward trend during the last 20 years, such as a significant decrease in streamflow in the simulated trend, which was 293 m³/s in 2005 and dropped to 158 m³/s in 2017. In contrast, the maximum actual vs. simulated discharge decreased by 10 m³/s in 2010 and 2019, respectively. The temperature has increased by approximately 1.5°C. Seasonal precipitation analysis reveals an increasing trend in winter, while other seasons have shown fluctuating trends. Where the precipitation trends were found to be non-significant, with p > 0.05. An analysis of sediment load and discharge of the model output suggests active erosion in the channel at a rate of approximately 40 megatons/ha. The study highlights the impacts of climate change on water availability and sedimentation dynamics in the Shyok River basin in the Karakoram region. It attempts to contribute to the existing literature on the evaluation of climate-induced changes in river channel morphology. The study also highlights the necessity of continuous climatic and hydrographic data at the basin scale.