Diagnosing Climate Change and Hydrological Responses in the Past Decades for a Minimally-disturbed Headwater Basin in South China

Identifying the trends of climate and hydrological changes is important for developing adaptive strategies for effective water resources management. Many studies focused on the prediction of future climate at a regional/global scale using General Circulation Models (GCM) or these models' downscaled outcomes. However, diagnosing historical trends is regarded valuable for local areas, especially considering the spatial heterogeneity (both occurrence and magnitude) of climate change and uncertainty of climate projection. In this study, we selected the headwater area of the East River Basin in South China, which has minimal human-induced disturbance, to detect climate change and its hydrological changes over a past 50-year (1955-2004) time period. Although the climate warming agreed with the global situation, its magnitude was small and no sign of intensified rainfall or change of annual rainfall was found. Nevertheless, no-rain days increased and light-rain days decreased, indicating a longer dry interval between rainfall events. There was a significant downtrend of wind speed with a substantial reduction in magnitude, resulting in a decrease in the estimated potential evapotranspiration and a slight increase in the soil water content. Risks of flooding may not be a big concern, but water availability may be affected marginally in May and June due to the decreased rainfall and increased no-rain days. Overall, our results can improve the understanding of climate change and help watershed managers take precautions when facing climate change. This study also implies the necessity of investigating climate change at a local scale and at different time scales.