Evidence of climate change impact on stream low flow from the tropical mountain rainforest watershed in Hainan Island, China

Stream low flow estimates are central to assessing climate change impact, water resource management, and ecosystem restoration. This study investigated the impacts of climate change upon stream low flows from a rainforest watershed in Jianfengling (JFL) Mountain, Hainan Island, China, using the low flow selection method as well as the frequency and probability analysis technique. Results showed that low flow at this watershed over a period of 18 years (1990–2007) was 0.58 m³/s and its recurrence probability and recurrence interval were, respectively, 99% and 1.01 years for low flow with a 60-day duration. Low flow rate decreased linearly both as time increment elapsed (R² = 0.62, p < 0.01) and as air temperature rose (R² = 0.60, p < 0.05), whereas the recurrence intervals of low flow were shorter (or occurred more frequently) as time increment elapsed. In contrast, no correlation existed between annual rainfall and low flow for this watershed, indicating that rainfall was not a factor influencing stream low flows. Since there were little to no anthropogenic activities rather than air temperature rise over time at this watershed, we attributed the decreased rate and frequent occurrence of low flow to the warming air temperature as time elapsed.