Impacts of Climate Variability and Human Activities on Streamflow in the Wanquan River Basin along the East Coast of Hainan Island, Southern China.

Zhao, Y.; Zou, X.; Liu, Q., and Chen, Y., 2019. Impacts of climate variability and human activities on streamflow in the Wanquan River Basin along the east coast of Hainan Island, southern China. Journal of Coastal Research, 35(2), 410–419. Coconut Creek (Florida), ISSN 0749-0208. The influences of climate change and human activities on streamflow change have received significant attention recently. In this study, daily data from seven precipitation gauges and one hydrological station are analyzed to assess the impacts of climate variability and human activities on streamflow over the past 54 years in the Wanquan River Basin (WRB). The Mann-Kendall test and Morlet wavelet method were employed to analyze the streamflow series, and the relative effects of climate change and human activities were empirically determined based on a coupled water and energy budget analysis. The results show that annual streamflow exhibited a statistically insignificant decreasing trend throughout the entire basin at an annual rate of –0.015 × 10⁸ m³/y. Meteorological factors, such as temperature, exhibited significant increases throughout the entire basin. A decreasing trend in precipitation and an increasing trend in potential evapotranspiration were identified in the upstream region, whereas the opposite trends were observed in the downstream region. Moreover, an abrupt change in streamflow at Jiaji station occurred in 1974, exhibiting periodicities of 2 to 4 and 8 to 11 years at a 95% confidence level during the periods of 1965–80 and 1970–75, respectively. Regarding the catchment-averaged water balance, a quantitative analysis revealed that climate change resulted in an increase in streamflow from the 1970s to the 2000s throughout the entire basin, and streamflow increased by 146%, 259%, 473%, and 128% in the 1970s, the 1980s, the 1990s, and 2000–13 relative to streamflow in the 1960s. However, human activities may have decreased streamflow (–46%, –159%, –373%, and –28% in the 1970s, the 1980s, the 1990s, and 2000–13, respectively). Therefore, the relative effect of climate change was greater than that of human activities. Further research is needed to clarify the mechanisms associated with the anthropogenic effects on runoff changes. [ABSTRACT FROM AUTHOR]