Spatial Trend of Summer Precipitation and its Implications for Flood Risks in the Huaihe River Basin, China

Trend detection of hydrological variables is important in the understanding of flood risks in a river basin. Nonparametric technique was applied to the analysis of summer precipitation in Huaihe River Basin (HRB). Results shows that mean precipitation varies greatly with greater values occurring in July temporally, and that greater values occur in the southern and eastern HRB and smaller values in the western and northern HRB spatially. In June, four stations, Xuzhou, Bengbu, Baofeng and Xuchang, which are in the upper to the middle reaches of the HRB, exhibit a statistically significant increasing trend; two stations show significant decreasing trend and one station increasing trend in July, they are Juxian, Rizhao and Kaifeng respectively, these three stations are mostly in the northern HRB; no significant trend is detected in August. Xihua and Rizhao have statistically significant increasing trend and decreasing trend in summer precipitation respectively. The Hurst H values indicate that there could be a slight decreasing trend in Gaoyou, Xuyi, Bengbu and Shangqiu in summer precipitation. For the rest stations, the future tendency of summer precipitation would be consistent with those of the past years. A long-range dependence characteristic exists in precipitation means that summer precipitation will maintain a detected significant decreasing trend in Rizhao and increasing trend in Xihua in the near future. Considering the trend of summer precipitation, it can not conclusively say that the flood risks are predominantly caused by climate change in the HRB, for the precipitation demonstrates no significant increasing trend in the HRB. Therefore, a more detailed research on the climate change and human activities is needed to obtain a wider understanding of the flood risks.