Trends And Influencing Factors Of Sea - Going Runoff In Tianjin Area In Recent 60 Years

Trends of precipitation and river discharge to the sea (1950-2009) have been calculated and analyzed by the Mann-Kendall test and Sen’s method, average removing method, locally weighted scatterplot smoothing and wavelet analysis in order to better quantify the hydrological processes and evaluate the role of climate variation and human activities in changing river discharge to Bohai Sea at Tianjin, North China. The results indicated that two obvious decreases in river discharge to Bohai Sea were observed after1965and1980in parallel with the observations before1965.The annual series of precipitation in Tianjin and the Haihe River basin presented downward trends. However, only that in the basin was significant at the95%confidence level and decreased with a rate of1.9mm year-1during1956-2009. If the period of1950-1965was considered as the baseline period, the reductions of river discharge to Bohai Sea in Tianjin were found to be at least66.8%and90.0%in the periods of1966-1979and1980-2009in comparison with6.1%and15.3%decreases in annual precipitation. The wavelet transform analysis result also demonstrated both climate change and human activities were responsible for the decrease of observed river discharge to Bohai Sea in Tianjin area. The combinated method indicated that precipitation had a clear effect on the reductions of river discharge to Bohai Sea in Tianjin, However, Human activities like increased water consumption due to increased population, development of industry and agriculture and urban expansion and damming and building reservoirs in upstream also played an important role. The research results facilitated the understanding of the impact of climate change and human activities on the decrease of river discharge to Bohai Sea in Tianjin and the improvement of sustainable management of regional water resources.