Streamflow annual distribution and its influencing factors in Dongjiang River,South China

The spatial-temporal variability of streamflow annual distribution during 1956 to 2009 in the Dongjiang River is analyzed.Both monthly observed and naturalized streamflow data and the monthly regional precipitation data are used in the study.The trend and change-point analysis are performed on the data to reveal the characteristics of streamflow.Likely contributions from various factors to the streamflow annual distribution are quantitatively analyzed.These factors include the climate change,the land use and coverage changes,the regulation of water reservoirs and the water consumption.The results show that the significant decreasing trend and change points in 1973 can be identified on the concentration and the nonuniformity in the observed streamflow data.The average change of the concentration degree in the naturalized streamflow data and the regional precipitation change are marginal.However,the nonuniform coefficient during 2000 to 2009 is significantly larger than that during the periods 1980-1989 and 1990-1999.The bigger catchment area is,the greater the concentration and the nonuniformity will be.The decrease of the concentration and nonuniformity is due to the effect of the regulations of water reservoirs and the land use and coverage changes;while,the increase is the result the water consumption and the climate change.The contributions to the spatial-temporal variability of streamflow annual distribution from the regulation of water reservoirs,the land use and coverage changes,the water consumption,and the climate change are respectively-33.5%,-9.0%,4.5% and 1.0%.Among the contribution from the regulation of water reservoirs,the Xinfengjiang,Fengshuba,and Baipenzhu reservoirs contribute-21%,-10%,-2%,respectively.There is an upward tendency in the contribution from the land use and coverage changes and the water consumption in the past 30 years.