Water Discharge and Sediment Transport Variability in a Chinese Coastal River: Effects of Intensive Damming

The present study aimed at assessing the effects of damming waterways on water discharge and sediment load variability in a coastal waterway of the Jiulong River, China. Long term records of water discharge and suspended sediments were divided into pre and post-damming periods and simple linear regressions were applied to find out trends. This was coupled by an analysis of short term suspended sediments data obtained by a field sampling within six months from a representing dam-reservoir in the Jiulong River. The results indicate a 7.9% decrease in cumulative water discharge and a 24% increase in cumulative sediment load from pre to post damming periods. Mean water discharge in the pre-damming period was 83.9×108m3yr-1 compared to 83.7×108m3yr-1 in the post-damming period. Mean sediment load observed in the pre-damming periods was 6.42×105 Kgyr-1 compared to 8.02×105 Kgyr-1 in the post-damming period. In addition, dry seasons of pre-damming period show high sediment load and low water discharge compared to post-damming periods. Suspended sediments in the dam-reservoir were observed increasing with water depth and with distance to dam wall. Long term trends in water discharge and sediment load might have been influenced by other factors including increased population, soil conservation, agricultural land use, soil type and forest cover change in the Jiulong River watershed. Various consequences related to water quality change, increased nutrient concentrations, sediment delivery to the sea, the distribution of particulate trace metals and potential for eutrophication were moderately attributed to the variability of water discharge and sediment load observed in this study.