Assessing The Effects Of Dams On Water Discharge And Sediment Load Variability In The Jiulong River

The recent growing concern on sediment load and water discharge has been arisen from climate change and increasing anthropologic activities affecting global rivers which in turn distress marine ecosystems through river input. It is this perspective that the present study aims at assessing the effects of damming waterways on water discharge and sediment load variability in the coastal waterway of the Jiulong River.Long term records of water discharge and suspended sediment were divided into pre and post-damming periods and simple linear regressions were applied to find out long term trends. This was coupled by an analysis of short term suspended sediments data obtained by field sampling within six months (November2013-April2014) from Xipi dam, representing dam-reservoir in Jiulong River.7.9%decrease in cumulative water discharge and24%increase in cumulative sediment load from pre to post-damming periods were estimated. Mean water discharge and sediment load observed in pre-damming period was83.9×108m3/a and6.42×105Kg/a respectively, compared to83.7×108m3/a and8.02×105Kg/a in post-damming period. Dry seasons (i.e. October-April) 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 partially influenced by other factors including increased population, failure of soil conservation measures; agricultural land use, soil type and forest cover change in the Jiulong River watershed. Various consequences such as those related to water quality change, increased nutrient concentrations, water stratification, sediment delivery to the sea, the distribution of particulate trace metals and potential for eutrophication were partially attributed to variability of water discharge and sediment load observed in this study. It is recommended that for appropriate management of river, a similar study would be conducted extending the scope to bed load. To Jiulong River Integrated Watershed Management, an extended study evaluating the environmental flows induced by dams is suggested.