Author(s): Il Won Seo, Jun Song Kim
Linked Author(s): Jun Song Kim
Keywords: Harmful algal bloom (HAB), pulse discharge, depth-averaged advection-dispersion-reaction model (ADRM), water temperature function, Nakdong River.
Abstract: Due to climate change, multi-purpose weirs are built across the rivers in South Korea to resolve drought problems. As for change of flow condition by these hydraulic structures, weir operation strategies have been considered as crucial part to control harmful algal bloom (HAB). HAB impairs ecological values in river ecosystems as this green-colored biomass of cyanobacteria involves toxicity and bad odor. This study is aimed at investigating effective approaches of pulse discharge from weirs to restrain HAB, using a 2D finite element model (FEM). In this study, the depth-averaged advection-dispersion-reaction model (ADRM) is used to analyze the transport and growth characteristics of cyanobacteria in the shallow water flow. Furthermore, the spatial-temporal measurements in the Nakdong River, South Korea are used to derive a water temperature function to calculate the growth rate of cyanobacteria and calibrate the model. As a result of the model calibration, simulation results showed a good agreement with the spatial measurements as showing average MAPE less than 13 %. Using the calibrated model, several weir operation scenarios with the pulse discharge from Gangjeong weir located at the upstream of the study area are simulated, varying duration time, frequency and total volume of the discharge. According to the simulation results, the reduction rate is not proportional to the frequency and duration time but increasing with the optimal combination of the both variables as ranging from 3. 82 to 4. 45 % in the reduction rate at a fixed amount of the flushing water
Year: 2017