1. National Institute of Environmental Research A consideration of the hydraulic simulation of a dam to reduce algal bloom S.J. Yu, S.R. Ha*, D.I. Jung, J.Y. Hwang, M.H. Chae National Institute of Environmental Research, Korea Chungbuk National University*

2. National Institute of Environmental Research Background Climate change frequent draught and flooding Water demand increase getting higher dam construction dependency Morphological and climate characteristics in lakes and stream in Korea The status of water quality in waterworks eutrophication Hydraulic control in eutrophicated reservoirs will be a key to reduce algal bloom

3. National Institute of Environmental Research 2 Algal Bloom Forecasting System 1 Daecheong dam reservoir in Korea Weather condition of the reservoir 3 Experimental method 4 Water quality and algal growth 5 Simulation using CE-QUAL-W2 6 Conclusion7 Content

4. National Institute of Environmental Research Janggye(T1) Chuso(T1) Hoinam(T2) Chudong(T2) Munyi (T3) Dam(M3) Experimental method Daily inflow, outflow, intake data www.warmis.go.kr www.warmis.go.kr Bathymetry data (KOWACO,2004) Meteorogical input data : temp., wind direction, wind speed, cloud, etc. (www.kma.go.kr) Water quality item at 6 points temp., Chl-a, COD etc. ( Guem river water quality lab., NIER) Daily inflow, outflow, intake data www.warmis.go.kr www.warmis.go.kr Bathymetry data (KOWACO,2004) Meteorogical input data : temp., wind direction, wind speed, cloud, etc. (www.kma.go.kr) Water quality item at 6 points temp., Chl-a, COD etc. ( Guem river water quality lab., NIER)

5. National Institute of Environmental Research Morphological and watershed characteristics Reservoir area 64.3 km 2 Watershed area 4,166.8 km 2 Reservoir length 86 km Mean depth 23.5 m Water capacity 1,490×10 6 m 3 Effective capacity 790×10 6 m 3 Yearly average inflow, outflow 2.76×10 9, 2.75×10 9 m 3 /s Hydraulic residence time 0.68 year Urban area in drainage basin 55 km 2 (1.3%) Paddy area 678 km 2 (16.3%) Forest and mountain area 3,107 km 2 (74.5%) Total population in drainage area 332,580 persons Daecheong dam reservoir in Korea Artificial dam for multipurpose Dendritric shaped stream network with 80 km long The catchment area of the dam reservoirs is covered with mountainous area with a forest Nutrient load is mainly originated from diffuse pollution sources

6. National Institute of Environmental Research Morphological status and sites Morphological status and sites Morphological status in Daecheong Reservoir Water Intake Tower Hoinam Dam Munyi Chudong Chuso Wastewater Treatment Plant

7. National Institute of Environmental Research CODTNTP Total load (ton/year)11,7943,407286 Base load (ton/year)3,8541,34098 Nonpoint pollution load (ton/year)7,9392,068188 Nonpoint pollution rate (%)67.360.765.7 Monthly pollutant loading to Daecheong Dam reservoir, 2002 Non-point source contribution rate in total pollution loading, 2002 Pollutant load in the reservoir Hydrodynamics and water quality in the reservoir are strongly influenced by a local monsoon climate

8. National Institute of Environmental Research Algal Bloom Forecasting System Algal Bloom Forecasting System LevelStandards Algal Caution Level 15-25 mg/m 3 Chlorophyll-a 500-5,000 cyanobacteria cells/ml be satisfied both condition with 2 times continuous data Algal Warning Level more than 25 mg/m 3 Chlorophyll-a more than 5,000 cyanobacteria cells/ml be satisfied both condition with 2 times continuous data Algal Outbreak Level more than 100mg/m Chlorophyll-a and 100 cyanobacteria cells/ml, and scum be satisfied both condition with 2 times continuous data Water quality deterioration and algal toxins in waterworks Duration : April to November 10 reservoirs

9. National Institute of Environmental Research DateJuneJulyAug.Sept.Oct. Site 2001 Hoinam (84day) 2002 Munyi(16day) 2003 Hoinam(61day), M2 Chudong(78day), T2 Munyi(78day), T3 2004 Muni(14day) 2005 Hoinam(67day) Chudong(30day) Munyi(30day) Chudong (T2) Hoinam(M2) Munyi,(T3) Algal caution level Algal warning level Algal outbreak level The status of Algal Bloom Forecasting System Heavy rainfall Low duration of sunshine draughty season Where nutrients come from?

10. National Institute of Environmental Research Water quality and algae M1T1M2T2M3T3 Main stream0.510.920.58 boundary0.880.710.33 The relationship between COD & chl-a in the surface water Is chl-a not always correlated with COD ?

11. National Institute of Environmental Research Hoinam, M2 Chuso, T1 Munyi, T3 Alagal propagation characteristics Alagal propagation characteristics After August, the number of cyanobacteria were dominant Cyanobacteria increase in high temperature

12. National Institute of Environmental Research * KOWACO (http://warmis.or.kr) Weather condition of the reservoir Monthly circulation rate influence on water current to move nutrient and algae !!

13. National Institute of Environmental Research Reliability of bathymetry file in the reservoir - water level (2001, 2003) Stratification of the reservoir The comparison between velocity and algal propagation Water current, temperature variation by hydraulic simulation(2003) Two scenarios based on augmentation of spill flow Simulation using CE-QUAL-W2 To interpret water current, water temperature of the reservoir To consider the hydraulic condition to reduce algal bloom

14. National Institute of Environmental Research CE-QUAL-W2 model is based on the assumption that flow and transport phenomena in lake with a distinct flow direction and a regular bathymetry can be computed from laterally integrated Navier-Strokes equation (Bloss et al., 1998). Flow and the distribution of heat are governed mainly by a dynamic balance between the advection transport in the longitudinal (and to some extent vertical) direction and the turbulence (diffusive) transport in the vertical direction. Water Quality Conservative tracer SS, Coliform bacteria, TSD Labile-, Refractory-DOM Algae Labile-, Refractory-POM Phosphorous NH3, NOX- nitrogen DO, pH, CBOD CO2, HCO3, CO3 Fe etc. (22 items) CE-QUAL-W2 Model CE-QUAL-W2 Model

15. National Institute of Environmental Research Model application in the reservoir Str. Sokcheon Main str. Geum river Dam 6 branches with different direction 117 segments so as be right against water flow 26 layers with 2 m interval in depth Period : 2001, 2003 Simulated Water Quality : Temp., Water velocity

16. National Institute of Environmental Research Model parameter

17. National Institute of Environmental Research * KOWACO(http://warmis.or.kr) 자료 Reliability of hydrodynamic model Reliability of hydrodynamic model Computing the distribution in terms of current discharges, velocities and the change in water surface elevation. Good agreement : water surface elevation from 63m to 78 m

18. National Institute of Environmental Research Calibration and verification Calibration and verification M1 M2 M1 M2 M3

19. National Institute of Environmental Research Calibration and verification Calibration and verification T1 T2 T3 T1 T2 T3

20. National Institute of Environmental Research The Stratification by temperature 26 ∼ 28 ℃ Main streamBoundary A important factor to induce algae propagation and cyanobacteria growth

21. National Institute of Environmental Research Chudong, T2 Hoinam Muni,T3 Chuso YearJuneJulyAug.Sept.Oct. Site(days) 2001 Hoinam (84) 2002 Munyi(16) 2003 Hoinam(61) Chudong(78) Munyi(78) 2004 Muni(14) 2005 Hoinam(67) Chudong(30) Munyi(30) urrent with density flow Water current with density flow nutrient Finally, back flow in the middle layer toward T2 and T3 resulted in nutrient supply. Back flow

22. National Institute of Environmental Research YearJuneJulyAug.Sept.Oct. Site(days) 2001 Hoinam (84) 2002 Munyi(16) 2003 Hoinam(61) Chudong(78) Munyi(78) 2004 Muni(14) 2005 Hoinam(67) Chudong(30) Munyi(30) urrent Water current Chudong, T2 Hoinam Munyi, T3 Chuso As temperature increased at the surfacewater, algal caution level occurred

23. National Institute of Environmental Research Chudong,T2 Hoinam Munyi,T3 Chuso YearJuneJulyAug.Sept.Oct. Site(days) 2001 Hoinam (84) 2002 Munyi(16) 2003 Hoinam(61) Chudong(78) Munyi(78) 2004 Muni(14) 2005 Hoinam(67) Chudong(30) Munyi(30) urrent Water current In according to temperature increase, algaecontinued to propagate in the stagnate zone withshallow depth

24. National Institute of Environmental Research Through the control of outflows, hydraulic condition during a storming shows dramatic changes not only temporally but also spatially due to an inner hydraulic balance of fluid flows (black dotted line). Considering outflow augmentation to control nutrient transport and temp. for the management of algal growth Two scenarios ; spill flow increase so as to maintain water level above 65 m - 1 st : after the early of August - 2 nd : 1 st + after the end of August Scenarios by spill flow augmentation Outflow changeWater level change

25. National Institute of Environmental Research Water current change Water current change Back water current Simulation results : proceed toward dam site 2 nd simulation results within proper velocity after heavy rainfall

26. National Institute of Environmental Research Temperature variation by scenarios T2 M2 T3 M2T2T3 it induced in the instability of water body of the stagnate zone so that water temperature declined. temperature drop Period shorten

27. National Institute of Environmental Research Conclusion This study is aimed to estimate the water current and temperature effect to reduce algal bloom by the simulation of dam spill flow control using water quality model, CE- QUAL-W2 in 2003. Water current was resulted in nutrient transport from the upstream of main reservoir and nutrients were delivered up to downstream by fast water velocity. Algal blooms occurred in stagnated zone of main reservoir downstream as the current of downstream was retarded according to dam out control.

28. National Institute of Environmental Research Conclusion Consequently, water balance in stagnate zone triggered a rise of water. The simulation result by outflow control scenarios showed that spill flow augmentation induced in water body instability of stagnate zone so that water temperature declined. It could be suggested that outflow control minimized algal bloom in the downstream in the flooding season as long as water elevation is maintained properly.

29. National Institute of Environmental Research A consideration of the hydraulic simulation of a dam to reduce algal bloom