MINISTRY OF EDUCATION NHA TRANG UNIVERSITY _ BUI VINH DAI ASSESSMENT OF O LOAN LAGOON’S WATER QUALITY FOR AQUACULTURE SECTOR BY MIKE 21 MODEL UNDER THE IMPACTS OF CLIMATE CHANGE MASTER THESIS KHANH HOA – 2017 MINISTRY OF EDUCATION NHA TRANG UNIVERSITY _ BUI VINH DAI ASSESSMENT OF O LOAN LAGOON’S WATER QUALITY FOR AQUACULTURE SECTOR BY MIKE 21 MODEL UNDER THE IMPACTS OF CLIMATE CHANGE MASTER THESIS Major: Code: Topic allocation Decision Decision on establishing the Committee: Defense date: Supervisor: Ass.Prof Ngo Dang Nghia Chairman of Committee: Ass.Prof Pham Quoc Hung Faculty Studies: of Graduate KHANH HOA – 2017 DECLARATION I hereby declare that this thesis titled “Assessment of O Loan lagoon’s water quality for aquaculture sector by Mike 21 model under the impacts of climate change” is the result of my own research It is original and no part of this work has been submitted for any other degrees or diploma All the given information is true to best of my knowledge Nha Trang, 25th April 2017 Bui Vinh Dai TABLE OF CONTENTS LIST OF FIGURES v LIST OF TABLES vii ACKNOWLEDGEMENT viii ABSTRACT ix PREFACE x CHAPTER INTRODUCTION AND LITERATURE REVIEW .1 1.1 Application of numerical models for assessment of water quality 1.1.1 International 1.1.2 In Vietnam .3 1.1.3 Numerical model: MIKE 21 1.2 Case study: O Loan lagoon .5 1.2.1 Natural characteristics 1.2.2 Community characteristics 1.2.3 Aquaculture sector 1.2.4 Environmental problems in O Loan lagoon 1.3 Research plan 11 CHAPTER METHODOLOGY 12 2.1 Data collection and Aggregation 12 2.2 Data processing 13 2.3 Assessment of water quality 13 2.4 Modeling method 14 CHAPTER 3: APPLICATION MODEL, RESULTS AND DISCUSSIONS 17 3.1 Model Application 17 3.1.1 Input data .17 3.1.2 Creating Mesh .23 3.2 Mike 21 Ecolab calibration 26 3.3 Model results in 2013 and 2014 .30 3.3.1 Hydrodynamic .30 3.3.2 Simulation results of pollution dispersion in 2013 and 2014 34 3.4 Model results in 2016 .45 iii 3.4.1 Hydrodynamic .45 3.4.2 Simulation results of pollution dispersion in 2016 49 CHAPTER CONCLUSION AND RECOMENTDATIONS 62 4.1 Conclusion 62 4.2 Recommendations 62 REFERENCES 64 APPENDICES iv LIST OF FIGURES Figure 1.1: Map of O Loan lagoon Figure 1.2: Shrimp farming in O Loan lagoon Figure 1.3: Total production and aquaculture area in O Loan lagoon in 2014 Figure 2.1: A flowchart of Mike 21 modules 15 Figure 3.1: O Loan lagoon’s bathymetry extracted from Mike 21 FM 18 Figure 3.2: Water level monitoring in O Loan lagoon (October, 2013) 19 Figure 3.3: Water level monitoring in O Loan lagoon (March, 2013) 19 Figure 3.4: Tidal water level monitoring in Tan Quy mouth (Octorber, 2013) 20 Figure 3.5: Tidal water level monitoring Tan Quy mouth (March, 2014) .20 Figure 3.6: Water sampling sites in O Loan lagoon 23 Figure 3.7: O Loan lagoon mesh extracted from Mike 21 FM 24 Figure 3.8: Domain boundaries in O Loan lagoon extracted from Mike 21 FM 25 Figure 3.9: COD calibration, 10/2013 .27 Figure 3.10:COD calibration, 3/ 2014 .27 Figure 3.11: BOD calibration, 10/2013 27 Figure 3.12: BOD calibration, 3/2014 .27 Figure 3.13: TSS calibration, 10/2013 .28 Figure 3.14:TSS calibration, 3/2014 28 Figure 3.15: N-NO3- calibration, 10/2013 .28 Figure 3.16: N-NO3- calibration, 3/2014 28 Figure 3.17: PO43- calibration, 10/2013 29 Figure 3.18:PO43- calibration, 3/2014 29 Figure 3.19: Current flow pattern during high tide (0:00, 11/10/2013) 31 Figure 3.20: Current flow pattern during low tide (8:00 am,10/10/2013) 32 Figure 3.21: Current flow pattern during high tide (2:00 pm, 24/3/2014) 33 Figure 3.22: Current flow pattern during low tide (11:00 pm,24/3/2014) .34 Figure 3.23: Distribution of average COD concentration, 10/2013 35 Figure 3.24: Distribution of average COD concentration, 3/2014 36 Figure 3.25: Distribution of average BOD concentration, 10/2013 37 Figure 3.26: Distribution of average BOD concentration, 3/2014 38 Figure 3.27: Distribution of average TSS concentration, 10/2013 39 v Figure 3.28: Distribution of average TSS concentration, 3/2014 40 Figure 3.29: Distribution of average N-NO3- concentration, 10/2013 41 Figure 3.30: Distribution of average N-NO3-concentration, 3/2014 42 Figure 3.31: Distribution of average P-PO43-concentration, 10/2013 .43 Figure 3.32: Distribution of average P-PO43 concentration, 3/2014 44 Figure 3.33: Current flow pattern during high tide (5:00 pm, 18/3/2016) 45 Figure 3.34: Current flow pattern during low tide (2:00 am, 19/3/2016) 46 Figure 3.35: Current flow pattern during high tide (11:00 pm, 20/10/2016) 47 Figure 3.36: Current flow pattern during low tide (7:00 am, 20/10/2016) 48 Figure 3.37: Distribution of average COD concentration, 3/2016 49 Figure 3.38: Distribution of average COD concentration, 10/2016 50 Figure 3.39: Distribution of average BOD concentration, 3/2016 51 Figure 3.40: Distribution of average BOD concentration, 10/2016 .52 Figure 3.41: Distribution of average TSSconcentration, 3/2016 .53 Figure 3.42: Distribution of average TSS concentration, 10/2016 54 Figure3.43: Distribution of average N-NO3-concentration, 3/2016 55 Figure3.44: Distribution of average N-NO3- concentration, 10/2016 56 Figure 3.45: Distribution of average P-PO43-concentration, 3/2016 57 Figure 3.46: Distribution of average P-PO43- concentration, 10/2016 58 vi LIST OF TABLES Table 1.1: Distribution of population in O Loan lagoon, 2014 .8 Table 1.2: Type of shrimp farming in O Loan lagoon in 2014 .9 Table 2.1: Data collection and sources 12 Table 2.2: Summary of water quality standards relevant to coastal water aquaculture .13 Table 3.1: Water depth in O Loan lagoon 17 Table3.2: Wind speed in O Loan lagoon 21 Table 3.3: Pollution loading in O Loan lagoon, 2014 22 Table 3.4: Initial conditions of Mike 21 Ecolab 26 Table 3.5: Pollution dipersion coefficients 29 vii ACKNOWLEDGEMENT First of all, I would like to express my sincere gratitude to NOHERD project for giving me a chance to study in international environment with experts and students from many countries around the world I would like to send my deep appreciation to my supervisors: Ass Prof Ngo Dang Nghia for his supports and teaching me from beginning to ending this master course, Prof.Sigurd Stefansson and Prof Henrik Glenner for giving me useful advices for my thesis My study could not be finished without their assistances My sincere gratitude goes to Ms Tran Xuan Hoang – Institute for Environment and Resources who help me to use Mike 21 model and Ms Nguyen Thanh Son who allow me to use data in his project I also express thanks to The South Central Station for Hydro - Meteorological and Institute of Nha Trang Oceanography give me data on hydro-meteorological for running the model I would like to thank all my Cohort classmates who have supported me in this course Finally, this thesis is dedicated to my family who have always stood by me and supported in my life viii ABSTRACT The economic activities in coastal area have been causing negative impacts on the environment nowadays O Loan is a coastal brackish water lagoon in Tuy An district, Phu Yen province It is a famous tourist destination and a national-level landscape of Phu Yen province However, the quality of water in the lagoon is currently being polluted by livelihood activities of people living around the lagoon, aquaculture in particular In addition, the influences of climate change in recent years have attributed to deterioration of water environment in area There have not been any studies using numerical model to assess its impacts on water quality in O Loan lagoon yet The purpose of the research is to create a numerical model to simulate hydrodynamics and dispersion process of pollutants in dry season and rainy season under the impacts of climate change aspects from pollution sources in lagoon and assessment water quality for aquaculture activities Among many numerical models exit today to simulate the dispersion process of pollutants, the Mike 21 model developed by DHI has been used because of many strong features Mike 21 model is a comprehensive coastal model to simulate hydrodynamics, sand transport, mud transport and advection-diffusion of pollutants The input data was collected from vary sources and model calibration based on data of water quality monitoring in O Loan lagoon in 2013 and 2014 by Ms Nguyen Thanh Son conducted Assessment of water quality for aquaculture based on available standards including: National technical regulation on coastal water quality applying for aquaculture and aquatic life conservation area ( NTR 10 : 2008/MONRE) approved by VietNam Ministry of Natural Resources and Environment and ASEAN Marine Water Quality Criteria The model results were found to be in good agreement with surveyed data and shown hydrodynamics pattern and dispersion process of five pollutants including COD, BOD, TSS, NO3-, PO43- in dry season and rainy season under vary hydro-meteorological conditions In general, the water quality in rainy season is better than in dry season The local pollution phenomenon appears in the Southwest and Northwest in O Loan lagoon for both seasons Evaluation of climate change impacts shows that it is greatly effect on simulation results, the quality of water is deteriorating in dry seasonwhile there was an improvement in rainy season In conclusion, limitations of the research and future direction are outlined ix ... lagoon, the trainee Bui Vinh Dai has decided to conduct a research title: "Assessment of O Loan lagoon’s water quality for the Aquaculture sector by Mike 21 model under the impacts of climate change" ... modules, the module MIKE 21 FM is the core of the MIKE 21 modeling suite It calculates hydrodynamic regime to build up the foundation for other modules The strong features of Mike 21 model compared... HOA – 2017 DECLARATION I hereby declare that this thesis titled ? ?Assessment of O Loan lagoon’s water quality for aquaculture sector by Mike 21 model under the impacts of climate change? ?? is the