Assessment of o loan lagoons water quality for aquaculture sector by mike 21 model under the impacts of climate change

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 chan

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

IMPACTS OF CLIMATE CHANGE

MASTER THESIS Major:

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 1 1

INTRODUCTION AND LITERATURE REVIEW 1

1.1 Application of numerical models for assessment of water quality 1

1.1.1 International 1

1.1.2 In Vietnam 3

1.1.3 Numerical model: MIKE 21 4

1.2 Case study: O Loan lagoon 5

1.2.1 Natural characteristics 5

1.2.2 Community characteristics 7

1.2.3 Aquaculture sector 8

1.2.4 Environmental problems in O Loan lagoon 9

1.3 Research plan 11

CHAPTER 2 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

3.4.1 Hydrodynamic 45

3.4.2 Simulation results of pollution dispersion in 2016 49

CHAPTER 4 CONCLUSION AND RECOMENTDATIONS 62

4.1 Conclusion 62

4.2 Recommendations 62

REFERENCES 64 APPENDICES

LIST OF FIGURES

Figure 1.1: Map of O Loan lagoon 6

Figure 1.2: Shrimp farming in O Loan lagoon 8

Figure 1.3: Total production and aquaculture area in O Loan lagoon in 2014 9

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

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

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

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 1 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

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

PREFACE

Sited at about 22km away from the city of Tuy Hoa in the North, O Loan lagoon is a typically coastal lagoon in mainland of Tuy An district, Phu Yen province, stretching from North to South O Loan lagoon is a approximately 17.5 km2 area with an average depth of 1.2 – 1.4 m This is a famous national landscape attracted tourists visiting Phu Yen province Surrounding the lagoon, there are 50.000 people living on five communes, whose livelihood has been getting from Agriculture, Tourism-service, Aquaculture and Fishing sector Aquaculture sector plays an important role and affects directly the day-to-day living of thousands of people However, in recent years, the dramatic increase in area

of aquaculture without reasonable planning strategy and the discharge of wastewater directly into lagoon have led to deterioration of water quality, affecting economic activities of people lived around

The untreated wastewater from aquaculture has been discharged directly into the O Loan lagoon The dynamic process (flow, wind, tidal pattern, disturbance ) causes diffusion process and brings pollutants in wastewater distributing over places of lagoon followed flow in local tidal pattern Moreover, in recent year, this area has witnessed increasing impacts of climate change The extreme weather phenomena such as: droughts and floods, thunderstorms, cyclones…have occurred frequently in dry and rainy seasons, affecting the lives of the people here

One of the approaches in studying impacts of wastewater sources is using mathematical models to calculate and simulate physical and biochemical process in interested area The results from model integrated actual data survey can continually simulate the dynamics and material transport process occurring in lagoon

A number of studies have been carried out in O Loan lagoon such as Survey of bottom sediment of Phu Khanh coastal area (Institute of HDH, 1997); Research on fisheries resources in O Loan lagoon (Nguyen Van Chung and Huynh Quang Nang, 1980); Study

of geomorphology and surface sediments (Pham Van Thom et al, 1981); Environmental quality in O Loan lagoon, Phu Yen province (Le Thi Vinh et al, 2009); Application of remote sensing and GIS in the study fluctuations shoreline at O Loan lagoon area from

1965 to 2011 (Tran Van Binh et al, 2011); Study of erosion - accretion processes and inlet opening/closing phenomenon in O Loan lagoon, Phu Yen province (Tran Van Binh and

Le Dinh Mau, 2012); Assessing the environment status and the risk of environmental catastrophe in O Loan lagoon, Tuy An district, Phu Yen province (Nguyen Thanh Son et

al, 2016) These studies provided quite adequate evaluation of aquatic resources, water and sediment quality, geomorphology and data on the socio-economic situation surrounding O Loan Lagoon However, no present studies has been conducted in the O Loan lagoon to assess the hydrodynamic regime and the dispersion of pollutants as well as those from pollution sources discharged into the lagoon under the influence of climate change, which is one of the most challenges facing us in early years of the 21st century Realizing the environmental problems occurring in O Loan 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" in order to simulate the pollutants dispersion that can affect

aquaculture sector in O Loan lagoon, Phu Yen province To assess the impacts of water pollution on aquaculture activities, the author selected recognized environmental parameters including: Nutrient Pollution Index (NPI) NO3-, PO43-, Organic Pollutant

Index (OPI) COD, BOD, TSS The data is get from the provincial research project:

“Assessing the environment status and the risk of environmental catastrophe in O Loan lagoon, Tuy An district, Phu Yen province" chaired by Nguyen Thanh Son and

The South Central Station for Hydro - Meteorological and Institute of Nha Trang Oceanography Trainee uses the Mike 21 modeling suite to simulate the pollutant dispersion that can be causing the water pollution for aquaculture in two seasons: the rainy season of 2013 and dry seasons of 2014 and assess impacts of climate change on this process in 2016 in O Loan lagoon

The results of the thesis provide additional scientific information on the impact of environment parameters for the aquaculture sector under different dynamics conditions

in O Loan lagoon This work also contribute to helping managers give more flexible responses, suitable planning policies for aquaculture activities in order to protect environment and improves the quality of people’s life in lagoon

CHAPTER 1

INTRODUCTION AND LITERATURE REVIEW

1.1 Application of numerical models for assessment of water quality

1.1.1 International

Numerical modeling is frequently used to assess water quality in coastal water area, estuary and sea over the world The application of numerical models can vary depending on the objectives and purposes of each research There are a number of models that are normally used to assess the water environmental quality, which are: The WASP7 model (Water Quality Analysis Simulation Program 7) is an enhancement of the original WASP is used to describe and predict the water quality to assist the managers in making decisions and taking measures to deal with environmental pollution problems This model allows users to spatially apply one, two and three-dimensional space with diversity of the composition of pollutants The WASP model can also be linked to hydrodynamic and sediment transport models to obtain flow regime, temperature, salinity and sediment loading The WASP model was used to simulate the anaerobic process in Tampa Bay; Phosphorus supply for Okeechobee Lake Anaerobic process at Neuse River; Pollution of biodegradable organic materials in the Delaware river, Heavy metal pollution in Deep River, North Carolina (Di Toro et al., 1983; Connolly and Winfield, 1984; Ambrose, R.B et al., 1988).The AQUATOX model simulates the aquatic ecosystem The model can forecast the decline process attributed to various types of environmental pollutants such as nutrients, organic chemicals and assess influences of process on entire ecosystem including fish, invertebrates and aquatic plants The AQUATOX model is an effective tool for the environmentalists, biologist and others who are interested in risk assessment and declining process of aquatic ecosystems (Robert A Pastorok et al., 2013)

The QUAL2K model (River and Stream Water Quality Model) was upgraded from the previous model (QUAL2E or Q2E) This one-dimensional model simulates the water quality in the streams and rivers involving the water disturbances process A flexible

feature of this model is that it isable to run in the Visual Basic Operating System and Excel software The characteristics of this model can be calculated on each segment of the river and its tributaries, the nitrogen cycle, based on nitrogen process to present carbon compounds and the ability of oxygen and nutrient exchange between sediment and water (Brown and Barnwell 7, 1987)

The DELFT 3D model (designed by Netherland Hydraulic Institute) allows combination of three-dimensional hydrodynamic model and water quality model The advantage of this model is the combination of complex modules to provide simulating results for multi-substances and processes involved (Anton J Schleiss, Giovanni De Cesare, 2014)

The SMS model (designed by Center for research and technical development of United States military) allows combination of one and two-dimensional hydraulic model with water quality model, in which, the RMA4 module is the numerical model of water quality elements uniformly distributed with depth It can be calculated in one-dimensional mesh or two- dimensional mesh (Militello and Zundel, 1999)

The ECOHAM model (version 1 and 2) is a 3D numerical model combining hydraulic module and ecological module that was developed by the research team of the Hamburg University (Germany) This model calculated based on cycles of nitrogen and phosphorus components It also can be calculated for both plants and zooplankton

in the seawater (Moll, 1997, 1998)

The BASINS model (Designed by EPA- United States Environmental Protection Agency) assists the assessment of environmental information system, environmental analysis system and analyzing of management measures One of the advantages of this model is already included in the new approach based on river basin incorporating spatial data through GIS geographic information system The Basins model can be used for the following purposes: Simulating the conditions of the basin and assessing the status of water quality, scenarios of pollution source, the impact of land use changing related to water balance, development of basins management measures The parameters of the model include nutrient compounds of nitrogen and phosphorus, DO, BOD, pesticides, sediment (Grady Hanrahan, 2010)

The MIKE 21 model is an engineering software developed by Danish Hydraulic Institute (DHI) and be commercialized It is used to simulate the hydraulic regime, water quality and sediment transportation in coastal, estuary area and the sea There are many modules integrated in the model Mike 21 suite and depending on research objectives these modules will be used The Mike 21 modeling suite has been used popularly in coastal engineering and application in many countries around the world (Sébastien Erpicum et al., 2016).

1.1.2 In Vietnam

In Viet Nam, application of the numerical modeling in environmental studies in coastal and estuary received attention in recent years Numerical models have been used to calculate water pollution in coastal area in many studies such as: Institute of Natural Resources and Marine Environment - Institute of Science and Technology of Vietnam under supported of the Japanese Government (Program JICA, 1995 - 1998) was initially used the Flux and Budget methods running on dedicated software CABARET of LOICZ (USA) to evaluate the accumulation and diffusion of pollutants

in Ha Long Bay Then, this research method was used to calculate the nutritional level

of the Tam Giang - Cau Hai lagoon (Hue province, Viet Nam) However, a disadvantage of this method is that it does not calculate the process of material diffusion in space and confined in a number of certain points (Truong Van Tuyen et al., 2006)

In Ministry of Fishery project, Tran Luu Khanh studied the carrying and purification capacity in fishing cages area in Phat Co (Quang Ninh province) and Tung Gau (Hai Phong province) The study based on the nutrient and organic metabolism process integrated the hydrodynamic processes in area (Tran Luu Khanh, 2004)

self-Phan Minh Thu, Nguyen Huu Huan (1999) were used the method of modelling biological processes to study the self- purification process in Nha Trang bay under impact of domestic wastewater However, this study did not calculate the influence of coastal hydrodynamic (transportation, diffusion) under the tidal pattern

Thai Ngoc Chien, Nguyen Tac An, Bui Hong Long (Institute of Nha Trang Oceanographic) were used the 3-dimensional ECOHAM model to calculate nutrient

dynamics in Van Phong Bay (Khanh Hoa province) and given out the seasonal fluctuations of nitrogen and phosphorus concentration in the Bay (Bui Hong Long et al., 2006)

A project chaired by Vietnam Academy of Science anh Technology has been carried out to study the carrying capacity of Cam Ranh Bay by the ECOSMO model Project used model to calculate the pollutants dispersion, biochemical processes in order to assess self-purification capacity in Bay (Phan Thanh Bac, 2012)

Nguyen Chi Cong – Ha Noi university of Natural Science, 2012 was used Mike 21 model to calculate pollutants dispersion in Nha Trang bay from Cai river and Tac river Simulation results from model give an overview of sea water quality in Nha Trang’s beaches which are affected by untreated domestic wastewater from city discharging into the Bay in recent years (Nguyen Chi Cong, 2012)

In O Loan lagoon, there are a number of studies undertaken but their focus on assessment of environmental situation, fishery resources, socioeconomic status There

is no study using numerical models to simulate the process of pollution dispersion under impacts of dynamics process and climate change Application of Mike 21 model

to calculate water quality for economic activities, aquaculture sector in particular is an approach trainee chose

1.1.3 Numerical model: MIKE 21

The MIKE 21 model is dedicated software is developed by Danish Hydraulic Institute (DHI) used to simulate the hydraulic regime, water quality and sediment transportation

in the river estuary, coastal and the sea There are many modules in MIKE 21 modeling suite with vary features such as:

 Hydrodynamics module (MIKE 21/3 HD)

 Spectral Wave module (MIKE 21 SW)

 Littoral Processes and Coastline Kinetics ( LITPACK)

 Flood Forcasting ( MIKE 21 FF)

 Sand Transport module (MIKE 21/3 ST, MT)

 Oil Spill module (MIKE 21 OS)

 Ecological module (MIKE 21 ECOLAB)

 Advection Dispersion (MIKE 21 AD)

Among MIKE 21 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 to other models: application for variant water bodies in river basin, estuary, coastal and the sea Because of it utilisable and friendly interface, Integrated Geographic Information System (GIS) is used to extract data exactly and visual, time setup quickly, provision of flexible mesh which enables more accurate representation of the actual area On the other hand, the disadvantages of this model is some calculation results is incorrect with actual data survey, the running speed is still limited, especially MIKE 21 FM module

In this thesis, the module FM and module ECOLAB of MIKE 21 modeling suite were used to simulate hydrodynamics regime, process of pollutants dispersion entire lagoon

in dry season and rainy season in 2013-2014 and 2016

1.2 Case study: O Loan lagoon

1.2.1 Natural characteristics

a) Geographical location

O Loan lagoon is located in the south of Tuy An district, next to Quan Cau Pass and adjacent to to An Cu, An Hoa, An Hai, An Hiep and An Ninh Dong commune Lagoon has geographic coordinates 13013'50" to 13019'00" north latitude and 109014'30" to

109017'30" east longitude

It is a brackish water and almost belonged to mainland with about 17.5 km2, stretching from North to South, the widest point of 2.5 km, longest point of 8 km, 1.2 km2 of the surface area and 1.2m -1.4m of average depth The mouth of lagoon is namely Tan Quy with about 100m of width

Figure 1.1: Map of O Loan lagoon (https://www.google.com/earth/)

b) Topographic

Topography around lagoon is complex, hills intervened by small valley The Eastern of lagoon was formed by many low sand dunes The average elevation of hills is lower than 200m and formed from granite, basalt layers The lagoon is surrounded by Dong

Chay mountain, Cam mountain and peninsulas of An Ninh Dong, An Hai, An Hoa

c) Hydro - Meteorological

 Wind

Trade wind and monsoon wind is prominent in Phu Yen province Wind direction was recorded from North, Northeast, East with average speed of 2.2m/s in coastal and of 1.7 m/s in mountain respectively In addition, the plain climate is harmonized partly

by phenomenon of "seabreeze" in coastal area

Precipitation in Phu Yen province is mostly concentrated in rainy season from August

to December every year and tends to be higher year to year In December of 2016, the highest precipitation was over 200mm per day in Tuy An district

 Water flow

Water flow in lagoon influenced by four factors: monsoon wind system, wind, bathymetry, tidal regime However, the water is exchanged daily between lagoon and the sea by only a Tan Quy mouth, the depth and width of lagoon were small, the top of the lagoon is narrow (200m - 500m) Thus, the water flow is completely affected by tidal current

 Salinity

Salinity in O Loan lagoon is not different to that of coastal lagoons in Viet Nam The

highest salinity is 3.6 %, the lowest is 2.15% and the average one is2.78% (Source:

Characteristics of Phu Yen hydro-meteorology).

 Tidal pattern

The tidal in Phu Yen coastal is similar to tidal pattern of South Central coastal of Viet Nam with mixed tidal O Loan lagoon's mixed tidal pattern may have characteristics of both diurnal and semidiurnal tides with amplitude of tidal increases from North to South

1.2.2 Community characteristics

The total population of five communes in O Loan lagoon was estimated 47,963 people

in 2014, according to Statistical Yearbook of Tuy An 2014 Table 1.1 provides detailed information about community in O Loan lagoon

Table 1.1: Distribution of population in O Loan lagoon, 2014 Commune Area (km 2 ) Population (P) Density (P/km 2 ) Village

(Source: Statistical Yearbook of Tuy An 2014)

There are many economic sectors that create employment and livelihoods for community in O Loan including fishery, agriculture, tourism services The aquaculture sector plays an important role to create the livelihoods for 3,900 people

1.2.3 Aquaculture sector

The total aquaculture area of five communes in O Loan lagoon in 2014 was 544 hectares, in which 97 hectares was used for fish and bivalves farming (17.8%) and 477 hectares was used for shrimp farming (82.2%)

Figure 1.2: Shrimp farming in O Loan lagoon

Total aquaculture production in O Loan lagoon in 2014 was 1549 tons, in which shrimp production reached 1524 tons (98.4%) Figure 1.2 shows total production and aquaculture area in five communes in O Loan lagoon 2014

Figure 1.3: Total production and aquaculture area in O Loan lagoon in 2014

(Source: Statistical Yearbook of Tuy An 2014)

The white shrimp and black tiger shrimp are main species cultured in O Loan lagoon Not many of fish and bivalve species were farmed in An Hai and An Cu commune.Intensive farming and extensive farming are types of aquaculture in lagoon Intensive shrimp farming in high tidal area has become a main form of aquaculture in most of communes surrounding the O Loan lagoon.Table 1.2 presents the percentage of aquaculture type in five communes in 2014

Table 1.2: Type of shrimp farming in O Loan lagoon in 2014 Type

An Ninh Dong An Hai An Cu An Hiep An Hoa

(Source: Statistical Yearbook of Tuy An 2014)

1.2.4 Environmental problems in O Loan lagoon

Recent environmental studies have shown that, the deterioration of water quality is due

to livelihood activities around the lagoon, especially aquaculture activities The increase in aquaculture area without reasonable planning led brought negative impacts

on water environment It can influence back to aquaculture and other area.This is the main problem that needs to be tackled by local managers because O Loan lagoon is not

0 100 200 300 400 500 600

Aquaculture production (tons)

only a famous scenic destination but also a livelihood source for thousands of people living around

The erosion - accretion phenomenon in O Loan coastal is seasonally occurring with strong in intensity and complicated in manner under impacts of human being and natural In recent years, due to impacts of climate change, the process erosion- accretion in O Loan lagoon has been intensively taken place, posing threats for human life and geological environment

Climate change has begun to show its impacts in O Loan lagoon in recent years The extreme weather phenomena have increased in frequency and intensity According to National Centre for Hydro - Meteorological Forecasting, the South Central region has suffered the El Nino phenomenon over past 3 years (2014-2016) The effects of El Nino led to high temperature, a shortage of precipitation, saltwater intrusion in South Central provinces In Tuy An district, prolonged drought appeared more frequent in dry season resulting in prolonged shortages in water supply, saltwater intrusion recent years In 2014, the satlwater intrusion was detected in upstream about 2km far from Hai Yen estuary that has not been recorded before

On other hand, under impact of La Nina phenomenon, the mechanism of storms and flood was unpredictable especially intensity, speed, direction of movement and heavy rain, thunderstorms related The storm frequency did occur in Phu Yen many years before and in December of 2016, Phu Yen province was recorded a historic flood after decades which caused serious damages people and heavy economic losses in community Overally, the quality of the environment is being threatened by the economic activities surrounding and the initial impacts of climate change aspects It is a key challenge for local authorities to develop strategy of sustainable development in O Loan lagoon in the near future

1.3 Research plan

A brief overview of research plan is shown in below flowchart

Reading references and Building research methodology

Data collection

Running Mike 21 model (Mike 21 FM and Mike 21 ECOLAB)

- Calibration and running model with data in 2013 and

CHAPTER 2 METHODOLOGY

2.1 Data collection and Aggregation

In this study, collecting and aggregating data including documents/data on environment, hydro-meteorological and socio-economic in O Loan lagoon, Tuy Hoa district, Phu Yen province for modelling is very important to run the model These were obtained by:

- Inheriting, analysis and synthesis of materials, data sources that related to Loan lagoon

- Collecting, assessing and analyzing the existing data sources according to the traditional analytical methods

- An overview of domestic and international documentsrelated to field of study, conferences, seminars seek to build research methodology

The table 2.1 shows the number of data and sources that will be used in running MIKE 21 model

Table 2.1: Data collection and sources

1 Bathymetry 2013, 2014 Project: “Assessing the environment status

and the risk of environmental catastrophe

in O Loan lagoon, Tuy An district, Phu Yen province” (2013-2016)

2

O Loan lagoon’s water

level 2013, 2014, 2016 The South Central Station for Hydro -

Meteorological and Institute of Nha Trang Oceanography

Tidal

Wind

3 Wave 2013, 2014, 2016 Global wave model (Wave – Watch III)

4 Pollution loading

2013, 2014, 2016 Project: “Assessing the environment status

and the risk of environmental catastrophe

in O Loan lagoon, Tuy An district, Phu Yen province” (2013-2016)

5 Water quality monitoring

2013, 2014 Project: “Assessing the environment status

and the risk of environmental catastrophe

in O Loan lagoon, Tuy An district, Phu Yen province” (2013-2016)

2.2 Data processing

In this study, Excel software was used to aggregate input data, assess calibration results of module ECOLAB, drawing graphs, charts to simulate This is a program package of Microsoft office software that is widely used in the world The Excel software can do many complex calculations and show through charts, graphs in a flexible in manner

2.3 Assessment of water quality

To assess the impacts of water pollution on aquaculture, the author selected recognized environmental parameters including: Nutrient Pollution Index (NPI) NO3-, PO43-, Organic Pollutant Index (OPI) COD, BOD, TSS The water quality assessments were based on available standards for coastal aquaculture 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.For BOD criteria, the National technical regulation on surface water quality (NTR 08:2015/MORNE) applying for aquatic life conservation will be used to evaluate The maximum allowable concentration of criteria was shown in Table 2.2

Table 2.2: Summary of water quality standards relevant to coastal water

aquaculture

NTR 10:2008/MONRE

The number of analytical methods approved for measuring water quality includes:

 BOD: Determination of biochemical oxygen demand after n days (BODn) –Method for undiluted samples (TCVN 6001-2: 2008/ ISO 5815-2 : 2003)

 CODKMnO4: Method for the derter mination of chemical oxygen demand (COD)

- Kali pemanganat (KMnO4) method (TCVN 4565 - 88)

 TSS: Water quality – Determination suspended solids by filtration through glass – fiber filters (TCVN 6625 : 2000 /ISO 11923 : 1997)

 NO3-: Standard Methods for the Examination of Water and Wastewater – Determination of Nitrate (APHA Method 4500-NO3-)

 PO43-: Standard Methods for the Examination of Water and Wastewater – Determination of Phosphorus (APHA Method 4500-P)

Water depth (Bathymetry) is measured by using sounding pole techniques - the wooden or aluminum pole carved with the customary unit of length (cm) with a handle on one end

2.4 Modeling method

This is main method in study Data of water quality observation will be imported to model 21 (FM and Ecolab) Firstly, the data of 2013, 2014 is used for calibration model and running dispersion simulation of pollutants in rainy season 2013 and dry season 2014) After that, the hydro-meteorological data of 2016 will be used for running based on calibrated model Finally, simulation results of pollution dispersion

will be discussed

The MIKE 21 model was used to simulate process of hydrodynamics and pollution dispersion of 5 environmental parameters including COD, BOD, TSS, N-NO3- and P-PO43-in O Loan lagoon in rainy season and dry season in 2013,2014 and 2016 In present study, modules MIKE 21 FM and MIKE 21 ECOLAB in MIKE 21 modeling suite were used Among MIKE 21 modules, the module MIKE 21 FM is the core of the MIKE 21 modeling suite It calculates hydrodynamics regime to build foundation for other modules Figure 2.1 shows a brief overview the interaction between MIKE

21 FM and MIKE 21 ECOLAB

Figure 2.1: A flowchart of Mike 21 modules

v h x

u h t

Where, h is the water depth and u and v are water particle velocities in x and y

direction respectively, S is the energy source-dissipation term

 The 2D shallow water equation

   hT hu S

y

hT x y

S x S

x

gh x

p h x gh h v f y

uv h x

u t

u

s xy xx

xy xx bx

0 2

0 2

S x S

y

gh y

p h y gh h u f y

v h x

uv h t

v h

s yy xy

yy yx

by sy

0 2

0 2

Where, t is the time; x and y are the Cartesian co-ordinates; n is the surface elevation; d

is the still water depth; h= n+d is the total water depth, u and v are velocity component in x and y direction; f is the Coriolis parameter, g is gravitational

 Numerical solution of 2D

shallow water equation Input

datas: wind, water level

variation, wave spectrum,

digitized bathmetry Ouput:

current variation in domain

 Ecological model calculates the pollution dispersion Input datas:

Outputs of module FM and pollution loading Output:

pollutants dispersion in different sites in research area

Mike 21 - Flow Model Flexible Mesh (FM)

Mike 21 - ECOLAB

acceleration, p is the density of water; t sx , t sy are x and y components of surface wind

and t bx and t by are the components of botton stress; T ij includes viscosity friction, turbulent friction and differential advection estimated using eddy viscosity formulation based on depth averaged velocity gradients

Txx, Txy, Tyy are calculated as follow:

y

v A T

x

v y

u A T x

u A

The dynamics of the state variables in ECOLAB can be described by non-conservative material transportation equation, in form:

The numerical solution methodswere used in ECOLAB module by method of Euler, Runge Kutta 4, Runge Kutta 5

CHAPTER 3: APPLICATION MODEL, RESULTS AND DISCUSSIONS

3.1 Model Application

3.1.1 Input data

a) Bathymetry

One of the most important input data for Mike 21 is bathymetry This data is obtained

from project: “Assessing the environment status and the risk of environmental

catastrophe in O Loan lagoon, Tuy An district, Phu Yen province’,(Table 3.1 and

Appendix 1) The bathymetry data was collected in digital data, converted to file.xyz format and use Mike Zero to interpolate the depth value in coordinates

Table 3.1: Water depth in O Loan lagoon

No Longitude Latitude Rainy season, 2013

Figure 3.1: O Loan lagoon’s bathymetry extracted from Mike 21 FM

b) Hydro-meteorological data

 O Loan lagoon’s water level

The hourly water levels in O Loan lagoon presented partly in following figures were measured by The South Central Station for Hydro – Meteorological in 2013 (Figure

3.2) and March, 2014 (Figure 3.3) (see more data in Appendix 2)

Figure 3.2: Water level monitoring in O Loan lagoon (October, 2013)

Figure 3.3: Water level monitoring in O Loan lagoon (March, 2013)

 Tidal water level

There is no a tidal monitoring station in O Loan lagoon, the tidal water level data is used from adjacent area (Nha Trang area- Cau Da station) to calibrate The data is presented below in Figure 3.4 and Figure 3.5 (see appendix 3)

Figure 3.4: Tidal water level monitoring in Tan Quy mouth (Octorber, 2013)

Figure 3.5: Tidal water level monitoring Tan Quy mouth (March, 2014)

 Wind

From September to December, wind direction is prominent North East – Southwest and Southeast – Northwest from March to July in O Loan lagoon The wind speeds were shown in Table 3.2

Table3.2: Wind speed in O Loan lagoon

 Wave

The impact of wave on water flow in O Loan lagoon is neglected Calculation of wave characteristic as input data for Mike 21 FM, wave at boundaries was referenced from Global wave model (Wave-Watch)

c) Pollution loading

According to the project: “Assessing the environment status and the risk of

environmental catastrophe in O Loan lagoon, Tuy An district, Phu Yen province",

pollution loads were calculated via COD, BOD, TSS, Total Nitrogen and Total Phosphorus (see Table 3.3)

Table 3.3: Pollution loading in O Loan lagoon, 2014

Unit: tons Commune

The main source of this pollution is wastewater withdrawing from aquaculture sectors

in five communes around A Loan lagoon

d) Water quality monitoring

Imported data of water quality for model is obtained from project: “Assessing the

environment status and the risk of environmental catastrophe in O Loan lagoon, Tuy

An district, Phu Yen province", (see Appendix 4) Water quality surveys in the lagoon

were carried out in 2013 and 2014 at 14 sites in the O Loan lagoon (Figure 3.6) Water quality data is used to setup boundary conditions, initial conditions, and calibration in Mike 21 Ecolab

Figure 3.6: Water sampling sites in O Loan lagoon 3.1.2 Creating Mesh

Because of the study area was not large with total area about 17.5 km2, mesh is divided smoothly and resolution of 200m was used The total number of elements used in the mesh is 2611 with 1343 nodes Figure 3.7 show the details of mesh created:

Figure 3.7: O Loan lagoon mesh extracted from Mike 21 FM

3.1.3 Boundaries and initial condition

3.1.3.1 Boundaries

O Loan lagoon is a closed coastal lagoon, the process of water exchanged with outside environment was happened through 2 positions: Ky Lo estuary and mouth of O Loan lagoon (Tan Quy mouth) Accordingly, the liquid boundaries defined in Mike 21 are shown in Figure 3.8

 Boundaries conditions of Mike 21 FM

- Water level at Ky Lo estuary

- Tidal water level at Tan Quy mouth

 Boundaries conditions of Mike 21 Ecolab

- Water quality monitored at Ky Lo estuary (site NM8)

- Water quality monitored at Ky Lo estuary (site NM1)

Figure 3.8: Domain boundaries in O Loan lagoon extracted from Mike 21 FM

Note:

B1: Estuary - Lagoon Boundary B2: Lagoon – Sea Boundary

Table 3.4: Initial conditions of Mike 21 Ecolab

No Parameter Unit October, 2013 March, 2014

3.2 Mike 21 Ecolab calibration

The Mike 21 Ecolab calibration was carried out at monitored sites in project:

“Assessing the environment status and the risk of environmental catastrophe in O Loan lagoon, Tuy An district, Phu Yen province" including MN3, MN5, MN6, MN11,

MN13 In order to evaluate calibration results, average concentration of pollutants in October, 2013 and March, 2014 compare with exact value at monitored sites The calibration results are shown from Figure 3.9 to 3.18

a) COD calibration

Figure 3.9: COD calibration, 10/2013 Figure 3.10:COD calibration, 3/ 2014

The calibration results of COD showed that the differences between simulation results and exact values was relatively small in both dry season and rainy season

In the rainy season of 2013, the most similarity obtained at the NM05 site with only 1.60% while the least onces was 6.00% at NM11 site

In the dry season of 2014, the smallest error achieved at NM11 site with 0.58% while the maximum error was 7.64% at NM13 site

b) BOD calibration

Figure 3.11: BOD calibration, 10/2013 Figure 3.12: BOD calibration, 3/2014

The differences between the calculated and the exact value for BOD parameters was fairly big in both dry and rainy seasons

The smallest error achieved at NM03 site with 4.43% in dry season of 2014 and only 1.19% in rainy season of 2013 Four points NM5, NM6, NM11, NM13 were between 5.74% and 20.00% in both rainy and dry seasons

mg/l COD calibration

0 1 2 3 4 5 6 7 8

NM03 NM05 NM06 NM11 NM13

Exact value Calculalted value

d value

mg/l BOD calibration

0 1 2 3 4 5

NM03 NM05 NM06 NM11 NM13

Exact value Calculalte

d value

mg/l BOD calibration

c) TSS calibration

Figure 3.13: TSS calibration, 10/2013 Figure 3.14:TSS calibration, 3/2014

Calibrated results of TSS parameter showed that there is similar with BOD calibration The smallest error achieved at NM03 site with 4.3% in dry season of 2014 and only 1.2% in rainy season of 2013 Four points NM5, NM6, NM11, NM13 ranged from 5.70% to 19.5% in both rainy and dry seasons

d) N-NO 3 - calibration

Figure 3.15: N-NO 3 - calibration, 10/2013 Figure 3.16: N-NO 3 - calibration, 3/2014

N- NO3 parameter showed a good calibration for both seasons, especially in the rainy season of 2013

In the dry season of 2014, the smallest error achieved just 4.24% at NM03 site while the maximal error reached 18.50% at NM05 site

In the rainy season 2013, the errors ranged from 1.60 to 5.90%, the best calibrated results at NM05 and NM 06 sites were 1.60% and 3.00% respectively

d value

mg/l TSS calibration

0 10 20 30 40 50 60

NM03 NM05 NM06 NM11 NM13

Exact value Calculalted value

Exact value Calcucalted value

N-NO 3 - calibration

g/l