Estimation of water quality trends in thua thien hue coastal zone, vietna

Institute UNESCO-IHE for Water Education Estimation of Water Quality Trends in Thua Thien-Hue Coastal Zone, Vietnam Nguyen Thi The Nguyen M.Sc Thesis HE 164 April 2004 NEDECOI ~~~ WL I delft hydraulics CCP/CZMCIRJJ(Z UNESCO-IHE Institute for Water Education WLI delft hydraulics CCPICZMCIRIKZ ESTIMATION OF WATER QUALITY TRENDS IN THUA THIEN-HUE COASTAL ZONE, VIETNAM Master of Science Thesis by Nguyen Thi The Nguyen Supervisors Drs Mindert de Vries (WL) Dr Randa M Hassan (UNESCO-IHE) Drs Maarten Scheffers (RIKZ) Examination committee Prof Bela Petry (UNESCO-IHE), Chairman Dr Randa M Hassan (UNESCO-IHE) Drs Mindert de Vdes (WL) Drs Robbert Misdorp (RIKZ) This research is done for the partial fulfilment of requirements for the Master of Science degree at the UNESCO-IRE Institute for Water Education, Delft, the Netherlands Delft April 2004 The findings, interpretations and conclusions expressed in this study neither necessarily reflect the views of the UNESCO- IHE Institute for Water Education, nor of the individual members of the MSc committee, nor of their respective employers ABSTRACT The coastal zone of Thua Thien Hue encompasses 34% of its total area and about 81% of its population are concentrated there It is largely dominated by the Tam Giang-Cau Hai lagoon, the biggest of its kind in Southeast Asia The socio-economic developments together with natural disasters are causing pressures on the coastal zone in general and in the lagoon in particular Intensification of agriculture and extension of aquaculture is increasing the pressure on the natural resources by introducing fertilizers, nutrients and pesticides into the system This study focuses on quantification of the relationship between agriculture in the drainage basin, aquaculture in the lagoon and the water quality of the coastal ecosystem Based on extensive literature research the use of fertilizers and some popular pesticides is estimated Through mapping of historic and present spatial extension and analysis of future planning, the load of substances from agriculture and aquaculture to the lagoon system, are quantified Implementation of a 2D hydrodynamic and water quality model allows the estimation of historic, present and future concentrations of substances in the water of the lagoon It is concluded that planned extension and intensification of agriculture and aquaculture will lead to serious exceedance of internationally accepted water quality standards, indicating overexploitation over resources and increasing risk of serious problems with ecosystem functioning The study result shows promising potential to develop this tool for optimization of land-use planning and for delivering relevant information to the policy-making process Key words: Water quality, water quality modeling, pesticides, fertilizers, agriculture, aquaculture, Thua Thien-Hue Acknow ledgment lt)('.1~~lt)('.1 -This work is completed with assistance of a number of people and organizations, all of whom I gratefully acknowledge I would like to express my sincere thanks and appreciation to all people who directly or indirectly contribute to the complement of this study I would like to deeply acknowledge Drs Mindert de Vries,for his supervision, significant technical assistance and encouragement I wish to thank Mr Gerben Boot for his kindly help on the modelling part during the time I worked at WL IDelft Hydraulics Greatly acknowledgement must be given to Assoc Dr Randa M Hassan for her constant support and encouragement during my studies in the Netherlands Moreover, my sincere thanks are extended to Drs Robbert Misdrop, Drs Maarten Scheffers, and Dr Joost Stronkhorst for their kind advices and support I am thankful to the Hanoi Water Resources University, especially Prof Dr Le Kim Truyen, Dr Vu Minh Cat, Dr Do Tat Tuc, Dr Le Dinh Thanh, Mr Nguyen Van Bao, Mr Tu Van Hai and all my colleagues at Section of Chemistryfor supporting my study in many ways I also wish to express my gratitude to all other members of UNESCO-IHE, especially the Department of Water Engineering, Prof Bela Petry, Ir Ronald de Heer and Ir Mick van der Wegenfor their academic guidance and thoughtful encouragement in everyday life I thank all Vietnamese, Dutch,foreign friends, and my colleagues at WL I Delft Hydraulics Finally, I am grateful my parents and my brothersfor their encouragement and for the way they overcome the difficulties during the time I was away Thank you all! Nguyen Thi The Nguyen UNESCO-IHE, Delft, The Netherlands April 2004 11 TABLE OF CONTENTS Abstract Acknowledgement List of table List of figure List of abbreviations Executive summary (in Vietnamese) ii v vi vii Vlll INTRODUCTION 1.1 1.2 1.3 1.4 1.5 1.6 1-1 1-2 1-3 1-4 1-4 1-6 DESCRIPTION OF THUA THIEN - HUE PROVINCE AND ITS COASTAL ZONE •••• 2.1 2.2 2.3 Brief description of study area Problem analysis Background of Integrated Coastal Zone Management in Vietnam Objectives of study Methodology Outline of the report Natural conditions 2.1.1 Thua Thien-Hue province topography 2.1.2 The structure of the Tam Giang-Cau Hai lagoon system 2.1.3 General climate 2.1.4 River system , 2.1.5 Soil Socio-economic conditions 2.2.1 Demography 2.2.2 Economic sectors 2.2.3 Land use 2.2.4 Infrastructures 2.2.5 Socio-economic development orientation by 2010 Water quality in the Thua Thien Hue lagoon 2-1 2-1 2-1 2-4 2-6 2-6 2-7 2-7 2-7 2-8 2-8 2-9 2-9 LITERATURE REVIEW AND DATA ANALISIS ON CHEMICAL USE AND LANDUSE IN VIETNAM AND THUA THIEN HUE PROVINCE .•• • • ••.• • • .• • • 3.1 3.2 3.3 3.4 Chemical used in rice culture and aquaculture 3.1.1 Introduction 3.1.2 Pesticides '" 3.1.1 Fertilizers State of rice culture and aquaculture in Vietnam and TTH province 3.2.1 Rice culture in Vietnam 3.2.2 Aquaculture in Vietnam 3.2.3 Rice culture and aquaculture in Thua Thien-Hue province State of chemical used in Vietnam and Thua Thien-Hue province 3.3.1 Pesticides used in Vietnam 3.3.2 Chemical fertilizers used in agriculture 3.3.3 Chemical use in aquaculture 3.3.4 Chemical use in Thua Thien-Hue province Conclusions '" 3-1 3-1 3-1 3-5 3-7 3-7 3-8 3-9 3-10 3-10 3-16 3-17 3-19 3-20 ESTIMATION OF WASTE LOADS INPUT IN THE THUA THIEN - HUE LAGOON 4.1 4.2 4.3 Selection of substances Rice culture and aquaculture areas Crop seasons 111 4-1 4-3 4-3 4.4 4.5 4.6 4.7 4.8 4.9 5.3 5.4 Introduction Model extension and application 5.2.1 Grid outline and bathymetry 5.2.2 Boundary data 5.2.3 Computational time step 5.2.4 First order decay and dispersion coefficients 5.2.5 Setting other parameters 5.2.6 Initial conditions Sensitivity analysis and model calibration 5.3.1 Introduction to sensitive analysis and model calibration 5.3.2 Sensitive analysis and model calibration 5.3.3 Result analysis 5.3.4 Conclusion Scenarios 5-1 5-1 5-1 5-1 5-3 5-3 5-4 5-4 5-5 5-5 5-5 5-6 5-8 5-9 MODEL RESULT INTERPRETATION AND WATER QUALITY ANALYSIS .• 6.1 6.2 Water quality objective and standards Current water quality of the lagoon 6.2.1 Dryseason 6.2.2 Wet season Water quality tendencies 6.3.1 Dry season 6.3.2 Wet season Proposal for additional monitoring program 6.4.1 Ongoing monitoring program of CCP on water quality 6.4.2 Considerations 6.4.3 Proposal for additional monitoring 6.3 6.4 4-4 4-4 4-5 4-5 4-6 4-7 WATER QUALITY SIMULATION S • •.•• .• •.• •.• • • 5.1 5.2 Loss coefficients of selected substances to water bodies Seasonal variation Loads of selected substances according to administrative units Input substance locations into the lagoon Loads and concentrations of selected substances into the lagoon Estimation of the loss factors for agricultural loads using monitoring data 6-1 6-1 6-1 6-4 6-6 6-6 6-9 6-9 6-9 6-10 6-11 CONCLUSIONS AND RECOMMEMDATIONS 7.1 7.2 Conclusions Recommendations 7-1 7-3 REFERENCES APPENDICES Appendix Appendix Appendix Appendix Appendix Appendix Appendix 1234567- Lists of some allowable pesticides in Vietnam Water quality monitoring records of CCP 2003 Waste load calculation DEFLT3D-FLOW model Model sensitivity analysis, calibration and results for future situations Impacts of dam river construction and global warming on lagoon water quality Total coliform bacteria simulation IV Appendix 6-Inpacts of dam construction and global warming on water quality Appendix - Impacts of dam river construction and global warming on lagoon water quality Input loads and concentrations from agriculture and aquaculture Under impact of dam construction in rivers for irrigation purposes, river discharges are modified The global warming in future can cause sea level rise and changed rainfall pattern, leading to changes in river discharges Consequently, input concentrations for agricultural load are changed For simplification, it is supposed that reservoir operation and global warming not alter agricultural load, which is already quantified in Chapter In fact, the loss rates of fertilizers (and agricultural load) can be different if river discharges and rainfall pattern are varied Substance concentrations in river discharges are now recalculated with the same load and different river discharges (different water volume) Aquaculture load also remains the same with the scenarios without dam construction and global warming effects All scenarios for water quality simulation under the impacts of dam construction and global warming have been given in Chapter 5, section 5.4 The results are roughly analyzed below Impacts of dam river construction on the water quality The scenarios with dam river construction are calculated with 60% decrease in wet season discharges and 40% increase in dry season discharges (the values are adopted from previous model of CCP) These are equivalent to an increase by 2.5 times in agricultural input concentrations during wet season and a decrease by 1.4 times during dry season The results of these calculations are presented in figure A.6.1 to A.6.6 and table A.6 In general, nutrient and pesticide concentrations increase in wet season and decrease in dry season in comparison with no dams The construction of dams in rivers causes very high substance concentrations in the lagoon during wet season, leading more polluted area in wet season than dry season In contrast to the situation without dams, water quality in dry season with dam seem to be better than wet season though aquaculture activities happen in dry season It could be due to reservoirs supply amount of water in dry season so that substance contents in the lagoon are more diluted Especially, phosphorus content is still higher in dry season that wet season This reveals that aquaculture load provides more phosphorus than nitrogen into the lagoon River discharge change has different effects on nutrient content during dry season at the present and in future It significantly affects present-nutrient concentrations (Figure A.6.1) However in future, the changes of river flow not alter much nutrient concentration values (Figure A.6.2) At present the reduction of river flows makes polluted area decrease by 20-28%, whist in future it decreases only by 5-6% It can be explained that in future aquaculture load is main pollution source and it does not depend on the river flows In sum, the operation of reservoirs upstream strongly modifies water quality in the lagoon In this situation, it should be paid much attention on aquaculture load during dry season and agricultural load during wet season (see figure A.6.l to A.6.6 and table A.6 for details) Impacts of dam river construction and global warming on the water quality The scenarios with impact of dam and global warming are calculated with 0.6 m sea level rise and 64% decrease in wet season discharges; 30% decrease in dry season discharges The results show that the nutrient content is significantly high in the Thanh Lam lagoon and Thuy Tu lagoons during dry season This is due to the decrease of rainfall and river discharge causing Jack of water to dilute A.6-1 Appendix 6-Inpacts of dam construction and global warming on water quality aquaculture load Under the effect of global warming together with dam river operation, water quality in the lagoon is very bad (see figure A.6.1 to A.6.6 and table A.6 for details) C ~ 1.2 C a a a:: aC: .) a 0.6 QI g :2 - f 0.4 No dam II' Tam Giang Wth dam No dam II' Wth dam No dam II' Wth dam OJ g :2 (5 I- 0.07 } :J (5 s: Q 0.05 s: 0.03 Q tti (5 I- 0.Q1 Cau Hai Wth dam No dam Wth dam No Wth dam dam No dam 41 iii III CauHai ThuyTu Thanh Lam Tam Giang ~Q; 0.05 (5 s: s: 0.03 i : v.:J ·r : + :t a Wth dam dam No dam iii III VVith No dam dam Wth dam (5 I Wth dam No dam ill! Tam Giang r• ·t r Wth dam dam Thanh Lam Wth dam ~ 0:- 10 Q; ): S v :§ t\