Salinity Risk to Agricultural Landuse due to Sea Level Rise: A Case Study in Dhalua Union of Barguna Sadar Upazila Md. Abdullah Al Baky Post Graduate Diploma in Water Resources Development Institute of Water and Flood Management BANGLADESH UNIVERSITY OF ENGINEERING AND TECHNOLOGY 2013 Salinity Risk to Agricultural Landuse due to Sea Level Rise: A Case Study in Dhalua Union of Barguna Sadar Upazila by Md. Abdullah Al Baky In partial fulfillment of the requirement for Post Graduate Diploma in Water Resources Development Institute of Water and Flood Management BANGLADESH UNIVERSITY OF ENGINEERING AND TECHNOLOGY June 2013 The project report titled ‘Salinity Risk to Agricultural Landuse due to Sea Level Rise: A Case Study in Dhalua Union of Barguna Sadar Upazila’ submitted by Md. Abdullah Al Baky, Student ID: 1009281002, Session: October 2009, has been accepted as satisfactory in partial fulfillment of the requirements for Post Graduate Diploma in Water Resources Development on June 2013. BOARD OF EXAMINERS …………………………… Dr. M Mozzammel Hoque Chairman Professor IWFM, BUET (Supervisor) …………………………….. Dr. G.M. Tarekul Islam Member Professor IWFM, BUET ………………………………. Dr. M. Shahjahan Mondal Professor Member IWFM, BUET i CANDIDATE’S DECLARATION It is hereby declared that this report or any part of it has not been submitted elsewhere for the award of any degree or diploma. …………………………. Md. Abdullah Al Baky Student ID: 1009281002 ii Dedicated to ............................................................................ My beloved parents iii Page No. DECLARATION i CONTENTS iii - iv LIST OF TABLES v LIST OF FIGURES vi – vii ABBREVIATIONS viii ACKNOWLEDGEMENT ix ABSTRACT x CHAPTER-1 INTRODUCTION 1.1 Background of the Study 1 1.2 Objective of the Study 2 1.3 Organization of the Report 2 1.4 Limitations 3 CHAPTER-2 LITERATURE REVIEW 2.1 Introduction 4 2.2 Salinity Problem 4 2.3 Salinity Situation in Bangladesh 6 2.4 Sea Level Rise and Salinity Problem in Bangladesh 8 2.5 High Tidal Salinity Mapping and Associated Risk to Agriculture 9 CHAPTER-3 STUDY AREA 3.1 Selection of the Study Area 11 3.2 Location of the Study Area 14 3.3 River System and Hydrologic Measuring Stations 14 3.3.1 Surface water 16 3.3.2 Groundwater 16 3.4 Climate 16 3.5 Land Use and Cropping Pattern 17 iv 3.6 Topography and Physiography 19 CHAPTER- 4 METHODOLOGY 4.1 Introduction 21 4.2 Data Collection 22 4.2.1 Primary Data 22 4.2.1 Secondary Data 22 4.3 Data Organization and Result 23 4.3.1 Future high tidal inundation mapping 23 4.3.2 Agricultural land use risk mapping 24 4.3.3 Spatial variation of salinity in different agricultural risk zones 24 CHAPTER- 5 RESULTS AND DISCUSSION 5.1 Future High Tidal Inundation Mapping 25 5.2 Agricultural Land Use Risk Mapping 29 5.3 Spatial Variation of Salinity in Different Agricultural Risk Zones 31 CHAPTER - 6 CONCLUSIONS AND RECOMMENDATIONS 6.1 Conclusions 39 6.2 Recommendations 40 References 41 v List of Tables Table No Title Page No Table 2.1 Quality Characterization of Water 5 Table 2.2 Water Salinity for Irrigation Purpose 5 Table 3.1 Land Use of The Study Area 17 Table 4.1 Collected Secondary Data and Sources 23 Table 5.1 Regression Parameters at Different Water Level 27 Stations Table 5.2 Regression Trend Analysis of Salinity (ECW) and 33 High Tides Table 5.3 Estimated Salinity Level (ECW) (µs / Cm) with Sea 33 Level Rise Impact Table 5.4 Salinity (ECw) Risk Classification 35 vi List of Figures Figure No Title Page No Figure- 3.1 Dhalua Union, Barguna Sadar Upazila, Barguna 12 Figure- 3.2 High Tide and Low Tide at Amtali Station, 2002 13 Figure- 3.3 High Tide and Low Tide at Patharghata Station, 13 2002 Figure- 3.4 River System and Hydrologic Measuring Stations 15 Figure- 3.5 Land Use Map, Dhalua Union 18 Figure- 3.6 Slope Map, Dhalua Union 20 Figure- 4.1 Methodology Flow Chart of Present Study 21 Figure- 5.1 Future Estimated Peak High Tidal Water Level at 25 Patharghata Station Figure- 5.2 Future Estimated Peak High Tidal Water Level at 26 Amtali Station Figure- 5.3 Future Estimated Peak High Tidal Water Level at 26 Mirzaganj Station Figure- 5.4 Peak High Tidal Inundation Maps at Different Years 28 Figure- 5.5 Peak High Tidal Inundation Extent in Different 29 Years Figure- 5.6 Peak High Tidal Inundation Hazard Maps and 30 Agricultural Land Figure- 5.7 Peak High Tidal Inundation Extent at Agricultural 31 Land in Different Years vii Figure- 5.8 Regression Analysis between ECW and High Tidal 32 Water level, Amtali Figure- 5.9 Regression Analysis between ECW and High Tidal 32 Water level, Patharghata Figure- 5.10 Regression Analysis between ECW and High Tidal 33 Water level, Mirzaganj Figure- 5.11 Interpolated Salinity (ECw) Surface Maps at 34 Different Years Figure- 5.12 Salinity (ECw) Risk Map in Agricultural Land at 37 Different Years Figure- 5.13 Salinity Risk on Agriculture at Dhalua Union 38 (agricultural land area) viii ABBREVIATIONS Term ABBREVIATIONS Aman is a one kind of paddy variety which usually sowed mid March to mid August and harvested time is Mid Nov. to Mid Aman December. ASTER Advanced Spaceborne Thermal Emission and Reflection Radiometer Boro is a one kind of paddy variety which usually sowed mid Boro November to mid February and harvested time is April to May. BWDB Bangladesh Water Development Board. Ca Calcium Cl Chlorine Environmental System Research Institute. This organization ESRI provides GIS related services. GEBCO General Bathymetric Chart of Ocean GPS Global Positioning System HYV High Yielding Variety K Potassium Kharif Winter Crop Season Mg Magnesium mha Mega Hector Na Sodium SAARC South Asian Association of Regional Cooperation SC-55 South Central – 55 Spline An Interpolation Technique SRTM Shuttle Rudder Topographic Mission TDS Total Dissolved Solid ix ACKNOWLEDGEMENT First of all, I would like to thank the almighty Allah for giving me the ability to complete the work. I would like to express my sincere and heartiest gratitude to my supervisor Dr. M. Mozzammel Hoque, Professor, IWFM, BUET, for his constant guidance, valuable advice, generous help and constructive discussion to carry out this research. I consider myself to be proud to have worked with him. I am deeply grateful to him especially for providing technical and conceptual knowledge on hydrology and advanced statistical analyses. I am also grateful to Dr. G.M. Tarekul Islam, Professor, IWFM, BUET and Dr. M. Shahjahan Mondal, Professor, IWFM, BUET for the amount of time they have given me and the genuine interest that they have shown in my work. I express my profound respect and deepest gratitude to all my respected teachers of IWFM, BUET for their valuable teachings and constant supports. I also wish to express my deepest thanks to IWFM staffs, IWM, BWDB and BARC authorities for providing me important papers, GIS data and other technical matters related to my project report. x ABSTRACT Gradual increase of areal extent of saline water with sea level rise in coastal region may cause a serious alarming situation for agriculture. Salinity affects crops depending on degree of salinity at the critical stages of growth, which reduces yield and in severe cases the total yield is lost. In this study, historic high tidal water level data in the study area shows a rising trend which indicates the increase of areal extent of tidal inundation in future. In addition, concentration of salinity shows an increasing trend over the years in the area. So there is a possibility of having consequence of increasing saline water concentration as well as areal extent of saline water with different levels in future. In this connection, the present study shows, the agricultural land use risk from salinity perspective due to sea level rise from 2015 to 2030 in Dhalua Union under Barguna Sadar Upazila. The study findings also show that, all water level stations are observing a rising trend which also influences on high tidal inundation extents in different years. Inundation extent will become more than doubled estimated to 9.64 sq. km to 20.58 sq.km from the year 2015 to 2030. In 2015, about 38% of total agricultural land will be inundated by peak high tidal inundation which will be also more than doubled in 2030. There is an inverse relationship exist between high tidal water level and salinity (Ec) level. Peak high tidal inundation with sea level rise induced salinity concentration will be decreased in future. The Dhalua union occupies a total 25.16 sq. km of agricultural land of which, in 2015, 17.52 %, 12.67 %, and 8.50 % agricultural land will be under moderate, high and very high risk categories respectively. In 2020, about 0.299 sq.km of agricultural land will be under low risk of salinity (441 – 680) which is absent for 2015 and on the other hand, no agricultural land will be found under very risk of salinity. Moderate risk of salinity area will be significantly increased amounted to 47.45 % of total agricultural land in 2020. In 2025, 75.31 % of total agricultural land will be under low risk of salinity. Almost 95 % of the inundated crop area will be exposed by very low risk of salinity and remaining will be under low risk of salinity in 2030. 1 CHAPTER ONE INTRODUCTION 1.1 Background of the Study Tidal effect in coastal region of Bangladesh is one of the noteworthy problems especially for farmer groups. On the other hand, for shrimp and salt cultivators saline water caused by tidal water intrusion is beneficial. But gradual increase of areal extent of saline water in coastal region will cause a serious alarming situation for agriculture.