56556 Implications of Climate Change for Fresh Groundwater Resources in Coastal Aquifers in Bangladesh February 1, 2010 South Asia Region Sustainable Development Department Agriculture and Rural Development Unit Document of the World Bank The World Bank World Bank Office Dhaka Plot- E-32, Agargaon, Sher-e-Bangla Nagar, Dhaka-1207, Bangladesh Tel: 880-2-8159001-28 Fax: 880-2-8159029-30 www.worldbank.org.bd The World Bank 1818 H Street, N.W. Washington DC 20433, USA Tel: 1-202-473-1000 Fax: 1-207-477-6391 www. worldbank.org Standard Disclaimer: This volume is a product of the staff of the International Bank for Reconstruction and DevelopmentlThe World Bank. The findings, interpretations, and conclusions expressed in this paper do not necessarily reflect the views of the Executive Directors of the World Bank or the governments they represent. The World Bank does not guarantee the accuracy of the data included in this work. 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Cover Image Credits: NASA Contents Acknowledgments ......................................................................................................................... vi Glossary of Terms ........................................................................................................................ vii Abbreviations and Acronyms .................................................................................................... viii Executive Summary ...................................................................................................................... ix 1. Introduction ......................................... " ................".............................................. 1 ................. " 1.1 Objective .......................................................................................................................... 3 1.2 Methodology.. ............................ .......................... ......................... .......................... ..... .... 4 1.3 Organization of the Report.......................... .......................... ...................... .... ................. 6 2. Groundwater in the Coastal Zone ...................................................................................... 7 2.1 Development Potential in the Coastal Zone..................................................................... 9 2.2 Government of Bangladesh Coastal Zone Policy and Planning ...................................... 9 2.3 Institutional Arrangements for ICZM .............................................................................. 11 2.4 A Changing Future in the Coastal Zone .......................................................................... 12 3. Data and Current Aquifer Conditions ............................................................................... 15 3.1 Overview .......................................................................................................................... 15 3.2 Geology and Lithologic Data ........................................................................................... 18 3.3 Geochemical Data ............................................................................................................ 19 3.4 Hydraulic Test Data ......................................................................................................... 20 4. Approach to Analysis ........................................................................................................... 25 4.1 Preassessment of Climate Change Effects on Groundwater System ............................... 26 4.2 Preassessment of Current and Future Usage of Groundwater System ............................ 27 4.3 Representation of the Aquifer System ............................................................................. 29 4.4 Intrusion Pathways Considered........................................................................................ 35 4.5 Model Setup ..................................................................................................................... 37 5. Simulation Results: Vulnerability Assessment .................................................................. 41 5.1 Homogeneous, Anisotropic Aquifers: Pumping and Sea-Level Rise .............................. 43 5.2 Heterogeneous Aquifers: Pumping and Sea-Level Rise .................................................. 50 5.3 Heterogeneous Aquifers: Storm Surge Inundation .......................................................... 56 5.4 Sensitivity Analysis ......................................................................................................... 59 6. Discussion and Recommendations ....................................................................................... 61 6.1 Primary Salinization Processes: Summary of Findings ................................................... 62 6.2 Vulnerability of Deep Aquifer Supply ............................................................................. 64 6.3 Limitations of the modeling analysis and future directions ............................................. 64 6.4 Improving the Management of Coastal Aquifers ............................................................. 65 Appendix A. Data Sets ........ " .................................................................................... 69 .................. " Appendix B. Technical Report on Numerical Modeling ......................................................... 89 Appendix C. Data A vailabUity on Land and Water in the Coastal Zone of Bangladesh ... 101 Appendix D. Institutional Setup for Integrated Coastal Zone Management ...................... 102 References .................................................................................................................................. 103 III Figures Figure 1.1 Maps of Projected Flooding in the Coastal Zone of Bangladesh due to Predicted Sea- Level Rise Scenarios............. ............... ....... ........ .... ... .... .... .... ... .... .... .... ........ ....... ........ .............. ... 3 Figure 1.2 Illustration of Modes of Salinization of Coastal Aquifers in Bangladesh .... ............... 4 Figure 2.1 Coastal Zone of Bangladesh....................................................... ................................. 7 Figure 3.1 Summary Map of Hydrologic and Geochemical Data Collected from Various Sources ....................................................................................................................................................... 17 Figure 3.2 Summary Map of Lithologic Data Collected from DPHE .......................................... 18 Figure 3.3 Maps and Representative Cross-Sections of Lithologic Logs Obtained from DPHE. 19 Figure 3.4 Maps and Representative Cross-Sections of Chloride Concentrations ....................... 21 Figure 3.5 Map of Chloride Concentrations (mg/L) Measured in Wells ...................................... 22 Figure 3.6 Pump Test Data Locations ........................................................................................... 23 Figure 4.1 Maps of Domestic (a) and Irrigation (b) Pumping (m 3/s per m2 of Map Area) Estimated for the Bengal Basin..................................................................................................... 28 Figure 4.2 Region of Bengal Basin Sedimentary Aquifer and Flow Paths Based on 3D Groundwater Model Showing General Location of Central (Low-Slope) and Eastern (High- Slope) Transects ............................................................................................................................ 30 Figure 4.3 Schematic of Model Cross-Section ............................................................................. 30 Figure 4.4 Image of Plausible Aquifer Fabric Based on Geostatistical Analysis ......................... 31 Figure 4.5 Aquifer Fabrics ............................................................................................................ 32 Figure 4.6 Heterogeneous Aquifer with Irregular Distribution ofIntruded Saltwater ................. 34 Figure 4.7 Schematic of Sea-Level Rise without Transgression .................................................. 37 Figure 4.8 Schematic of Vertical Infiltration from Storm Inundation .......................................... 37 Figure 4.9 Model Description ....................................................................................................... 38 Figure 5.1 Comparison of 2% Seawater Contours for Simulations of Central Transect Homogeneous and Anisotropic Aquifers with Base-Case Permeability Values .......................... 45 Figure 5.2 Comparison of Aquifer Area Freshened and Salinized as a Result of Aquifer Forcing for Simulations of Central Transect Homogeneous and Anisotropic Aquifers with Base-Case Permeability Values ...................................................................................................................... 46 Figure 5.3 Comparison of2% Seawater Contours for Simulations of Central Transect Homogeneous and Anisotropic Aquifers with High Permeability Values ................................... 47 Figure 5.4 Comparison of Aquifer Area Freshened and Salinized as a Result of Aquifer Forcing for Simulations of Central Transect Homogeneous, Anisotropic Aquifers with High Permeability and Anisotropy .............................................................................................................................. 48 Figure 5.5 Comparison of Aquifer Area Freshened and Salinized as a Result of Aquifer Forcing for Simulations of Eastern Transect Homogeneous, Anisotropic Aquifers with High Permeability and Anisotropy .............................................................................................................................. 49 Figure 5.6 Comparison of2% Seawater Contours for Simulations of Central Transect Heterogeneous Aquifers with Base-Case Permeability Values: Random Clay ............................ 51 Figure 5.7 Comparison of Aquifer Area Freshened and Salinized as a Result of Aquifer Forcing for Simulations of Central Transect Heterogeneous Aquifers with Base-Case Permeability Values: Random Clay ................................................................................................................... 52 Figure 5.8 Comparison of2% Seawater Contours for Simulations of Central Transect Heterogeneous Aquifers with Base-Case Permeability Values: Ordered Clay ............................ 53 IV Figure 5.9 Comparison of 2% Seawater Contours for Simulations of Central Transect Heterogeneous Aquifers with a High Sand Permeability Value ................................................... 54 Figure 5.10 Comparison of Aquifer Area Freshened and Salinized as a Result of Aquifer Forcing for Simulations of Central Transect Heterogeneous Aquifers with a High Sand Permeability Value ............................................................................................................................................. 55 Figure 5.11 Infiltration of Saltwater due to a Single Storm Surge Inundation over a 200-Year Period for a Heterogeneous Aquifer with Base-Case Parameters and a High Pumping Rate ...... 57 Figure 5.12 Infiltration of Saltwater due to a Periodic Storm Surge Inundation Every lOYears over a 200-Year Period for a Heterogeneous Aquifer with Base-Case Parameters and a High Pumping Rate ................................................................................................................................ 58 Tables Table 2.1 Predicted Sea-Level Rise from the IPCC Third Assessment Report ............................ 14 Table 3.1 Coastal Zone Data Collected and Data Source ............................................................. 16 Table 4.1 Estimated Pumping Rates and Depths .......................................................................... 28 Table 5.1 Subset of Simulations Performed ................................................................................. 42 v Acknowledgments This report was prepared by Winston Yu (Task Team Leader, World Bank). The technical modeling and analysis was carried out by Clifford Voss (U.S. Geological Survey), Holly Michael (University of Delaware), Kazi Matin Ahmed (Dhaka University), Lawrence Feinson (U.S. Geological Survey), and Md. Mahfuzur Rahman Khan (Dhaka University). Albert Tuinhof (Acacia Water) contributed to the sections on groundwater management and policy. The following individuals provided helpful feedback during the preparation of this report: Rafik Fatehali Hirji (World Bank), Catherine Tovey (World Bank), Stephen Foster (GW-MATE), Charles Harvey (Massachusetts Institute of Technology), and Peter Ravenscroft (University of Cambridge). The Team wishes to also thank Mr. Jalaluddin Mohammad Abdul Hye, Director General, Water Resources Planning Organization (WARPO), and his staff for their close cooperation. Finally, the Team would like to thank the following World Bank staff for their continuous support during the preparation of this report: Xian Zhu (former Country Director), John Henry Stein, Gajan Pathmanathan, Karin Kemper, Adolfo Brizzi, Simeon Ehui, Richard Damania, Shakil Ferdausi, Khawaja Minatullah, Nagaraja Harshadeep, Nihal Fernando, S Rafiquzzaman, Rachel Susan Palmer, and Ryma Aguw. The Team is grateful to the Bank- Netherlands Water Partnership Program (BNWPP) for financing this study. This study is a product of the staff and consultants of the World Bank. The findings, interpretations, and conclusions expressed in this paper do not necessarily reflect the views of the Executive Directors of The World Bank or the governments they represent. VI Glossary of Terms Anisotropy The condition under which the hydraulic properties of an aquifer vary according to the direction of flow. Aquifer Rock or sediment in a geologic formation that is saturated with water and sufficiently permeable to transmit quantities of water to wells and springs. Confined A confined aquifer is one that is immediately overlain by a low-permeability unit (confining layer), and thus does not have a water table. Darcy's Law Q = KiA. The discharge of water (Q) through a unit area of porous medium is directly proportional to the hydraulic gradient (i) normal to that area (A). The constant of proportionality is the hydraulic conductivity (K). Deposition The geologic process by which material (sediment) is added to a land mass. Dispersion The spread of solutes, colloids, particulate matter, or heat by the combined processes of diffusion and physical mixing of fluids along the path of groundwater flow. Heterogeneous The condition in which the property of a parameter or a system varies with space. Homogeneous The condition in which the property of a parameter or a system does not vary with space. Hydraulic conductivity The volume of fluid that flows through a unit area of porous medium for a unit hydraulic gradient normal to that area. Hydraulic conductivity = (permeability)(water density)(gravitational acceleration)/(water viscosity). Hydraulic gradient The change in hydraulic head with a change in distance in a given direction. Hydraulic head The fluid mechanical energy per unit weight of fluid, which correlates to the elevation that water will rise to in a well. Groundwater flows along this potential gradient, from high to low head. Permeability A measure of the ease of flow of fluid through a porous medium. Porosity The ratio of the volume of void space in a rock or sediment to the total volume of rock or sediment In aquifers, this is the fraction of water volume per subsurface volume of material. Storage coefficient The volume of water released from an aquifer per unit surface area of the aquifer per unit change in head. Unconfined An unconfined (or water table) aquifer is one where the upper surface ofthe aquifer is the water table. Water table aquifers are directly overlain by an unsaturated zone or a surface water body. vii Abbreviations and Acronyms BMD Bangladesh Meteorology Department BWDB Bangladesh Water Development Board BWSPP Bangladesh Water Supply Program Project CDS Coastal Development Strategy CEGIS Center for Environmental and Geographic Information Services CZP Coastal Zone Policy DANIDA Danish International Development Agency DPHE Department of Public Health and Engineering GDP gross domestic product ICZM integrated coastal zone management IPCC Intergovernmental Panel on Climate Change IWM Institute of Water Modelling MoEF Ministry of Environment and Forests NWRC National Water Resources Council PCU Program Coordination Unit PIP priority investment program WARPO Water Resources Planning Organization V1l1 Executive Summary Background The coastal zone of Bangladesh sustains the livelihoods of over 40 million people with a diversity of natural resources that include fisheries, shrimp farms, forests, and deposits of salt and minerals. It also provides sites for export-processing zones, harbors, airports, land ports, and tourism. However, the coast of Bangladesh is vulnerable. A combination of natural events, including storm surges, cyclones, flooding, high groundwater arsenic levels, and anthropogenic hazards such as erosion, waterlogging, soil salinity, pollution, and increasing population pressures, have adversely affected the pace of social and economic development in this region. Compounding these issues are increasing risks from climate change, particularly sea-level rise. A I-meter rise in sea level will inundate an estimated 18% of the total land in Bangladesh, directly threatening about 11 % of the population. Moreover, the indirect effects of climate change, such as changes in river flows and drainage and the nature of extreme events, could have a large impact on the population, with disproportionate impacts on the rural poor. Sea-level rise may also alter the salinity in groundwater and surface water, with corresponding impacts on soil salinity. Saltwater intrusion in groundwater means the gradual or sudden change from freshwater conditions in the ground to saline conditions. Saltwater intrusion can adversely impact the quality and potability of groundwater pumped from wells and the suitability of such water for irrigation. Saltwater intrusion can also cause soil salinization, which may adversely impact crop yields. Saltwater intrusion may occur from saline waters that naturally move up rivers under tidal or storm surge pressures, or from surface flooding associated with storm surges, or from natural processes such as long-term rise in sea level, driving saltwater already underground farther inland. The implications of climate change for saltwater intrusion in the groundwater system of the coastal region have not been investigated in great detail. Drinking water is mainly derived from deep wells and irrigation is limited to surface sources when available. Given the importance of fresh groundwater to the viability of the coastal zone, and its relative scarcity, understanding and modeling these processes is a key for long-term development and sustainability of the coastal regions in Bangladesh. These are priority areas for the government, as outlined in the Coastal Zone Policy and the Coastal Development Strategy. This Study Evaluation of these consequences and means of mitigating negative impacts via groundwater resource management are the focus of this initial study. Evaluation is carried out by (a) obtaining available geologic, hydrologic, and geochemical information on the coastal aquifer of Bangladesh; (b) developing groundwater flow and salt transport models representing general features and conditions along the coast of Bangladesh; and (c) simulating potential changes in the groundwater systems due to naturally occurring hydrologic processes and to various aspects of human activity and climate change. IX There are three primary paths of salinization in the coastal aquifer: (a) classical lateral seawater intrusion within the aquifer, with the Bay of Bengal as the saltwater source, caused by a rising sea level or falling inland groundwater levels; (b) vertical downward seawater intrusion from saline surface water carried inland by repeated storm saltwater surges and by possible future transgression of the coast; and (c) migrating preexisting pockets of subsurface saline water from vertical intrusion, lateral intrusion, or relic seawater that was deposited with the aquifer sediment. The rate of saltwater intrusion along all of these paths may be greatly increased by pumping. Climate change-driven sea-level rise would provide sources of saltwater in new places inland of the current coastal zone, and new saltwater intrusion would occur along these paths. The groundwater system in the coastal region of Bangladesh was evaluated by a computer simulation model. The model represents the physical behavior of groundwater flow from regions of high to low hydraulic head and also the flow that occurs due to fluid density differences. In an aquifer, denser water (saltwater) will move downward, driven by its own weight, through less dense freshwater. The model also represents this density effect. Two-dimensional vertical cross- sectional simulations perpendicular to the coast were constructed one through the central low- topography region of Bangladesh and the other through the higher-topography region on the eastern side of Bangladesh. The geologic structure of the coastal aquifer of Bangladesh is largely unknown, so various types of layering of sand and clay were tested in these cross-sectional models. Two effects of climate change were simulated over a range of hydrogeologic conditions: (a) sea-level rise with a constant coastline location (for example behind coastal barrier walls); and (b) storm surge inundation of land with saltwater, occurring singly and periodically. Simulations were also run with and without pumping, and at several pumping rates representing current and possible future demand conditions. Scientific Understanding Gained The modeling analysis provided three general findings regarding salinization of fresh coastal groundwater resources in Bangladesh. First, saltwater intrusion has already been occurring in some areas due to previous rise in sea level and storm surges. As a result of historical sea-level rise in the last thousands of years, the subsurface saltwater has been moving inland, especially in the low-topography regions of central Bangladesh. Subsurface migration of seawater inland is a very slow process and will reach a state of equilibrium, but only after many thousands of years. In this state, fresh groundwater could only exist at shallow depths (less than 40 meters to 120 meters in the coastal zone, where water table elevations are between 1 meter and 3 meters above mean sea level). However, it was found that vertical infiltration of saltwater due to storm surges or intrusion from brackish tidal rivers can occur more quickly than lateral subsurface migration of saltwater, particularly when inundation events are repetitive. This process may explain in part why shallow groundwater in much of the coastal area is brackish; in some parts of this area brackish water may also be relic saltwater deposited at the same time as the sediments. x Second, pumping of fresh groundwater in the coastal aquifer accelerates saltwater intrusion and degradation of water quality along both horizontal and vertical salinization paths. This indicates a clear need for hydrogeologic characterization, management of pumping, and hydrologic and geochemical monitoring of the coastal aquifer in Bangladesh - irrespective of future climate change. Third, any future sea-level rise will increase the adverse impact of the already-occurring salinization processes to some extent, as follows. Within the current coastal zone, the primary impact of sea transgression on coastal groundwater resources is the direct loss of land area (assuming a net balance between deposition and subsidence of sediment) and loss of the possibility to easily pump any fresh groundwater that remains below the areas covered by the sea. The speed of lateral seawater intrusion is increased somewhat in these areas, with the greatest increase within the horizontal aquifer zones wherein groundwater flows most easily. Moreover, an increased frequency of storm surges, or storm surges that cover a greater area of the land surface due to the higher sea stand, will increase the likelihood of vertical downward intrusion of saltwater to wells that currently produce fresh groundwater, wherever the saline floodwater is able to infiltrate. These findings suggest that the direct impacts of sea-level rise on coastal inundation and extent of storm surges is of greater concern for groundwater conditions than classical lateral seawater intrusion. Moreover, pumping in the coastal zone, even without climate change, is an important determinant of salinization rate, and pumping-induced salinization rate is dependent on the pattern of the various sediment types that compose the aquifer fabric. Sea-level rise may shorten the lifetime of the fresh groundwater resource in the current coastal zone, although this impact may not appreciably increase salinization rates. Coastal Zone Vulnerability Given these major findings, the overall vulnerability of the current deep freshwater portions of the coastal aquifers in Bangladesh (the major source of freshwater in the coastal zone for economic activity and supporting livelihoods) can be described as follows. · Deep fresh coastal groundwater is vulnerable to vertical infiltration of saltwater due to periodic storm surge flooding, particularly where clay layers above pumping wells are absent and an unsaturated zone (which may be filled with saline floodwater during storms) exists or where saline ponded water is allowed to remain following the surge. · There is moderate vulnerability of the fresh coastal groundwater resource to lateral saltwater migration. The location of more vulnerable regions depends on the spatial distribution of aquifer hydraulic properties. More permeable and lower-porosity regions of the aquifer are more vulnerable than less permeable and higher-porosity regions. · There is high vulnerability to salinization due to pumping-induced mixing of preexisting fresh and saline groundwater, irrespective of the source of that saline water. Areas with pumps in aquifer material of low permeability or low porosity and areas where pumping Xl occurs from freshwater pockets surrounded by saltwater are particularly vulnerable to mixing of saltwater into the water produced from wells. · Groundwater in areas with lower topographic relief (central delta) is far more vulnerable to vertical and lateral intrusion pathways than groundwater in higher-relief (eastern delta) areas. Guidance for Management The deep fresh groundwater in the current coastal zone is likely not a permanent resource, even without sea-level rise. Natural processes are causing the inland migration of subsurface seawater. To make matters worse, extraction of groundwater is likely to increase in the future. Despite this apparently negative prospect, careful management may enable use of the current coastal zone freshwater resource for a very long period of time, should sea level not rise appreciably. Measurements, characterization, and analysis today may help to identify areas within the coastal zone from which fresh groundwater can be extracted sustainably or for long times. Management should be proactive in all coastal regions, including monitoring and modeling efforts that evolve over time as more information is obtained. Indeed, proper management of the coastal aquifer in the current situation is an absolute prerequisite to management and mitigation of future salinization problems caused by possible sea-level rise. Concerns about coastal groundwater resources already exist, and alternative freshwater supplies are needed in some areas. Improving land and water management today can help to mitigate future salinization problems. A critical need to inform improved management is better knowledge of aquifer structure, properties, and current salinity distribution. To characterize these aquifers, which are highly heterogeneous and vary regionally, a network of observation wells, installed for the specific purpose of hydrogeologic and geochemical data collection and monitored on a regular basis, is required. Basic chemistry and temperature data in both saline and brackish zones at various depths of the aquifer are needed to fully understand the current flow field and salinity distribution. As more wells in the coastal zone are installed, the sedimentary column at each observation well should be observed and recorded during drilling. This will improve knowledge of the overall aquifer structure, a key control of future salinization. Stable and carbon isotope sampling of groundwater would clarify the age and origin of both fresh and saline groundwater. This will improve understanding of how the system responded to past changes in climate, allowing more certain prediction of future saltwater migration and overall resource sustainability when using computer simulation of the groundwater system. From a pragmatic view, this monitoring program will also serve as an early warning system of production well salinization. Moreover, given that storm surges may be a primary salinization mechanism, improved monitoring of these events and modeling analysis will be critical from the groundwater management perspective. Structural investments to protect against these events, for example removal of standing saltwater ponds created by a surge, are also certainly possible, but must be evaluated. xu Finally, this study only aims to better understand the generic behavior of the coastal aquifer system. It was possible to represent only general features and conditions along the coast of Bangladesh across various aspects of human activity and climate change. Precise future estimates of localized salinization are currently unavailable; thus, continued detailed modeling efforts concomitant with data collection are important for better understanding the spatial and temporal scales of these processes and for making site-based optimal management decisions. This is critical in supporting long-term planning and development efforts by the government in the coastal zone. Xlll 1. Introduction Bangladesh has perhaps the most complex hydraulic regime in the world. The country sits at the confluence of three of the world's largest rivers the Ganges, Brahmaputra, and Meghna Rivers transporting the third-largest amount of water annually and the largest amount of sediment of any world river, through terrain with extremely low elevations into the Bay of Bengal. This low topography makes nearly the entire country vulnerable to a variety of natural disasters, including major inland and coastal flooding caused by monsoonal rains and storm surges and cyclones from the Bay of Bengal. Of particular importance are the coastal resources that sustain the livelihoods of over 40 million inhabitants. The coastal zone, home to several critical ecosystems such as the Sundarbans mangrove forests, also offers an immense potential for economic growth that can be instrumental in reducing poverty and contributing to the development of Bangladesh as a whole. The zone has a diversity of natural resources, including coastal fisheries, shrimp farms, forests, and deposits of salt and minerals. It also has sites for export-processing zones, harbors, airports, and tourism. 1 However, the coast of Bangladesh is also vulnerable. A combination of natural events, including storm surges, cyclones, flooding, and high groundwater arsenic levels, as well as anthropogenic hazards such as erosion, waterlogging, soil salinity, pollution, and increasing population pressures, have adversely affected the pace of social and economic development in this region. Compounding these issues are increasing risks from climate change, particularly via possible sea-level rise. It is estimated that a I-meter rise in global sea levels (assuming a static coast') will inundate 18% of the total land in Bangladesh, directly threatening about 11 % of the population. Using Bangladesh specific sea-level rise predictions, various patterns of average land inundation in the coastal zone may also change (see Figure 1.1). Cyclones and associated storm surges are also predicted to increase in severity and perhaps frequency in the coastal zone of Bangladesh (Ali 1996). The indirect effects of climate change, such as changes in river flows and the nature of extreme events, could also have a large impact on the population, with disproportionate impacts on the rural poor. Sea-level rise may also alter the salinity in groundwater and surface water, with corresponding impacts on soil salinity. Surface saline intrusion along the main river channels is highly seasonal, at a minimum during the monsoon season when about 80% of the annual freshwater flow is provided. In the winter months, the saline front moves inland. Data indicate that soil salinity has been increasing over time due to processes such as seawater inundation, tidal flooding, and saline groundwater flow (Harun-ur-Rashid and Islam 2007). Some previous estuarine modeling work demonstrates that sea-level rise will result in the ingress of surface salinity (MoEF 2006). Effects of seawater intrusion occurring as a result of groundwater abstraction have also been studied in particular areas, such as Khulna (LGED and BRGM 2005). What has not been investigated in great detail, however, are the implications of climate change for saltwater intrusion in the groundwater system of the coastal region. Given the importance of groundwater to the viability of the coastal zone, understanding and modeling these processes is vital to long-term development and sustainability of the coastal regions in Bangladesh. I Given the massive deposition of sediment in the coastal zone, competing erosion and accretion processes may make the impact of sea-level rise worse or better. 2 Figure 1.1 Maps of Projected Flooding in the Coastal Zone of Bangladesh due to Predicted Sea- Level Rise Scenarios (a) Baseline (b) 15 em rise (e) 27 em rise (d) 62 em rise Note: Flood land types defined as FO (0-30 em), Fl (30-90 em), F2 (90-180 em), F3 (180-300 em), and F4 (over 300 em). Source: Center for Environmental and Geographical Information Systems. 1.1 Objective The objective of this study is to improve understanding of the implications of climate change for the groundwater systems in coastal Bangladesh. This is achieved by (a) obtaining available geologic, hydrologic, and geochemical information on coastal aquifers of Bangladesh; (b) 3 developing groundwater flow and salt transport models representing general features and conditions along the coast of Bangladesh; and (c) simulating potential changes in the groundwater systems due to various aspects of human activity and climate change. The simulation analysis will focus on both the pattern and response time of the saltwater-freshwater distribution in subsurface aquifers, with a view towards sustainability of current and future water use under stress due to climate change. The study is aimed at understanding processes and rates of change for systems representative of a range of conditions in coastal Bangladesh, but it is expected that regional and local differences occur. Thus, only general conclusions and guidance should be drawn from this work. 1.2 Methodology Sources of salinization in the groundwater aquifers in the coastal region include: · classical lateral seawater intrusion within the aquifer, with saltwater source areas in the Bay of Bengal caused by a rise in sea level or a drop in landward groundwater levels (Figure 1.2a); · vertical seawater intrusion from saline surface water deriving from both storm surges and transgressions of the coast (Figures 1.2a and 1.2b); · preexisting pockets of saline water that may migrate in the subsurface naturally and due to groundwater pumping (Figure l.2c). Figure 1.2 Illustration of Modes of Salinization of Coastal Aquifers in Bangladesh a. Sea-level rise induces lateral movement of saline groundwater into the aquifer and vertical infiltration at the surface. b. More frequent and intensive storm surges result in more vertical infiltration of seawater into previously fresh zones. c. Pumping in fresh groundwater zones can induce mixing and salinization. 4 The U.S. Geological Survey's SUTRA2 finite element model, which solves the groundwater flow and contaminant transport equations for fluids of variable density, necessary for representing the physics of flow of fresh (lower density) and saline (higher density) groundwater, is used to simulate these seawater infiltration processes. Simulations of these processes are applied separately and jointly to both simple and complex spatial representations of the cross-sectional structure of the coastal aquifer system. Geologic features incorporated into the cross-sections include (a) continuous and broken confining units; (b) embedded patches of clay and sand; and (c) variations in homogeneous anisotropy previously evaluated in groundwater flow models by Michael and Voss (2008, 2009a, 2009b). Topographic features include high- and low-gradient topography (central basin and eastern margin of basin). Anthropogenic activities to be tested include (a) increased pumping for domestic and agricultural supplies; (b) flood irrigation practices; and (c) the effects of potential inland population migration resulting from coastal transgression. The analysis focuses on the lateral and vertical pattern of groundwater flow and salinity distribution in the coastal region with an emphasis on the response time of the saline-freshwater distribution in subsurface aquifers (that is, how long it will take to salinize the aquifers after sea- level rise or a storm event, and how long it will take, if ever, to return to presalinized conditions). This includes the relative impacts of seawater infiltration and the timescale of change from the different salinization mechanisms described in each of the alternative structural descriptions of the aquifer system. This study also seeks to evaluate the effects of salinization on domestic and agricultural water supplies as well as the influences of increased anthropogenic activity. These simulations should serve to improve understanding of the vulnerability of coastal aquifers to various aspects of climate change. The study includes only the aspects of climate change predicted to substantially affect groundwater salinization in Bangladesh. These aspects are sea-level rise and more frequent and severe storm surges. Changes in precipitation and temperature have the potential to affect groundwater salinization in coastal areas because the difference between groundwater levels on land and sea level is the primary factor that drives lateral seawater intrusion. However, in Bangladesh, the groundwater levels on land are not limited by the amount of precipitation, which is enough to flood the land surface during part of the year in many areas. Instead, groundwater levels are limited by the elevation of the land surface, which is very low in nearly all areas in the vulnerable central coastal region. Thus, an increase in precipitation, which is predicted for this region (Cruz et al. 2007), will not substantially change current groundwater conditions (though 2 SUTRA (Voss and Provost 2002) is a computer program that simulates fluid movement and transport of either energy or dissolved substances in a subsurface environment. SUTRA employs a two-dimensional hybrid fmite- element and integrated finite-difference method to approximate the governing equations that describe the two interdependent processes that are simulated: (1) fluid density-dependent saturated or unsaturated groundwater flow; and either (2a) transport of a solute in the groundwater, in which the solute may be subject to equilibrium adsorption on the porous matrix, and both first-order and zero-order production or decay, or (2b) transport of thermal energy in the groundwater and solid matrix of the aquifer. This program has been widely used to simulate coastal groundwater systems throughout the world. 5 changes in river flows could be important, and would tend to reduce surface water salinity). The predicted increase in temperature (Cruz et al. 2007) in the already very humid climate may not increase evapotranspiration enough to substantially affect groundwater levels on land. This study therefore neglects the effects of changing precipitation and temperature, and instead focuses on effects of sea-level change and storm surges. 1.3 Organization of the Report This report is organized in six major sections. The first two sections provide an introduction and background information on the use of groundwater in the coastal zone. In particular, a description of current government of Bangladesh policies and development plans for the region are assessed in the context of future climate change. The third section details the current data available regarding the aquifer conditions. This includes a summary of the geochemical data available. The fourth section describes the modeling approach used, including a description of both the climate and anthropogenic changes that could alter the groundwater system. Section five provides model simulation results under a variety of different aquifer conditions and a summary of a sensitivity analysis to assumed parameters. The impacts of sea-level rise, pumping, and storm surge inundation are investigated. Finally, section six provides some general conclusions and recommendations, including consideration of implications for future land and water use scenarios and future policy decisions. 6 2. Groundwater in the Coastal Zone Figure 2.1 Coastal Zone of Bangladesh ZONE I ""',Afl:T&1 BANGLADESH Source: W ARPO 2006. The coastal zone of Bangladesh contains 18 districts3 (covering about 47,000 square kilometers) and faces a multitude of natural hazards, for example cyclones, storm surges, floods, drought, earthquakes, erosion, salinity intrusion, and arsenic contamination. Substantial investment in protection has been made over the last several decades, including construction of 123 polders (reclaimed land protected from flooding), over 5,000 kilometers of embankments, and over 2,000 cyclone shelters. A higher percentage of the coastal population (almost 40 million) lives below the absolute poverty line compared to the country as a whole (52% versus 49%). Fifteen districts also have lower gross domestic product (GDP) per capita than the country average. Moreover, about 54% of the people in the coastal zone are functionally landless and more than 30% are absolutely landless (Islam 2006). Land use in the coastal zone is diverse (and at times conflicting) and includes agriculture, shrimp farming, salt production, forestry, ship-breaking yards, ports, industry, settlements, and wetlands. Over 50,000 hectares ofland have been reclaimed. 3 The districts are Bagerhat, Barguna, Barisal, Bhola, Chandpur, Chittagong, Cox's Bazar, Feni, Gopalganj, Jessore, Thalakati, Khulna, Lakshmipur, Narail, Noakhali, Pirojpur, Satkhira, and Shariatpur. 7 The poor quality of groundwater in the coastal zone limits the use of the resource. Drinking water is mainly derived from (a) ponds and shallow wells tapping groundwater near the surface but which often turn brackish during the dry season; and (b) deep groundwater wells (> 150-200 meters depth), of which there are currently more than 50,000-60,000. These include deep handpump tubewells and production wells for piped water supply to rural towns and a number of large villages. Land use in the 1950s was primarily for paddy cultivation in the coastal zone. However, salinity intrusion and tidal flooding have prevented further intensification. Currently, irrigation water is mainly from surface water when available (typically at the end or the beginning of the wet season). Consequently, only 15% of the area (about 760,000 hectares) is under irrigation during the dry season. For instance, some 70% of the land in Barisal and Khulna Districts is affected by some degree of salinity, which has significantly reduced agricultural productivity (Rahman and Ahsan 2001). Crop yields in the coastal zone are lower than the national average (about 10% lower for paddy). Brackish groundwater is predominately unused except for some shrimp farms and biosaline agricultural pilot projects. 8 2.1 Development Potential in the Coastal Zone Despite the constraints mentioned above, the coastal zone offers several distinct development opportunities that can both reduce poverty and contribute significantly to regional economic growth. Shrimp farming developed extensively in the 19908, making use of the constructed polders and brackish waters. Land previously used for agriculture and mangroves was being transformed rapidly (with some contention) to meet increasing demands and the high price for shrimp on the international market. Shrimp is the second largest export item in Bangladesh and contributes about US$300 million annually to GDP. It is a key economic activity in Cox's Bazar, Khulna, Bagerhat, and Satkhira and is expanding to several other districts. Other aquatic resources and products (for example hilsha, shutki, crabs, and duck) also have potential for further development. Gas and oil reserves in the coastal areas are immense. It is estimated that about 20 trillion cubic feet of gas can be extracted from the Bay of Bengal. Moreover, economically viable mineral resources (for example cesium, zircon, and rutile) are abundant. The bulk of external trade is handled through two primary ports at Chittagong and Mongla. It is estimated that trade will expand to 43 million tonnes by 2016 from 19 million tonnes in 2000 (Chittagong Port Authority, quoted in Islam and Ahmad 2004). Surrounding these ports, opportunities for industrial development exist. Exports, for instance, from the Chittagong Export Processing Zone were valued at over US$621 million in 2002. Over 250,000 people are also either directly or indirectly involved in the ship-breaking industry (WARPO 2006). Given the several distinctive environmental assets in the coastal zone, there is the potential to develop ecotourism further. Special environmental areas, from the Sundarbans to the St. Martin Islands and Sonadia Island (Cox's Bazar), can be developed to meet growing domestic and international demand. Finally, agriculture remains a dominant activity for most households living in the coastal zone. However, with declining availability of land and competing pressures from other land uses, the scope for further expansion is limited. Productivity gains will be largely driven by the introduction of salt-tolerant varieties of crops, expanded coconut cultivation, and floating or biosaline agriculture. 2.2 Government of Bangladesh Coastal Zone Policy and Planning The main government policy and planning documents for the coastal zone are the Coastal Zone Policy (Ministry of Water Resources 2005) and the Coastal Development Strategy (WARPO 2006). The Coastal Zone Policy was drafted for the following reasons: (a) the coastal zone is lagging behind the rest of the country in socioeconomic development; (b) the coastal zone is lacking in initiatives to cope with different disasters; (c) the environment is deteriorating in the coastal zone; and (d) the coastal zone has the potential to contribute to national development. The Policy identified integrated coastal zone management (ICZM) as the primary principle in developing the coastal zone and identified the overall goal of the Policy as: 9 To create conditions, in which the reduction ofpoverty, development ofsustainable livelihoods and the integration of the coastal zone into national processes can take place (Ministry of Water Resources 2005). To achieve this goal, the policy framework for implementation includes economic growth, basic needs and opportunities for livelihoods, reduction of vulnerabilities, sustainable management of natural resources, equitable distribution, empowerment of communities, women's development and gender equity, and conservation and enhancement of critical ecosystems. Interestingly, the issue of climate change appears largely under the last objective (conservation and enhancement of critical ecosystems). In particular, the Policy identifies the need to enhance existing institutional mechanisms for monitoring climate change in Bangladesh, improving the capacity for generation of better data and more accurate long-term predictions, implementation of adaptive measures, efforts to maintain coastal embankments on a frequent basis, and the establishment of an institutional framework for monitoring and detecting sea-level rise with concomitant contingency plans. 10 The Coastal Development Strategy is based on the Coastal Zone Policy and provides the link between policy and concrete investment interventions. It does not represent one overall framework for all development actions in the entire coastal zone but rather provides a targeted approach with respect to particular regions (islands and chars, exposed coastal zone districts, high tsunami risk areas, southwest region), disadvantaged groups (women and children, fishers and small farmers), issues (shrimp farming, groundwater management, climate change), and opportunities (tourism, renewable energy, marine fisheries, baseline agriculture). Nine strategic priorities are identified and include: · ensuring fresh and safe water availability · safety from man-made and natural hazards · optimizing use of coastal lands · promoting economic growth emphasizing non-farm rural employment · sustainable management of natural resources · improving of livelihoods conditions of people, especially women · environmental conservation · empowerment through knowledge management · creating an enabling institutional environment. These correspond closely with the policy framework in the Coastal Zone Policy. The operational extension of the Coastal Development Strategy is a set of priority investment programs (PIPs), which were identified in 2006 by the Water Resources Planning Organization (WARPO). The PIPs are packages of investment projects (about 26 projects in all) for action in the nine strategic priority areas identified above. One of the PIP activities (under strategic priority "ensuring fresh and safe water availability") is directly related to groundwater. This activity focuses on hydrogeologic investigations of the deep aquifers in the coastal zone and the development of an information system to manage groundwater use and supply information. Most of the projects under the PIP have not yet started or are still in an initial phase of implementation. 2.3 Institutional Arrangements for ICZM The Coastal Zone Policy and Coastal Development Strategy do not create a supra-body for their implementation. Rather, the Policy and Strategy assume that the concerned line ministries and agencies would be the best institutions with the responsibility to implement ICZM processes and programs, which are planned centrally and consistent with an agreed framework (see Appendix D for overall institutional setup). At the national level, the primary institutions are the National Water Resources Council, the Inter-Ministerial Steering Committee, the Inter-Ministerial Technical Committee, and the Program Coordination Unit. The Program Coordination Unit within W ARPO for ICZM was established under the Coastal Zone Policy and is responsible for overall implementation of the Coastal Zone Policy and the 11 Coastal Development Strategy. Among other things, the Program Coordination Unit is tasked with promoting an enabling institutional environment for ICZM, coordinating a PIP across agencies, monitoring and assessing the PIP, and formulating rules, regulations, guidelines, and manuals to support the Coastal Development Strategy. The National Water Resources Council within the lead Ministry of Water Resources acts as a higher-level coordinating and decision-making body. The Program Coordination Unit is also supported by the Inter-Ministerial Steering Committee, which provides policy and strategic guidelines on issues related to the coastal zone. Issues may include main streaming coastal issues into national policies, plans, and strategies. The Program Coordination Unit is also supported by the Inter-Ministerial Technical Committee, which may provide technical guidance on key issues (for example coastal zone regulations, prioritization of resource use, and land zoning), contribute to identifying strategic prioritization, monitor the performance of the Program Coordination Unit, approve and monitor the investment program, resolve conflicts between projects and programs, and form task forces on specific coastal issues. Finally, the Coastal Development Strategy stipulates working down to the local-level government structures (for example district council, upazila parishad, union parishad, or gram sarkar) to ensure public participation in the planning and implementation of coastal zone aetivities. 2.4 A Changing Future in the Coastal Zone As the coastal zone develops over the next several decades, competition for scarce land and water resources may intensify. Thus these institutional arrangements will be critical to managing development in a sustainable manner. Making better use of these resources will, among other things, require improvements in land and water use planning and management. Several emerging challenges are apparent. First, securing provision of safe drinking water for a growing population is needed. Initial projections indicate that the population may grow to about 60 million in the coastal zone by 2050. Second, increasing the availability of freshwater for irrigation during the dry season to meet changing food demands will be critical. This may be achieved either through augmentation of lean season flows through upstream diversions or further development of deep groundwater aquifers. The potential for saline-resistant seeds remains to be explored on a large seale. Third, economic activities that can utilize brackish groundwater must be expanded. Fourth, with continued development, the implications of increased groundwater abstraction must be better understood. Finally, activities to reduce land degradation and soil salinization need to be identified to support the sustainability of many of these developments. Moreover, it is critical to better understand how changes in the freshwater aquifers of the coastal zone may impact this development. In particular, the impact of exogenous climate change (for example sea-level rise, increased storm surges, or changes in river flow regimes) on groundwater resources remains largely unknown and will influence the efforts required to meet these challenges. There is strong evidence that global sea level has risen during the last century at an increased rate (approximately 1.7 millimeters per year). Sea level is not rising uniformly around the world. The two major causes of sea-level rise are thermal expansion of the oceans (water expands as it warms) and the loss of land-based ice due to increased melting. 12 According to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC 2007), the average estimate of the rate of global sea-level rise by 2100 across the range of Special Report on Emissions Scenarios (SRES) is 3.8 millimeters per year (IPCC 2000). Specific modeled scenarios for the coastal zone of Bangladesh are nonexistent. Previous work (for example Agrawala et aL 2003) has relied on the IPCC Third Assessment Report (IPCC 2001) global estimates of9 to 88 centimeters by 2100. In a study on coastal communities and impacts on livelihoods, the U.K. Department for Environment, Food and Rural Affairs (DEFRA 2007) uses the following specific scenarios given in Table 2.1. A precise estimate of sea-level rise relative to the land surface is complicated by simultaneous and competing accretion and subsidence dynamics. The coastal zone is morphologically active. Approximately 1 billion tons of sediment is transported into the coastal zone each year. Moreover, compaction and subsidence of sediment, plus erosion processes, playa key role in defining the landforms in the coastal zone. Thus the net change in coastal position is unclear. Previous work assumed that sediment deposition cancels the effects of compaction and subsidence and that the global average as projected by the IPCC can therefore be used. This study focuses on investigating the physical response of the system to sea-level rise resulting in 13 sea transgression of the land and aims not to represent any particular scenario. Thus the actual estimates of sea-level rise and coastal migration used are of secondary importance here. Table 2.1 Projected Sea-Level Rise Estimated sea-level rise SRES 2020 2050 2080 A2 (High 6em 27 em 62 em estimate) A2 (Low Ocm Scm 9cm estimate) BI (High 5cm 23cm 48cm estimate) BI (Low Ocm 8cm 15 cm estimate) Source: DEFRA 2007. 14 3. Data and Current Aquifer Conditions 3.1 Overview Data on coastal zone hydrology, geology, subsurface hydraulic properties, geochemistry, and numbers of groundwater pumping wells were collected for the coastal zone as part of this project. A list of data and sources are given in Table 3.1 and locations are mapped in Figures 3.1 and 3.2. These data were collected and used to develop an understanding ofthe current state of the aquifer system in order to evaluate current and future vulnerabilities and to aid in development of numerical models. The data that most influenced development of the conceptual and numerical models are lithologs and porewater salinity data, discussed in sections 3.2 and 3.3. This large amount of data has not been previously assembled in this manner. The high spatial density provides potential for detailed geologic an4 geochemical analyses in three dimensions; however, the latter analyses were not within the scope of this project. 15 Table 3.1 Coastal Zone Data Collected and Data Source Data Number of Data type source Measured parameter Data format measurements ology DPHE Depth vs. lithology Excel 1,470 DPHE CI, Fe, Mn, As Excel/GIS 744 Temperature, Ph, EC, TDS, Tb, SS, Water quality BWSPP HC0 3, CI, Ca, Mg, NH 3, N0 3, S04, Excel/GIS 2,156 Na, K, As, Fe, Mn DANIDA Fe, CI, As Excel/GIS 20,979 Surface water Daily high and low tide level BWDB Excel 95 levels (historical record> 50 years) Groundwater Daily water level (historical record> BWDB Access 278 levels 20 years) Daily rainfall, daily temperature, evaporation, daily sunshine hours, BMD daily relative humidity, wind speed ASCIIlExcel 21 Meteorological and direction (historical record> 20 data years) Daily rainfall (historical record> 20 BWDB Access 93 years) Specific capacity, horizontal hydraulic conductivity, Pumping tests BWDB Excel 49 transmissivity, storage coefficient, leakage factor DPHE: Department of Public Health and Engineering; BWSPP: Bangladesh Water Supply Program Project; DANIDA: Danish International Development Agency; BWDB: Bangladesh Water Development Board; BMD: Bangladesh Meteorological Department (see also Appendix C). 16 Figure 3.1 Summary Map of Hydrologic and Geochemical Data Collected from Various Sources ummary Map on Collected Data Coastal Zone, Bangladesh a 125 25 50 75 100 ....- - ~Iom.tets i Legend Mettorologleal Data Stillion · ElMO · ewoe (Rainfall) Wllter Llvet M...urement Stillion SWL(BWDB) ... GWL(8WOB) Salinity Oata Site Om Source · BWSPl"IOPloE · OPIE · DANDA COIattl River D Coltttl Ciatrlett 17 Figure 3.2 Summary Map of Lithologic Data Collected from DPHE ~eJ&Map Showing Lithologic Data Site " Coastal Zone, Bangladesh o 125 25 75 100 1""1.-- kilometers i Legend Uthologic Data Site · DPI-E - Coastal River D Coastal Districts 3.2 Geology and Lithologic Data The geologic development of the coastal plain of Bangladesh has been influenced by changes in sea level, active tectonics, and very rapid sedimentation by rivers that have moved and changed course over geologic time. The deposits that make up the coastal aquifer system consist of alternating deposits of sand and clay or mud. These sand and clay layers are clearly seen in the lithologic data collected throughout the coastal zone (Figures 3.3b and 3.3d and Appendix A). The lithologic data illustrate the complex structure of the aquifer system in coastal Bangladesh. Approximately 1,000 logs have been collected during well drilling for the coastal region from the Department of Public Health and Engineering (DPHE). The logs contain detailed descriptions of lithology with associated depth intervals, to a maximum depth of approximately 400 meters. Sediments are extremely variable spatially on various spatial scales, dominated by vertical stacking of alternating high- and low-permeability (k) sediments (sands and clays) ranging in thickness from meters to tens of meters. Higher occurrences of sands or clays in certain depth intervals are apparent in some areas, but exceptions are numerous, indicating a high level of variability and laterally discontinuous geologic structures. The locations of lithologic logs are 18 mapped in Figures 3.3a and 3.3c, along with transect lines of cross-sections that have been plotted in north-south and east-west directions. Examples of cross-sections are shown in Figures 3.3b and 3.3d. Figure 3.3 Maps aud Representative Cross-Sections of Lithologic Logs Obtained from DPHE D Multilog Profile along Line D-D' D' .-~.~~-.-.-----.--------- ---~~--- Lithology · Clay I:::~:d Medium Sand Coarse Sand a. Map of lithologic log locations and north-south transect lines. b. Example cross-section displaying all logs located within 25 km of line D-D'. c. Map of lithologic log locations and east-west transect lines. d. ExampJe cross-section displaying all logs located within 25 km of transect line 0-0'. There may be some trends in geologic structure in both north-south and east-west directions. Depositional patterns appear to dip toward the coast in some locations, becoming deeper toward the south (see Figure 3.4c and Figure A.I). The thickness of depositional layers also appears to decrease toward the south, with thinner and less continuous beds toward the coastline in some locations. The clay content of the aquifers tends to be greater west of the Meghna River, particularly at depth (Figure 3.3d). 3.3 Geochemical Data High salinity groundwater is known to threaten drinking water wells in the coastal zone, particularly in shallow depths. Deeper in the aquifer, at depths greater than about 150 meters, groundwater is fresh, thus much of the groundwater used for drinking water supply is drawn from greater than 150 meters. Geochemical data have been collected from DPHE and the Comilla and Barisal offices ofthe Danish International Development Agency (DANIDA). Over 23,000 measurements with 19 associated depth intervals were obtained; measured species included chloride, arsenic, iron, and manganese. Despite the known high salinity levels in shallow groundwater, porewater salinities measured in the subsurface are largely fresh: chloride concentrations over 1,000 milligrams per liter are measured in fewer than 2% of the data points. This is because measurement locations are not distributed uniformly in the subsurface and these measurements are largely obtained from wells installed for drinking water supply purposes and is thus biased toward low chloride content. The few measurements at shallow depths (less than 1% of wells are screened less than 150 meters deep) indicate that shallow strata are more saline. Figures 3.4a and 3.4b map geochemical measurement locations and associated transect lines. Figure 3.4c is a cross-section of chloride measurements along the transect line C-C' shown in Figure 3.3a and Figures 3.4a and 3.4b. The figures show that deep groundwater is nearly uniformly low in chloride, with only small variability. Figure 3.5 is a map view of all chloride measurements collected through this project. There are a few high measurements locally, but nearly all of the measurements are below drinking water salinity levels. Because measurements were collected in water supply wells, no measurements exist below the first freshwater zone encountered by each boring. Regrettably, it is unknown whether deeper fluid is fresh or saline, or where a transition from fresh to saline water might take place, making it impossible to assess the present quantity of freshwater available. 3.4 Hydraulic Test Data The results of78 pump tests give estimates of horizontal aquifer hydraulic conductivity (kh) and storage coefficient (S) at 49 locations (Figure 3.6) in the coastal zone. The average kh is 17.9 meters per day with a standard deviation of 11.4 meters per day, and the average Sis 0.022 with a standard deviation of 0.029. The range in kh is 1.7 to 46, a difference of a factor of 27. This is a narrow range, considering that hydraulic conductivity values may vary by 10 orders of magnitude between clay and sand, both of which are common in this aquifer system. This means that the hydraulic properties of the system, as measured by pump tests, are relatively uniform across the lower delta. 20 Figure 3.4 Maps and Representative Cross-Sections of Chloride Concentrations c.) c Measured Chloride Concentrations along Line C-C' C· " " Chloride Concentration .g §: ~ . ~;It , ... , [mgIL] " I ·· ~~ " /I)' a ~ . · :::00 ;~ 500·1000 ~ ~ 1000·2000 I 2000·5000 · 5ooQ.100oo Distance [m] d.) c Multilog Profile along Line C-C' C· " -~ ,..------~-;. Lithology " I~ · Clay 1:- I=~ t: CoarseSand r a. Map of chloride measurement locations and north-south transect lines. b. Map of lithologic log locations and north-south transect lines. c. Example cross-section displaying all chloride measurements located within 25 km of transect line C-C'. d. Example cross-section displaying aU logs located within 25 km oftransect line C-C'. Sources; DPHE and DANIDA. 21 Figure 3.5 Map of Chloride Concentrations (mgIL) Measured in Wells water qualitl/ welts Clmg/I · 0- 25G · 2SO- SOO ~ 500- 1000 ~ 1000- 2000 · 2000- 5000 · 500()' 10000 c:::J F§ ~·E .!!; § "W.~ --'-;!'F-"~d-:~~~--"---+--t"'---::;~--'~:--~~--1'i~~::r.----:~~"'-----";Tlo::- i"~o.~~~~~-4--~~~~~~~~--~~~--~~~~--~~ z '11"11 ........;i'-..,.;;......l,-----'\'--...!'.~_F_~...,._=_-.....:-.~iri_-_+r_-Hc'H_-~."L+__\_---+__ W-"12-+-...!'.~r-~--.~~+'......~~~&....-':""..&..7f+--.;J.o.-i+-+-~-------'---..,...-:I-· 'll"1:<-~~--'~~+---if.!-~~w..:;:&~~L..;+?-----,I-.~!-;-'~------:"----+, ~4--+"""""'" W-"15-~rtjo.~ W'16-..,..r~fi'w UthoIogy ,...., "f; I Clay ~ I Silty clay .....- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - / Fine sand r---------------------------------------------------~ Medium sand ''; Coarse sand 69 70 Figure A.l, continued C --,:;;,11 Line E10-W10 ~-.tn 1t~1111 I III , II I il l I ~: - - ~- - - - I II I I I I .',wv I I ,..... I I I I ,..1,., I I I I -.t:II,WU I I .:tLJJW I I I I :J1>UIJ.U I I I .u.:wu I Line E11-W11 ~ ~W;- ~j " ~ II I I I I I I III III, 1 1 1 I III , I I I I I I I ' , II , , 1 I ' " '1: IK,ooo imo:o :40,(00 :Il$(I;O: 3000:0 -P.·.' " ,100.:0: Line E12-W12 :f' I,II F,!'? ~ II I I - - - tw,l.u_ ,,,,~...u I' ... J.v. II . '" J.V~ i:lbu.l.u. 4U'U..u -~ - - - . W-"'j Line E13-W13 I::-l:i :rl I _~ " 1 1 I I , 111111111111 , I 1 I I 1 I I I 1 I I I II 1 1 I 1 I I ( -g q IO:JlOO ;0.000 ;m.:o.;: ~o::o m.:o: ~f)OO 4:0.000 1N_I.:I Line E14-W14 =-l~ d III~II'I ~; - ~ - - III I x 1 I , I I Iii I 1 Iii I i I 1 i I I i I I i r :0.... 1£p«J ::000:0 250,:0: !(i:POO 3!Q,OOO «>0,:1>: Line E15-W15 ~ '1>11; EI" I I~ - - I- I- - 1-, ~- - r-~ 1-' l- I- I I I r UlIll'fltW 2,49).000 "",,oco 2)5C.(IItl K-K' Ilf II~' 1IIIII1 'rr-T I I lNJ).JOO I I I 'J~' I r, I I I 1,'j),tUJ III tlI.~.,",," .. I .aw.uoo -:. . · I I I I I l.-aJ.IllI I 1 I I I f :lJt-ll/..Ul L-L' III~IIIIIIIIII 'I i I I I I I I I I i I I I I ' , , I I I , , , I I , I , I " lUlttll l,W:!Ml ~m~ o.Jt~.1II"'" l..aSCJ)lI :lCD,aD .l,lIitPi8 74 Figure A.2, continued M-MJ ~l~·m. I In IIIIIIIIIIII-¥~: Q.Q' . IlI1lJllnr 75 Figure A.2, continued ~f-···-··················-r······iur r· FL 0 f~ fi S-S' T-T' lULU! -r,---,,----rl-----'--------'-""-'-,-'1-'1---'1 '1'---'----'-'---'-1 1.tsllXJl ~1Dl ~"--'-I-'-1-'1-,--.,-....,-,--rl-:.......-r--r--r-I"""-'1 OIfII __ tic'tttnw ~__ lJOO.m I' lS,(fJ) U-U ' V-V' ~llllr 11 I ! ! : 11! r II r ! r T i 1'._. I i I r·· :- ..<1» I' :-.0 l-Matn Il.UliM.... MlIM/ l-W:O 76 Figure A.2, continued Z-Z' t I f 77 Figure A.2, continued CC-CC' 'I rTll 1 II ·1 ~1fJ'1ftt< tJ!1!Witl!llHsOO 1fhirtf' DO-DO' 78 Figure A.2, continued EE-EE' EF' . il 11 l- - t- ~-.~ 'I i I I I I I I iii I I i I I ,I I I "...,,'" 1M'),.." 'MTIj'tt'1 ~"i.,-.r.lnfl'llil''' HIMi'D :t..m,t'IM l- i :a- .! - GG-GG' II HH-HH' Y( I I I I I 1 I I I I I I Ii 1 I I II I i I Ii 1 1 I ,21u:tnl ~:;a,1JX) ;:!nHOO ~l/I _ _ ;r..@,00.1 1,400LUJ 2;.m~ 79 A.2 Porewater Salinity Data Figure A.3 Subsurface Chloride Concentration Data: East-West Transects Top panel is map of well locations and east-west transect lines 1-16. Other panels are profiles of salinity data located along each transect line 1-16. , 200,000 UneE1-W1 \ ~ ,. -."_:" &A.' - «.;,1: '0 . 0 «I 10.. Task Forces N ;.;.. C Sector wise Task Force. chaired by the secretaI}' of the concerned Ministry e l~~ WARPO o i l 0 !"""O ProfE'ssioDal ~ z I I ~t a!i:.W Supporting Staffs and DE'puted GoB c.,r.n Expt'rts. FoulPoiuts ~ = Selected from GoB agencies, Universities, ~ ~ "ii -a:; ... ... Ngo's, Research Institutes, Trade bodies and ~ ... .W .... oS 'i ~ ..,J -~ = >0 s: ';.;.. 1: Civil Societies . "" - «I ,112 ~ ~ '--- '---- I Source: W ARPO 2006. References Agrawala, S., T. Ota, A. Uddin Ahmed, l. Smith, and M. van Aalst. 2003. Development and Climate Change in Bangladesh: Focus on Coastal Flooding and the Sundarbans. Organisation for Economic Co-operation and Development, Environment Directorate. Ali, A. 1996. "Vulnerability of Bangladesh to Climate Change and Sea Level Rise through Tropical Cyclones and Storm Surges." Water, Air, and Soil Pollution 92: 171-9. Begg, S.H., and P.R King. 1985. Modeling the Effects ofShales on Reservoir Performance: Calculation ofEffective Vertical Permeability. Paper SPE 13529 presented at the SPE Reservoir Simulation Symposium, Dallas, TX, February 10-13, 1985. Burgess, W.G., M. Burren, l. Perrin, and K.M. Ahmed. 2002. "Constraints on the Sustainable Development of Arsenic-Bearing Aquifers in Southern Bangladesh. Part 1: A Conceptual Model of Arsenic in the Aquifer." In Sustainable Groundwater Development, ed. K.M. Hiscock, M.O. Rivett, and RM. Davison, 145-63. Special Publication 193. London: Geological Society. Cruz, RV., H. Harasawa, M. Lal, S. Wu, Y. Anokhin, B. Punsalmaa, Y. Honda, M. lafari, C. Li, and N. Huu Ninh. 2007. "Asia." In Climate Change 2007: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change (ed. M.L. Parry, O.F. Canziani, l.P. Palutikof, PJ. van der Linden, and C.E. Hanson), 469-506. Cambridge, United Kingdom: Cambridge University Press. Department for Environment Food and Rural Affairs (DEFRA), UK. 2007. Investigating the Impact ofRelative Sea-Level Rise on Coastal Communities and their Livelihoods in Bangladesh. Final Report. Prepared by the Center for Environmental and Geographic Information Services and the Institute for Water Modeling. 137 pp. Harun-ur-Rashid, M., and M.S. Islam. 2007. Adaptation to Climate Change for Sustainable Development ofBangladesh Agriculture. Presentation at third session of the Technical Committee of the Asian and Pacific Center for Agricultural Engineering and Machinery (APCAEM), November 20-21, Beijing, China. IPCC (Intergovernmental Panel on Climate Change). 2000. Special Report on Emissions Scenarios. Cambridge, United Kingdom: Cambridge University Press. IPCC (Intergovernmental Panel on Climate Change). 2001. Climate Change 2001. Third Assessment Report of IPCC. Cambridge, United Kingdom: Cambridge University Press. IPCC (Intergovernmental Panel on Climate Change). 2007. Climate Change 2007. Fourth Assessment Report ofIPCC. Cambridge, United Kingdom: Cambridge University Press. Islam, M.R 2006. "Managing Diverse Land Uses in Coastal Bangladesh: Institutional Approaches." In Environment and Livelihoods in Tropical Coastal Zones, ed. C.T. Hoanh, T.P. Tuong, l.W. Gowing, and B. Hardy, 237-48. Wallingford, United Kingdom: CABI Publishing. 103 Islam, M.R., and M. Ahmad. 2004. Living in the Coast: Problems, Opportunities and Challenges. Dhaka: Program Development Office for Integrated Coastal Zone Management Plan. LGED and BRGM (Local Government Engineering Department and Bureau of Geological and Mining Research). 2005. Municipal Services Project, Groundwater Resources and Hydro- Geological Investigations in and around Khulna City. Final Report. Michael, H.A, and C.I. Voss. 2008. "Evaluation of the Sustainability of Deep Groundwater as an Arsenic-Safe Resource in the Bengal Basin." Proceedings of the National Academy ofSciences 105 (25): 8531-{j. Michael, H.A., and C.L Voss. 2009a. "Controls on Groundwater Flow in the Bengal Basin of India and Bangladesh: Regional Modeling Analysis." Hydrogeology Journal doi: 10.1007/sI0040-008-0429-4. Michael, H.A., and C.L Voss. 2009b. "Estimation of Regional-Scale Groundwater Flow Properties in the Bengal Basin of India and Bangladesh." Hydrogeology Journal doi: 10.1 007/s 10040-009-0443-1. Ministry of Water Resources. 2005. Coastal Zone Policy. Dhaka: Government of Bangladesh, Ministry of Water Resources. Ministry of Environment and Forests. 2006. Impact of Sea Level Rise on Landuse Suitability and Adaptation Options. Prepared by the Center for Environmental and Geographic Infonnation Services and United Nations Development Program, Dhaka, 153 pp. Patrick, M. 2001. Hydrogeology Summary Report. Five Districts Water Supply and Sanitation Group (5DWSG), DPHE-DANIDA Water Supply and Sanitation Component, Bangladesh. Rahman, M., and M. Ahsan. 2001. "Salinity Constraints and Agricultural Productivity in Coastal Saline Area of Bangladesh." In Soil Resources in Bangladesh: Assessment and Utilization, 1-14. Proceedings of the Annual Workshop on Soil Resources, February 14-15,2001. Ravenscroft, P., and 1.M. McArthur. 2004. "Mechanism of Regional Pollution of Groundwater by Boron: The Examples of Bangladesh and Michigan, USA." Applied Geochemistry 19: 1413-30. Serway, R.A 1996. Physics For Scientists and Engineers, 4th ed. Philadelphia: Saunders College Publishing. Voss, C.l., D. Boldt, and AM. Shapiro. 1997. A Graphical User Interfacefor the US. Geological Survey's SUTRA Code Using Argus ONE (for Simulation of Variable-Density Saturated-Unsaturated Ground-Water Flow with Solute or Energy Transport). U.S. Geological Survey Open-File Report 97-421. Voss, C.I., and A.M. Provost. 2002. SUTRA: A Modelfor Saturated-Unsaturated Variable- Density Ground-Water Flow with Solute and Energy Transport. U.S. Geological Survey Water Resources Investigation Report 02-4231. WARPO (Water Resources Planning Organization). 2006. Coastal Development Strategy. Dhaka, Bangladesh: Government of Bangladesh, Ministry of Water Resources. 104 WARPO and EKN (Water Resources Planning Organization and Embassy of the Kingdom of the Netherlands). 2009. Identification Mission/or an Integrated Coastal Zone Development Program. Draft Final Report. 105