Influence of landscape features on the large variation of shallow groundwater salinity in southwestern Bangladesh

Floris Loys Naus; Paul Schot; Kazi Matin Ahmed; Jasper Griffioen

doi:10.1016/j.hydroa.2019.100043

Influence of landscape features on the large variation of shallow groundwater salinity in southwestern Bangladesh

Floris Loys Naus^*, Paul Schot, Kazi Matin Ahmed, Jasper Griffioen

^*Corresponding author for this work

University of Dhaka

Research output: Contribution to journal › Article › Academic › peer-review

Abstract

In southwestern Bangladesh, the large variation in groundwater salinity has only been elucidated in small-scale study areas and along large regional-scale gradients. We aimed to assess the regional shallow (<60 m) groundwater salinity variation with a higher resolution as a function of landscape features and associated hydrological processes. Spatial variation in groundwater salinity was assessed using 442 EC measurements from previous studies and 1998 new EC measurements. Groundwater EC values were correlated with well location data (latitude, longitude and depth of the filter) and landscape feature data (elevation, soil type, land use and surface clay thickness). Additionally, we performed a geomorphological analysis of landscape features to infer associated hydrological processes. We interpret wide fluvial zones to be remnants of sandy deposits in large paleo channels which allow freshwater recharge, resulting in groundwater that is mostly (75%) fresh. Narrow fluvial zones, tidal fluvial zones, and fluvial zones next to tidal rivers are more susceptible to lateral saline water flow or saline water recharge by occasional tidal flooding, and only contain some shallow fresh groundwater in high-lying zones. Tidal flat or tidal fringe zones hardly contain any fresh groundwater. This study is the first to demonstrate the relation between landscape features, hydrological processes and regional groundwater salinity throughout southwestern Bangladesh. The main lines of our approach may be applicable in other coastal areas with available spatial landscape feature data, enabling a first prediction of groundwater salinity variation.

Original language	English
Article number	100043
Number of pages	15
Journal	Journal of Hydrology X
Volume	5
DOIs	https://doi.org/10.1016/j.hydroa.2019.100043
Publication status	Published - 2019

Funding

This work is part of the Delta-MAR project funded by the Urbanizing Deltas of the World programme of NWO-WOTRO (Grant number: OND1357179 ). We would like to thank Chelsea Peters, Steven Goodbred, John Ayers from Vanderbilt University for allowing us to use their Electrical Conductivity measurements throughout the region. Additionally, we would like to acknowledge the help of all the staff from the Delta-MAR office in Khulna for their support during the fieldwork campaigns, particularly Abir Delwaruzzaman, who always was ready to assist during the fieldwork and who collected some of the EC measurements throughout the region. We would like to acknowledge all MSc students that assisted during the fieldwork, particularly Ruth Wijland, Luc Essink, Kennard Burer, Jan Dirk Smidt from Utrecht University and Atikul Islam and Arif Hasan from Dhaka University. Lastly, Dr Joy Burrough is acknowledged for editing a near-final version of the manuscript. Appendix A

Keywords

Bangladesh
Coastal zone hydrology
Freshwater lens
Hydrogeology
Salt water intrusion

UN SDGs

This output contributes to the following UN Sustainable Development Goals (SDGs)

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10.1016/j.hydroa.2019.100043

Influence of landscape featuresFinal published version, 9.49 MBLicence: CC BY

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title = "Influence of landscape features on the large variation of shallow groundwater salinity in southwestern Bangladesh",

abstract = "In southwestern Bangladesh, the large variation in groundwater salinity has only been elucidated in small-scale study areas and along large regional-scale gradients. We aimed to assess the regional shallow (<60 m) groundwater salinity variation with a higher resolution as a function of landscape features and associated hydrological processes. Spatial variation in groundwater salinity was assessed using 442 EC measurements from previous studies and 1998 new EC measurements. Groundwater EC values were correlated with well location data (latitude, longitude and depth of the filter) and landscape feature data (elevation, soil type, land use and surface clay thickness). Additionally, we performed a geomorphological analysis of landscape features to infer associated hydrological processes. We interpret wide fluvial zones to be remnants of sandy deposits in large paleo channels which allow freshwater recharge, resulting in groundwater that is mostly (75%) fresh. Narrow fluvial zones, tidal fluvial zones, and fluvial zones next to tidal rivers are more susceptible to lateral saline water flow or saline water recharge by occasional tidal flooding, and only contain some shallow fresh groundwater in high-lying zones. Tidal flat or tidal fringe zones hardly contain any fresh groundwater. This study is the first to demonstrate the relation between landscape features, hydrological processes and regional groundwater salinity throughout southwestern Bangladesh. The main lines of our approach may be applicable in other coastal areas with available spatial landscape feature data, enabling a first prediction of groundwater salinity variation.",

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author = "Naus, {Floris Loys} and Paul Schot and Ahmed, {Kazi Matin} and Jasper Griffioen",

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AU - Naus, Floris Loys

AU - Schot, Paul

AU - Ahmed, Kazi Matin

AU - Griffioen, Jasper

PY - 2019

Y1 - 2019

N2 - In southwestern Bangladesh, the large variation in groundwater salinity has only been elucidated in small-scale study areas and along large regional-scale gradients. We aimed to assess the regional shallow (<60 m) groundwater salinity variation with a higher resolution as a function of landscape features and associated hydrological processes. Spatial variation in groundwater salinity was assessed using 442 EC measurements from previous studies and 1998 new EC measurements. Groundwater EC values were correlated with well location data (latitude, longitude and depth of the filter) and landscape feature data (elevation, soil type, land use and surface clay thickness). Additionally, we performed a geomorphological analysis of landscape features to infer associated hydrological processes. We interpret wide fluvial zones to be remnants of sandy deposits in large paleo channels which allow freshwater recharge, resulting in groundwater that is mostly (75%) fresh. Narrow fluvial zones, tidal fluvial zones, and fluvial zones next to tidal rivers are more susceptible to lateral saline water flow or saline water recharge by occasional tidal flooding, and only contain some shallow fresh groundwater in high-lying zones. Tidal flat or tidal fringe zones hardly contain any fresh groundwater. This study is the first to demonstrate the relation between landscape features, hydrological processes and regional groundwater salinity throughout southwestern Bangladesh. The main lines of our approach may be applicable in other coastal areas with available spatial landscape feature data, enabling a first prediction of groundwater salinity variation.

AB - In southwestern Bangladesh, the large variation in groundwater salinity has only been elucidated in small-scale study areas and along large regional-scale gradients. We aimed to assess the regional shallow (<60 m) groundwater salinity variation with a higher resolution as a function of landscape features and associated hydrological processes. Spatial variation in groundwater salinity was assessed using 442 EC measurements from previous studies and 1998 new EC measurements. Groundwater EC values were correlated with well location data (latitude, longitude and depth of the filter) and landscape feature data (elevation, soil type, land use and surface clay thickness). Additionally, we performed a geomorphological analysis of landscape features to infer associated hydrological processes. We interpret wide fluvial zones to be remnants of sandy deposits in large paleo channels which allow freshwater recharge, resulting in groundwater that is mostly (75%) fresh. Narrow fluvial zones, tidal fluvial zones, and fluvial zones next to tidal rivers are more susceptible to lateral saline water flow or saline water recharge by occasional tidal flooding, and only contain some shallow fresh groundwater in high-lying zones. Tidal flat or tidal fringe zones hardly contain any fresh groundwater. This study is the first to demonstrate the relation between landscape features, hydrological processes and regional groundwater salinity throughout southwestern Bangladesh. The main lines of our approach may be applicable in other coastal areas with available spatial landscape feature data, enabling a first prediction of groundwater salinity variation.

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KW - Freshwater lens

KW - Hydrogeology

KW - Salt water intrusion

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Influence of landscape features on the large variation of shallow groundwater salinity in southwestern Bangladesh

Abstract

Funding

Keywords

UN SDGs

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Landschapsvormen, hydrologische processen en zoutgehalte

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