Application of a GIS-Based DRASTIC Model for Groundwater Vulnerability Assessment: A Case Study of Lai City, Tandjile East Department, Southern Chad

Tidjani Bahar; Mahamat Moussa

doi:doi:10.11648/j.wros.20261505.13

Research Article |

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Application of a GIS-Based DRASTIC Model for Groundwater Vulnerability Assessment: A Case Study of Lai City, Tandjile East Department, Southern Chad

Tidjani Bahar^*

, Mahamat Moussa

Published in Journal of Water Resources and Ocean Science (Volume 15, Issue 5)

Received: 28 August 2026 Accepted: 17 September 2026 Published: 29 September 2026

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Abstract

Groundwater resource protection is a worldwide issue because groundwater plays a crucial role in meeting water supply demands for both natural ecosystems and human activities. Effective groundwater management and protection therefore require appropriate approaches for assessing contamination risks and identifying areas that are particularly vulnerable to pollution. In this study, a GIS-based DRASTIC model was applied to assess groundwater vulnerability in Lai City, southern Chad. Seven hydrogeological parameters were considered, namely depth to water, net recharge, aquifer media, soil media, topography, impact of the vadose zone, and hydraulic conductivity. A weighted overlay analysis based on the DRASTIC Index (DI) was subsequently used to generate the groundwater vulnerability map of the study area. The results show that the DRASTIC Index values range from 119 to 175, enabling the study area to be categorized into three groundwater vulnerability classes: low, moderate, and high. The high-vulnerability class covers approximately 35% of the study area, highlighting areas that require particular attention for groundwater protection and management. The average and low class of vulnerability covers portions of the study area 31% and 34%, respectively. The northern and south-western portion of the catchment, namely Lai, Gabri Mbassa, Sategui, and Django, possesses high groundwater vulnerability. GIS-based Drastic model validation is performed via water quality parameters such as Nitrate and Total Dissolved Solids, with the accuracy of 97% and 75% respectively. The resulting groundwater vulnerability map provides a valuable tool for groundwater protection and sustainable land-use planning in Lai City and its surrounding areas.

Published in	Journal of Water Resources and Ocean Science (Volume 15, Issue 5)
DOI	10.11648/j.wros.20261505.13
Page(s)	200-220
Creative Commons	This is an Open Access article, distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution and reproduction in any medium or format, provided the original work is properly cited.
Copyright	Copyright © The Author(s), 2026. Published by Science Publishing Group

Keywords

Drastic, Geographic Information System, Groundwater Vulnerability, Nitrate and Total Dissolved Solids Concentration, Lai City

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Bahar, T., Moussa, M. (2026). Application of a GIS-Based DRASTIC Model for Groundwater Vulnerability Assessment: A Case Study of Lai City, Tandjile East Department, Southern Chad. Journal of Water Resources and Ocean Science, 15(5), 200-220. https://doi.org/10.11648/j.wros.20261505.13

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Bahar, T.; Moussa, M. Application of a GIS-Based DRASTIC Model for Groundwater Vulnerability Assessment: A Case Study of Lai City, Tandjile East Department, Southern Chad. J. Water Resour. Ocean Sci. 2026, 15(5), 200-220. doi: 10.11648/j.wros.20261505.13

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Bahar T, Moussa M. Application of a GIS-Based DRASTIC Model for Groundwater Vulnerability Assessment: A Case Study of Lai City, Tandjile East Department, Southern Chad. J Water Resour Ocean Sci. 2026;15(5):200-220. doi: 10.11648/j.wros.20261505.13

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  author = {Tidjani Bahar and Mahamat Moussa},
  title = {Application of a GIS-Based DRASTIC Model for Groundwater Vulnerability Assessment: A Case Study of Lai City, Tandjile East Department, Southern Chad},
  journal = {Journal of Water Resources and Ocean Science},
  volume = {15},
  number = {5},
  pages = {200-220},
  doi = {10.11648/j.wros.20261505.13},
  url = {https://doi.org/10.11648/j.wros.20261505.13},
  eprint = {https://article.sciencepublishinggroup.com/pdf/10.11648.j.wros.20261505.13},
  abstract = {Groundwater resource protection is a worldwide issue because groundwater plays a crucial role in meeting water supply demands for both natural ecosystems and human activities. Effective groundwater management and protection therefore require appropriate approaches for assessing contamination risks and identifying areas that are particularly vulnerable to pollution. In this study, a GIS-based DRASTIC model was applied to assess groundwater vulnerability in Lai City, southern Chad. Seven hydrogeological parameters were considered, namely depth to water, net recharge, aquifer media, soil media, topography, impact of the vadose zone, and hydraulic conductivity. A weighted overlay analysis based on the DRASTIC Index (DI) was subsequently used to generate the groundwater vulnerability map of the study area. The results show that the DRASTIC Index values range from 119 to 175, enabling the study area to be categorized into three groundwater vulnerability classes: low, moderate, and high. The high-vulnerability class covers approximately 35% of the study area, highlighting areas that require particular attention for groundwater protection and management. The average and low class of vulnerability covers portions of the study area 31% and 34%, respectively. The northern and south-western portion of the catchment, namely Lai, Gabri Mbassa, Sategui, and Django, possesses high groundwater vulnerability. GIS-based Drastic model validation is performed via water quality parameters such as Nitrate and Total Dissolved Solids, with the accuracy of 97% and 75% respectively. The resulting groundwater vulnerability map provides a valuable tool for groundwater protection and sustainable land-use planning in Lai City and its surrounding areas.},
 year = {2026}
}

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TY  - JOUR
T1  - Application of a GIS-Based DRASTIC Model for Groundwater Vulnerability Assessment: A Case Study of Lai City, Tandjile East Department, Southern Chad
AU  - Tidjani Bahar
AU  - Mahamat Moussa
Y1  - 2026/09/29
PY  - 2026
N1  - https://doi.org/10.11648/j.wros.20261505.13
DO  - 10.11648/j.wros.20261505.13
T2  - Journal of Water Resources and Ocean Science
JF  - Journal of Water Resources and Ocean Science
JO  - Journal of Water Resources and Ocean Science
SP  - 200
EP  - 220
PB  - Science Publishing Group
SN  - 2328-7993
UR  - https://doi.org/10.11648/j.wros.20261505.13
AB  - Groundwater resource protection is a worldwide issue because groundwater plays a crucial role in meeting water supply demands for both natural ecosystems and human activities. Effective groundwater management and protection therefore require appropriate approaches for assessing contamination risks and identifying areas that are particularly vulnerable to pollution. In this study, a GIS-based DRASTIC model was applied to assess groundwater vulnerability in Lai City, southern Chad. Seven hydrogeological parameters were considered, namely depth to water, net recharge, aquifer media, soil media, topography, impact of the vadose zone, and hydraulic conductivity. A weighted overlay analysis based on the DRASTIC Index (DI) was subsequently used to generate the groundwater vulnerability map of the study area. The results show that the DRASTIC Index values range from 119 to 175, enabling the study area to be categorized into three groundwater vulnerability classes: low, moderate, and high. The high-vulnerability class covers approximately 35% of the study area, highlighting areas that require particular attention for groundwater protection and management. The average and low class of vulnerability covers portions of the study area 31% and 34%, respectively. The northern and south-western portion of the catchment, namely Lai, Gabri Mbassa, Sategui, and Django, possesses high groundwater vulnerability. GIS-based Drastic model validation is performed via water quality parameters such as Nitrate and Total Dissolved Solids, with the accuracy of 97% and 75% respectively. The resulting groundwater vulnerability map provides a valuable tool for groundwater protection and sustainable land-use planning in Lai City and its surrounding areas.
VL  - 15
IS  - 5
ER  -

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Author Information

Tidjani Bahar

Department of Rural Engineering, National School of Public Works of N’Djamena, N’Djamena, Chad

Contact Email

http://orcid.org/0009-0004-1853-5537
Mahamat Moussa

Department of Geology, University of N’djamena, N’Djamena, Chad

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APA Style

Bahar, T., Moussa, M. (2026). Application of a GIS-Based DRASTIC Model for Groundwater Vulnerability Assessment: A Case Study of Lai City, Tandjile East Department, Southern Chad. Journal of Water Resources and Ocean Science, 15(5), 200-220. https://doi.org/10.11648/j.wros.20261505.13

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ACS Style

Bahar, T.; Moussa, M. Application of a GIS-Based DRASTIC Model for Groundwater Vulnerability Assessment: A Case Study of Lai City, Tandjile East Department, Southern Chad. J. Water Resour. Ocean Sci. 2026, 15(5), 200-220. doi: 10.11648/j.wros.20261505.13

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AMA Style

Bahar T, Moussa M. Application of a GIS-Based DRASTIC Model for Groundwater Vulnerability Assessment: A Case Study of Lai City, Tandjile East Department, Southern Chad. J Water Resour Ocean Sci. 2026;15(5):200-220. doi: 10.11648/j.wros.20261505.13

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@article{10.11648/j.wros.20261505.13,
  author = {Tidjani Bahar and Mahamat Moussa},
  title = {Application of a GIS-Based DRASTIC Model for Groundwater Vulnerability Assessment: A Case Study of Lai City, Tandjile East Department, Southern Chad},
  journal = {Journal of Water Resources and Ocean Science},
  volume = {15},
  number = {5},
  pages = {200-220},
  doi = {10.11648/j.wros.20261505.13},
  url = {https://doi.org/10.11648/j.wros.20261505.13},
  eprint = {https://article.sciencepublishinggroup.com/pdf/10.11648.j.wros.20261505.13},
  abstract = {Groundwater resource protection is a worldwide issue because groundwater plays a crucial role in meeting water supply demands for both natural ecosystems and human activities. Effective groundwater management and protection therefore require appropriate approaches for assessing contamination risks and identifying areas that are particularly vulnerable to pollution. In this study, a GIS-based DRASTIC model was applied to assess groundwater vulnerability in Lai City, southern Chad. Seven hydrogeological parameters were considered, namely depth to water, net recharge, aquifer media, soil media, topography, impact of the vadose zone, and hydraulic conductivity. A weighted overlay analysis based on the DRASTIC Index (DI) was subsequently used to generate the groundwater vulnerability map of the study area. The results show that the DRASTIC Index values range from 119 to 175, enabling the study area to be categorized into three groundwater vulnerability classes: low, moderate, and high. The high-vulnerability class covers approximately 35% of the study area, highlighting areas that require particular attention for groundwater protection and management. The average and low class of vulnerability covers portions of the study area 31% and 34%, respectively. The northern and south-western portion of the catchment, namely Lai, Gabri Mbassa, Sategui, and Django, possesses high groundwater vulnerability. GIS-based Drastic model validation is performed via water quality parameters such as Nitrate and Total Dissolved Solids, with the accuracy of 97% and 75% respectively. The resulting groundwater vulnerability map provides a valuable tool for groundwater protection and sustainable land-use planning in Lai City and its surrounding areas.},
 year = {2026}
}

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TY  - JOUR
T1  - Application of a GIS-Based DRASTIC Model for Groundwater Vulnerability Assessment: A Case Study of Lai City, Tandjile East Department, Southern Chad
AU  - Tidjani Bahar
AU  - Mahamat Moussa
Y1  - 2026/09/29
PY  - 2026
N1  - https://doi.org/10.11648/j.wros.20261505.13
DO  - 10.11648/j.wros.20261505.13
T2  - Journal of Water Resources and Ocean Science
JF  - Journal of Water Resources and Ocean Science
JO  - Journal of Water Resources and Ocean Science
SP  - 200
EP  - 220
PB  - Science Publishing Group
SN  - 2328-7993
UR  - https://doi.org/10.11648/j.wros.20261505.13
AB  - Groundwater resource protection is a worldwide issue because groundwater plays a crucial role in meeting water supply demands for both natural ecosystems and human activities. Effective groundwater management and protection therefore require appropriate approaches for assessing contamination risks and identifying areas that are particularly vulnerable to pollution. In this study, a GIS-based DRASTIC model was applied to assess groundwater vulnerability in Lai City, southern Chad. Seven hydrogeological parameters were considered, namely depth to water, net recharge, aquifer media, soil media, topography, impact of the vadose zone, and hydraulic conductivity. A weighted overlay analysis based on the DRASTIC Index (DI) was subsequently used to generate the groundwater vulnerability map of the study area. The results show that the DRASTIC Index values range from 119 to 175, enabling the study area to be categorized into three groundwater vulnerability classes: low, moderate, and high. The high-vulnerability class covers approximately 35% of the study area, highlighting areas that require particular attention for groundwater protection and management. The average and low class of vulnerability covers portions of the study area 31% and 34%, respectively. The northern and south-western portion of the catchment, namely Lai, Gabri Mbassa, Sategui, and Django, possesses high groundwater vulnerability. GIS-based Drastic model validation is performed via water quality parameters such as Nitrate and Total Dissolved Solids, with the accuracy of 97% and 75% respectively. The resulting groundwater vulnerability map provides a valuable tool for groundwater protection and sustainable land-use planning in Lai City and its surrounding areas.
VL  - 15
IS  - 5
ER  -

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