Comparison of RS/GIS analysis with classic mapping approaches for siting low-yield boreholes for hand pumps in crystalline terrains. An application to rural communities of the Caimbambo province, Angola

Martín-Loeches, Miguel; Reyes-López, Jaime Alonso; Ramírez‐Hernández, Jorge; Temiño-Vela, Javier; Martínez‐Santos, Pedro

doi:10.1016/j.jafrearsci.2017.10.025

Cited by 9 publications

(5 citation statements)

References 14 publications

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“…Within this mantle, the lower part is generally more transmissive due to the lower clay content, and the upper part is less permeable to flow but can still be important as a groundwater reservoir. Fractures increase reservoir permeability, although their storage capacity is typically low (Martín-Loeches et al, 2018). Borehole yields range from 4 to 6 m 3 /h (Traore et al, 2018).…”

Section: Study Areamentioning

confidence: 99%

“…Groundwater in basement aquifers is most often found in weathered formations and piedmonts of the outcrops. Piedmonts may exhibit high GPM because these are essentially a mixture of weathered and transported materials (Martín-Loeches et al, 2018). This area presents smooth orography, which means that high GPM is mainly determined by the weathered mantle.…”

Section: Groundwater Potential Mapsmentioning

confidence: 99%

“…There are two main approaches to GPM, namely expertbased decision systems and machine learning methods. Expert-based techniques have been used for a long time (DEP, 1993) and include multi-influencing factor approaches (Magesh et al, 2012;Nasir et al, 2018;Martín-Loeches et al, 2018), analytical hierarchy processes (Mohammadi-Behzad et al, 2019;Al-Djazouli et al, 2021) and Dempster-Shafer models (Mogaji and Lim, 2018;Obeidavi et al, 2021). Other frequently used expert methods are weight of evidence and frequency ratio analysis (Falah and Zeinivand, 2019;Boughariou et al, 2021).…”

Section: Introductionmentioning

confidence: 99%

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Preprocessing approaches in machine-learning-based groundwater potential mapping: an application to the Koulikoro and Bamako regions, Mali

Gómez-Escalonilla¹,

Martínez‐Santos

Martín-Loeches

2022

Hydrol. Earth Syst. Sci.

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Abstract. Groundwater is crucial for domestic supplies in the Sahel, where the strategic importance of aquifers will increase in the coming years due to climate change. Groundwater potential mapping is a valuable tool to underpin water management in the region and, hence, to improve drinking water access. This paper presents a machine learning method to map groundwater potential. This is illustrated through its application in two administrative regions of Mali. A set of explanatory variables for the presence of groundwater is developed first. Scaling methods (standardization, normalization, maximum absolute value and max–min scaling) are used to avoid the pitfalls associated with reclassification. Noisy, collinear and counterproductive variables are identified and excluded from the input dataset. A total of 20 machine learning classifiers are then trained and tested on a large borehole database (n=3345) in order to find meaningful correlations between the presence or absence of groundwater and the explanatory variables. Maximum absolute value and standardization proved the most efficient scaling techniques, while tree-based algorithms (accuracy >0.85) consistently outperformed other classifiers. The borehole flow rate data were then used to calibrate the results beyond standard machine learning metrics, thereby adding robustness to the predictions. The southern part of the study area presents the better groundwater prospect, which is consistent with the geological and climatic setting. Outcomes lead to three major conclusions: (1) picking the best performers out of a large number of machine learning classifiers is recommended as a good methodological practice, (2) standard machine learning metrics should be complemented with additional hydrogeological indicators whenever possible and (3) variable scaling contributes to minimize expert bias.

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Section: Study Areamentioning

confidence: 99%

Section: Groundwater Potential Mapsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Preprocessing approaches in machine-learning-based groundwater potential mapping: an application to the Koulikoro and Bamako regions, Mali

Gómez-Escalonilla¹,

Martínez‐Santos

Martín-Loeches

2022

Hydrol. Earth Syst. Sci.

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“…Fractures can produce significant quantities of water, although their storage capacity is typically low (Martín-Loeches et al, 2018). Borehole yields range from 4 to 6 m 3 /hour (Traore et al, 2018).…”

Section: Study Areamentioning

confidence: 99%

“…There are two main approaches to GPM: expert-based decision systems and machine learning methods. Expert-based systems have existed for a long time (DEP, 1993), and include multi-influence factor techniques (Magesh et al, 2012;Nasir et al, 2018;Martín-Loeches et al 2018) and analytical hierarchy processes (Mohammadi-Behzad et al, 2019;Al-Djazouli et al, 2020), among others. Machine learning is comparatively newer.…”

Section: Introductionmentioning

confidence: 99%

Preprocessing approaches in machine learning-based groundwater potential mapping: an application to the Koulikoro and Bamako regions, Mali

Gómez-Escalonilla

Martínez‐Santos

Martín-Loeches

2021

Preprint

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Abstract. Groundwater is crucial for domestic supplies in the Sahel, where the strategic importance of aquifers can only be expected to increase in the coming years due to climate change. Groundwater potential mapping is gaining recognition as a valuable tool to underpin water management practices in the region, and hence, to improve water access. This paper presents a machine learning method to map groundwater potential and illustrates it through an application to two regions of Mali. A set of explanatory variables for the presence of groundwater is developed first. Several scaling methods (standardization, normalization, maximum absolute value and min-max scaling) are used to avoid the pitfalls associated with the reclassification of explanatory variables. A number of supervised learning classifiers is then trained and tested on a large borehole database (n = 3,345) in order to find meaningful correlations between the presence or absence of groundwater and the explanatory variables. This process identifies noisy, collinear and counterproductive variables and excludes them from the input dataset. Tree-based algorithms, including the AdaBoost, Gradient Boosting, Random Forest, Decision Tree and Extra Trees classifiers were found to outperform other algorithms on a consistent basis (accuracy > 0.85), whereas maximum absolute value and standardization proved the most efficient methods to scale explanatory variables. Borehole flow rate data is used to calibrate the results beyond standard machine learning metrics, thus adding robustness to the predictions. The southern part of the study area was identified as the better groundwater prospect, which is consistent with the geological and climatic setting. From a methodological standpoint, the outcomes lead to three major conclusions: (1) because there is no aprioristic way to know which algorithm will work better on a given dataset, we advocate the use of a large number of machine learning classifiers, out of which the best are subsequently picked for ensembling; (2) standard machine learning metrics may be of limited value when appraising map outcomes, and should be complemented with hydrogeological indicators whenever possible; and (3) the scaling of the variables helps to minimize bias arising from expert judgement and maintains robust predictive capabilities.

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Groundwater and Space Technology: Issues and Challenges

Bhunia

Shit²,

Gupta

et al. 2021

Groundwater and Society

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Comparison of RS/GIS analysis with classic mapping approaches for siting low-yield boreholes for hand pumps in crystalline terrains. An application to rural communities of the Caimbambo province, Angola

Cited by 9 publications

References 14 publications

Preprocessing approaches in machine-learning-based groundwater potential mapping: an application to the Koulikoro and Bamako regions, Mali

Preprocessing approaches in machine-learning-based groundwater potential mapping: an application to the Koulikoro and Bamako regions, Mali

Preprocessing approaches in machine learning-based groundwater potential mapping: an application to the Koulikoro and Bamako regions, Mali

Groundwater and Space Technology: Issues and Challenges

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