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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

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... This is one of the reasons why many hydrogeologists worldwide have become accustomed to making use of remote sensing and geographic information systems (GIS). Jha et al. (2007) identified six major applications of RS/GIS in the field of groundwater, including the exploration and assessment of groundwater resources (Abdalla 2012;Fashae et al. 2014;Martín-Loeches et al. 2018), the selection of artificial recharge sites (Samadder et al. 2011), subsurface flow and/or pollution modelling (Leblanc et al. 2007), aquifer vulnerability and protection (Vias et al. 2005;Hernández-Espriú et al. 2014;Hadzic et al. 2015), estimations of natural recharge (Yeh et al. 2016;Mokadem et al. 2018) and hydrogeological data analysis and process monitoring (Crossman et al. 2012;Dailey et al. 2015;Sahoo et al. 2018). The number of applications of satellite information in groundwater science continues to grow. ...
... For instance, Siddha and Sahu (2018) took into account multiple water quality and pumping test parameters to develop a groundwater potential map to underpin domestic water supplies in Gandhinagar, India. Similarly, Martín-Loeches et al. (2018) developed a groundwater potential map for the specific purpose of siting drinking water boreholes for rural communities in Caimbambo, Angola. ...
... Areas in close proximity to permanent water bodies also tend to correlate with a higher groundwater potential (Naghibi et al. 2017;Singh et al. 2018). Conversely, hills, human settlements and wastelands are generally disregarded (Magesh et al. 2012;Martín-Loeches et al. 2018;Patra et al. 2018). ...
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Groundwater resources can be expected to be increasingly relied upon in the near future, as a consequence of rapid population growth and global environmental change. Cost-effective and efficient techniques for groundwater exploration are gaining recognition as tools to underpin hydrogeological surveys in mid- and low-income regions. This paper provides a state of the art on groundwater potential mapping, an explorative technique based on remote sensing and geographical databases that has experienced major developments in recent years. A systematic review of over 200 directly relevant papers is presented. Twenty variables were found to be frequently involved in groundwater potential investigations, of which eight are almost always present: geology, lineaments, landforms, soil, land use/land cover, rainfall, drainage density, and slope. The more innovative approaches draw from satellite images to develop indicators related to vegetation, evapotranspiration, soil moisture and thermal anomalies, among others. Data integration is carried out either through expert judgement or through machine-learning techniques, the latter being less common. Three main conclusions were reached: (1) for optimal results, groundwater mapping must be used as a tool to complement field work, rather than a low-cost substitute; (2) the potential of remote-sensing techniques in groundwater exploration is enormous, particularly when the power of machine learning is harnessed by involving human judgement; (3) quality assurance remains the main challenge ahead, as exemplified by the fact that a majority of the existing studies in the literature lack adequate validation.
... 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). ...
... 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). ...
... 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. ...
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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.
... 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. ...
... 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). ...
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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.
... K.K. Mandal et al. Remote Sensing Applications: Society and Environment 24 (2021) 100631 communities of Caimbambo, Angola to solve their drinking water needs, GWPZ mapping was done by (Martín-Loeches et al. (2018). Again, a study was done for GWPZ mapping in Sarajevsko Polje for understanding the vulnerability of groundwater resources and protection of groundwater resources (Hadžić et al., 2015). ...
Article
This study intended to delineate the groundwater potential zones (GWPZ) of Port Blair and its surrounding areas using the Multi Influencing Factor (MIF) method and geospatial techniques. Multiple data such as geology, geomorphology, slope, soil, drainage density, lineament density, rainfall, NDVI, and LULC were considered for delineating GWPZ. Spatially distributed maps/thematic layers of all the factors mentioned above were prepared using remotely sensed data and by using ground data. These thematic layers were allotted weights after referring to previous literature and study and by considering each layer's influence on groundwater. Finally, all the thematic layers were integrated, and overlay analysis was done to produce a map showing the GWPZ of Port Blair and its surrounding areas. The result (map) was categorized into high, medium, and low groundwater potential zones. This study shows that most of Port Blair's areas come under the medium GWPZ (63.4% of the study area), followed by high GWPZ (27% of the study area), and 10.6% of the area comes under low GWPZ. The most important and innovative part of this study is the physical verification of all the results obtained from the remote sensing and GIS techniques. The GWPZ map was compared with existing well discharge data and validated through the ROC curve, and it shows the study has “very good” accuracy. Finally, this study provides an expedient approach to delineate the GWPZ for practicable management and use of groundwater resources of the area to maintain the sustainability of this island.
... Two main components, namely, the weights comparative and intrinsic, exist in each of the variables on groundwater potential (Das et al. 2017). This process is based on an expert evaluation that always requires a certain degree of subjectivity (Martín-Loeches et al. 2018;Govindaraj et al. 2017). Previous researchers used probabilistic models, for example, frequency ratio (Ozdemir 2011;Razandi et al. 2015), multi-criteria decision analysis (Chowdhury et al. 2009;Rahmati et al. 2015), weight of evidence (Corsini et al. 2009;Pourghasemi and Beheshtirad 2015), logistic regression , evident belief function (Mogaji et al. 2015), artificial neural network model (Lee et al. 2012), certainty factor (Razandi et al. 2015), Shannon's entropy (Naghibi et al. 2015), decision tree (Chenini and Ben 2010), machine learning techniques such as random forest (RF), maximum entropy (ME) , and so on to delineate the groundwater potential zone. ...
Chapter
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Most of the world’s freshwater resources are known as groundwater. In just a few areas, increased groundwater depletion causes significant consequences for a water table fall, water quality deterioration, stream base flow loss, etc. Water resources, especially in developing countries, are poorly controlled and hydrologically educated offer valuable metrics for groundwater resources recognition. This chapter explains the capabilities of various satellite sensors to derive specific primary and secondary parameters associated with soil water studies. Different spatial models have been studied to demonstrate how spectral indices, digital elevation models (DEM) and their potential as passive, low-cost investigation techniques for groundwater studies are. Possible application of space technology in assessment, monitoring, and use of groundwater resources was established. This chapter also explains the specific problems and challenges associated with space and groundwater study. Also possible potentials of groundwater space technology are briefly summarized.
... Alluvial fans, sand dunes, weathering mantles, and, in general, accumulations of unconsolidated materials, can be expected to store groundwater. In contrast, inselbergs, scarps, and ridges can be assumed unlikely to contain groundwater and impractical for drilling (Martín-Loeches et al. 2018). Geomorphological maps can be developed from field surveys, aerial photos and satellite images. ...
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Groundwater resources are crucial to safe drinking supplies in sub Saharan Africa, and will be increasingly relied upon in a context of climate change. The need to better understand groundwater calls for innovative approaches to make the best out of the existing information. A methodology to map groundwater potential based on an ensemble of machine learning classifiers is presented. A large borehole database (n = 1848) was integrated into a GIS environment and used to train, validate and test twelve machine learning algorithms. Each classifier predicts a binary target (positive or negative borehole) based on the minimum flow rate required for communal domestic supplies. Classification is based on a number of explanatory variables, including landforms, lineaments, soil, vegetation, geology and slope, among others. Correlations between the target and explanatory variables were then generalized to develop groundwater potential maps. Most algorithms attained success rates between 80% and 96% in terms of test score, which suggests that the outcomes provide an accurate picture of field conditions. Statistical learners were observed to perform better than most other algorithms, excepting random forests and support vector machines. Furthermore, it is concluded that the ensemble approach provides added value by incorporating a measure of uncertainty to the results. This technique may be used to rapidly map groundwater potential for rural supply or humanitarian emergencies in areas where there is sufficient historical data but where comprehensive field work is unfeasible.
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Groundwater is the largest available freshwater resource in the world. Aquifers provide drinking water to at least 50% of the global population, and account for 43% of all water used for irrigation. Groundwater resources can be expected to be increasingly relied upon, in the near future, as a consequence of rapid population growth and global environmental change. Cost-effective and efficient techniques for groundwater exploration, especially in karstic regions, can be used to as an appropriate tool to recognition of karst hydrogeological potential. This paper provides a method based on the RS/GIS for the recognition of high groundwater potential areas and geoelectrical tomography for precise determination of the water well drilling location. Groundwater mapping has been defined as a tool for systematic development and planning of water resources (Elbeih, 2015). Hydrogeological maps provide spatially distributed information about aquifers, including their geological, hydrogeological and hydrochemical characteristics . In this study, a hydro-tectonic model include effective layers on karst hydrogeology applied for the recognition of the high groundwater potential in karstic areas of Izeh, northeast Khuzestan. The combination of remote sensing and GIS used to overlay the major layers, i.e. distance from discharge point, elevation difference, fracture density, slope, and fracture intersection density. Generally, high altitude regions have a low groundwater potential and more groundwater can be found at lower altitudes; therefore, the altitude map generated from the DEM represents difference to known elevation of the discharge points. The areas away from the discharge point generally have lower probability of groundwater occurrence. The distance analysis in GIS was used to determine the map of distance from discharge point. Slope angle can be considered as a surrogate of surface runoff velocity and vertical percolation which affects recharge processes. However, in this study, the slope angle was considered as a positive factors on groundwater potential in the karstic areas. Geological fractures can have a significant effect on storage and flow of groundwater reservoirs. Especially in areas with shallow bedrock fractures, water infiltration can be enhanced due to increased porosity and hydraulic conductivity (Rao et al. 2001). The fracture locations in the study area were determined from the remote sensing techniques. The parameter are weighted from 1 to 5 based on their importance in karst hydrogeology. For the exact determination of the water well drilling locations in high groundwater potential areas, the geoelectrical operation is done in two profiles using Dipole-Dipole array followed by electrical resistivity tomography. 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The parameters used in the inversion were the same for both of profiles, and topography was taken to normalize profile elevations to the actual ground surface. A robust algorithm was chosen for the inversion, because it provides more net changes in resistivity between different parts of the section. However, care must be taken when studying the final sections, because the geometry and boundaries of the structures are not always clearly identified and may be influenced by changes in resistivity due to rocks outside the plane of the section. The interpreted sections must be understood as an indication of the approximate location of the lithological boundaries, and not as its true geometry. The interpretation of the resistivity sections for all the ERT profiles has been drawn with the help of the correlation between the resistivity and the lithology along with the hydrogeologic data, and taking into account the continuity of the resistivity values at the crossing of the profiles. Overall, a very complicated structure is interpreted with the presence of dry and wet limestones, cavities, and marly layers interbeded with carbonates. Finally, two locations were proposed for drilling of water wells in the Izeh karstic area . The drilling of a high yield water well (discharge of 61 L/S) and the low drawdown (0.48 m) in the karst of west Izeh at autumn 2019 indicates the effectiveness of the integration of the applied exploration methods. This work shows the power of geoelectrical method in poorly understood and tectonically complex areas in addition to the RS/GIS groundwater potential mapping to evaluate karst hydrogeology.
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While access to water remains an issue in arid and semiarid regions across the world, aquifers have the potential to help millions of people out of poverty by providing a reliable source of drinking and irrigation water. Manual boreholes are increasingly advocated as a safe and cost-effective substitute to mechanized drilling, as well as to traditional excavation methods. This research banks on the assumption that field and remote sensing data can be integrated within a geospatial database in order to map the viability of manual boreholes based on factors such as rock type, water table depth, landforms, or water quality. The approach presents three main novelties in relation to methodological precedents: (1) outcomes are not only expressed in terms of technical feasibility, but also as a function of drilling time and cost; (2) maps refer to a specific drilling technique; and (3) results take into account borehole diameter, as this constrains both drilling time and cost. The method provides univocal outcomes that can be immediately useful for non-experts, donors, planners, or practitioners and that can be readily exported to other catchment-scale settings. Results were validated against geophysical data.
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Crystalline basement rocks, with a mantle of weathered alternation products, occur beneath very extensive areas of tropical Africa. Low-productivity aquifers are widely, but rather unpredictably, present in this formation. They yield small water supplies vital to the rural population for domestic purposes and for livestock watering. On a more localised basis, a potential may exist to develop larger supplies that are adequate for small towns or for small-scale irrigation. This paper reviews advances in the understanding of this extensive hydrogeological system, resulting from British research and experience since 1980.
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The increasing demand for fresh water has necessitated the exploration for new sources of groundwater, particularly in hard rock terrain, where groundwater is a vital source of fresh water. A fast, cost effective and economical way of exploration is to study and analyze remote sensing data. Interpreted remote sensing data was used to select sites for carrying out surface geophysical investigations. Various geomorphologic units were demarcated and the lineaments were identified by interpretation of remote sensing satellite images. The potential for occurrence of groundwater in the watershed areas was classified as very good, good, moderate and poor by interpreting the images. Sub-surface geophysical investigations, namely vertical electrical soundings, were carried out to delineate potential water-bearing zones. Integrated studies of interpretation of geomorphologic and geophysical data were used to prepare a groundwater potential map. The studies reveal that the groundwater potential of shallow aquifers is due to geomorphologic features and the potential of deeper aquifers is determined by lineaments such as faults and joints.
Chapter
Nearly half of the population of Sub-Saharan Africa is in a state of severe and chronic poverty. Lack of access to safe domestic water, and indeed to significant quantities of water for other productive uses, defines and contributes to that poverty. Between one-third and one half a billion people in the region rely on unprotected and protected groundwater sources for their domestic water requirements. Further targeted development of groundwater could make a major contribution to the Millennium Development target of halving the proportion of people without access to safe and sustainable water supplies by 2015, as well as contributing significantly to incomes and livelihoods. Extending access to groundwater will be assisted by (a) significantly reducing the costs of mechanised borehole drilling and construction, (b) promoting very low cost drilling technologies in niche hydrogeological environments, preferably through the indigenous private sector, and (c) ensuring the functional sustainability of groundwater abstraction points so constructed. The development of groundwater for poverty alleviation must take account of people’s requirements for domestic, agricultural and small-scale industrial water; the importance of building on user need, demand and initiative; water supply as a permanent service, not merely a short-term issue of construction and access targets; and the importance of generating far more detailed hydrogeological understanding in the region, through mapping, monitoring and groundwater data collection.
Chapter
Conventional methods for recharge estimation have limitations when applied to arid and semi-arid regions; the use of tritium profiles is also not always applicable. Unsaturated zone solute profiles, using a reference solute such as chloride, offer an alternative technique. Sampling may be undertaken by percussion drilling, augering or from dug wells; the methods developed are described and examples discussed. Recharge estimates using chloride profiles from Cyprus (420 mm mean annual rainfall) are in good agreement with results estimated from tritium profiles and indicate a mean annual recharge of around 50 mm/year. In Central Sudan (180 mm mean annual rainfall), good agreement was found between adjacent unsaturated zone chloride profiles and these indicated a net annual direct recharge via interfluve areas of around 1 mm/year. It is concluded that solute profiles offer a cheap and effective tool for estimating direct recharge in porous lithologies of semi-arid regions and also for investigating recharge history, providing input data for chloride are available. In more arid regions, however, a component of discharge may occur during hyperarid episodes. Further validation of moisture composition using stable isotope techniques is required under such conditions.
Article
The first resistivity soundings applied to borehole siting in Basement areas of Africa were probably measured by Dr. Sydney Shaw in 1933 in Southern Rhodesia, now Zimbabwe. Using a Megger Earth Tester and Wenner array, soundings were measured at a selection of both dry and successful boreholes, and compared. Re-examination of Shaw's soundings using modern technology shows that the sounding curves are of surprisingly high quality even on today's standards and indicate a strong relationship between interpreted depth to unfractured granite and drilling results. His survey helped the adoption in Africa of resistivity methods as standard practice in the location of drilling sites for water supply.
Article
Geologically complex crystalline aquifers underlie large parts of the semi-arid Limpopo Province where some of the greatest groundwater needs in South Africa occur. It is important to identify potentially high-yielding zones that can be targeted for water supply. The study covered four distinct geologic and morpho-structural domains within Limpopo Province, together covering about 23,500 km 2. Results from over 2,500 pumping test analyses indicate that bedrock type (e. g. pegmatite), lithological setting (e.g. aureole of granitoids), proximity and orientation of dykes and lineaments, topographic setting (e.g. slopes or valleys) and proximity of surface-water drainages may exert an influence on borehole productivity. No correlation between borehole productivity and weathering depth was found. Lineaments and dykes striking perpendicular to the current maximum horizontal stress seem to be more favourable targets, which is inconsistent with the predicted regime. Due to the complex geologic history, it is difficult to link open discontinuities to a distinct recent or past tectonic event. Regional stress-field data, as in this case, may not account for local, possibly highly significant, stress-field variations. The hydrogeologic importance of several factors related to groundwater occurrence, here presented, can be used as a working reference for future groundwater development programmes.
Article
: Now that personal computers (pc's) have become more powerful, potable, and affordable, geoscientists can make full use of developments in computer-aided mapping, particularly Geographical Information Systems (GIS). The IDRISI GIS was used to 1) carry out image processing on satellite images; 2) assess the reliability of the interpreted lineaments; 3) create maps showing individual lineament lengths, areal extent of interconnected lineaments, and targets for groundwater boreholes; and 4) incorporate socio-economic factors, by creating maps that show the proximity of villages to sites considered favourable for boreholes. The exact location of each site for drilling was decided on the basis of geophysical surveys over the areas that had been targeted by the remote sensing and GIS analysis. Most of the remote sensing and GIS work was carried out in Ghana in two weeks, during which the ‘ground truth’ of lineament maps was checked. The total cost of the hardware and software used in this project (16-colour laptop pc, portable colour printer, and IDRISI) was slightly less than US$ 2,600. The relatively low cost and ease of use of this system make it a technology that is readily transferable to developing countries.
Article
Groundwater is one of the most valuable natural resources, which supports human health, economic development and ecological diversity. Overexploitation and unabated pollution of this vital resource is threatening our ecosystems and even the life of future generations. With the advent of powerful personal computers and the advances in space technology, efficient techniques for land and water management have evolved of which RS (remote sensing) and GIS (geographic information system) are of great significance. These techniques have fundamentally changed our thoughts and ways to manage natural resources in general and water resources in particular. The main intent of the present paper is to highlight RS and GIS technologies and to present a comprehensive review on their applications to groundwater hydrology. A detailed survey of literature revealed six major areas of RS and GIS applications in groundwater hydrology: (i) exploration and assessment of groundwater resources, (ii) selection of artificial recharge sites, (iii) GIS-based subsurface flow and pollution modeling, (iv) groundwater-pollution hazard assessment and protection planning, (v) estimation of natural recharge distribution, and (vi) hydrogeologic data analysis and process monitoring. Although the use of these techniques in groundwater studies has rapidly increased since early nineties, the success rate is very limited and most applications are still in their infancy. Based on this review, salient areas in need of further research and development are discussed, together with the constraints for RS and GIS applications in developing nations. More and more RS- and GIS-based groundwater studies are recommended to be carried out in conjunction with field investigations to effectively exploit the expanding potential of RS and GIS technologies, which will perfect and standardize current applications as well as evolve new approaches and applications. It is concluded that both the RS and GIS technologies have great potential to revolutionize the monitoring and management of vital groundwater resources in the future, though some challenges are daunting before hydrogeologists/hydrologists.
Article
The present study attempts to delineate different groundwater potential units using remote sensing and geographic information system (GIS) in Khallikote block of Ganjam disrict, Orissa. Thematic maps of geology, geomorphology, land use and land cover, drainage density, lineament density, slope and DEM (digital elevation model) were prepared using the Landsat Thematic Mapper data in 3 spectral bands, band 7 (mid-infrared light), band 4 (near-infrared light), Band 2 (visible green light). Relationship of each layer to the groundwater regime has been evaluated through detailed analysis of the individual hydrological parameters. The SMCE (Spatial Multi-Criteria Evaluation) module in ILWIS (Integrated Land and Water Information System) supports the decision-making process for evaluating the ground water potential zones in the area. The study shows that more than 70% of the block is covered by medium to excellent category having good ground water potential. KeywordsGIS–Hydrogeolgy–SMCE–Ground water potential
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