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.

Groundwater management and development by integrated remote sensing and geographic information systems: prospects and constraints

Remote sensing (RS) and geographic information system (GIS) are promising tools for efficient planning and management of vital groundwater resources, especially in data-scarce developing nations. In this study, a standard methodology is proposed to delineate groundwater potential zones using integrated RS, GIS and multi-criteria decision making (MCDM) techniques. The developed methodology is demonstrated by a case study in Udaipur district of Rajasthan, western India. Initially, ten thematic layers, viz., topographic elevation, land slope, geomorphology, geology, soil, pre- and post-monsoon groundwater depths, annual net recharge, annual rainfall, and proximity to surface water bodies were considered in this study. These thematic layers were scrutinized by principal component analysis technique to select influential layers for groundwater prospecting. Selected seven thematic layers and their features were assigned suitable weights on the Saaty’s scale according to their relative importance in groundwater occurrence. The assigned weights of the thematic layers and their features were then normalized by using AHP (analytic hierarchy process) MCDM technique and eigenvector method. Finally, the selected thematic maps were integrated by weighted linear combination method in a GIS environment to generate a groundwater potential map. Thus, four groundwater potential zones were identified and demarcated in the study area, viz., ‘good’, ‘moderate’, ‘poor’ and ‘very poor’ based on groundwater potential index values. The area falling in the ‘good’ zone is about 2,113 km2 (17% of the total study area), which encompasses major portions of Sarada, Salumber, Girwa, Dhariawad, and Mavli blocks of the study area. The northeast and southwest portions along with some scattered patches fall in the ‘moderate’ zone, which encompasses an area of 3,710 km2 (about 29%). The ‘poor’ zone is dominant in the study area which covers an area of 4,599 km2 (36% of the total area). The western portion and parts of eastern and southeast portions of the study area are characterized as having ‘very poor’ groundwater potential, and this zone covers an area of 2,273 km2 (18%). Moreover, in the ‘good’ zone, the mean annually exploitable groundwater reserve is estimated at 0.026 million cubic metres per km2 (MCM/km2), whereas it is 0.024 MCM/km2 in the ‘moderate’ zone, 0.018 MCM/km2 in the ‘poor’ zone, and 0.013 MCM/km2 in the ‘very poor’ zone. The groundwater potential map was finally verified using the well yield data of 39 pumping wells, and the result was found satisfactory.

Assessment of Groundwater Potential in a Semi-Arid Region of India Using Remote Sensing, GIS and MCDM Techniques

Multi-criteria decision analysis (MCDA) as an advantageous tool has been applied by various researchers to improve their management ability. Management of groundwater resource, especially under data-scarce and arid areas, encountered a lot of problems and issues which drives the planers to use of MCDA. In this research, a standard methodology has been applied to delineate groundwater resource potential zonation based on integrated analytical hierarchy process (AHP), geographic information system (GIS), and remote sensing (RS) techniques in Kurdistan plain, Iran. At first, the effective thematic layers on the groundwater potential such as rainfall, lithology, drainage density, lineament density, and slope percent were derived from the spatial geodatabase. Then, the assigned weights of thematic layers based on expert knowledge were normalized by eigenvector technique of AHP. To prepare the groundwater potential index, the weighted linear combination (WLC) method was applied in GIS. Finally, the receiver operating characteristic (ROC) curve was drawn for groundwater potential map, and the area under curve (AUC) was computed. Results indicated that the rainfall and slope percent factors have taken the highest and lowest weights, respectively. Validation of results showed that the AHP method (AUC = 73.66 %) performed fairly good predication accuracy. Such findings revealed that in the regions suffering from data scarcity through the MCDM methodology, the planners would be able to having accurate knowledge on groundwater resources based on geospatial data analysis. Therefore, the developing scenario for future planning of groundwater exploration can be achieved in an efficient manner.

Groundwater potential mapping at Kurdistan region of Iran using analytic hierarchy process and GIS

Estimation of rock modulus: For intact rocks with an artificial neural network and for rock masses with a new empirical equation

The importance of groundwater is growing based on an increasing need and decreasing spring discharges in the Burdur area. Remote Sensing and the Geographic Information System (GIS) have been used for investigation of springs, which are an important groundwater source. The chemical composition of groundwater is not of drinking water quality in Burdur city and water in the Burdur residential area is being obtained from the Cine plain. The purpose of this study was to investigate new water sources by using remote sensing and GIS methods. Geology, lineament and land use maps of the research area were prepared using the Landsat TM satellite image composed of different analyses on the TM 7–4-1 band. In addition, contours, creeks, roads and springs were digitized using a topographic map of 1/100,000 scale to produce a drainage density map. A groundwater potential map was produced which integrated thematic maps, such as annual rainfall, geology, lineament density, land use, topography, slope and drainage density. According to this investigation, the surrounding villages of Askeriye, Bugduz, Gelincik, Taskapi and Kayaalti were determined to be important from the point of view of groundwater potential in the research area.

An integration of GIS and remote sensing in groundwater investigations: A case study in Burdur, Turkey

The Cross River State, Nigeria, is underlain by the Precambrian-age crystalline basement complex and by rocks of Cretaceous to Tertiary age. The exploration for groundwater in this area requires a systematic technique in order to obtain optimum results, but the non-availability of funds and facilities has made it extremely difficult to carry out site investigations prior to the drilling of water wells. Therefore, the failure rate is as high as 80%. In order to delineate areas that are expected to be suitable for future groundwater development, black and white radar imagery and aerial photographs were used to define some hydrological and hydrogeological features in parts of the study area. Lineament and drainage patterns were analysed using length density and frequency. Lineament-length density ranges from 0.04–1.52; lineament frequency is 0.11–5.09; drainage-length density is 0.17–0.94, and the drainage frequency is 0.16–1.53. These range of values reflect the differences in the probability of groundwater potentials. Results were then used to delineate areas of high, medium, and low groundwater potential. Study results also indicate that correlations exist between lineament and drainage patterns, lithology, water temperature, water conductivity, well yield, transmissivity, longitudinal conductance, and the occurrence of groundwater.

Application of remote-sensing data to groundwater exploration: A case study of the Cross River State, southeastern Nigeria

Determination of potential groundwater sites using geological and geophysical techniques in the Cross River State, southeastern Nigeria

Fifteen groundwater samples from functional boreholes in Khana and Gokana areas of Rivers State were collected and analysed for various physico-chemical parameters using standard field and laboratory techniques. This was done to assess the suitability of the water for domestic and other purposes on the basis of the parameters studied. Results show the following mean values for the physical parameters: temperature, 24.80C; Electrical Conductivity (EC), 15.9m s/cm. For the chemical parameters, the following average concentration levels were obtained: pH 6.99; total iron, 0.04mg/l; magnesium 0.85mg/l; sodium, 0.89mg/l; and potassium 0.05mg/l. Others include bicarbonate, 8.19mg/l; chloride 32.52mg/l; sulphate, 0.92mg/l; nitrate, 0.82mg/l; and Total Dissolved Solids (TDS), 7.73mg/l. These results show that the groundwater in these areas is slightly acidic to slightly basic, soft and low in dissolved constituents. Chloride contents in the water show salt-water encroachment into the aquifers in both areas. However, when compared with the World Health Organisation (WHO) standards for drinking water, the results show that the water is suitable for drinking and other domestic purposes in view of the parameters determined. It is also suitable for agricultural purposes. The major sources of ions in the water include mineral assemblages in the rocks, geochemical processes operating within the groundwater system, as well as atmospheric precipitation. Moreover, these geochemical processes, and exploitation of water from different depths are suggested as reasons for the variations in the geochemical parameters with borehole locations. 
(Journal of Applied Sciences & Environmental Management: 2002 6(1): 53-59)

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E. O. Esu

Papers

Application of remote-sensing data to groundwater exploration: A case study of the Cross River State, southeastern Nigeria

Determination of potential groundwater sites using geological and geophysical techniques in the Cross River State, southeastern Nigeria

A Geochemical Survey of Groundwater in Khana and Gokana Local Government Areas of Rivers State, Nigeria

Lineament analysis for groundwater exploration in Precambrian Oban Massif and Obudu Plateau, SE Nigeria

A study of some Nigerian carbonate rocks for the building construction industry