Groundwater Supply Sources Research Articles

Tracing contaminants of emerging concern in the Awash River basin, Ethiopia

Study regionAwash River basin, Central Ethiopia Study focusThe study focuses on characterization of Emerging Organic Contaminants (EOCs) in the Awash River basin. Characterization of the EOCs was supplemented by chemical analysis of samples from river, boreholes, tap water, and surface water reservoirs. Analyses of environmental isotopes (δ 2 H, δ 18 O, and 222Rn) were used to investigate the exchange of contaminants between surface and groundwater supply sources. New hydrological insights for the regionMore than 100 EOCs are identified in all water supply sources. The EOCs are linked to agricultural applications, urban, and industrial sources. Based on the analysis of chemical and environmental tracers, the deep groundwater has greater protection from contamination than the river and the shallow groundwater. The heavy metal analysis prevails the same. The shallow aquifers are affected by urban, industrial, and agricultural pollutants. Attributed to the different contaminant sources, distinct variations in terms of compound types were observed at different locations. Water supply sources located upstream are dominated by urban and industrial contaminants while compounds from agricultural applications dominate the downstream sites. Artificial infrastructures serve as attenuation points for urban and industrial sourced compounds. Characterization of EOCs showed new contaminant loads in the water supply sources, which haven’t been tested before, with potential impact on human and wider environmental health, and may necessitate a revision of the customary water quality test and monitoring practices.

Geochemical evolution along regional groundwater flow in a semi-arid closed basin using a multi-tracing approach

Groundwater is the main source for domestic drinking water supply, irrigation, and industrial activities in Zacatecas in central Mexico, a good example for numerous semiarid regions worldwide, however, there is insufficient information about characterization and evolution of the baseline water quality to create hydrogeological conceptual models, fundamentals for the future planning of new sources of groundwater supply for the population, especially under ongoing global climate change conditions. By a multi-method analysis that included geological, geophysical, hydrochemical and isotopic tools this investigation allowed the identification of: a) local flows, represented by shallow groundwater and shallow wells, hosted over basin fill sediments with low average temperatures (≈ 23.3 °C), variation in water types related to anthropogenic activities, low trace elements concentrations, δ18O and δ2H signatures indicating surface water and tritium being present in this system, b) intermediate flows (25 °C), identified in wells with depths of 100 to 200 m, water circulating through the basin fill sediments and the sequence of volcanic rocks characterized by intermediate concentrations of trace elements, and groundwater ages calculated for this system vary from 1,000 to 6,000 years, c) regional flows in volcanic rocks, characterized by groundwater from wells with depths of more than 200 m, high temperatures (up to 31.5 °C) and elevated concentrations of trace elements. The δ18O and δ2H signals are more homogenous and the 14C residence times for this flow system are greater than 8,000 years, and d) regional flows in Cretaceous rocks, with depths greater than 400 m, the highest temperatures (≈ 43.7 °C) and intermediate concentrations of trace elements. The δ18O and δ2H signals are homogenous and δ13C can widely be associated with carbonate shales. The hydrogeochemical evolution has been documented along a 62 km flow line to develop a robust conceptual model, reflecting the water–rock interaction in the system. Physicochemical parameters, as well as major and trace element concentrations, reflect a distinct evolution according to the flow paths and their increase is generally proportional to the residence time. Likewise, processes of dissolution of feldspars and some clay minerals from initial weathering in the basin fill sediments, as well as devitrification of the glassy matrix in the volcanic rocks are taking place in the evolution of the system.The results obtained through the analysis of water–rock interaction in this research can be applied to other semi-arid regions with geogenically impacted aquifers, due to the geological and climatic similarity with numerous volcano-sedimentary basins around the world.

EVALUACIÓN DE LA VULNERABILIDAD INTRÍNSECA A LA CONTAMINACIÓN DE LAS AGUAS SUBTERRÁNEAS EN LAS CUENCAS CUYAGUATEJE Y COSTERA SUR DE PINAR DEL RÍO, CUBA

Las cuencas hidrogeológicas Cuyaguateje y Costera Sur de Pinar del Río constituyen importantes fuentes de abasto de agua subterránea a la provincia de Pinar del Río en Cuba, por lo que es necesario el desarrollo de investigaciones que permitan la alerta temprana de su posible contaminación. El objetivo de este artículo fue evaluar la susceptibilidad a la contaminación de ambas cuencas subterráneas debido al impacto de contaminantes potenciales vertidos en su superficie. Por primera vez fue empleado en esta región el método de superposición de índices ponderados RISK. El mapa de vulnerabilidad intrínseca obtenido a escala 1:100 000 reveló que las zonas de moderada vulnerabilidad alcanzan el 55,1% de la región estudiada, y las zonas de alta y muy alta vulnerabilidad representan el 44,6%, resultados que se corresponden con la naturaleza geológica de las cuencas, con el diagnóstico ambiental de la provincia y con reportes de otros estudios realizados en la región. El método RISK demostró su elevado poder resolutivo y la factibilidad de su aplicación en otras cuencas del territorio nacional.

Impact of Natural and Anthropogenic Stresses on Surface and Groundwater Supply Sources of the Upper Awash Sub-Basin, Central Ethiopia

Improving water security is critical to delivering the best outcomes for development. In Ethiopia, the upper Awash sub-basin supports expanding urban and industrial areas, with increasing water demands. Studies have preferentially focused either on surface water hydrology or on groundwater characterization. However, novel tools are required to support the conjunctive use of surface and groundwater for competing users under potential climate change impacts. In this paper, we present research based on a WEAP-MODFLOW link configured for four catchments in the upper Awash sub-basin (Akaki, Melka Kunture, Mojo, and Koka). The Akaki catchment supplies water for Addis Ababa city. Unlike most surface water hydrological models, both supply (surface water and groundwater) and demand (domestic, industrial, and livestock) are modeled. The tool was used to evaluate the impacts of population growth, leakage, expansion of surface and groundwater supply schemes, and climate change scenarios up to the year 2030. Considering the high population growth rate scenario for Addis Ababa city, the unmet domestic water demand may increase to 760 MCM in 2030. Water leakage through poor water supply distribution networks contributed about 23% of the unmet water demand. Though not significant compared with population and water loss stresses, climate change also affect the supply demand condition in the basin. Planning for more groundwater abstraction without considering additional surface water reservoir schemes will noticeably impact the groundwater resource, with groundwater levels projected to decline by more than 20 m. Even more groundwater level decline is observed In the Akaki catchment, where Addis Ababa city is located. Conjunctive use of surface and groundwater not only boosts the supply demand situation in the basin but will lift off some of the stresses from the groundwater resources. Even under the likely increase in temperature and low precipitation climate scenarios, the conjunctive use resulted in a significant increase in domestic water demand coverage from 26% for the reference condition to 90% in 2030, with minimum effect on the groundwater resources. To improve water security conditions through sustainable utilization of both surface and groundwater resources, policy responses need to consider surface and groundwater conjunctive use. Minimizing water leakage should also be given the highest priority.

Forecasting of Dangerous Influence of Avermectin Insecticides to Human Organism Using Surface and Groundwater for Drinking

More than 400 types of harmful organisms cause damage to agricultural crops. Insecticides occupy one of the last places in the structure of the pesticides assortment among formulations authorized for application in the world. However, they occupy the first place according to their toxicity and the hazard effect to the human body. The purpose of our study was comparative hygienic assessment of soil stability, surface and groundwater migration potential, prediction of dangerous effects of insecticides-avermectins on the human body after using surface and groundwater for drinking needs. For an integral assessment of the potential danger of pesticide exposure to the human body after consumption of water from surface and groundwater supply sources, a scale of four gradations was used. It includes the LEACH (index of potential contamination of groundwater and river waters), half-life period (DT50) in water and an allowable daily dose (ADD) or acceptable daily intake (ADI). It has been established that in different soil and climatic conditions, according to the LEACH index, there is a very low risk of groundwater and surface water contamination. This is due to their relatively high solubility in water, low soil persistence and very high values of the organic carbon sorption coefficient. According to the IIWH index (integral index of water hazard), abamectin and emamectin benzoate in different soil and climatic conditions are moderately hazardous for a person after consumption of contaminated drinking water (class 3); emamectin benzoate in the soil and climatic conditions of Ukraine is hazardous (class 2). It is necessary to monitor carefully the boundaries of sanitary-protective areas from treated areas to water bodies, and control the process of exploitation of water supply sources, especially decentralized in rural areas. In regions with intensive agricultural production, it is recommended to use the IIWH index to make a decision about the necessity of monitoring research on insecticides in water.

Identifying anthropogenic sources of groundwater contamination by natural background levels and stable isotope application in Pinggu basin, China

The assessment of natural background levels (NBLs) in groundwater is considered as an efficient way to distinguish the geogenic compound from anthropogenic pollution of groundwater—a basic issue in groundwater environmental management. At present, most studies only assess NBLs of single parameters in groundwater. Such method, however, ignored the complex components and interaction in the groundwater, which leads to the inaccuracy of the assessment. In this study, 51 groundwater samples were investigated in November 2018 in Pinggu basin—one of the most important emergency groundwater supply sources of Beijing. Hierarchical cluster analysis (HCA) was used firstly to divide the study area into four zones. By combining single-parameter NBLs assessment and comprehensive NBLs assessment, the possible anthropogenic impact on groundwater quality in different zones could be determined with the use of land use map. For single-parameter NBLs assessment, iterative Grubbs’ test was used to assess NBLs of the data following Gaussian distribution, and the median plus/minus twofold the median of the absolute deviations from the median (median ± 2MAD) method was used to assess NBLs of the data for the non-Gaussian distribution. For comprehensive NBLs assessment, Mahalanobis distances of scatters in scatter plots which express the hydrogeological evolution processes were involved. In addition, δ15N-NO3− and δ18O-NO3− were used to analyze the sources of nitrate in groundwater. The results showed that the groundwater was affected by industrial activities, agricultural activities, urban domestic sewage and landfills. And the groundwater quality in the east of the study area was better than that in the west. Nitrate in the groundwater of study area mainly came from nitrification, and denitrification occurred in the groundwater near the landfills. This study provides a way to assess the NBLs of groundwater quality, and to determine sources and transformation of nitrate in the groundwater, which contributes to the identification of anthropogenic pollution in groundwater.

Decision Support System Based on Genetic Algorithms to Optimize the Daily Management of Water Abstraction from Multiple Groundwater Supply Sources

The use of irrigation water extracted from aquifers with submerged pumps is essential to ensure agricultural production mainly in water-scarce regions.. However, the use of the water source requires of a considerable energy consumption by water user associations (WUAs) being key factor to consider due to their high share of total management, operation, and maintenance costs. In this work, a new tool (MOPWE, model to optimize water extraction) to optimize the water and energy use of wells in WUAs was developed. MOPWE was applied to a real WUA located in Castilla-La Mancha region (southeast of Spain). This WUA utilizes groundwater as water source that is extracted from several different wells of different characteristics (discharges, water table levels, efficiency, variable speed drives…).. Therefore, these kind of WUAs must decide not only which well to activate at a certain time but also at what frequency the variable-speed drive should run the pump. With the aim of aiding decision-making in groundwater abstraction, a new management model (MOPWE), which is based on multi-objective genetic algorithms and is implemented in MATLAB®. This model helps determine the optimal daily management of a WUA with multiple underground supply sources and focuses on the management of wells while considering the water reservoir level. After 18,000 generations of the genetic algorithm, the pareto front was obtained with the best WUA managements achieving a water and energy savings of 25% and 54%, respectively. At the end of the irrigation season, the optimal total energy consumption per unit of water applied was 38% lower than that achieved by the current management. Results showed that a more realistic approach can be implemented when several water supplies operate jointly under a collaborative principle.

Geochemical and Multivariate Statistical Evaluation of Trace Elements in Groundwater of Niğde Municipality, South-Central Turkey: Implications for Arsenic Contamination and Human Health Risks Assessment.

This study was conducted to determine the concentrations of trace elements, their sources, and human health risks associated with arsenic contamination in groundwater of the Niğde Municipality, south-central Turkey. Fourteen groundwater samples were collected from groundwater supply sources fed by the Niğde water distribution system and were analysed for Al, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, and Ba concentrations. Multivariate statistical analyses were applied to decipher the source and interrelationships among trace elements in groundwater. The groundwater is mainly tapped from Quaternary alluvial and volcanic aquifers of the Niğde Massif. The pH of groundwater is slightly acidic to neutral, which controls the solubility and mobility of the trace elements. The mean concentrations of the trace elements vary in the order Zn > Fe > Ba > As > Cr > Ni > Se > Cu > Co > Mn > Al. All of the trace element concentrations comply with the maximum permissible values provided by the Turkish Standards Institution and the World Health Organization, except Zn, Cr, and As. However, approximately 7.14% of the studied samples are contaminated with Zn and Cr, whereas 86% are contaminated with As. The As concentrations range from 9.47 to 32.9µg/L with an average value of 16.8µg/L. Contamination assessment indicates that the As contamination is dominant in the southern and southwestern parts of the area. The primary source of As in groundwater is attributed to geogenic processes involving weathering and dissolution of bed rocks and other factors, such as pH conditions, adsorption, and surface complexation. Three bimetallic complex associations are distinguished in groundwater: Fe-coordination group, As-coordination group and Ba-coordination group, all showing strong positive correlation with Cu and Ni. The As-coordination group is the most dominant in groundwater, which resulted in the high As content of groundwater. Multivariate statistical analyses indicate that As mobilization in groundwater is associated with pH, EC, Ni, Cu, and Ba depending on the redox conditions of the aquifer, controlled mainly by geogenic processes. The carcinogenic risk of arsenic affecting children and adults reaches 2 × 10-4 and 3 × 10-4, respectively, exceeding the guideline value of 1 × 10-4. The estimated hazard quotient for children is in the range of 1.79-6.21, whereas that of adults is 0.77-2.66, indicating that children in the municipality are more exposed to the noncarcinogenic effects of the consumption of high groundwater arsenic.

Evaluation of desalination and groundwater supply sources for future water resources management in Riyadh city

Evaluation of desalination and groundwater supply sources for future water resources management in Riyadh city

Dynamic Analysis and Relationship Research on Precipitation and Groundwater Depth in Zhenlai County

Groundwater is an important source of water resources in Zhenlai County. In recent years, the groundwater level in Zhenlai County has been decreasing. Precipitation as one of the important sources of groundwater supply, the impact on the groundwater level cannot be ignored. In order to derive the relationship between precipitation and groundwater level, this research analysed the relationship between precipitation and groundwater characteristics, typical years and the whole from 2006 to 2012. The results show that the Yinghua and the Yanjiangdongerlong groundwater monitoring points have decreased by 2.03m and 0.42m respectively during 2006-2012, and the increase of precipitation will cause the groundwater level to rise. The research results can provide support for water resources management in Zhenlai County.

Characterizing the Spiritwood Valley Aquifer, North Dakota, using helicopter time-domain EM

Buried valley aquifers, consisting of permeable sand and gravel deposits in eroded bedrock valleys, are important sources of groundwater supply in many regions of the United States and Canada. Investigations of the Spiritwood aquifer in southern Manitoba by the Geological Survey of Canada and other workers, have demonstrated the value of helicopter time domain electromagnetic (HTEM) surveys in aquifer mapping and characterization using the contrasts between Quaternary glacio-lacustrine sand-gravels (high resistivity) that are relatively permeable and clay-tills (low resistivity) that are relatively impermeable, as well as the deeper, much less resistive Cretaceous Pierre Formation Shale basement rocks. This success provided the impetus for the North Dakota State Water Commission to fly a VTEM helicopter EM survey in the Jamestown, ND region in October, 2016. The VTEM data collected over the Spiritwood-JT block allowed for geological mapping from near surface to depth, in spite of relatively weak resistivity contrasts (<10X). These data were inverted with a layered-earth algorithm to produce resistivity-depth models. These models were able to resolve the location and depths to the top and bottom of the Spiritwood aquifer throughout the central portion of the block providing more detailed pictures of the aquifer’s geometry. In addition to resolving the main aquifer as well as its deeper channels, the VTEM data and models highlighted several smaller, previously undiscovered aquifers that cross-cut/branch-off from the main Spiritwood channel. These are interpreted as probable transverse low-K barriers that were apparent from the existing test drilling and aquifer testing.

WEAP-MODFLOW dynamic modeling approach to evaluate surface water and groundwater supply sources of Addis Ababa city

The integration between WEAP and MODFLOW models coupled via LinkKitchen helps to create a dynamic link between surface water and groundwater supply sources of Addis Ababa city. Possible impacts of natural and anthropogenic stresses on surface water reservoirs volume and groundwater storage have been assessed through water supply scenario analysis. Besides, contrary to other surface water hydrological models, the unique nature of WEAP adds water demand assessment by simulating Addis Ababa city near future water demand coverage under three population projection scenarios. The water demand projections of Addis Ababa city indicates 100% water demand coverage will not be achieved for high (4.6%), medium (3.8%) and low (2.8%) population growth rate projections, even with all the emerging and planned water supply projects start production up until 2025. Supply scenario projections indicate, as surface water reservoirs are highly sensitive to climate change and variability, the city groundwater supply sources will be noticeably affected by the emerging and planned groundwater supply expansion schemes. If groundwater abstraction continues to reach to zero unmet demand, more than 30-meter groundwater level decline can be registered in 2025. To foresee the combined effect of both natural and anthropogenic stresses on Addis Ababa city water supply sources, best case (considering conditions which improve Addis Ababa city water supply) and worst case (considering conditions stressing Addis Ababa city water supply) scenarios were tested. The best case scenario results zero unmet water demand in Addis Ababa city in most wet months of future projection years up to 2025, with likely decline of about 6 meter on the groundwater level. The worst case scenario to the contrary shows, Addis Ababa city water demand coverage will potentially be reduced to a maximum of 35% in 2025, with seasonal and annual variability. The dynamic link between surface water reservoirs and groundwater supply sources helps to gain insight into the potential consequences of continuously changing natural and anthropogenic conditions on Addis Ababa city water supply sources. Consequently, the significant predicted near future pressure on Addis Ababa city surface water and groundwater supply clearly indicate planning and developing alternative water supply sources outside of the boundary (Upper Awash basin) where the city is located should be immediately started in order to endure the pressure from the ever increasing demand. Otherwise, not only Addis will continue suffering unmet water demand for the years to come, but also the water supply sources will be severely impacted. Nonetheless, wherever the water supply sources, minimizing water loss, recycling and improving water use efficiency should be given at most priority.

Planning for desalination in the context of the Western Cape water supply system

As water demands continue to grow, South Africa is starting to consider seawater desalination as a potential future supply source, and it is currently being investigated at a feasibility level in a number of coastal cities, including Cape Town. Desalination is different to conventional surface and groundwater supply sources in that it is climate-resilient, having an assurance of supply of essentially 100 percent. However, the increased reliability comes at a great cost. This paper presents a methodology developed for modelling a proposed desalination plant as an integrated component of the Western Cape Water Supply System, in order to optimise system operating rules and cost. The modelling entailed short-term and long-term system analyses in the Water Resources Yield Model and Water Resources Planning Model, and estimation of first-order capital and operating costs in order to calculate and compare Unit Reference Values. The maximum increase in yield was found to occur when the seawater desalination plant is used as a base supply, operational all the time. There was little benefit, in terms of system yield, in using the desalination plant as an emergency supply source only. Unit reference values for the desalination plant decrease as the percentage supply from the plant increases, meaning that the lowest possible cost per cubic metre of water supplied is when the desalination plant is used as a base supply. It was also apparent that the unit reference values decrease with an increase in desalination plant capacity, suggesting that, from an economic perspective, the optimal solution would be to have one large desalination plant operational immediately.

The recharge process in alluvial strip aquifers in arid Namibia and implication for artificial recharge

Alluvial strip aquifers associated with ephemeral rivers are important groundwater supply sources that sustain numerous settlements and ecological systems in arid Namibia. More than 70 % of the population in the nation’s western and southern regions depend on alluvial aquifers associated with ephemeral rivers. Under natural conditions, recharge occurs through infiltration during flood events. Due to the characteristic spatial and temporal variability of rainfall in arid regions, recharge is irregular making the aquifers challenging to manage sustainably and they are often overexploited. This condition is likely to become more acute with increasing water demand and climate change, and artificial recharge has been projected as the apparent means of increasing reliability of supply. The article explores, through a case study and numerical simulation, the processes controlling infiltration, significance of surface water and groundwater losses, and possible artificial recharge options. It is concluded that recharge processes in arid alluvial aquifers differ significantly from those processes in subhumid systems and viability of artificial recharge requires assessment through an understanding of the natural recharge process and losses from the aquifer. It is also established that in arid-region catchments, infiltration through the streambed occurs at rates dependent on factors such as antecedent conditions, flow rate, flow duration, channel morphology, and sediment texture and composition. The study provides an important reference for sustainable management of alluvial aquifer systems in similar regions.

A pragmatic approach to study the groundwater quality suitability for domestic and agricultural usage, Saq aquifer, northwest of Saudi Arabia.

The present study deals with detailed hydrochemical assessment of groundwater within the Saq aquifer. The Saq aquifer which extends through the NW part of Saudi Arabia is one of the major sources of groundwater supply. Groundwater samples were collected from about 295 groundwater wells and analyzed for various physico-chemical parameters such as electrical conductivity (EC), pH, temperature, total dissolved solids (TDS), Na(+), K(+), Ca(2+), Mg(2+), CO3 (-), HCO3 (-), Cl(-), SO4 (2-), and NO3 (-). Groundwater in the area is slightly alkaline and hard in nature. Electrical conductivity (EC) varies between 284 and 9,902 μS/cm with an average value of 1,599.4μS/cm. The groundwater is highly mineralized with approximately 30% of the samples having major ion concentrations above the WHO permissible limits. The NO3 (-) concentration varies between 0.4 and 318.2mg/l. The depth distribution of NO3 (-) concentration shows higher concentration at shallow depths with a gradual decrease at deeper depths. As far as drinking water quality criteria are concerned, study shows that about 33% of samples are unfit for use. A detailed assessment of groundwater quality in relation to agriculture use reveals that 21% samples are unsuitable for irrigation. Using Piper's classification, groundwater was classified into five different groups. Majority of the samples show Mix-Cl-SO4- and Na-Cl-types water. The abundances of Ca(2+) and Mg(2+) over alkalis infer mixed type of groundwater facies and reverse exchange reactions. The groundwater has acquired unique chemical characteristics through prolonged rock-water interactions, percolation of irrigation return water, and reactions at vadose zone.

Isotopic and geochemical identification of main groundwater supply sources to an alluvial aquifer, the Allier River valley (France)

Isotopic and geochemical identification of main groundwater supply sources to an alluvial aquifer, the Allier River valley (France)

Isotopic and geochemical identification of main groundwater supply sources to an alluvial aquifer, the Allier River valley (France)

Summary Hydrodynamic, hydrochemical, and isotopic investigations were carried out on 18 points, including boreholes, piezometers, and surface waters, from February 2011 to August 2012, to assess groundwater quality in the unconfined shallow alluvial aquifer of the Allier River (one of the main tributary of the Loire River). The study area, located near the city of Clermont-Ferrand (France), plays an important socio-economic role as the alluvial aquifer is the major source of drinking water for about 100,000 inhabitants. The objective of the project aims at understanding the functioning of alluvial aquifers that occupy a pre-eminent position in the hydrogeologic landscape both for their economic role – production of drinking water and agricultural development – and for their ecological role. Moreover, this study also targets at determining the factors and processes controlling shallow groundwater quality and origin. The water circulates from the south, with a natural alimentation from the hills in the non-pumped part of the alluvial aquifer. In the pumping zone, this general behaviour is altered by the pumping that makes the water from the Allier River enter the system in a large proportion. Four end-members have been identified for the recharge of the alluvial groundwater: rainfall, Allier River, surrounding hills’ aquifer and the southern non-pumped part of the alluvial system. Results indicate that, despite the global Ca–HCO 3 water type of the groundwater, spatial variations of physico-chemical parameters do exist in the study area. Ionic concentrations increase from the Allier River towards east due either to the increase in the residence time or a mixing with groundwater coming from the aquifer’s borders. Stable isotopes of the water molecule show the same results: boreholes close to the river bank are recharged by the Allier River (depleted values), while boreholes far from the river exhibit isotopic contents close to the values of hills’ spring or to the southern part of the alluvial aquifer, both recharged by local precipitation. One borehole (B65) does not follow this scheme of functioning and presents values attesting of a probable sealing of the Allier River banks. Based on these results, the contribution of each end-member has been calculated and the functioning of the alluvial system determined.

Alternative water resources in granitic rock: a case study from Kinmen Island, Taiwan

Kinmen Island is a small, tectonically stable, granitic island that has been suffering from a scarcity of fresh water resources due to excessive annual evapotranspiration over annual precipitation. Recent studies further indicate that shallow (0–70 m) sedimentary aquifers, the major sources of groundwater supply, have already been over-exploited. Therefore, this preliminary study is to investigate the existence of exploitable water resources that can balance the shortage of fresh water on this island. Site characterization data are obtained from island-wide geophysical surveys as well as small-scale tests performed in a study area formed by three deep (maximum depth to 560 m) vertical boreholes installed in mid-east Kinmen northeast to Taiwu Mountain. Vertical fracture frequency data indicate that the rock body is fractured with a spatially correlated pattern, from which three major fracture zones (depths 0–70, 330–360, and below 450 m) can be identified. Geologic investigations indicate that the deepest fracture zone is caused by the large-scale, steeply dipping Taiwushan fault. This fault may have caused a laterally extensive low-resistivity zone, a potential fractured aquifer, near Taiwu Mountain. The middle fracture zone is induced by the Taiwushan fault and intersects the fault approximately 21 m southeast of the study area below a depth of 350 m. Slug testing results yield fracture transmissivity varying from 4.8 × 10−7 to 2.2 × 10−4 m2/s. Cross-hole tests have confirmed that hydraulic connectivity of the deeper rock body is controlled by the Taiwushan fault and the middle fracture zone. This connectivity may extend vertically to the sedimentary aquifers through high-angle joint sets. Despite the presence of a flow barrier formed by doleritic dike at about 300 m depth, the existence of fresh as well as meteoric water in the deeper rock body manifests that certain flow paths must exist through which the deeper fractured aquifers can be connected to the upper rock body. Therefore, groundwater stored within the Taiwushan fault and the associated low-resistivity zone can be considered as additional fresh water resources for future exploitation.

Adapting existing experience with aquifer vulnerability and groundwater protection for Africa

Whilst groundwater vulnerability mapping and the delineation of resource and source protection zones have become an appropriate set of management tools for Britain as incorporated in European policy, much of semi-arid Africa is still dealing with more pressing issues centred on water supply coverage. There are a number of fundamental differences with Britain which disallow conventional vulnerability mapping and land zonation in much of Africa. Firstly, the scale of groundwater occurrence in weathered basement aquifers does not encourage vulnerability mapping to be undertaken at a field scale, whereas the Karoo and some of the larger areas of unconsolidated sedimentary aquifers could more readily be zoned according to aquifer vulnerability. Secondly, analysis needs to disregard the productivity (or recharge potential) of the aquifer so that poorly productive but socially important aquifers can be assessed. Such practice also avoids the need to identify a value for effective rainfall, a problematical value in semi-arid climates given current uncertainties. Thirdly, it is difficult to protect the many small and dispersed groundwater supply sources typical of many African communities when compared with the fewer and larger sources characteristic of Britain and Europe. Some aspects of European groundwater management practice have been transferred to the African context, notably by South Africa, but there are other practices that should not be attempted. Lessons from experience in South Africa highlight capacity to implement as a key inhibiting factor. Examples of vulnerability assessment and land zonation in a variety of African settings indicate only limited success so far with standard vulnerability assessment and land zonation techniques. Alternative means of quantifying the problem of the optimum proximity of the pit latrine from the well are highlighted, with a minimum separation of 10 m suggested for typical weathered basement rocks.

Afghanistan: An Overview of Ground Water Resources and Challenges

Afghanistan: An Overview of Ground Water Resources and Challenges