Good Quality Groundwater Research Articles

Geophysics used to help find good quality groundwater in the Vientiane Plain, Lao PDR

Lao PDR is a poorly developed country, with a large rural population which relies heavily on agricultural production. The Vientiane Plain is one of the most important and largest agricultural produ...

Contribution to the hydrogeology of Six Hills sandstone aquifer in East El-Oweinat area, south Western desert, Egypt

El-Oweinat area is located in southwestern Egypt and is considered to be one of the new land reclamation projects in the Western Desert. The Nubian Sandstone aquifer has high potentiality and good groundwater quality. The results of geologic and hydrogeologic studies reveal that the Six Hills sandstone aquifer represents the sole groundwater resource used for all purposes (agriculture, drinking, domestic, livestock and poultry) in East El-Oweinat area. The Six Hills sandstone aquifer overlies directly the Precambrian basement rocks. The concerned aquifer exists under unconfined conditions as it is exposed on the surface. The hydrogeological cross sections show that the fully saturated thickness of the Six Hills sandstone aquifer ranges between 150.2 m and 651 m and increases towards the west. The groundwater generally flows towards the northeast direction with an average hydraulic gradient of 0.6 ‰. The calculated groundwater volume of the Six Hills sandstone aquifer in East El-Oweinat area (4,340 km2) reaches 350 bcm of fresh water. The comparison of the depth to water in the same monitoring wells during 14 years (2003 and 2016) reveals that the head decline rate in groundwater depths were ranging between 5 cm/year and 80 cm/year. The pumping rate increased from 600,000 m3/day in year 2003 to 3,600,000 m3/day in 2016. The average transmissivity attains 2,060 m2/day reflecting the high potential of the Six Hills sandstone aquifer in East El-Oweinat area. The groundwater flow model (MODFLOW) has been used to investigate the impact of groundwater withdrawal on groundwater levels for sustainable groundwater management. Four scenarios were applied to predict the probable head changes in the Six Hills sandstone aquifer and their impact on the availability of groundwater. The fourth scenario is recommended in order to sustain the groundwater resources in the study area and keep the drawdown rates in the range of 0.66 m/year through reducing the present discharging rates (10,000 m3/day/well) by about 40%.

Geological-geomorphological and geochemical control on low arsenic concentration in the Lerma valley groundwater between the two high arsenic geologic provinces of Chaco-Pampean plain and Puna

Argentina is known for having one of the most extensive areas with high arsenic (As) concentration in groundwater in the world. These areas correspond to two geological provinces, the Altiplano-Puna plateau and the Chaco-Pampean plain. In this large territory, there are some specific environments where the As concentration in groundwater is lower, and in some cases within the recommended limits for drinking water. In our study, we analyze and interpret the low As concentrations reported for the Lerma valley, the easternmost intermontane basin of the Cordillera Oriental, located between the aforementioned high‑arsenic areas. The groundwater from this valley is used for the consumption of >600.000 inhabitants in the city of Salta and nearby towns. The incipient geological development of the valley since the late Miocene and the subsequent tectonic and climatic evolution favored low As concentrations with respect to the Altiplano-Puna plateau and the Chaco-Pampean plain. The high-energy sedimentary environments that characterized the area during Plio-Quaternary times and the composition of the sediments have controlled the characteristics of the multilayered aquifer. Moreover, the absence of geogenic As sources, climate, high rain infiltration rate, near neutral pH, redox conditions, and wells construction with screens settled in coarse productive layers favor groundwater of good quality. The geological and tectonic evolution of the Lerma valley could be extrapolated to other similar valleys in NW Argentina and can be a useful tool for exploration of good quality groundwater. This is of high importance in Latin American territories with high As concentration in groundwater such as Argentina.

Impact of climate smart agriculture (CSA) through sustainable irrigation management on Resource use efficiency: A sustainable production alternative for cotton

Climate-smart agriculture (CSA) improves agricultural productivity and enhance farm income on a sustainable basis, enhance water and nutrients use efficiency, resilient to climatic stresses, and lowering the emissions of Greenhouse Gas (GHG) to a minimum level. Water-smart, energy-smart, carbon-smart and knowledge-smart practices and technologies significantly contributed directly or indirectly to improve productivity, enhance resilience and reduce GHG emission. Cotton is one of the important cash crops of Pakistan. It is a climate sensitive crop and suffered by multiple shocks as climate change and market discrepancies during the last two decades. The present paper aimed to estimate and compare the resource use efficiency including technical, economic and water use efficiency of adopters of CSA and non-adopters in cotton production. The study was conducted along Lower Bari Doab Canal (LBDC) irrigation system in Punjab, Pakistan. First-hand information was gathered through a well-structured and comprehensive questionnaire from 133 adopters of CSA and 65 farmers cultivating cotton with traditional methods. Input-oriented Data Envelopment Analysis technique was employed to investigate the technical, economic and water use efficiency, assuming variable return to scale. The Bootstrap Truncated Regression was used to identify the factors influencing the resource use efficiency. The results showed that the adopters of CSA were using inputs more efficiently. The analysis revealed that adopters have higher cotton yield from per m3 irrigation water than non-adopters. Adopters were found to be financially sound, having easy access to credit and fast adaptation behavior towards environmental changes, and therefore, economically better off as compared to non-adopters. Bootstrap Truncated Regression analysis revealed that easy access to credit, provision of extension services, awareness regarding CSA, availability of good quality groundwater and right of ownership of tubewell were significantly affecting resource use efficiency. The finding suggested certain policy implications for creating awareness and financial support for the cotton growers to expedite the adaptation of CSA practices and technologies in the cotton growing area. This can enhance resource use efficiency, net farm income and livelihood of rural masses.

An Integrated Novel Approach to Understand the Process of Groundwater Recharge in Mountain and Riparian Zone Aquifer System of Tamil Nadu, India

The nature of groundwater recharge along the mountain front (MF) and riparian zone (RZ) was discerned by multiple tools involving rain/water level relationship, geophysical of subsurface, seasonal hydrochemistry and environmental isotopic signatures. The proposed study has been carried out in Courtallam Hills, the north-western part of Tirunelveli District, South India. The study area is a hilly terrain with narrow valleys endowed with steep slopes. The relationship between water-level fluctuation and precipitation were evaluated by observing daily water level in 8-h interval at three piezometer zones and regular rainfall data. It was inferred that the RZ played a role in storage zone and gets recharged from mountain block (MB) and lateral flow. The seasonal geochemistry of the groundwater was studied to determine the sources of recharge in MF and RZ. Geostatistical treatment of factor analysis revealed that weathering was the dominant recharge process along the foothill. The geophysical studies reveal good quality of groundwater observed in the northern part along with low conductance and high resistivity. The increased level of groundwater conductivity and lower resistivity was noted in southern part of the study area due to the irrigation activities. The isotopic tracers range from − 2.5 to − 12.6‰ for δ18O and from − 91.2 to − 15.5‰ for δ2H. Moreover, the groundwater recharge was evaluated by source of rainfall moisture. High-altitude recharge from MB along the MF was clearly indicated by depleted isotopic content of the water samples. It was also supported by hydrogeochemical and statistical evidences, showing that rainfall over both MB and MF zones provided the recharge to foothill aquifers, while the RZ zone was mainly recharged by local precipitation with less contribution from regional flows.

Spatial interpolation approach-based appraisal of groundwater quality of arid regions

Abstract The primary objective was appraisal of groundwater quality during pre- and post-monsoon seasons for irrigation purposes. Good quality groundwater is required for high crop yields in arid regions. A total of 45 samples were collected from wells and analyzed in the laboratory for this research work. Different water quality parameters were determined from these samples, namely electrical conductivity (EC), sodium adsorption ratio (SAR), residual sodium carbonate (RSC), sodium percent (Na%), and permeability index (PI) during the pre- and post-monsoon season. The water types were identified through a Piper-trilinear diagram. Fifty per cent of the water samples of the total basin area fall under the saline category. The local farmers heavily rely on groundwater for the irrigation of crops. Excess use of groundwater for irrigation raises soil salinity. Some parts of the study area are facing serious problems such as loss of crop yields, and low availability of good quality groundwater even for drinking purposes. The results highlight that the study area has a high salinity content (C3) and low sodium (S1). The maps for different water quality parameters were generated using inverse distance weighted (IDW) interpolation method in ArcGIS 10.3 software.

Temperature-dependent redox zonation, nitrate removal and attenuation of organic micropollutants during bank filtration

River bank filtration (RBF) is considered to efficiently remove nitrate and trace organic micropollutants (OMP) from polluted surface waters. This is essential for maintaining good groundwater quality and providing high quality drinking water. Predicting the fate of OMP during RBF is difficult as the biogeochemical factors controlling the removal efficiency are not fully understood. To determine in-situ removal efficiency and degradation rates of nitrate and OMP indicator substances we conducted a field study in a RBF system during a period of one and a half years incorporating temporally and spatially varying redox conditions and temperature changes typically occurring in temperate climates. RBF was analyzed by means of mixing ratios between infiltrated river water and groundwater as well as average residence times of surface water towards the individual groundwater observation wells. These results were used to calculate temperature dependent first order degradation rates of redox sensitive species and several OMP. Five out of ten investigated OMP were completely removed along RBF pathways. We demonstrate that degradation rates of several OMP during bank filtration were controlled by redox conditions and temperature whereby temperature itself also had a significant influence on the extent of the most reactive oxic zone. The seasonal variations in temperature alone could explain a considerable percentage of the variance in dissolved oxygen (34%), nitrate (81%) as well as the OMPs diclofenac (44%) and sulfamethoxazole (76%). Estimated in-situ degradation rates roughly varied within one order of magnitude for temperature changes between 5 °C and 20 °C. This study highlights that temporal variability in temperature and redox zonation is a significant factor for migration and degradation of nitrate and several OMPs.

Methods to supply seawater to desalination plants along the Spanish mediterranean coast and their associated issues

Many coastal areas of our planet receive only scarce precipitation, and have limited or often non-existent surface water resources. Over the last four decades, the intensive agriculture and tourism along the Spanish mediterranean coast have led to a large increase in water demand. The economic development of this, the most arid stretch of the Mediterranean coast has been dependent on the availability of good quality groundwater. Desalination in Spain has contributed to the progress and development of these areas, being considered as the solution to this increased demand. Along the Spanish mediterranean coast, around 30 desalination plants of medium–high capacity, between 20,000 and 125,000 m3/day, have been built over the last 25 years, and there are several plants in the planning stage, to be constructed in the near future. In addition, 100 small plants desalinate brackish water. Desalination plants are usually supplied from coastal boreholes if there is a coastal aquifer with hydraulic connection to the sea. Nevertheless, the water to desalinate in other cases comes from evaporitic aquifers or even fossil water. Regarding the water intake systems, horizontal directional drilling can give good results, not to mention a number of other sophisticated and curious designs, each with their particular advantages and drawbacks. This paper describes the main problems and also the benefits concerning water intake systems to some desalination plants along the Spanish mediterranean coast.

INTERPRETASI KONDISIAIR BAWAH TANAH STUDI KASUS DI KECAMATAN TENAYAN RAYA KOTA PEKANBARU DENGAN MENGGUNAKAN METODE PUMPING TEST

The purpose of the research on the potential of underground water in ring wells in the District of Tenayan Raya Pekanbaru City using the experimental method of pumping test is to determine the potential of underground water, and determine the value of transmissivity so that it can be known the feasibility of well water for surrounding communities. Data was taken on 30 ring wells in Tenayan Raya District, Pekanbaru City. The results obtained are wells that have the lowest potential for underground water in Kadiran Street, Kulim Village with a value of drawdown is 2.1610 m. Wherea the highest potential as good underground water is in the well at Gunung Kidul Street, Tangkerang Timur Village with value of drawdown is 2.0407 m. This ring well has the potential of underground water which is likely to provide water for a long time. The transmissivity obtained from the 30 ring wells is 10.7684 m2 / day. This value shows good groundwater quality and has the potential to meet the needs of residential areas.

Geospatial Analysis of Groundwater Quality in Ludhiana, Punjab (India)

This paper presents a geospatial analysis of the groundwater quality of Ludhiana, Punjab, India. The groundwater samples were collected from 99 locations using grid based sampling procedure and analysed for parameters viz. pH, total dissolved solids (TDS), total hardness (TH), calcium (Ca2+), magnesium (Mg2+), sodium (Na+), potassium (K+), fluoride (F-), chloride (Cl-), nitrate (NO3-), sulphate (SO24-) and bicarbonate (HCO3-). Sampling was done during both pre-monsoon and post-monsoon periods. Water quality index (WQI) was used to represent the groundwater quality of the study area. The WQI coupled with the spatial maps indicated that merely (1%) of the total study area had good groundwater quality and the rest of the study area fell under poor, very poor and unsuitable for drinking purpose. The geographical information system (GIS) based groundwater quality mapping presented in this paper could be a potential tool for groundwater quality management.

The Application of CRU-Resistivity Meters for Groundwater Investigation in Chantaburi, Thailand

This research proposes an investigation of groundwater by using 2D electrical resistivity techniques with the low-cost Chandrakasem Rajabhat University Resistivity Meter (CRU-Resistivity Meter) and processing with the Chandrakasem Rajabhat University Resistivity Images software (CRU-Resistivity Images). The resistivity meter, constructed of parts costing less than $1,000 USD, was tested at Soi Dao in Chantaburi, Thailand with a profile length of 90 m. Using a Wenner electrode array, the results showed that high resistivity zones greater than 100 ohm-m at a depth of 8 m generally considered to be topsoil with sand. Through testing, it was also found that low resistivity zones about 10 ohm-m at a depth of 20 to 50 m depth were generally considered a suitable subsurface range for good quality groundwater. The results of total dissolved solid (TDS) from water samples confirmed that groundwater at the sites of this example survey may be used for agriculture.

Potential recharge areas of deep aquifers: an application to the Vercelli–Biella Plain (NW Italy)

Deep aquifers typically serve as a key source of drinking water due to their good groundwater quality. Then the identification of deep aquifers recharge areas provides the local administration with a management tool to protect groundwater, through the implementation of legislative measures for the control of pollution sources. However, the location and size of recharge areas of deep aquifers are often difficult to define and generally require a large amount of data. The aim of this paper is to propose a method to identify potential recharge, throughflow and discharge areas of deep aquifers on a regional scale, due to their hydrodynamic features. As the proposed method identifies where deep-aquifer recharge can occur, but not the recharge rate, delimited areas are defined as “potential”. Particularly, the method analyses piezometric level differences between shallow and deep aquifers to understand groundwater flow direction. The areas where groundwater flow is downward are delimited as potential recharge areas of deep aquifers (PRADAs). The method represents a qualitative approach to the identification of PRADAs, because it permits to narrow down large plain areas extension, highlighting where potentially recharge areas are located. Then PRADAs location and shape can be defined effectively, expanding data sets and furthering analyses (hydrogeological reconstruction, hydraulic connectivity, hydro-chemical and isotopic methods…) in the identified areas. The hydrogeological setting investigated by this method is representative of many anthropized and groundwater-demanding plains around the world that require to be protected. Thus, the method represents a suitable approach for PRADAs’ identification in such settings, especially in low-income countries, where resource availability for studies and analyses is scarce. This method was then applied to a plain area of Northwest Italy, and the locations and sizes of potential recharge, throughflow and discharge areas of deep aquifers were identified on a regional scale.

Short-term geochemical investigation and assessment of dissolved elements from simulated ash reclaimed soil into groundwater

A soil column migration trough was used to study the leaching behavior and geochemical partitioning of fifteen elements Al, As, Cr, Cu, Fe, Mg, Sn, Sb, Zn, V, Co, Mn, Pb, Ni and Cd in simulated ash reclaimed soil. According to the results of cluster analysis for the sampling stations, there were three clusters: Cluster 1 of 7 wells with relative good groundwater quality originated from the background control area, Cluster 2 of 9 wells with worst groundwater quality in the downstream parts of the simulated ash reclaimed soil, and Cluster 3 of 2 wells with representative of samples influenced by the combined effect of injection of leaching solution and the main current. Statistical analysis identified five factor types that accounted for 83.055% of the total variance, which declined in the order: ash-soil rate > leaching intensity > water depths > flow velocity > leaching time. As, Sb, Cd, Pb and Ni were the dominant contaminants. The water around ash reclaimed soil was unsuitable for drinking. As, Mn, Cd, Sb, Co and V were the largest contributors to health risks. Soils reclaimed with fly ash can consequently be a long-time source for the transfer of toxic elements into groundwater.

Responding to salinity in a rural African alluvial valley aquifer system: To boldly go beyond the world of hand-pumped groundwater supply?

Effective response to groundwater salinity in the developing world may critically safeguard drinking-water supplies. Groundwater resources throughout rural Africa are exploited by a vast and increasing number of hand-pumped boreholes for community supply. Our research in TA Ngabu (Shire Valley), Southern Malawi aims to: define groundwater-salinity problem occurrence within the semi-arid alluvial-valley aquifer, rural developing-world setting; critique current capacity to respond; and, to discuss future response options - in particular considering the need to explore alternative options that boldly go beyond the world of hand-pumped groundwater supply. Salinity problem definition was achieved through survey of 419 hand-pumped boreholes that revealed widespread brackish groundwater leading to non-potable (unpalatable) drinking-water supplies. Persistent non-functionality or abandonment of boreholes was typically ascribed to salinity. Whilst salinity is conceptualised to arise from shallow-groundwater evaporation, formation-evaporite dissolution and faulted-area upwelling, sparse data locally renders attribution of salinity sources to individual boreholes difficult. There is a significant need to better resolve the vertical distribution of salinity and local controlling processes. Problem response capacity was hampered by multiple factors, including, sector inertia, low drilling costs compromising water-point integrity, and lack of technical vision for alternatives. Various recommendations are made to improve response capacity continuing to work at the hand-pump supply scale. However, in areas where salinity is significant, exploring the feasibility of other options is advocated in conjunction with technical capacity development. Groundwater options may utilise high borehole yields possible from alluvial aquifers, grossly under-exploited by hand pumps. Groundwater at depth, albeit of unknown quality typically, or pipeline transfers of probable good-quality groundwater from valley-margin units, should be considered. Surface-water pipeline supplies may be viable for (growing) population centres. Canal-fed irrigation schemes (pending for the area), should be multiple-use, protective of groundwater and embrace pipeline drinking-water supply and managed-aquifer-recharge opportunities. Advancing desalination technologies, although presently unaffordable, should be kept under review.

Geostatistical multimodel approach for the assessment of the spatial distribution of natural background concentrations in large-scale groundwater bodies

Quantification of the (spatially distributed) natural contributions to the chemical signature of groundwater resources is an emerging issue in the context of competitive groundwater uses as well as water regulation and management frameworks. Here, we illustrate a geostatistically-based approach for the characterization of spatially variable Natural Background Levels (NBLs) of target chemical species in large-scale groundwater bodies yielding evaluations of local probabilities of exceedance of a given threshold concentration. The approach is exemplified by considering three selected groundwater bodies and focusing on the evaluation of NBLs of ammonium and arsenic, as detected from extensive time series of concentrations collected at monitoring boreholes. Our study is motivated by the observation that reliance on a unique NBL value as representative of the natural geochemical signature of a reservoir can mask the occurrence of localized areas linked to diverse strengths of geogenic contributions to the groundwater status. We start from the application of the typical Pre-Selection (PS) methodology to the scale of each observation borehole to identify local estimates of NBL values. The latter are subsequently subject to geostatistical analysis to obtain estimates of their spatial distribution and the associated uncertainty. A multimodel framework is employed to interpret available data. The impact of alternative variogram models on the resulting spatial distributions of NBLs is assessed through probabilistic weights based on model identification criteria. Our findings highlight that assessing possible impacts of anthropogenic activities on groundwater environments with the aim of designing targeted solutions to restore a good groundwater quality status should consider a probabilistic description of the spatial distribution of NBLs. The latter is useful to provide enhanced information upon which one can then build decision-making protocols embedding the quantification of the associated uncertainty.

Hydro-chemical Survey and Quantifying Spatial Variations in Groundwater Quality in Coastal Region of Chennai, Tamilnadu, India – a case study

The good quality of groundwater is important for the purpose of future planning and management. The present study has been undertaken to provide an overview on the status of groundwater quality through physicochemical parameters namely pH, alkalinity, total hardness, total dissolved solids, chloride, fluoride, nitrate, phosphate and iron through laboratory analysis. Samples have been collected from seven wells located in Chennai costal region of state Tamilnadu, India. The laboratory-based results shows that the mean value of pH is 7.29, alkalinity (308.57 mg/l), total hardness (285.71 mg/l), chloride (175.71 mg/l), iron (0.71 mg/l), nitrate (13.57 mg/l), phosphorus (2.71 mg/l) and total dissolved solids (924 mg/l), respectively. The geo-database water quality parameters were created in Geographical an Information System. Further, the kriging a geo-statistical method of interpolation is applied to know the health of groundwater in the then-sampled area. This interpolation method has been used to predict spatial distribution physicochemical parameters in the form of contour. Local planners and policy makers may utilize these results for efficient management of groundwater resources in this area.

Application of Geospatial Techniques for Groundwater Quality and Availability Assessment: A Case Study in Jaffna Peninsula, Sri Lanka

Groundwater is one of the most important natural resources in the northern coastal belt of Sri Lanka, as there are no major water supply schemes or perennial rivers. Overexploitation, seawater intrusion and persistent pollution of this vital resource are threatening human health as well as ecosystems in the Jaffna Peninsula. Therefore, the main intent of the present paper is to apply geospatial techniques to assess the spatial variation of groundwater quality and availability for the sustainable management of groundwater in the coastal areas. The electrical conductivity (EC) and depth to water (DTW) of 41 wells were measured during the period from March to June 2014, which represents the dry period of the study area. Surface interpolation, gradient analysis, a local indicators of spatial autocorrelations (LISA) and statistical analysis were used to assess the quality and availability of groundwater. The results revealed that the drinking and irrigation water quality in the study area were poor and further deteriorated with the progression of the dry season. Good quality and availability of groundwater were observed in the western zone compared to other zones of the study area. A negative correlation was identified between depth to water and electrical conductivity in the western zone. Hence, relatively deep wells in the western zone of the study area can be used to utilize the groundwater for drinking, domestic and agricultural purposes. The outcomes of this study can be used to formulate policy decisions for sustainable management of groundwater resources in Jaffna Peninsula.

Evaluating groundwater quality for irrigated agriculture: spatio-temporal investigations using GIS and geostatistics in Punjab, Pakistan

Groundwater is cornerstone of global food production, and its quality plays a vital role in crop development. Success of agriculture in Pakistan relies heavily on groundwater because of reduced surface water supplies and rainfalls. The current study was conducted to assess the spatio-temporal quality of groundwater in the Lower Chenab Canal (LCC) east area with emphasis on characterizing groundwater quality zones for irrigation applications. Groundwater samples from 289 observation wells were collected and chemically analyzed. A geostatistical approach using kriging interpolation was applied to express spatial variation and minimize estimation error in data. Three water quality parameters, electrical conductivity (EC), sodium absorption ratio (SAR), and residual sodium carbonate (RSC), were utilized to develop groundwater quality maps for two seasons including pre-monsoon and post-monsoon. To describe the spatial autocorrelation, suitable semivariogram models were identified and cross validated. The exponential model gave the best results for EC and RSC, whereas the spherical model was found to be the best fit for SAR. The overlay analysis was performed to create composite water quality maps according to which 40% LCC area is showing good groundwater quality for irrigation, 49% is exhibiting marginal quality, and 10% unsuitable during pre-monsoon and post-monsoon seasons. Groundwater quality is 100% good for Sultanpur irrigation subdivision, and only 3.75% is good for Paccadala subdivision. The results of the study may provide guidelines for the planners/policy makers to devise area-specific strategies for sustainable groundwater use.

Comprehensive evaluation method of groundwater environment in a mining area based on fuzzy set theory

Disordered mining activities have significantly affected the eco-geological environment of groundwater in mining area. Based on the fuzzy set theory, this paper considered three factors: the quantity of groundwater resources, groundwater environmental quality and groundwater vulnerability, and established a multi-index and multi-parameter non-linear evaluation system to make a comprehensive evaluation of the groundwater environment in the mining area. The results showed that the groundwater eco-geological environmental issues in this region were serious. The distribution area of poor quality of groundwater environment was very large, accounting for 72.5% of the studied area, and it mainly distributed in the middle and southern regions. The areas with general groundwater quality covered about 19.0% and mainly distributed in the central and northern parts in a strip shape. The areas with good groundwater quality covered about 8.5% and distributed sporadically. Moreover, in the study area, because the groundwater vulnerability was at a high level and the groundwater environmental quality was poor, the groundwater was extremely susceptible to contamination. Therefore, the groundwater environment in the area should be significantly protected during coal mining. In addition, the predicted results can provide a scientific reference for the planning and sustainable development of large coalfields.

Degradation of groundwater quality in coastal aquifer of Sabratah area, NW Libya

Overextraction of groundwater is widely occurring along the coast where good quality groundwater is at risk, due to urbanization, tourist development and intensive agriculture. The Sabratah area at the northern central part of Jifarah Plain, Northwest Libya, is a typical area where the contamination of the aquifer in the form of saltwater intrusion, gypsum/anhydrite dissolution and high nitrate concentrations is very developed. Fifty groundwater samples were collected from the study area and analysed for certain parameters that indicate salinization and pollution of the aquifer. The results demonstrate high values of the parameters electrical conductivity, sodium, potassium, magnesium, chloride and sulphate which can be attributed to seawater intrusion. The intensive extraction of groundwater from the aquifer reduces freshwater outflow to the sea, creates drawdown cones and lowering of the water table to as much as 30 m below mean sea level. Irrigation with nitrogen fertilizers and domestic sewage and movement of contaminants in areas of high hydraulic gradients within the drawdown cones probably are responsible for the high nitrate concentration towards the south of the region. Seawater intrusion and deep salt water upconing result in general high SO4 2− concentrations in groundwater near the shoreline, where localized SO4 2− anomalies are also due to the dissolution of sebkha deposits for few wells in the nearby sebkhas. Upstream, the increase in SO4 2− concentrations in the south is ascribed to the dissolution of gypsum at depth in the upper aquifer.