Response of groundwater to climate variation: fluctuations of groundwater level and well yields in the Halacli aquifer (Cankiri, Turkey)

The aim of this study was to investigate the response of groundwater level and well yields in the Halacli aquifer to climate variations in Central Anatolia, Turkey. The Halacli aquifer is a typical aquifer due to its vulnerability to the climate variations. The aquifer is shallow and its recharge area is small. The waters from rains and snow melts can rapidly infiltrate down to the groundwater body because the vadose zone is thin and formed from coarse material. Therefore, the groundwater system responds to the short-term recharges by raising its level. Although any exploitation did not occur, the groundwater levels have declined from 1989 to 1997. However, the groundwater levels began rising when the exploitation started in the summer of 1998. After the year 2000, although the amount and duration of yearly exploitation was constant, fluctuations of water level continued. Fluctuation of groundwater levels and well yields bewilders the water users and imperils the sustainable water management in the study area and also in arid and semi-arid regions of Turkey. In order to overcome this problem, behavior of groundwater level and discharges of the wells must be recorded and the water users must be informed about the current conditions and the possible trend in the future of the system.     

Future groundwater extraction scenarios for an aquifer in a semiarid environment: case study of Guadalupe Valley Aquifer,Baja California,Northwest Mexico

Semiarid northwestern Mexico presents a growing water demand produced by agricultural and domestic requirements during the last two decades. The community of Guadalupe Valley and the city of Ensenada rely on groundwater pumping from the local aquifer as its sole source of water supply. This dependency has resulted in an imbalance between groundwater pumpage and natural recharge. A two-dimensional groundwater flow model was applied to the Guadalupe Valley Aquifer, which was calibrated and validated for the period 1984–2005. The model analysis verified that groundwater levels in the region are subject to steep declines due to decades of intensive groundwater exploitation for agricultural and domestic purposes. The calibrated model was used to assess the effects of different water management scenarios for the period 2007–2025. If the base case (status quo) scenario continues, groundwater levels are in a continuous drawdown trend. Some wells would run dry by August 2017, and water demand may not be met without incurring in an overdraft. The optimistic scenario implies the achievement of the mean groundwater recharge and discharge. Groundwater level depletion could be stopped and restored. The sustainable scenario implies the reduction of current extraction (up to about 50 %), when groundwater level depletion could be stopped. A reduction in current extraction mitigates water stress in the aquifer but cannot solely reverse declining water tables across the region. The combination of reduced current extraction and an implemented alternative solution (such as groundwater artificial recharge), provides the most effective measure to stabilize and reverse declining groundwater levels while meeting water demands in the region.     

Groundwater Modeling in Agricultural Watershed under Different Recharge and Discharge Scenarios for Quaternary Aquifer Eastern Nile Delta,Egypt

Different scenarios of recharge and discharge were assessed for sustainable management of groundwater in Quaternary aquifer east of Nile Delta. MODFLOW was utilized to investigate the effect of land use change and damming construction in the upstream of the Nile River on the current and short-term groundwater management strategies. The interpretive transient simulation was performed between 2004 and 2016 after steady-state calibration in 2004, and transient state from 2004 to 2013 with different irrigation recharges associated with land use change in this period. Sensitivity analysis was performed for hydraulic conductivities, recharge, and conductance parameters. The predictive transient simulation was run till 2023 under three scenarios of increasing pumping rates by 15, 30, and 50% for agriculture expansion and specified head reduction of Port Said Canal by 0.2, 0.4, and 0.6 m associated with the reduction of Nile water levels after Grand Ethiopian Residence Dam, GERD operation in 2017. Results from the in- and out-flow budgets showed that groundwater aquifer is stable at the current rate of pumping till 2023. Groundwater heads decreased by 0.2 and 0.42 m in the southern section, and a slight increase in the northern part was noticed for the first and second scenarios, respectively. When additional pumping stress is applied (50% increase), groundwater head dropped by 0.66 m, and the storage is no longer able to maintain the aquifer capacity after 2020 (worst-case scenario).     

Groundwater modeling of Saq Aquifer Buraydah Al Qassim for better water management strategies

Saudi Arabia is an arid country. It has limited water supplies. About 80?C90% of water supplies come from groundwater, which is depleting day by day. It needs appropriate management. This paper has investigated groundwater modeling of Saq Aquifer in Buraydah Al Qassim to estimate the impact of its excessive use on depletion of Saq Aquifer. MODFLOW model has been used in this study. Data regarding the aquifer parameters was measured by pumping tests. Groundwater levels and discharge of wells in the area for the year 2008 and previous record of year 1999 have been collected from Municipal Authority of Buraydah. Location of wells was determined by Garmin. The model has been run for different sets of pumping rates to recommend an optimal use of groundwater resources and get prolonged life of aquifer. Simulations have been made for a long future period of 27?years (2008?C2035). Model results concluded that pumping from the Saq Aquifer in Buraydah area will result into significant cones of depression if the existing excessive pumping rates prevail. A drawdown up to 28?m was encountered for model run for 27?years for existing rates of pumping. Aquifer withdrawals and drawdowns will be optimal with the conservation alternative. The management scheme has been recommended to be adopted for the future protection of groundwater resources in Kingdom of Saudi Arabia.     

Groundwater quality assessment in semi-arid regions using integrated approaches: the case of Grombalia aquifer (NE Tunisia)

As many arid and semi-arid regions in the Mediterranean Basin, the Grombalia coastal aquifer (NE Tunisia) is affected by severe groundwater exploitation and contamination. Therefore, quality assessments are becoming increasingly important as the long-term protection of water resources is at stake. Multidisciplinary investigations, like the one presented in this paper, are particularly effective in identifying the different origins of mineralization within an aquifer and investigating the impact of anthropogenic activities on groundwater quality. An integrated assessment, focused on the combined use of geostatistical, geochemical and isotopic (δ¹⁸O, δ²H and ³H) tools, was performed in the Grombalia aquifer between February and March 2014. The overall goal was to study the main processes controlling aquifer salinization, with special focus to nitrate contamination. Results indicate a persisting deterioration of water quality over the whole basin except the south-eastern zone juxtaposing the recharge area of the aquifer. Nitrate contents exceed the drinking water standard (50 mg/l) in 70% of groundwater samples, mainly due to the excessive use of fertilizers and urban activities. Stable isotope measurements showed the contribution of modern rainwater to aquifer recharge and proved the presence of evaporation contributing to the salinity increase. Tritium values of groundwater samples suggested two hypotheses: the existence of mixture between old and recent water or/and the existence of two recharge periods of the aquifer, pre- and post-nuclear weapons test. Principal component analysis confirmed the geochemical interpretation, highlighting that water-rock interaction evaporation effect and intensive anthropogenic activities constitute the main processes controlling the regional groundwater mineralization.     

A groundwater flow model for water resources management in the Ismarida plain,North Greece

This paper presents the development of a regional flow simulation model of the stream–aquifer system of Ismarida plain, northeastern Greece. It quantifies the water budget for this aquifer system and describes the components of groundwater and the characteristics of this system on the basis of results of a 3-year field study. The semiconfined aquifer system of Ismarida Lake plain consists of unconsolidated deltaic clastic sediments, is hydraulically connected with Vosvozis River, and covers an area of 46.75 km². The annual precipitation ranges in the study area from 270 to 876 mm. Eighty-seven irrigation wells are densely located and have been widely used for agricultural development. Groundwater flow in this aquifer was simulated with MODFLOW. Model calibration was done with observed water levels, and match was excellent. To evaluate the impacts of the current pumping schedule and propose solutions, four management scenarios were formulated and tested with the model. Based on model results, the simulated groundwater budget indicates that there must be approximately 33% decrease of withdrawals to stop the dramatic decline of groundwater levels. The application of these scenarios shows that aquifer discharge to the nearby river would be very low after a 20-year period.     

A Compartmental Model for Stable Time-Dependent Modeling of Surface Water and Groundwater

Water resource system planners make decisions that guide water management policy. The fundamental tools for assessing management and infrastructure strategies are combined hydro-economic models of river basins (RBHE models). These models have improved the economic efficiency of water use in situations of competition for scarce water resources. In RBHE models, a groundwater model is coupled with surface water models of the various water resources. Today, the groundwater models used in an RBHE model can be of two types: cell models or numerical models. Cell models are easy to use, but they are too simple to realistically describe the geology and hydrology of the area under investigation. Numerical models, in contrast, are closer to the physical behavior of the aquifer. However, the vast quantity of data to be analyzed makes them impractical for many management scenarios. Moreover, the calibrations of these high-resolution models are generally difficult and sensitive to the variation of parameters, especially when boundary conditions are dynamic. This is the case when dynamic river data or dynamic surface lake data are present. In this work, a compartmental cell model is built on the hydrogeology of the aquifer. In this approach, the hydrogeology of the aquifer and the dynamic boundary conditions are treated with separate models. A general mathematical formulation is presented where the calibration stage, the validation stage, and the prediction stage are formulated as a series of sub-model calibrations and solved using a general least squares routine. With this approach, it becomes possible to treat both the water level and the pumping rate in each cell as variables to be predicted. In most of the models, the pumping rates are known and the goals of the computation are to estimate the groundwater level. However, when for political or technical reasons access to some of the wells is difficult, the pumping rates are only partially known. Then, both groundwater levels and pumping rates are variables to be predicted by the groundwater model. A computer program was developed using MATLAB, with a Visual Basic graphical user interface using COM technology to access the advanced mathematical libraries. The approach was implemented with a real case study of the Yarkon–Taninim aquifer in Israel. The results indicate that the method is more stable than the classical approach.     

Computation of groundwater resources and recharge in Chithar River Basin, South India

Groundwater recharge and available groundwater resources in Chithar River basin, Tamil Nadu, India spread over an area of 1,722 km² have been estimated by considering various hydrological, geological, and hydrogeological parameters, such as rainfall infiltration, drainage, geomorphic units, land use, rock types, depth of weathered and fractured zones, nature of soil, water level fluctuation, saturated thickness of aquifer, and groundwater abstraction. The digital ground elevation models indicate that the regional slope of the basin is towards east. The Proterozoic (Post-Archaean) basement of the study area consists of quartzite, calc-granulite, crystalline limestone, charnockite, and biotite gneiss with or without garnet. Three major soil types were identified namely, black cotton, deep red, and red sandy soils. The rainfall intensity gradually decreases from west to east. Groundwater occurs under water table conditions in the weathered zone and fluctuates between 0 and 25 m. The water table gains maximum during January after northeast monsoon and attains low during October. Groundwater abstraction for domestic/stock and irrigational needs in Chithar River basin has been estimated as 148.84 MCM (million m³). Groundwater recharge due to monsoon rainfall infiltration has been estimated as 170.05 MCM based on the water level rise during monsoon period. It is also estimated as 173.9 MCM using rainfall infiltration factor. An amount of 53.8 MCM of water is contributed to groundwater from surface water bodies. Recharge of groundwater due to return flow from irrigation has been computed as 147.6 MCM. The static groundwater reserve in Chithar River basin is estimated as 466.66 MCM and the dynamic reserve is about 187.7 MCM. In the present scenario, the aquifer is under safe condition for extraction of groundwater for domestic and irrigation purposes. If the existing water bodies are maintained properly, the extraction rate can be increased in future about 10 % to 15 %.     

Hydrochemical and geoelectrical investigation of the coastal shallow aquifers in El-Omayed area, Egypt

Monitoring and assessment of the coastal aquifers are becoming a worldwide concern for the need of additional and sustainable water resources to satisfy demographic growth and economic development. A hydrochemical and geoelectrical investigation was conducted in the El-Omayed area in the northwestern coast of Egypt. The aim of the study was to delineate different water-bearing formations, provide a general evaluation of groundwater quality, and identify the recharge sources in aquifers. Thirty-seven water samples were collected and chemically analyzed from the sand dune accumulations and oolitic limestone aquifers. Fifteen profiles of vertical electrical soundings (VESs) were obtained in the oolitic limestone aquifer to examine the variations of subsurface geology and associated groundwater chemistry. The groundwater reserves in the El-Omayed area are mainly contained in sand dune accumulations and oolitic limestone aquifers. The aquifer of sand dune accumulations contains freshwater of low salinity (average total dissolved solids (TDS)?=?974 mg/l). Groundwater of oolitic limestone aquifer is slightly brackish (average TDS?=?1,486 mg/l). Groundwater of these aquifers can be used for irrigation under special management for salinity control, and regular leaching as indicated by electrical conductivity and sodium adsorption ratio. Results of VES interpretation classified the subsurface sequence of oolitic limestone aquifer into four geoelectric zones, with increasing depth, calcareous loam, gypsum, oolitic limestone, and sandy limestone. Oolitic limestone constitutes the main aquifer and has a thickness of 12–32 m.     

A novel high-frequency groundwater quality monitoring system

High-frequency, long-term monitoring of water quality has revolutionized the study of surface waters in recent years. However, application of these techniques to groundwater has been limited by the ability to remotely pump and analyze groundwater. This paper describes a novel autonomous groundwater quality monitoring system which samples multiple wells to evaluate temporal changes and identify trends in groundwater chemistry. The system, deployed near Fresno, California, USA, collects and transmits high-frequency data, including water temperature, specific conductance, pH, dissolved oxygen, and nitrate, from supply and monitoring wells, in real-time. The system consists of a water quality sonde and optical nitrate sensor, manifold, submersible three-phase pump, variable frequency drive, data collection platform, solar panels, and rechargeable battery bank. The manifold directs water from three wells to a single set of sensors, thereby reducing setup and operation costs associated with multi-sensor networks. Sampling multiple wells at high frequency for several years provided a means of monitoring the vertical distribution and transport of solutes in the aquifer. Initial results show short period variability of nitrate, specific conductivity, and dissolved oxygen in the shallow aquifer, while the deeper portion of the aquifer remains unchanged—observations that may be missed with traditional discrete sampling approaches. In this aquifer system, nitrate and specific conductance are increasing in the shallow aquifer, while invariant changes in deep groundwater chemistry likely reflect relatively slow groundwater flow. In contrast, systems with high groundwater velocity, such as karst aquifers, have been shown to exhibit higher-frequency groundwater chemistry changes. The stability of the deeper aquifer over the monitoring period was leveraged to develop estimates of measurement system uncertainty, which were typically lower than the manufacturer’s stated specifications, enabling the identification of subtle variability in water chemistry that may have otherwise been missed.     

Fluoride in groundwater, Varaha River Basin, Visakhapatnam District, Andhra Pradesh, India

Excess intake of fluoride through drinking water causes fluorosis on human beings in many States of the country (India), including Andhra Pradesh. Groundwater quality in the Varaha River Basin located in the Visakhapatnam District of Andhra Pradesh has been studied, with reference to fluoride content, for its possible sources for implementing appropriate management measures, according to the controlling mechanism of fluoride concentration in the groundwater. The area occupied by the river basin is underlain by the Precambrian Eastern Ghats, over which the Recent sediments occur. Results of the chemical data of the groundwater suggest that the considerable number of groundwater samples show fluoride content greater than that of the safe limit prescribed for drinking purpose. Statistical analysis shows that the fluoride has a good positive relation, with pH and bicarbonate. This indicates an alkaline environment, as a dominant controlling mechanism for leaching of fluoride from the source material. Other supplementary factors responsible for the occurrence of fluoride in the groundwater are evapotranspiration, long contact time of water with the aquifer material, and agricultural fertilizers. A lack of correlation between fluoride and chloride, and a high positive correlation between fluoride and bicarbonate indicate recharge of the aquifer by the river water. However, the higher concentration of fluoride observed in the groundwater in some locations indicates insufficient dilution by the river water. That means the natural dilution did not perform more effectively. Hence, the study emphasizes the need for surface water management structures, with people's participation, for getting more effective results.     

Using GA-Ridge regression to select hydro-geological parameters influencing groundwater pollution vulnerability

For groundwater conservation and management, it is important to accurately assess groundwater pollution vulnerability. This study proposed an integrated model using ridge regression and a genetic algorithm (GA) to effectively select the major hydro-geological parameters influencing groundwater pollution vulnerability in an aquifer. The GA-Ridge regression method determined that depth to water, net recharge, topography, and the impact of vadose zone media were the hydro-geological parameters that influenced trichloroethene pollution vulnerability in a Korean aquifer. When using these selected hydro-geological parameters, the accuracy was improved for various statistical nonlinear and artificial intelligence (AI) techniques, such as multinomial logistic regression, decision trees, artificial neural networks, and case-based reasoning. These results provide a proof of concept that the GA-Ridge regression is effective at determining influential hydro-geological parameters for the pollution vulnerability of an aquifer, and in turn, improves the AI performance in assessing groundwater pollution vulnerability.     

Managed aquifer recharge by a check dam to improve the quality of fluoride-rich groundwater: a case study from southern India

In many regions around the globe, including India, degradation in the quality of groundwater is of great concern. The objective of this investigation is to determine the effect of recharge from a check dam on quality of groundwater in a region of Krishnagiri District of Tamil Nadu State, India. For this study, water samples from 15 wells were periodically obtained and analysed for major ions and fluoride concentrations. The amount of major ions present in groundwater was compared with the drinking water guideline values of the Bureau of Indian Standards. With respect to the sodium and fluoride concentrations, 38% of groundwater samples collected was not suitable for direct use as drinking water. Suitability of water for agricultural use was determined considering the electrical conductivity, sodium adsorption ratio, sodium percentage, permeability index, Wilcox and United States Salinity Laboratory diagrams. The influence of freshwater recharge from the dam is evident as the groundwater in wells nearer to the check dam was suitable for both irrigation and domestic purposes. However, the groundwater away from the dam had a high ionic composition. This study demonstrated that in other fluoride-affected areas, the concentration can be reduced by dilution with the construction of check dams as a measure of managed aquifer recharge.     

Decision support model for assessing aquifer pollution hazard and prioritizing groundwater resources management in the wet Pampa plain, Argentina

This paper gives an account of the implementation of a decision support system for assessing aquifer pollution hazard and prioritizing subwatersheds for groundwater resources management in the southeastern Pampa plain of Argentina. The use of this system is demonstrated with an example from Dulce Stream Basin (1,000 km² encompassing 27 subwatersheds), which has high level of agricultural activities and extensive available data regarding aquifer geology. In the logic model, aquifer pollution hazard is assessed as a function of two primary topics: groundwater and soil conditions. This logic model shows the state of each evaluated landscape with respect to aquifer pollution hazard based mainly on the parameters of the DRASTIC and GOD models. The decision model allows prioritizing subwatersheds for groundwater resources management according to three main criteria including farming activities, agrochemical application, and irrigation use. Stakeholder participation, through interviews, in combination with expert judgment was used to select and weight each criterion. The resulting subwatershed priority map, by combining the logic and decision models, allowed identifying five subwatersheds in the upper and middle basin as the main aquifer protection areas. The results reasonably fit the natural conditions of the basin, identifying those subwatersheds with shallow water depth, loam–loam silt texture soil media and pasture land cover in the middle basin, and others with intensive agricultural activity, coinciding with the natural recharge area to the aquifer system. Major difficulties and some recommendations of applying this methodology in real-world situations are discussed.     

Impact of urbanization on the groundwater regime in a fast growing city in central India

This paper describes the impact of urbanization on the groundwater regime in a fast growing city, Solapur, in central India, giving special emphasis on the management of the present and ultimate demand of water in 2,020 AD. The objective is to apprise the city planners and administrators of the effects of urbanization on the groundwater regime in a fast growing medium-sized city in a developing country where the infrastructure developments are not in conformity with the rapid growth in population. Solapur city with an area of 178.57 km2 receives a recharge of about 24 million m3 of groundwater from various sources annually. Reduction in recharge, as conventionally assumed due to the impact of urbanization, could not, however, be well established. Instead, there was a rise in recharge as water use in the city grew from time to time and more and more water was supplied to satisfy the human needs. Compared to mid-1970s, groundwater levels have increased within the main city area due to increased recharge and decreased groundwater abstraction. However, outside the main city area, there is a general decline in groundwater levels due to increased groundwater utilization for irrigation purposes. Groundwater quality deterioration has been highly localized. Water quality has deteriorated during the last 10 years, especially in dugwells, mainly due to misuse and disuse of these structures and poor circulation of groundwater. However, in case of borewells, comparison of the present water quality with that in mid-1970s and early 1980s does not show any perceptible change. Deeper groundwater tapped by borewells can still be used for drinking purposes with caution.     

Assessment of groundwater vulnerability in the Yinchuan Plain,Northwest China using OREADIC

Groundwater vulnerability assessments provide a measure of the sensitivity of groundwater quality to an imposed contaminant load and are globally recognized as an essential element of all aquifer management and protection plans. In this paper, the vulnerability of groundwaters underlying the Yinchuan Plain of Northwest China is determined using OREADIC, a GIS-based assessment tool that incorporates the key characteristics of the universally popular DRASTIC approach to vulnerability assessment but has been modified to consider important additional hydrogeological factors that are specific to the region. The results show that areas of high vulnerability are distributed mainly around Qingtongxia City, Wuzhong City, Lingwu City, and Yongning County and are associated with high rates of aquifer recharge, shallow depths to the water table, and highly permeable aquifer materials. The presence of elevated NO₃⁻ in the high vulnerability areas endorses the OREADIC approach. The vulnerability maps developed in this study have become valuable tools for environmental planning in the region and will be used for predictive management of the groundwater resource.     

Modeling interactions between saturated and un-saturated zones by Hydrus-1D in semi-arid regions (plain of Kairouan,Central Tunisia)

In semi-arid areas like the Kairouan region, salinization has become an increasing concern because of the constant irrigation with saline water and over use of groundwater resources, soils, and aquifers. In this study, a methodology has been developed to evaluate groundwater contamination risk based on the unsaturated zone hydraulic properties. Two soil profiles with different ranges of salinity, one located in the north of the plain and another one in the south of plain (each 30 m deep) and both characterized by direct recharge of the aquifer, were chosen. Simulations were conducted with Hydrus-1D code using measured precipitation data for the period 1998–2003 and calculated evapotranspiration for both chosen profiles. Four combinations of initial conditions of water content and salt concentration were used for the simulation process in order to find the best match between simulated and measured values. The success of the calibration of Hydrus-1D allowed the investigation of some scenarios in order to assess the contamination risk under different natural conditions. The aquifer risk contamination is related to the natural conditions where it increased while facing climate change and temperature increase and decreased in the presence of a clay layer. Hydrus-1D was a useful tool to predict the groundwater level and quality in the case of a direct recharge and in the absence of any information related to the soil layers except for the texture.     

Application of drastic model and GIS: for assessing vulnerability in hard rock granitic aquifer

Geographic information system (GIS) has become one of the leading tools in the field of hydrogeological science that helps in assessing, monitoring, and conserving groundwater resources. Groundwater is a finite resource, which is being overexploited due to increase in demand over the years leading to decrease in its potentiality. In the present study, DRASTIC model has been used to prepare groundwater vulnerable zone in hard rock aquifer of granitic terrain. The main objective is to determine susceptible zone for groundwater pollution by integrating hydrogeological layers in GIS environment. The layers such as depth of aquifer, recharge, aquifer yield, soil type, topography, vadose zone, and transmissivity are incorporated in the DRASTIC model. The final output of the map shows that around 60% of the area falls under low to no risk of pollution zone. The high risk of pollution zones are mostly present towards the margin of southeastern periphery. The lower part of the basin as well as small area on northern side falls under moderate risk of pollution zone. For the assessment of groundwater pollution zone, 24 groundwater samples have been collected from different vulnerable zones. The chemical analysis of sample shows that the southeastern margin of basin has relatively high concentration of nitrate as compared to other parts of the basin. It is present in high pollution zone as well as moderate pollution zone. The present model can be used for assessment and management of groundwater.     

Implications of depletion of groundwater levels in three layered aquifers and its management to optimize the supply demand in the urban settlement near Kahota Industrial Triangle area, Islamabad, Pakistan

This study deals with the implications of depletion of groundwater levels in three layered aquifers and its management to optimize the supply demand in the urban settlement near Kahota Industrial Triangle area, located adjacent to the Soan River, Islamabad Pakistan. Initially, a groundwater 3-D steady-state flow model has been developed, calibrated to the known observed heads of 24 water wells, verified, and confirmed that convergence has actually arrived and hydraulic heads are no more changing. Later, the transient simulation was carried out with the constant discharge rates of groundwater by means of pumping wells, storage factor, porosity, and observed drawdown matched with the simulated drawdown that appears to fall in close agreement with a difference of 0.25 m. As such, the developed groundwater model has facilitated to understand, evaluate, and to predict regional trends of groundwater flow regimes and their ultimate utilization at a maximum rate of 4.5 million gallons/day for the growing urban settlement. The calibrated and verified model was then used to simulate the depletion of groundwater level, annual water balance, discharge versus time drawdown, and a temporal behavior of the system over an extended period of pumping. The modeling results indicate that, due to the pumping, the direction of flow has changed: first from groundwater regimes to the Soan River and then it is entirely reversed from the Soan River to the groundwater regimes as the drawdown started to deepen.     

Groundwater levels time series sensitivity to pluviometry and air temperature: a geostatistical approach to Sfax region,Tunisia

In this paper, the pattern of groundwater level fluctuations is investigated by statistical techniques for 24 monitoring wells located in an unconfined coastal aquifer in Sfax (Tunisia) for a time period from 1997 to 2006. Firstly, a geostatistical study is performed to characterize the temporal behaviors of data sets in terms of variograms and to make predictions about the value of the groundwater level at unsampled times. Secondly, multivariate statistical methods, i.e., principal component analysis (PCA) and cluster analysis (CA) of time series of groundwater levels are used to classify groundwater hydrographs regard to identical fluctuation pattern. Three groundwater groups (A, B, and C) were identified. In group “A,” water level decreases continuously throughout the study periods with rapid annual cyclic variation, whereas in group “B,” the water level contains much less high-frequency variation. The wells of group “C” represents a steady and gradual increase of groundwater levels caused by the aquifer artificial recharge. Furthermore, a cross-correlation analysis is used to investigate the aquifer response to local rainfall and temperature records. The result revealed that the temperature is more affecting the variation of the groundwater level of group A wells than the rainfall. However, the second and the third groups are less affected by rainfall or temperature.