Mass balance simulation and principal components analysis applied to groundwater resources: Essaouira basin (Morocco)

The water resources of the Essaouira coastal basin (west of Marrakesh) are characteristic of a semi-arid climate and are severely impacted by the climate in terms of quantity and quality. Considering the importance of the Essaouira aquifer in the groundwater supply of a vast region (nearly 1,200 km²), a research study was conducted in order to better understand groundwater evolution in this aquifer system. It is a coastal aquifer located on the Atlantic coastline, southern Morocco, and salinization problems have been reported. Covering the Palaeozoic bedrock, the sedimentary series range from the Triassic to the Quaternary. Besides the possibility of seawater intrusion problems, the geological structures delineate a syncline bordered by the Tidzi diapir (of Triassic age) outcropping to the east and south. This is a recharge area for the aquifer, whereas the main groundwater flow direction is from SE to NW towards the Atlantic Ocean. In spite of the occurrence of calcareous and dolomitic levels, all waters in the Essaouira basin are of the Na–Cl-type. Based on a range of experimental methodologies, combined with PCA and geochemical modelling, it was possible to identify the mineralization processes occurring in the groundwater system, and the importance of the water–rock interaction in the water chemistry. Scenarios were tested using a simple mass balance model through the PHREEQC programme. The reaction path was assumed to be such that waters observed at shallow depths evolved to more mineralized waters. An important contribution of water–rock interaction in groundwater mineralization was found, corroborating the influence of preferential recharge from the Tidzi diapir in the water’s signature. Anthropogenic contamination was also identified and could lead to serious problems with groundwater degradation in the near future, in a country with scarce water resources.     

Spatial modeling of groundwater quality based on using Schoeller diagram in GIS base: a case study of Khorramabad,Iran

Regulating the water supply for a specified district needs comprehensive quality information about the nearest aquifer. There are many methods to investigate the water quality, but in most cases, they involve time series study and do not consider space dimension. The application of advanced qualitative assessments such as geographical information systems (GIS) could be a reasonable choice. In addition, the classic Schoeller diagram (CSD) is one of the diverse drinking water assessments in which aquifer quality is distinguished according to major ions concentrations. However, the results of this diagram are limited to one point, and there is no possibility of qualitative classification of the surrounding area. Because of this, in this investigation, a new procedure, called the Schoeller-GIS (S-GIS) approach, is presented in order to apply CSD onto a district through GIS tools. For this project, the quality information of 105 wells in the study area (near Khorramabad, Iran) has been collected, and a quality assessment of the aquifer has been conducted based on both classic and novel approaches. Results indicated that, according to the CSD method, all qualitative parameters of the aquifer except Ca and Mg were located within the Good range, whereas the results of S-GIS approach categorized the study area into Good (55%), Permissible (36%), and Moderately suitable (8%). This indicates that the latest method may be more accurate by about 30% which could lead to more efficient management of water resources.     

GIS支持下人类活动对地下水动态影响的定量分析

应用地球动力学原理分析和研究了人类活动对水资源变化的影响,提出可将人为作用影响作为一个综合性的抽象指数,通过求取其它因素的变化利用余差法反求得到的计算思路.借助于GIS技术,建立了度量人为作用对地下水动态影响的通用数学模型,并用实例进行了验证,计算结果与实际情况相符,表明所提的方法是可行的.     

Characterization and assessment of groundwater resources using hydrogeochemical analysis,GIS, and field data in southern Wadi Qena,Egypt

An integrated approach using hydrogeochemical analysis, remote sensing, GIS, and field data was employed to characterize the groundwater resources in southern Wadi Qena, Egypt. Various thematic maps showing topography, lineaments, wadi deposits, slope, and stream networks were combined through GIS analysis to discriminate groundwater potential zones on the valley floor. The resulting map classifies the area into five groups of groundwater potentiality from very high to very low zones, supported by the groundwater level, well locations, and by the results of previous geophysical studies. Thirty-seven groundwater well data were tested from the Quaternary and Nubian Sandstone aquifers and analyzed for physio-chemical parameters. Results of hydrochemical analysis show that water quality varies widely through the aquifers, and groundwater in the Quaternary aquifer shows the highest salinity values and a predominance of Na and Cl in water chemical facies. Overlay GIS maps of alkalinity (SAR and RSC) and salinity hazards (EC and Cl) of the Quaternary aquifer were prepared. The resulting maps show that samples do not present an alkalinity hazard in most areas but are potentially salinity hazard. Therefore, the water is fit for agricultural use with certain restrictions, but is not suitable for direct human consumption because it is either very hard or too saline.     

Modeling groundwater/surface-water interactions in an Alpine valley (the Aosta Plain,NW Italy): the effect of groundwater abstraction on surface-water resources

A groundwater flow model of the Alpine valley aquifer in the Aosta Plain (NW Italy) showed that well pumping can induce river streamflow depletions as a function of well location. Analysis of the water budget showed that ～80% of the water pumped during 2 years by a selected well in the downstream area comes from the baseflow of the main river discharge. Alluvial aquifers hosted in Alpine valleys fall within a particular hydrogeological context where groundwater/surface-water relationships change from upstream to downstream as well as seasonally. A transient groundwater model using MODFLOW2005 and the Streamflow-Routing (SFR2) Package is here presented, aimed at investigating water exchanges between the main regional river (Dora Baltea River, a left-hand tributary of the Po River), its tributaries and the underlying shallow aquifer, which is affected by seasonal oscillations. The three-dimensional distribution of the hydraulic conductivity of the aquifer was obtained by means of a specific coding system within the database TANGRAM. Both head and flux targets were used to perform the model calibration using PEST. Results showed that the fluctuations of the water table play an important role in groundwater/surface-water interconnections. In upstream areas, groundwater is recharged by water leaking through the riverbed and the well abstraction component of the water budget changes as a function of the hydraulic conditions of the aquifer. In downstream areas, groundwater is drained by the river and most of the water pumped by wells comes from the base flow component of the river discharge.     

Spatial variation assessment of groundwater quality using multivariate statistical analysis(Case Study: Fasa Plain,Iran)

Groundwater is considered as one of the most important sources for water supply in Iran. The Fasa Plain in Fars Province, Southern Iran is one of the major areas of wheat production using groundwater for irrigation. A large population also uses local groundwater for drinking purposes. Therefore, in this study, this plain was selected to assess the spatial variability of groundwater quality and also to identify main parameters affecting the water quality using multivariate statistical techniques such as Cluster Analysis (CA), Discriminant Analysis (DA), and Principal Component Analysis (PCA). Water quality data was monitored at 22 different wells, for five years (2009-2014) with 10 water quality parameters. By using cluster analysis, the sampling wells were grouped into two clusters with distinct water qualities at different locations. The Lasso Discriminant Analysis (LDA) technique was used to assess the spatial variability of water quality. Based on the results, all of the variables except sodium absorption ratio (SAR) are effective in the LDA model with all variables affording 92.80% correct assignation to discriminate between the clusters from the primary 10 variables. Principal component (PC) analysis and factor analysis reduced the complex data matrix into two main components, accounting for more than 95.93% of the total variance. The first PC contained the parameters of TH, Ca²⁺, and Mg²⁺. Therefore, the first dominant factor was hardness. In the second PC, Cl^-, SAR, and Na⁺ were the dominant parameters, which may indicate salinity. The originally acquired factors illustrate natural (existence of geological formations) and anthropogenic (improper disposal of domestic and agricultural wastes) factors which affect the groundwater quality.     

Shallow groundwater temperature in the Turin area (NW Italy): vertical distribution and anthropogenic effects

This study investigated the thermal regime of shallow groundwater in the Turin area (NW Italy), where the large energy demand has motivated a new interest for renewable sources, such as the use of ground-source heat pumps for domestic heating and cooling. The vertical variability of the groundwater temperature between the ground surface and 10–20 m was detected: deeper temperatures were higher than shallow temperatures in spring, while a decrease with depth occurred in autumn. These variations are connected with the heating and cooling cycles of the ground surface due to the seasonal temperature oscillation. Variations below the seasonal oscillation are likely to be connected with the presence of advective heat transport due to the groundwater flow, according to the hydraulic features of a shallow aquifer. Temperature values mostly ranged between 12 and 14 °C in rural areas, while the values were between 14 and 16 °C below the Turin city. This groundwater warming is attributed to a widespread urban heat island phenomenon linked to warmer land surface temperatures in Turin city. Sparse warm outliers are connected with point heat sources and site-specific conditions of land and subsurface use, which may cause the aquifer temperature to rise. A relatively stable temperature below the seasonal fluctuation zone combined with high productivity and legislated limits for deeper groundwater use represent favourable conditions for a large-scale diffusion of groundwater heat pumps within the shallow aquifer. Moreover, this heat surplus should be regarded as a resource for future geothermal installations.     

Spatial control of groundwater contamination,using principal component analysis

A study on the geochemistry of groundwater was carried out in a river basin of Andhra Pradesh to probe into the spatial controlling processes of groundwater contamination, using principal component analysis (PCA). The PCA transforms the chemical variables, pH, EC, Ca²⁺, Mg²⁺, Na⁺, K⁺, HCO \(_3^- \) , Cl^?, SO \(_4^{2-} \) , NO \(_3^-\) and F^?, into two orthogonal principal components (PC1 and PC2), accounting for 75% of the total variance of the data matrix. PC1 has high positive loadings of EC, Na⁺, Cl^?, SO \(_4^{2-} \) , Mg²⁺ and Ca²⁺, representing a salinity controlled process of geogenic (mineral dissolution, ion exchange, and evaporation), anthropogenic (agricultural activities and domestic wastewaters), and marine (marine clay) origin. The PC2 loadings are highly positive for HCO \(_3^- \) , F^?, pH and NO \(_3^- \) , attributing to the alkalinity and pollution controlled processes of geogenic and anthropogenic origins. The PC scores reflect the change of groundwater quality of geogenic origin from upstream to downstream area with an increase in concentration of chemical variables, which is due to anthropogenic and marine origins with varying topography, soil type, depth of water levels, and water usage. Thus, the groundwater quality shows a variation of chemical facies from Na⁺ > Ca²⁺ > Mg²⁺ > K⁺: HCO \(_3^- \) > Cl^? > SO \(_4^{2-}>\) NO \(_3^- \) > F^?at high topography to Na⁺ > Mg²⁺ > Ca²⁺ > K⁺: Cl^? > HCO \(_3^- \) > SO \(_4^{2-}>\) NO \(_3^- \) > F^? at low topography. With PCA, an effective tool for the spatial controlling processes of groundwater contamination, a subset of explored wells is indexed for continuous monitoring to optimize the expensive effort.     

Impact of anthropogenic activities on the groundwater resources of the unconfined aquifer of Triffa plain (Eastern Morocco)

Located at the northeastern part of Morocco, the plain of Triffa is characterized by a semi-arid climate where water resources are rather fragile and influenced by a highly irregular rainfall distribution, both in time (annual and inter-annual distribution) and in space. The mean annual rainfall does not exceed 240 mm. In the Triffa plain, the impact of anthropogenic activities on the groundwater resources is reflected both by (a) the decrease in the piezometric level due to the over exploitation and droughts and (b) the deterioration of the chemical quality of water. Currently, this situation is felt mainly by the farmers. The unconfined aquifer is under stress due to the increase of the pollution rate, especially by nitrates that are above the WHO standards, and salinity. Organochlorine pesticides are ubiquitous and persistent organic pollutants used widely in agriculture. Due to their extensive use in agriculture, organic environment contaminants such as hexachlorocyclohexane, DDT, and DDD along organochlorine pesticides are distributed globally by transport through water. Pesticides such as aldrin, lindane, and heptachlor have also been detected and were considered as indicators showing the need to inform and to train farmers on the pesticides and fertilizers use in order to reduce the threat of groundwater contamination.     

Spatial and statistical assessment of nitrate contamination in groundwater:Case of Sais Basin,Morocco

The objective of this study is to evaluate the nitrate contamination in the plioquaternary aquifer of Sais Basin based on a statistical approach. A total of 98 samples were collected in the cultivated area during the spring and autumn period of 2018. The results show that 55% and 57% of the samples in spring and autumn respectively exceed the threshold fixed by WHO(50 mg/L). However, nitrate concentrations do not show seasonal and spatial variation(p0.05). The results of the correlation matrix, principal component analysis(PCA), and hierarchical cluster analysis(HCA) suggest that nitrate pollution is related to anthropogenic source. Moreover, multiple linear regression results show that NO_3 is more positively explained in the spring period by Ca and SO_4 and negatively explained by pH and HCO_3. Regarding the autumn period, nitrate pollution is positively explained by Ca and negatively by pH. This study proposes a useful statistical platform for assessing nitrate pollution in groundwater.     

Salinity mapping of coastal groundwater aquifers using hydrogeochemical and geophysical methods: a case study from north Kelantan,Malaysia

Integrated hydrogeochemical and geophysical methods were used to study the salinity of groundwater aquifers along the coastal area of north Kelantan. For the hydrogeochemical investigation, analysis of major ion contents of the groundwater was conducted, and other chemical parameters such as pH and total dissolved solids were also determined. For the geophysical study, both geoelectrical resistivity soundings and reflection seismic surveys were conducted to determine the characteristics of the subsurface and groundwater contained within the aquifers. The pH values range from 6.2 to 6.8, indicating that the groundwater in the study area is slightly acidic. Low content of chloride suggests that the groundwater in the first aquifer is fresh, with an average concentration of about 15.8 mg/l and high geoelectrical resistivity (>45 ohm m). On the other hand, the groundwater in the second aquifer is brackish, with chloride concentration ranging from 500 mg/l to 3,600 mg/l and very low geoelectrical resistivity (<45 ohm m) as well as high concentration of total dissolved solids (>1,000 mg/l). The groundwater in the third aquifer is fresh, with chloride concentrations generally ranging from 2 mg/l to 210 mg/l and geoelectrical resistivity of greater than 45 ohm m. Fresh and saltwater interface in the first aquifer is generally located directly in the area of the coast, but, for the second aquifer, both hydrogeochemical and geoelectrical resistivity results indicate that the fresh water and saltwater interface is located as far as 6 km from the beach. The considerable chloride ion content initially suggests that the salinity of the groundwater in the second aquifer is probably caused by the intrusion of seawater. However, continuous monitoring of the chloride content of the second aquifer indicated no significant changes with time, from which it can be inferred that the salinity of the groundwater is not affected by seasonal seawater intrusion. Schoeller diagrams illustrate that sulphate concentrations of the groundwater of the second aquifer are relatively low compared to those of the recent seawater. Therefore, this result suggests that the brackish water in the second aquifer is probably from ancient seawater that was trapped within the sediments for a long period of time, rather than due to direct seawater intrusion.     

An application of factor analysis for the study of the hydrogeological conditions in Plio-Pleistocene aquifers of NW Achaia (NW peloponnesus, Greece)

R- andQ-mode factor analysis is applied to 51 groundwater samples collected from wells drilled in the Plio-Pleistocene aquifers of NW Achaia, Greece. The purpose ofR- andQ-mode factor analysis application is to identify (i) the regional groundwater flow pattern, and (ii) the deterioration of groundwater quality. Sixteen hydrogeological parameters are used in order to examine their importance and to provide significant insight into their correlations. In theR-mode factor analysis, a six-factor model is suggested which can explain more than 77.5% of the total variance. The contribution of each factor at every site (factor scores) also is computed. Maps are constructed showing the geographical distribution of the factor scores. From these maps, the high salinity areas are delineated (seawater intrusion, possible appearance of halite layers) and the areas with elevated contribution of karastic-water are defined. Using theQ-mode correspondence analysis the meaning of the electrical conductivity as the most important variable in groundwater quality characterization is demonstrated.     

Comparative approach of three popular intrinsic vulnerability methods: case of the Beni Amir groundwater (Morocco)

The study of the intrinsic vulnerability of groundwater resources to pollution is an effective tool to control their quality degradation and contribute to their protection. It is used to delimit the vulnerable zones which do not withstand a large flow of pollutants introduced from the soil surface. Three methods of assessing the intrinsic vulnerability of groundwater: DRASTIC (Depth to water table, Recharge, Aquifer, Soil type, Topography, Impact of zone vadose, Hydraulic conductivity), DRSTI, and GOD (Groundwater occurrence, Overall aquifer class and Depth of water table) coupled with a geographic information system (GIS) are applied to the groundwater of Beni Amir, and they are compared in order to adopt the method which better characterizes the vulnerability of the aquifer to pollution. The validation of this application was made by measurements of the nitrate levels in the aquifer. Because the pollution of groundwater, in this plain, is a direct consequence of agricultural activities characterized by an intensive fertilizer application. The results clearly show that the rate of the coincidence, between the measured nitrate concentrations and the different classes of vulnerability of three methods, is 81.81, 54.54, 72.72, and 27.27%, respectively, for methods DRASTIC (classification of Engel et al. (Int Assoc Hydrol Sci Publi 235:521–526, 1996)), DRASTIC (classifications of Aller et al. (1987)), DRSTI, and GOD. Of this rate of coincidences, the DRASTIC method, with the classification of Engel et al. (Int Assoc Hydrol Sci Publi 235:521–526, 1996), allows a finer assessment and turns out the most representative of the study area.     

Hydrogeological and thermal characterization of shallow aquifers in the plain sector of Piemonte region (NW Italy): implications for groundwater heat pumps diffusion

The low annual and seasonal variability of the shallow groundwater temperature in the alluvial plain aquifers of the Piemonte region (NW Italy) confirmed the potentiality of the low-enthalpy open-loop groundwater heat pumps (GWHP) diffusion to contribute to the reduction of regional greenhouse gas emissions. The distribution of mean groundwater temperatures ranged from a minimum of 10.3°C to a maximum of 17.9°C with a mean of 14.0°C. Differences among diverse areas were slight according with the modest variations in the general climatic condition. Like the air, temperature distribution of the shallow groundwater temperatures is generally similar to topographic elevations in reverse manner. Higher temperature values recorded were typical of summer months (June, July). On the opposite lower values were measured in January and February. No significant difference phase (time) difference between air and groundwater temperature appeared in the data analysis. Besides air-temperature influence (seasonal variability) seemed strictly connected to the depth to groundwater in the measure point and it was negligible when the value was over 9.5 m. For the application of the open-loop systems, extensive examinations of the hydrogeological local conditions should be conducted at site scale and groundwater heat transport modelling should be developed.     

Calculating groundwater mixing ratios in groundwater-inrushing aquifers based on environmental stable isotopes (D, 18O) and hydrogeochemistry

Conventional hydrogeochemical data and environmental stable isotopes are used to identify the recharge sources and the water–rock interactions in the groundwater-flowing direction within the multilayer groundwater system of the Sulin coal-mining district in the north Anhui province in China. δD and δ ¹⁸O of groundwater in the mining district decrease along the groundwater-flowing direction in the recharge areas, yet in the runoff or discharge areas, they rise and fall along average δ values (δ ¹⁸O = ?8.68 ‰, δD = ?67.4 ‰), which are lower than average δ values of local atmospheric precipitation (δ ¹⁸O = ?7.80 ‰, δD = ?52.4 ‰). Principal component analysis is used to analyze the conventional hydrogeochemical data (K⁺ + Na⁺, Mg²⁺, Ca²⁺, Cl^?, SO₄ ^2?, HCO₃ ^?, CO₃ ^2?) in the groundwater. The first and second principal components have large variance contributions, and represent “pyrite oxidation or groundwater hardening” and “desulfurization or cation exchange and adsorption,” respectively. From conventional hydrogeochemical data and environmental stable isotopes, it is demonstrated that groundwater of the Sulin coal-mining district is characterized by a mixing type, which is confirmed by three recharge end-members: fresh groundwater, leaching groundwater, and retained groundwater. By means of a sample dot-encompassed triangle in the scatter diagram of load scores for Component 1–Component 2, whose vertexes stand for the three end-members, a model for calculating groundwater mixing ratio is established and applied successfully to the evaluation and management of groundwater hazards in the coal-mining districts.     

Determination of groundwater availability in shallow arid region aquifers utilizing GIS technology: a case study in Hada Al-Sham, Western Saudi Arabia

A simple, physically based method is developed in this paper to assist in the allocation of areas with high groundwater potential and for the determination of maximum allowed pumping rate to ensure proper groundwater management. This method utilizes the aquifer physical properties as well as GIS technology to accomplish this purpose. The design of this method was considered to be applicable in areas with little data, such as in most arid regions. This technique was applied to a catchment in an arid environment where qualitative as well as quantitative analyses of the results were undertaken. Locations of available groundwater and rates of maximum allowable pumping were compared with observations and experiments in the field and a good agreement was found. It was concluded that the best groundwater location was in the alluvial area, which represents only 16% of the total aquifer, which is a typical case in arid region catchments. The rate of maximum pumping was estimated to be 65 m³/h. However, to benefit 55% of the area, the maximum pumping rate should only be 40 m³/h with an average rate throughout the area (55%) of about 24 m³/h.This revised version was published online in December 2004 with corrections to the category.