High Groundwater Salinity Research Articles

Groundwater recharge and salinization in the arid coastal plain aquifer of the Wadi Watir delta, Sinai, Egypt

The Quaternary coastal plain aquifer down gradient of the Wadi Watir catchment is the main source of potable groundwater in the arid region of south Sinai, Egypt. The scarcity of rainfall over the last decade, combined with high groundwater pumping rates, have resulted in water-quality degradation in the main well field and in wells along the coast. Understanding the sources of groundwater salinization and amount of average annual recharge is critical for developing sustainable groundwater management strategies for the long-term prevention of groundwater quality deterioration. A combination of geochemistry, conservative ions (Cl and Br), and isotopic tracers (87/86Sr, δ81Br, δ37Cl), in conjunction with groundwater modeling, is an effective method to assess and manage groundwater resources in the Wadi Watir delta aquifers. High groundwater salinity, including high Cl and Br concentrations, is recorded inland in the deep drilled wells located in the main well field and in wells along the coast. The range of Cl/Br ratios for shallow and deep groundwaters in the delta (∼50–97) fall between the end member values of the recharge water that comes from the up gradient watershed, and evaporated seawater of marine origin, which is significantly different than the ratio in modern seawater (228). The 87/86Sr and δ81Br isotopic values were higher in the recharge water (0.70,723 < 87/86Sr < 0.70,894, +0.94 < δ81Br < +1.28‰), and lower in the deep groundwater (0.70,698 < 87/86Sr < 0.70,705, +0.22‰ < δ81Br < +0.41‰). The δ37Cl isotopic values were lower in the recharge water (−0.48 < δ37Cl < −0.06‰) and higher in the deep groundwater (−0.01 < δ37Cl < +0.22‰). The isotopic values of strontium, chloride, and bromide in groundwater from the Wadi Watir delta aquifers indicate that the main groundwater recharge source comes from the up gradient catchment along the main stream channel entering the delta. The solute-weighted mass balance mixing models show that groundwater in the main well field contains 4–10% deep saline groundwater, and groundwater in some wells along the coast contain 2–6% seawater and 18–29% deep saline groundwater.A three-dimensional, variable-density, flow-and-transport SEAWAT model was developed using groundwater isotopes (87Sr/86Sr, δ37Cl and δ81Br) and calibrated using historical records of groundwater level and salinity. δ18O was used to normalize the evaporative effect on shallow groundwater salinity for model calibration. The model shows how groundwater salinity and hydrologic data can be used in SEAWAT to understand recharge mechanisms, estimate groundwater recharge rates, and simulate the upwelling of deep saline groundwater and seawater intrusion. The model indicates that most of the groundwater recharge occurs near the outlet of the main channel. Average annual recharge to delta alluvial aquifers for 1982 to 2009 is estimated to be 2.16 × 106 m3/yr. The main factors that control groundwater salinity are overpumping and recharge availability.

Survival and growth of three afforestation species under high saline drip irrigation in the Taklimakan Desert, China

AbstractAfforestation of shelterbelts is a sustainable practice to protect highways from shifting sand dunes in desert areas. The Taklimakan Desert Highway Shelterbelt (TDHS) in China is known as “the Great Green Wall of Taklimakan Desert” and borders a 436‐km distance along the highway. This study assessed the early survival, above‐ground growth, and root growth of three salt‐ and drought‐tolerant plant species (Calligonum aborescensLitv., Tamarix ramosissimaLedeb.,andHaloxylon ammodendron(C. A. Mey.) Bunge) inTDHS; those were drip‐irrigated with local high saline groundwater. The results demonstrated that more than 80% ofHaloxylon ammodendronseedlings could survive regardless of irrigation water salinities ranging from 2.82 to 29.70 g/L. In contrast, survival rates ofCalligonum aborescensseedlings were greater than 65% when using irrigation water salinities ≤13.99 g/L and less than 50% when irrigated with water having salinities of 20.99–29.70 g/L, respectively. However, plant survival rates ofTamarix ramosissimawere much lower than 50% when irrigated with water having salinities &gt;4.82 g/L. Furthermore, under the same salinity, the height, crown width, and maximum width of basal stems were the greatest forCalligonum aborescensplants and the lowest forTamarix ramosissimaplants. Root length varied among the species depending on tree age and the applied water characteristics. We conclude that afforestation is feasible with saline water in this extreme arid shifting desert, particularlyCalligonum aborescensplants should be grown at the outer margin of the shelterbelt due to its faster growth to more quickly stabilize the shifting sand. Our study may provide a good resolution for afforestation and marginal saline water utility in most arid and semiarid regions.

Integrated Geochemistry, Isotopes, and Geostatistical Techniques to Investigate Groundwater Sources and Salinization Origin in the Sharm EL-Shiekh Area, South Sinia, Egypt

The Sharm El-Sheikh area is one of the most attractive touristic resorts in Egypt and in the world in general. The Sharm El-Shiekh area is located at the arid region of the South Sinai Peninsula, Egypt. Water desalination is considered the main freshwater supply for hotels and resorts. Scarcity of rainfall during the last decades, high pumping rates, disposal of reject brine water back into the aquifer, and seawater intrusion have resulted in the degradation of groundwater quality in the main aquifer. Water chemistry, stable isotopes, Seawater Mixing Index (SWMI), and factorial analyses were utilized to determine the main recharge and salinization sources as well as to estimate the mixing ratios between different end members affecting groundwater salinity in the aquifer. The groundwater of the Miocene aquifer is classified into two groups: group I represents 10 % of the total samples, has a moderately high saline groundwater, and is mostly affected by seawater intrusion. Group II represents 90 % of the total samples and has a high groundwater salinity due to the anthropological impact of the reject brine saline water deeper into the Miocene aquifer. The main groundwater recharge comes from the western watershed mountain and the elevated plateau while the seawater and reject brine are considering the main sources for groundwater salinization. The mixing ratios between groundwater recharge, seawater, and reject brine water were calculated using water chemistry and isotopes. The calculated mixing ratios of group I range between 25 and 84 % recharge groundwater to 75 and 16 % seawater, respectively, in groundwater located close to the western watershed mountain indicating further extension of seawater intrusion. However, the mixing percentages of group II range between 21 and 88 % reject brine water to 79 and 12 % seawater, respectively, in groundwater located close to the desalination plants. The outcomes and conclusion of this study highlight the importance of groundwater management to limit further groundwater deterioration of the Miocene groundwater aquifer and limit seawater intrusion along the coast.

The influence of diapir brine on groundwater quality of surrounding aquifers, Larestan, Iran

Hormuz salt breaches the surface in 122 diapirs in southern Iran that source brines that generally degrade the groundwater quality in adjacent aquifers. The Karmustadj salt diapir (Larestan, Iran) is surrounded by one karstic and two alluvial aquifers. We use hydrochemical and hydrogeological measurements of brine springs and exploitation wells to investigate the impact of the Karmustadj salt diapir on water quality in its surrounding aquifers. Our study indicates that the Karmustadj salt diapir does not degrade the quality of the adjacent karstic aquifer because impermeable geological formations interrupt the potential hydraulic connectivity between them. By contrast, the diapir does significantly degrade water quality in part of the western alluvial aquifer and all of the eastern alluvial aquifer. Infiltration of surface brines draining from the diapir and discharge from perennial brine springs account for the high salinity of groundwater in the surrounding aquifers.

Spatial Variations of Soil Microbial Activities in Saline Groundwater-Irrigated Soil Ecosystem.

Spatial variations of soil microbial activities and its relationship with environmental factors are very important for estimating regional soil ecosystem function. Based on field samplings in a typical saline groundwater-irrigated region, spatial variations of soil microbial metabolic activities were investigated. Combined with groundwater quality analysis, the relationship between microbial activities and water salinity was also studied. The results demonstrated that moderate spatial heterogeneity of soil microbial activities presented under the total dissolved solids (TDS) of groundwater ranging from 0.23 to 12.24 g L(-1). Groundwater salinity and microbial activities had almost opposite distribution characteristics: slight saline water was mainly distributed in west Baqu and south Quanshan, while severe saline and briny water were dominant in east Baqu and west Huqu; however, total AWCD was higher in the east-center and southwest of Baqu and east Huqu, while it was lower in east Baqu and northwest Huqu. The results of correlation analyses demonstrated that high-salinity groundwater irrigation had significantly adverse effects on soil microbial activities. Major ions Ca(2+), Mg(2+), Cl(-), and SO4(2-) in groundwater decisively influenced the results. Three carbon sources, carbohydrates, amines, and phenols, which had minor utilization rates in all irrigation districts, were extremely significantly affected by high-salinity groundwater irrigation. The results presented here offer an approach for diagnosing regional soil ecosystem function changes under saline water irrigation.

Spatial-Temporal Distribution of Soil Salt Crusts under Saline Drip Irrigation in an Artificial Desert Highway Shelterbelt

Understanding the formation and spatial-temporal distribution of soil salt crusts (SSCs) is important for the sustainable management of the artificial shelterbelt and high-salinity groundwater utility in the Taklimakan Desert in Northwest China. The SSCs in this area were sampled, and their thickness and electrical conductivity (EC) were analyzed to examine the formation mechanism and the spatial-temporal patterns of the SSCs in the shelterbelt, which is drip irrigated with high-salinity groundwater in the Taklimakan Desert. Results demonstrated the following: (1) Soil-moisture depletion and salt accumulation at the soil surface occurred simultaneously. The soil water and salt in the different areas around the drip irrigation emitter showed different temporal dynamics in an irrigation cycle; (2) SSCs EC increased at a logarithmic rate, and SSCs thickness increased linearly with irrigation water salinity; (3) SSCs showed evident spatial distribution around the drip irrigation emitter. The EC initially increased with increasing distance from the emitter but subsequently decreased in different directions around the emitter. The highest EC was recorded at 40 cm from the emitter; (4) Topography had a significant effect on the spatial distribution of SSCs. The EC at the upslope of the emitter was higher than that at the downslope; (5) SSCs thickness showed an initial rapid increase with shelterbelt age, which was followed by a gradual increase. However, EC decreased with shelterbelt age. Our findings can contribute to the shelterbelt design, construction, utility, and sustainable management and the soil and water conservation in shifting desert regions.

Hydrogeological and hydrogeochemical control of groundwater salinity in an arid inland basin: Dunhuang Basin, northwestern China

High groundwater salinity has become a major concern in the arid alluvial plain of the Dunhuang Basin in northwestern China because it poses a significant challenge to water resource management. Isotopic and geochemical analyses were conducted on 55 water samples from springs, boreholes and surface water to identify potential sources of groundwater salinity and analyse the processes that control increasing salinity. The total dissolved solid (TDS) content in the groundwater ranged from 400 to 41 000 mg/l, and high TDS values were commonly associated with shallow water tables and flow-through and discharge zones in unconfined aquifers. Various groundwater contributions from rainwater, agricultural irrigation, river water infiltration and lateral inflows from mountains were identified by major ions and δD and δ18O. In general, HCO3− and SO42− were the dominant anions in groundwater with a salinity of 2500 mg/l. The major ion concentrations indicated that mineral weathering, including carbonate and evaporite dissolution, primarily affected groundwater salinity in recharge areas. Evapotranspiration controlled the major ion concentration evolution and salinity distribution in the unconfined groundwaters in the flow-through and discharge areas, although it had a limited effect on groundwater in the recharge areas and confined aquifers. Agricultural irrigation increased the water table and enhanced evapotranspiration in the oasis areas of the basin. TDS and Cl became more concentrated, but H and O isotopes were not enriched in the irrigation district, indicating that transpiration dominated the increasing salinity. For other places in the basin, as indicated by TDS, Cl, δD and δ18O characteristics, evaporation, transpiration and water–rock interactions dominated at different hydrogeological zones, depending on the plant coverage and hydrogeological conditions. Groundwater ages of 3H, and δD and δ18O compositions and distributions suggest that most of the groundwaters in Dunhuang Basin have a paleometeoric origin and experienced a long residence time. These results can contribute to groundwater management and future water allocation programmes in the Dunhuang Basin. Copyright © 2015 John Wiley & Sons, Ltd.

Distribution and chemical species of Pu(IV) in high salinity groundwater from granite area

Distribution and chemical species of Pu(IV) in high salinity groundwater from granite area

‘Keeping salt on the farm’—Evaluation of an on-farm salinity management system in the Shepparton irrigation region of South-East Australia

High watertables and land salinisation in irrigation areas worldwide can often be managed with various forms of sub-surface drainage, but constraints on the disposal of saline drainage water to downstream users and environments often requires on-site management methods. In the Shepparton Irrigation Region of northern Victoria, Australia, groundwater pumping with on-farm re-use is a well-established and effective salinity management method, provided the groundwater salinity is less than 5dS/m. In this study, a trial system established on an operating dairy farm could utilise 60Ml/yr of 10dS/m groundwater without requiring any off-site disposal. Normally in this region, such a circumstance would require evaporation basin disposal, but in this trial system, a salt-tolerant tree plantation established on already salinized land within the area of influence of the groundwater pump replaced an evaporation basin.Evaluation of the system was accomplished using monitoring data collected since the establishment of the trial in 1998. This data supported the development of a mass balance model to calculate where the salt loads mobilised by the groundwater pumping move to and evaluate the longer-term operation of the system. Re-distribution of the salt, both diluted with irrigation water onto the broader farm area and undiluted onto the tree plantation, appears to approach a dynamic equilibrium in about 20 years. Modelling results suggest the tree plantation might reach equilibrium at soil salinities of 45dS/m.Transferability of this system to other sites would require some similarities in respect to soils, hydraulic properties, salinities, groundwater gradients, and irrigation practices. Overall, the model of the system demonstrates a viable means of sustainably managing irrigation salinity through groundwater pumping with on-site re-use. Partitioning of the pumped high salinity groundwater to a combination of conjunctive use and undiluted irrigation to a salt tolerant tree plantation is able to meet the criteria of not requiring off-site disposal.

Reverse ion exchange as a major process controlling the groundwater chemistry in an arid environment: a case study from northwestern Saudi Arabia.

Assessment of groundwater quality is of utmost significance in arid regions like Saudi Arabia where the lack of present-day recharge and high evaporation rates coupled with increasing groundwater withdrawal may restrict its usage for domestic or agricultural purposes. In the present study, groundwater samples collected from agricultural farms in Hail (15 samples), Al Jawf (15 samples), and Tabuk (30 samples) regions were analyzed for their major ion concentration. The objective of the study was to determine the groundwater facies, the main hydrochemical process governing the groundwater chemistry, the saturation index with respect to the principal mineral phases, and the suitability of the groundwater for irrigational use. The groundwater samples fall within the Ca-Cl type, mixed Ca-Mg-Cl type, and Na-Cl type. Evaporation and reverse ion exchange appear to be the major processes controlling the groundwater chemistry though reverse ion exchange process is the more dominating factor. The various ionic relationships confirmed the reverse ion exchange process where the Ca and Mg in the aquifer matrix have been replaced by Na at favorable exchange sites. This phenomenon has accounted for the dominance of Ca and Mg ions over Na ion at all the sites. The process of reverse ion exchange was further substantiated by the use of modified Piper diagram (Chadha's classification) and the chloro-alkaline indices. Evaporation as a result of extreme aridity has resulted in the groundwater being oversaturated with aragonite/calcite and dolomite as revealed by the saturation indices. The groundwater samples were classified as safe (less than 10) in terms of sodium adsorption ratio (SAR) values, good (less than 1.25) in terms of residual sodium carbonate (RSC) values, and safe to moderate (between 0 and 3) in terms of Mg hazard for irrigation purposes. Though the high salinity groundwater in the three regions coupled with low SAR values are good for the soil structure, it can have a negative impact on the crop production by adversely affecting the crop physiology. Cultivation of high-salinity-resistant varieties of crops is recommended for maximum agricultural productivity.

Influence of seawater intrusion on microbial communities in groundwater

Groundwater is the sole source of potable water on Jeju Island in the Republic of (South) Korea. Groundwater is also used for irrigation and industrial purposes, and it is severely impacted by seawater intrusion in coastal areas. Consequently, monitoring the intrusion of seawater into groundwater on Jeju is very important for health and environmental reasons. A number of studies have used hydrological models to predict the deterioration of groundwater quality caused by seawater intrusion. However, there is conflicting evidence of intrusion due to complicated environmental influences on groundwater quality. Here we investigated the use of next generation sequencing (NGS)-based microbial community analysis as a way to monitor groundwater quality and detect seawater intrusion. Pristine groundwater, groundwater from three coastal areas, and seawater were compared. Analysis of the distribution of bacterial species clearly indicated that the high and low salinity groundwater differed significantly with respect to microbial composition. While members of the family Parvularculaceae were only identified in high salinity water samples, a greater percentage of the phylum Actinobacteria was predominantly observed in pristine groundwater. In addition, we identified 48 shared operational taxonomic units (OTUs) with seawater, among which the high salinity groundwater sample shared a greater number of bacterial species with seawater (6.7%). In contrast, other groundwater samples shared less than 0.5%. Our results suggest that NGS-based microbial community analysis of groundwater may be a useful tool for monitoring groundwater quality and detect seawater intrusion. This technology may also provide additional insights in understanding hydrological dynamics.

Hydrochemical disturbances measured in groundwater during the construction and operation of a large-scale underground facility in deep crystalline rock in Japan

Changes in the hydrochemical conditions of groundwater were evaluated following the construction of a large-scale underground facility at the Mizunami Underground Research Laboratory (MIU), Japan. The facility was constructed to a depth of 500 m in sedimentary and granitic rocks. Drawdown of the groundwater level in the range of several tens to hundreds of meters was observed up to hundreds of meters away from the shafts during the first ten years of facility construction and operation. Subsequent changes in groundwater chemistry occurred due to upconing of high-salinity groundwater from the deepest part of the shaft and the infiltration of low-salinity shallow groundwater. We predict that future deep groundwater chemistry in the vicinity of the MIU facility will resemble that of the present-day shallow groundwater. Multivariate statistical analysis provides fundamental insights into such a site. We found that the extent of hydrochemical variability related to MIU construction and operation was dependent on the distance from the facility shafts and galleries and on hydrogeological compartmentalization resulting from lithological boundaries (such as permeable conglomerates vs. more compact lithological units) and other features (such as faults or clay layers). We conclude that hydrochemical impact assessment of groundwater in low-permeability rock is essential prior to the construction of such a facility. This should include characterization of hydrogeological structures and compartments to propose suitable location of shafts and galleries.

Assessment of groundwater pollution from ash ponds using stable and unstable isotopes around the Koradi and Khaperkheda thermal power plants (Maharashtra, India)

The impact on local water resources due to fly ash produced in the Koradi and Khaperkheda thermal power plants (district of Nagpur, Maharashtra — India) and disposed in large ponds at the surface was assessed through the study of environmental variation of ratios of stable and unstable isotopes. Analyses of oxygen and hydrogen isotopes suggest scarce interaction between the water temporarily stored in the ponds and the groundwater in the study area. Data also highlight that the high salinity of groundwater measured in the polluted wells is not due to evaporation, but to subsequent infiltration of stream waters draining from the ponds to the local aquifer. 87Sr/86Sr values, when associated with Sr/Ca ratios, demonstrate the dominant role of waste waters coming from tens of brick kilns surrounding the pond sulfate pollution. Uranium isotopic analyses clearly show evidence of the interaction between groundwater and aquifer rocks, and confirm again the low influence of ash ponds. A new conceptual model based on the study of the isotopes of radium is also proposed and used to estimate residence times of groundwater in the area. This model highlights that high salinity cannot be in any case attributed to a prolonged water–rock interaction, but is due to the influence of untreated waste water of domestic or brick kiln origin on the shallow and vulnerable aquifers.

Identification of urine scale problems in urinals and the solution using rainwater

Water-saving urinals, such as waterless and low-flush urinals, have a great potential for water conservation by using 0 ∼ 0.8 l/flush compared with ordinary urinals, which use 2 ∼ 4 l/flush. However in some cases, water-saving urinals are not desirable because of technical problems, such as urine scale formation which makes the urinal dirty and blocks pipes. Also, some cultures do not allow the use of waterless urinals because of their notion of cleanliness. In this paper, factors causing urine scale formation have been identified from laboratory tests on pure urine and several types of flushing water. Some meaningful solutions for managing and solving urine scale problems have been suggested. In particular, the results show that mixing urine with seawater or high salinity groundwater will increase the potential of urine scale formation by increasing total dissolved solids (TDS) and pH. However, using rainwater for urinal flushing can significantly reduce the TDS and pH. These findings could support the use of water-saving toilets in Islamic societies by ensuring that the cleanliness of urinals can still be achieved.

Assessment of Groundwater Quality using GIS Techniques in Vaniyar Watershed, Ponnaiyar River, Tamil Nadu

Water quality assessment is essential to ensure viable safe use of the resources for drinking, agricultural, and industrial purposes. Sixty groundwater samples were collected systematically during pre and post monsoon season in the Vaniyar watershed in the Dharmapuri district, Tamil Nadu. Understand the geochemistry of the groundwater and to assess the overall physicochemical faces in the study area. Vaniyar watershed lies between the latitudes 11°46’ N to 12°09’39” N and longitudes 78°12’27” E to 78°36’65” E and covering an area of 982.25 km2. Out of which plain land covers an area of 591.43 km2. The study area is underlain by the Archaean crystalline rocks surrounded by hills. The physical and chemical parameters of the analytical results of groundwater were compared with the standard guideline of values recommended by the Bureau of Indian Standards (BIS) and World Health Organization (WHO) standards for irrigational suitability, domestic usage further hydrogeochemical data have been plotted in a standard graphs such as United State Salinity Laboratory (USSL) and Wilcox's diagrams. Based on the United State Salinity Laboratory (USSL) results of C3-S1 (452.75 Km2) class is good and could be used for all types of crops. Base on the Wilcox's diagrams that the groundwater near the downstream is good for irrigation and the contamination are found to be high in some places. This may be due to the rock water interactions because highly weathered rock noticed during field validation. Result reveals that 377.41 Km2 (61.67%) areas fall in (Wilcox) Good to Permissible category and 452.75 Km2 area falls in (USSL) C3-S1 category. Above said areas indicate that the groundwater could be used for all types of crops. According to U.S. Salinity Laboratory diagram, the majority of groundwater samples belongs to C3–S1 (High Salinity – Low SAR) category and spatially covers an area 452.75 Km2 under “Suitable” zone. In the present study, it is evident that high salinity of groundwater persists at majority of sites. Hence, for high to very high salinity of waters, soil must be permeable with adequate drainage facilities for satisfactory crop growth.

Deterioration of Soil-Cement Piles in a Saltwater Region and Its Influence on the Settlement of Composite Foundations

AbstractSoil-cement mixed piles are widely used to improve soft subsoil. But in regions with high-salinity groundwater, the soil-cement is susceptible to deterioration. At present, however, the design code for soil-cement pile composite foundations does not consider the deterioration effect of soil-cement. The saltwater region in the Yellow River Delta of China is used as a case study. Based on early strength tests of soil-cement, a practical prediction method for the lifecycle bearing capacity of soil-cement piles is put forward, and the influence of deterioration on the settlement of composite foundations is studied using model tests and numerical simulation. The prediction method of pile bearing capacity considers the progressive deterioration of soil-cement, and it shows that the deterioration of soil-cement has a great influence on bearing capacity of mixed piles with an increase in age, and the loss ratio of bearing capacity quickly reduces with a decrease in pile diameter. The deterioration also in...

Identifying the effects of human pressure on groundwater quality to support water management strategies in coastal regions: A multi-tracer and statistical approach (Bou-Areg region, Morocco)

Groundwater pollution from anthropogenic sources is a serious concern affecting several coastal aquifers worldwide. Increasing groundwater exploitation, coupled with point and non-point pollution sources, are the main anthropogenic impacts on coastal environments and are responsible for severe health and food security issues. Adequate management strategies to protect groundwater from contamination and overexploitation are of paramount importance, especially in arid prone regions, where coastal aquifers often represent the main freshwater resource to sustain human needs.The Bou-Areg Aquifer (Morocco) is a perfect example of a coastal aquifer constantly exposed to all the negative externalities associated with groundwater use for agricultural purposes, which lead to a general increase in aquifer salinization. In this study data on 61 water samples, collected in June and November 2010, were used to: (i) track groundwater composition changes related to the use of irrigation water from different sources, (ii) highlight seasonal variations to assess aquifer vulnerability, and (iii) present a reproducible example of multi-tracer approach for groundwater management in rural coastal areas.Hydrogeochemical results show that Bou-Areg groundwater is characterized by – high salinity, associated with a remarkable increase in bicarbonate content in the crop growing season, due to more intense biological activity in irrigated soils. The coupled multi-tracer and statistical analysis confirms the strong dependency on irrigation activities as well as a clear identification of the processes governing the aquifer’s hydrochemistry in the different seasons. Water Rock Interaction (WRI) dominates the composition of most of groundwater samples in the Low Irrigation season (L-IR) and Agricultural Return Flow (ARF) mainly affects groundwater salinization in the High Irrigation season (H-IR) in the same areas naturally affected by WRI. In the central part of the plain River Recharge (RR) from the Selouane River is responsible for the high groundwater salinity whilst Mixing Processes (MIX) occur in absence of irrigation activities.

Predicting Salinization Trends in a Lowland Coastal Aquifer: Comacchio (Italy)

The coastal aquifer salinization is an urgent problem caused by groundwater resources overexploitation and climate change. This phenomenon is enhanced in areas lying below the sea level, like the polders in the Netherlands or the Po River lowland in Italy. In these reclaimed lands the saltwater intrusion is usually controlled by a network of irrigation canals that supplies freshwater to the shallow aquifer, maintaining soil salinity at acceptable levels. The 2012 was dramatic in terms of agricultural water supply, since the Po River plain experienced a prolonged drought. Despite this, continuous monitoring of piezometric heads and total dissolved solids (TDS) near a canal (Canale della Gronda) demonstrated that freshening was occurring in the shallow portion (first 4 m) of the unconfined aquifer, while the bottom part was characterized by elevated relic salinity. The two-dimensional model SEAWAT was calibrated using piezometric heads and TDS depth profiles measured along a transect perpendicular to the canal. The calibrated model was then used to predict the behaviour of this cross section using a multiple scenario approach: increase in evapotranspiration induced by temperature increase; increase in the frequency of extreme high rainfall events; extreme drought conditions; and canal dewatering due to salinization of the water courses. Moreover, for each scenario, two sub-scenarios were run to account for projected sea level rise. The first three scenarios had only a minor influence on the aquifer salinization rate, while the fourth one predicted serious upward flux of the high salinity groundwater actually residing in the bottom of the unconfined aquifer. The scenarios quantified the possible future effects on groundwater salinization and could be useful to find adaptation strategies to manage the water resources of this and similar areas.

Using discriminant analysis to determine sources of salinity in shallow groundwater prior to hydraulic fracturing.

High-volume hydraulic fracturing (HVHF) gas-drilling operations in the Marcellus Play have raised environmental concerns, including the risk of groundwater contamination. Fingerprinting water impacted by gas-drilling operations is not trivial given other potential sources of contamination. We present a multivariate statistical modeling framework for developing a quantitative, geochemical fingerprinting tool to distinguish sources of high salinity in shallow groundwater. The model was developed using new geochemical data for 204 wells in New York State (NYS), which has a HVHF moratorium and published data for additional wells in NYS and several salinity sources (Appalachian Basin brines, road salt, septic effluent, and animal waste). The model incorporates a stochastic simulation to predict the geochemistry of high salinity (>20 mg/L Cl) groundwater impacted by different salinity sources and then employs linear discriminant analysis to classify samples from different populations. Model results indicate Appalachian Basin brines are the primary source of salinity in 35% of sampled NYS groundwater wells with >20 mg/L Cl. The model provides an effective means for differentiating groundwater impacted by basin brines versus other contaminants. Using this framework, similar discriminatory tools can be derived for other regions from background water quality data.

Different isotopic evolutionary trends of δ34S and δ18O compositions of dissolved sulfate in an anaerobic deltaic aquifer system

Concentration and isotope ratios (δ34SSO4 and δ18OSO4) of dissolved sulfate of groundwater were analyzed in a very large anaerobic aquifer system under the Lower Central Plain (LCP) (25,000km2) in Thailand. Groundwater samples were collected in two different kinds of aquifers; type 1 with a saline water contribution and type 2 lateritic aquifers with no saline water contribution. Two different isotopic compositional trends were observed: in type 1 aquifers sulfate isotope ratios range from low values (+2.2‰ for δ34SSO4 and +8.0‰ for δ18OSO4) to high values (+49.9‰ for δ34SSO4 and +17.9‰ for δ18OSO4); in type 2 aquifers sulfate isotope ratios range from low values (−0.1‰ for δ34SSO4 and +12.2‰ for δ18OSO4) to high δ18OSO4 ratios (+18.4‰) but with low δ34SSO4 ratios (<+12.9‰). Isotopic comparison with possible source materials and theoretical geochemical models suggests that the sulfate isotope variation for type 1 aquifer groundwater can be explained by two main processes. One is the contribution of remnant seawater, which has experienced dissimilatory sulfate reduction in the marine clay, into recharge water of freshwater origin. This process accounts for the high salinity groundwater. The other process, explaining for the modest salinity groundwater, is the bacterial sulfate reduction of the mixture water between high salinity water and fresh groundwater. Isotopic variation of type 2 aquifer groundwater may also be explained by bacterial sulfate reduction, with slower reduction rate than that of the groundwater with saline water effect. The origin of groundwater sulfate with low δ34SSO4 but high δ18OSO4 is recognized as an important topic to be examined in a future investigation.