Groundwater in southwestern Buenos Aires, Argentina: conditioning factors of the phreatic sandy aquifer for the supply to the town of Médanos

doi:10.21203/rs.3.rs-4724681/v1

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Groundwater in southwestern Buenos Aires, Argentina: conditioning factors of the phreatic sandy aquifer for the supply to the town of Médanos

https://doi.org/10.21203/rs.3.rs-4724681/v1

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Groundwater quality and quantity are critical issues in semi-arid regions, where it often serves as the sole water source. The study area is located in the Villarino district, Buenos Aires, Argentina, featuring a dune chain with high infiltration capacity, leading to variable hydrochemical conditions. The town of Médanos relies on a phreatic aquifer within this eolian dune chain for its supply, with water quality being influenced by well location and depth, with the occasional presence of undesirable ions. This study aims to determine the hydrogeological conditions and limitants of the aquifer in the area, using well surveys, in-situ measurements, physicochemical analyses, and electrical resistivity tomographies (ERT). Results indicate a hydrochemical stratification, with low salinity water lens overlying more saline water. Groundwater conductivity varies, with lowest values in central and southwestern preferential recharge areas and higher values near discharge zones. Chloride content follows a similar pattern. Saturated thicknesses of fresh water, determined by means of ERTs, vary significantly, revealing potential paleochannels that could act as preferential zones for future wells. Analysis of existing pumping fields shows that well location and depth critically affect water yield and quality. The Mascota pumping field, with the highest fresh water saturated thickness, provides the best water quality and yield, while Las Escobas field faces issues of low yield (due to low saturated thickness) and interference among wells. This emphasizes the importance of these kind of studies for the strategic well placement and depth to improve water supply quality and sustainability for the town of Médanos.

sandy aquifer

supply

Médanos

dune chain

The quantity and quality of groundwater is a frequent problem in semi-arid climate zones, where it is usually the only source of supply for use by the population (Kruse, 2015) and the availability of the resource is strongly linked to rainfall. The town of Médanos is supplied from pumping fields that exploit a phreatic aquifer of reduced thickness, contained within the eolian dunes in the study area. Its waters are generally of good chemical quality, although this is largely influenced by the location of the catchment and its depth, with frequent occurrence of undesirable ions, such as arsenic (As) and fluoride (F), which are common throughout the area, both in surface and groundwaters (Puntoriero et al., 2014; Nicolli et al., 2012).

These sandy accumulations are generally found covering the finer deposits of the Río Negro and Chasicó formations, which host waters of higher salinity, with variable contents of undesirable elements. This lithological variation of the sediments, together with the physicochemical differences of the groundwater, result in a hydrochemical stratification, with a lens of low salinity water resting on a more saline and extensive one. This contrast makes geoelectric prospecting, by means of electrical resistivity tomography (ERT), an excellent methodology to define thicknesses saturated with fresh water.

By the recollection of antecedent information and conducting well surveys, in-situ measurements, physicochemical analysis and electrical resistivity tomographies (ERT) to determine saturated thicknesses of interest in different sectors of the study area, the objective of this work was to determine the hydrogeological conditions of the aquifer in the study area, which in turn determine the groundwater supply for the town of Médanos. Based on the above, the different factors that limit the quality and quantity of the available resource were identified, also taking into account the characteristics of the wells of the pumping fields and their location.

CHARACTERISTICS OF THE STUDY AREA

The study area is located in the northern sector of the Villarino district, in the southwest of the province of Buenos Aires, Argentina, including the towns of Médanos, La Mascota and Argerich (Fig. 1). Regionally, it is part of the Buenos Aires plains, comprising a chain of gently sloping continental sand dunes that extend about 50 km in a northwest-southeast direction, from the Chasicó lagoon and the homonymous stream to the northwest, to the Bahía Blanca estuary, to the southeast. To the northeast it borders the Salitral de la Vidriera, while to the southwest it partially borders the Salinas Chicas depression, which reaches a minimum elevation of 42 m.b.s.l (meters below sea level).

Its southeastern portion has a gentle slope of 0.2% towards the NE and an average height of 30 m.a.s.l. (meters above sea level) (Carrica et al., 2012), while the northwestern sector of the chain has an average slope of 0.5% towards the SW, with an average elevation of 3 m.b.s.l.

According to Thornthwaite's climatic indexes (Thornthwaite, 1948), the climate in the area is C1 B'2 d a', that is, subhumid (C1), cool temperate mesothermal (B'2), with no or little excess water (d) and a thermal efficiency of less than 48% (a'), bordering the semiarid sector (D B'1 d a') (Sánchez et al.,1998).

The mean annual precipitation is 546,8 mm (1972–2005 series) for the locality of Médanos, with minimums in July (20.8 mm) and maximums in March (78.2 mm). The mean annual temperature is 14.2 ºC, with mean extremes in January and July of 22.5 ºC and 7 ºC, respectively. Three pumping fields manager by the local water service provider, called Las Escobas, La Mascota and La Morocha, are located on the dune chain. The first of these is located to the west of the Las Escobas lagoon, on the southwestern edge of the dunes. The La Mascota pumping field is located near National Route 22, between the town of the same name and Argerich. Finally, the La Morocha pumping field is located about 2 km east of the city of Médanos. A reverse osmosis plant is located in the town of Médanos for the potabilization of water that does not meet the potability requirements established by law.

GEOLOGY AND HYDROGEOLOGY

In a simplified manner, the sequence in the sector begins with the continental silty-clayey deposits corresponding to the Chasicó Formation (Pascual, 1961), on which, at times, the sandy fluvial materials of the Río Negro Formation (Andreis, 1965) rest. Both units are Pliocene in age. Discontinuously and on top of the above, a level of conglomerates can be found, denominated "Rodados Patagónicos", of Pleistocene age (Fidalgo, 1999). Discordantly above it are the sandy sediments that make up the Holocene-age dune chain that is the subject of this study, which is called by different names depending on the author. These are sands of eolian origin and are called: "Arenas Médanos" (Spaletti and Isla, 2003), Estancia La Aurora Formation (Fidalgo et al., 1987), La Postrera Formation or Médanos Formation (Bonorino, 1974), the latter being the denomination adopted for this work.

These dunes, which cover the entire study area, are composed, in general terms, of fine to medium unimodal sands, sometimes very fine, which tend to slightly decrease in grain size towards the NW of the chain. They are mainly composed of quartz, plagioclase, microcline, pyroxene, epidote, titaniferous magnetite and do not contain calcium carbonate (Bonorino, 1979). Rossetto (1953) attributes to them, in addition to an aeolian origin, a pyroclastic component, after having carried out an exhaustive study of their granometry and mineralogy.

Morphologically, these accumulations of sands reach 15 meters in height and form barjans ranging from 150 to 200 meters in length, frequently aligned in a northwest-southeast direction, with the steepest slope dipping to the northeast, although they can also be observed transversal to this predominant direction. To the south they develop in the form of a mantle.

Hydrogeologically, the study area is within the Bahía Blanca Basin Hydrogeological Region (Auge, 2004). Through previous research (Bonorino, 1974, 1979) and vertical electrical soundings (VES) carried out in the area, Lexow and Bonorino (2012) determined the hydrostratigraphic scheme of the sector (Table 1).

Table 1

Hydrostratigraphic scheme for the area, modified from Lexow and Bonorino (2012)
FORMATION	LITHOLOGY	AQUIFER PROPERTIES
Médanos (Holocene)	Aeolian deposits, composed of medium to fine sands, in the form of mantles or sandy bodys. It lays on top of Río Negro Fm. or Rodados Patagónicos.	Shallow water table. Water in pore spaces. High porosity and good permeability. Water with low saline content. (3 m average thickness)
Rodados Patagónicos (Pleistocene)	Medium to fine gravels, of fluvial origin, developed mainly south of the Colorado River, strongly cemented by calcium carbonate on its upper terms. It lays on top of the Río Negro Fm., and on some areas on top of the Chasicó Fm.	The upper level acts as a low secondary permeability layer through which rainwater infiltrates. Does not form aquifers. (between 2 and 4 m thick)
Río Negro Fm. (Pliocene)	Medium to fine sandstones, grey colored, with crossbedding.	Good porosity and permeability. Variable yield aquifers. Medium to high salinization waters. (saturated thicknesses between 4 and 9 m)
Limos Loessoides a.k.a. Chasicó Fm. (Lower Pliocene)	Reddish-brown clayey silts, massive, with intercalations of sands and clays and calcareous and gypsiferous levels.	Low permeability and porosity. Confined aquifer levels approximately between 50 and 200 m of depth. (between 150 and 200 m thick)

The phreatic aquifer that is the subject of this work is located in the dune chain, with groundwater with an electrical conductivity (EC) that is generally in the range of 400 to 1000 µS/cm. These sands have a high infiltration capacity due to their lithological characteristics, which prevents the development of a defined drainage network. This allows the rapid incorporation of precipitation water into the saturated zone as recharge to the system. Recharge calculated for the area is between 33 and 35% of the average annual precipitation (Carrica et al., 2012). In the field measurements carried out, the water table was found, at most, at 13,5 m depth, with the most frequent measurements being less than 8 m. The groundwater flow direction (determined from own piezometric level measurements at numerous water points in and around the study area) roughly follows the slope of the terrain. Locally, overlapping radial flows occur, discharging into topographically depressed or interdune areas (Albouy, 2005). These topographic lows can give rise to an upwelling of the water table, forming sectors of permanent or seasonal wetlands. In this manner, two flow systems can be identified: a shallow, local flow system, with short distances, and a deeper, regional flow system with longer distances.

Based on previous data and pumping tests, the specific yield of the aquifer is 0,2, while the hydraulic conductivity is around 17 m/d. The average hydraulic gradient is around 3‰, with a maximum of 13‰ and a minimum of 1.5‰. These are higher in the western portion of the chain, as a product of greater topography in that area. The effective groundwater velocity averages 0.26 m/d, with a maximum of 1.1 m/d and a minimum of 0.12 m/d (Rey et al., 2023a).

This free aquifer is superimposed and hydraulically connected to the one hosted in the Río Negro and Chasicó formations, which contains waters with a higher saline content (with conductivities generally above 3000 µS/cm) and frequently presents important concentrations of undesired trace elements (Fig. 2). Below 50 m of depth, semiconfined-confined aquifer levels can be found, with naturally salinized waters.

Previous geophysical studies (Lexow and Bonorino, 2012) detected an appreciable increase in groundwater salinity between 14 and 29 m depth. This would mark the lower boundary of a low-salinity water lens, which rests on a more saline and extensive one. The greatest thickness of fresh water would be found in the center of the dune chain, decreasing laterally. The recharge process by precipitation contributes to the development of the freshwater lens, which displaces the surrounding saltwater downward (Falkland and Custodio, 1991).

The great variability of the saturated thickness determined in these studies (from 5 to 15 m), in a relatively small area, added to the geological/geomorphological background, indicates an interaction between different depositional environments.

The work methodology was based, in principle, on the recollection of background information on the study area. Subsequently, several field trips were made to carry out a census of water points, mapping and measuring both water table outcrops and wells, totaling 40 measurements, which were geographically located using a Garmin Etrex Vista e30x GPS. Simultaneously to this, visits were made to the pumping fields mentioned above, where inspections of the wells were carried out and information about these catchments was collected.

In-situ measurements of pH, electrical conductivity (EC) and temperature of the water samples were performed with a LUTRON WA-2015 probe. The equipment was calibrated before each field trip using pH buffer solutions and a standard conductivity solution of 1413 µS/cm. In turn, 17 water samples were collected throughout the study area for laboratory chemical analysis to determine their chloride (Cl⁻) content, as well as F and Cl in part of them. In order to guarantee the representativeness of the samples and the aforementioned measurements, prior to the collection of the samples, the wells were purged, extracting 3 to 5 times the volume of water contained in the borehole at the time of extraction. The extracted samples were collected in 1 liter plastic containers, which were labeled and kept until they were sent to the laboratory. The methodology and instruments used for these anionic determinations were carried out according to the "Standard Method for the Examination of Water and Wastewater", 17th edition (1989). Cation determinations were carried out with an Inductively Coupled Plasma Atomic Emission Spectrometer (ICP-OES) Shimadzu Simultaneous 9000, according to EPA Standard 200.7. For fluoride, an Orion fluoride selective combination electrode (ISE) was used. Finally, maps of EC and chloride isolines were produced based on the data obtained.

Regarding the estimation of the saturated thicknesses of interest, data were taken from previous works by this author, where several electrical resistivity tomographies (ERT) were performed in the study area. For this purpose, an ARES model automatic resistivimeter (GF Instruments) with 48 electrodes was used, with a maximum spacing of 5 m between them. The equipment is powered by an external source (battery). This unit is in charge of verifying the state of the connections and executing, based on the pre-established requirements, the sequence of measurements and storing the field results. The electrode array used was a Wenner Alpha type, with a distance between electrodes of 3 or 5 m, depending on the case, thus obtaining progressives (straight line between the first and last electrode) of 141 and 235 m in length, respectively. In this way, an exploration depth of between 25 to 45 m was achieved.

The inversion of the data was performed in using Geotomo's Res2DInv software (Loke, 2004), which allows obtaining, from the field data (apparent resistivities), an electrical resistivity image (ERI). This software uses the Gauss-Newton least squares inversion method (Sasaki, 1992) subject to a smoothing constraint. The program automatically defines the optimal inversion parameters for a given data set. The model was improved by the software by applying the L-Curve method (Farquharson and Oldenburg, 2004), which, from the data misfit and model roughness, estimates the optimal lambda parameter to be used. Additionally, due to the resistivity variations measured on the surface of the terrain, the software proposed the use, in certain cases, of the "Model Refinement" option, with which a cell width of half the spacing between electrodes is considered. In this way, the resistivity images obtained were "cleaner" than those resulting without applying this function. In order to give a geological and hydrogeological sense to the images obtained, it was necessary to parameterize the method. This was based on well cuttings, water table measurements and groundwater electrical conductivity from a well located a few meters from the beginning of one of the tomographies. With these data it was possible to define the thickness saturated with fresh water in different sectors of the dune chain, and at the same time it allowed the detection of structures of interest in the resulting resistivity models.

By putting all this information together, the different factors and situations throughout the aquifer that condition the water supply to the town of Médanos where determined. In this way, the best locations and depths were identified for catchments that supply the locality with water of good chemical quality.

Hydrochemical variability of the phreatic groundwater layer

Based on the results of the analyses carried out, isoline maps of electrical conductivity and chloride content in the groundwater of the study area were generated (Fig. 3), in order to identify, in general terms, the areas with the best chemical quality of the phreatic aquifer. The EC values measured averaged 1890 µS/cm, with a maximum of 9090 and a minimum of 385 µS/cm. Of a total of 41 measurements obtained during the census of water points, 5 presented values higher than 2000 µS/cm. Values around 1000 µS/cm can be recognized in the SE and NW parts of the dune chain and central areas, while in the NE and SW sectors higher values were recorded, around 3000 µS/cm, even reaching extremes north of the town of Argerich, where values of more than 5440 µS/cm were measured, and the absolute maximum in the study area, 9090 µS/cm.

The conductivity shows a general increase that, for the E part of the dune chain, occurs from SW to NE, with the highest values located in the vicinity of the Salitral de la Vidriera, while, for the W sector of the chain, the increase in conductivity occurs in the opposite direction, without reaching values as high as in the previous case. In turn, the central zones of the study area, due to their characteristics, could be considered local recharge zones, with conductivity values between 600 and 1000 µS/cm. The progressive increase in conductivity would be caused by the enrichment of dissolved ions in the groundwater along its transit.

With respect to chloride content, the average chloride concentration is 309,4 mg/L, with maximums measured at 1602 mg/L and minimums of 35,9 mg/L. In most of the study area, values below 300 mg/L are observed. On the other hand, the highest values are located near the Salitral de la Vidriera (higher than 600 mg/L), where, in addition to the increase due to groundwater transit, chloride could also be contributed by the dissolution of salts and evaporite crusts. The lower levels of this ion, together with the low electrical conductivity measurements, can be associated with preferential recharge zones. On the other hand, the zones with the highest recorded conductivities and Cl concentrations clearly represent discharge zones of the aquifer system. As expected, there is a good correlation between the contents of this ion and the electrical conductivity measured in the samples.

Elevated As and F were observed in the plain surrounding the dune chain and in samples where the catchment was at least partially penetrating the pelitic layer underlying the sand dunes. In general, values within the dune chain are low and irregularly distributed: in the samples analyzed, As has an average value of 48.8 µg/L, with a maximum of 216 and a minimum of 10 µg/L, while F exhibits an average value of 2.5 mg/L, with a maximum of 9.9 and a minimum of 1 mg/L. The mineralogy of fine sediments would affect the water chemistry, strongly limiting its potability and use. Smedley et al. (2000) have proposed this phase as the most important potential source of F and As in La Pampa province. The weathering of ash and volcanic material present in these materials, when altered in contact with groundwater, can release undesirable elements into the aquifer. Similar hydrogeochemical behaviors of these ions have already been detected in other Pampean regions (Florentino et al., 2007; Smedley et al., 2002).

These hydrochemical constraints are similar and concordant to those described by other authors in zones similar to the study area (Albouy et al., 2022; Galliari, 2022; Rodrigues Capítulo, 2015; Ruffo, 2022). Thus, groundwater chemistry in the phreatic aquifer is mainly linked to groundwater transport, with a progressive increase in mineralization and salinity from recharge to discharge areas.

Variations in saturated thickness of the phreatic aquifer

Taking into consideration the knowledge of the area and pre-existing data, studies were carried out by these same authors where the thicknesses saturated with fresh water at different points of the dune chain were determined by means of seven ERTs (Rey et al., 2023b).

Two of the tomographies were carried out at the location of pumping fields of the local water supply company, where particular features of the study area could be observed (Fig. 4). In the ERI carried out in the Las Escobas pumping field, information was available from borehole cuttings and measurements of the water table obtained from a well located about 20 m before the beginning of the progressive. In this image it was possible to recognize an unsaturated zone (UZ) with resistivities higher than 100 Ω.m, while values lower than 25 Ω.m would correspond to the fine deposits of the Chasicó Fm., with salinized waters. Thus, values between 25 and 100 Ω.m correspond to sands with low salinity water (between 500 and 600 µS/cm, according to measurements from wells located in the sector that exploit this aquifer layer). In this portion of the area, according to all of the above, the saturated thickness of interest is around 4 m.

On the other hand, the La Mascota pumping field sector presented particular characteristics that result in it being of great hydrogeological interest from the point of view of exploitation. Although a saturated thickness of interest of around 5 m is observed, there are sectors of the progressive (between 55 and 85 m, and between 148 and 194 m) in which it seems to show an important increase, reaching more than 30 m. This increase in thickness could be associated with structures similar to paleochannels, filled by the sands of the dune chain, giving place to preferential zones from the hydrogeological point of view. The water extracted from wells located a few meters from the ERT, presents electrical conductivities of about 600 µS/cm, so it is inferred that these structures would contain water of similar quality.

The methodology used provides a large amount of useful data and information about the subsurface, however, as it is an indirect exploration tool, so the results obtained must be contrasted with validated data. The presence of possible paleochannels in a coastal dune chain, similar to the study case, was noted by Ruffo et al. (2022) using the same geoelectric method used here. Farías et al. (2009) proposed the existence of a paleochannel system in the area to explain the presence of arsenic in the subsurface waters of the Villarino district.

From the integration of the data obtained, it was determined that the saturated thickness of the phreatic aquifer with fresh water is approximately 4 m on average along the dune body. Subdividing the study area according to the geophysical data resulting from the ERTs, the calculated volume of water reserves is 344 Hm³ (Fig. 5).

Although previous estimates of these reserves (García and García, 1964; Bonorino, 1979), yielded a value of 276 Hm³ for the study area, the volume calculated in this work is considered to be the most accurate estimate according to the current data available.

Analysis of pre-existing pumping fields

In the town of Médanos, the water supply service is operated by ABSA (Aguas Bonaerenses S.A.) and is provided by 3 batteries of groundwater wells with a combined production capacity of about 45 m3/h: Las Escobas, La Morocha and La Mascota. It should be noted that not all of the wells are fully operational at all times due to maintenance or repairs.

The Las Escobas pumping field is a battery located on the western boundary of the dune chain, with about 9 operational wells (the remaining ones are temporarily out of use due to repairs or pump replacement). The depths of the wells are around 12 to 14 m, with 1.5 HP submersible pumps. The water obtained is of good quality (with an EC of around 550 µS/cm), so it is not necessary to treat it with reverse osmosis. Approximately 15 m3/h are extracted from this pumping field.

The La Mascota pumping field is located 1.5 km northeast of the town of the same name, along the road. It consists of 4 catchments (although there are plans to incorporate one more in the near future), located approximately in the center of the chain. The wells are about 45 m deep and are equipped with 3 HP pumps. The water extracted is of good quality (with an EC around 600 µS/cm), so it is not treated in the reverse osmosis plant. A total of about 15 m3/h is extracted from these catchments, which are by far the wells with the best individual yield of all those used by the service provider.

Finally, La Morocha pumping field is a battery of wells located about 2 km east of Médanos. It has a total of 40 catchments between 30 and 35 m deep, equipped with 0,75 HP pumps. Although it was not possible to measure the water table (because all the boreholes were sealed), a water sampe was analyzed in situ, obtaining results of poorer quality than those of the two pumping fields described above. Because of its high F and As content, the water extracted from these wells is treated with reverse osmosis for its potabilization. A total of about 15 m3/h is obtained from these catchments (not all of the wells are fully operational).

Taking into account the analysis of the situation in each pumping field, it is evident that the catchments with the best performance are those located in La Mascota, given that they are located in an area with good chemical quality and a saturated thickness above the average of the study area, taking advantage of the paleochannels identified by tomographies, without capturing water from aquifer levels contained in the finer materials located below the sand dunes (Fig. 6). The low yield and quality of the water extracted from the La Morocha pumping field is due to the fact that the catchments extract water, at least partially, from levels below the sandy layer, resulting in elevated F and As levels.

Finally, Las Escobas pumping field, although it has good quality water, has low rumping rates, with numerous catchments whose drawdown cones interfere with each other. This causes steep drawdowns in the aquifer water table, causing the wells to dry up and the submersible pumps to malfunction and need to be replaced.

The study area exhibits important limitations both in groundwater quality and in the freshwater-saturated thickness of the aquifer, considering its exploitation as a source of supply for the population. Both show a remarkable variability along the dune chain, so that the yield of a well pumping field and the chemical quality of the water extracted from them will be strongly conditioned by the location of the catchments within the dunes, as well as their depth.

Regarding the chemical quality of the groundwater, the sectors with the best conditions for extraction would be those located in Las Escobas and around La Mascota, which, being preferential recharge areas, have the lowest electrical conductivity (values between 400 and 1000 µS/cm) and chloride concentrations (between 35 and 50 mg/L). As for F and As, although they present an irregular distribution, both would have a common origin in the groundwater, mainly from the weathering of volcanic material present in the sediments of the Chasicó Fm. Thus, the wells within the sand dune chain with high levels of these elements would be associated with scenarios where the well penetrates below the sands of the dune chain and captures water, at least in part, contained in the units below them, as is the case of the wells of the La Morocha pumping field.

As for the saturated thickness, the areas of greatest interest are on the SW flank of the dune chain and its central sector. More specifically, in the area surrounding the town of La Mascota, a sector with structures similar to paleochannels was recognized, where the thickness saturated with fresh water increases significantly.

The management of water resources in sectors with the climate and hydrogeological conditions such as the study area is of enormous importance for its correct use. The possibility of building a new pumping field in a suitable sector (determined by geophysical studies) where the saturated thickness of fresh water is adequate according to the exploitation needs should be carefully studied. Although the calculated volume of reserves is fragile, the area is sparsely populated (only about 5400 inhabitants, with 5245 concentrated in the town of Médanos), so its exploitation is possible.

In view of the above, it is recommended in all cases that the depth of the wells does not exceed the depth reached by the sandy package, in order to extract water of good physical-chemical quality and avoid, as far as possible, the high costs associated with the reverse osmosis treatment that is currently carried out on the water extracted from the La Morocha pumping field. In this field, the exploited resource contains significant amounts of fluoride and arsenic. In case of continuing with the exploitation of the resource in the Las Escobas pumping field, where the thickness saturated with fresh water is rather reduced, the use of conventional wells may not be convenient, due to the pronounced drawdown that they cause. Thus, for a sustained exploitation in time, it is suggested to consider other well construction methods, such as wells with horizontal drains (Ranney or Well Point type), which produce a lesser decrease on the water table, and are more efficient than conventional ones, in aquifers of low thickness, as in the case studied.

Funding

The authors declare that no funds, grants, or other support were received during the preparation of this manuscript.

Author contributions

All authors contributed to the study conception and design. Material preparation, data collection and analysis were performed by Matias Rey and Andrés Ruffo. The first draft of the manuscript was written by Matias Rey and all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript.

Competing Interests

The authors have no relevant financial or non-financial interests to disclose.

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Groundwater in southwestern Buenos Aires, Argentina: conditioning factors of the phreatic sandy aquifer for the supply to the town of Médanos

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Abstract

Figures

INTRODUCTION

CHARACTERISTICS OF THE STUDY AREA

GEOLOGY AND HYDROGEOLOGY

MATERIALS AND METHODS

RESULTS AND DISCUSSION

Hydrochemical variability of the phreatic groundwater layer

Variations in saturated thickness of the phreatic aquifer

Analysis of pre-existing pumping fields

CONCLUSIONS AND RECOMMENDATIONS

STATEMENTS & DECLARATIONS

References

Additional Declarations

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