Network Of Piezometers Research Articles

Developing Systems-Level Criteria for Evaluating Performance of Horizontal Drains toward Landslide Mitigation: Case Study of the US20 Pioneer Mountain-Eddyville Realignment Project

Opened to traffic in 2016, the Pioneer Mountain-Eddyville (PME) realignment was a major highway infrastructure project that began in 2005 and created approximately 9 km of new highway on US Route 20 in the Oregon Coast Range. Due to the renewed activity of a series of paleolandslides that traversed the project right-of-way, deliver of the construction project was significantly delayed. Owing to the size and activity of these slope failures, a large monitoring network of piezometers and other instrumentation was deployed as a precursor to the installation of an extensive system of horizontal drain arrays (176 km of drain length) intended as one means of landslide mitigation through control of in situ groundwater. Because there is limited guidance regarding monitoring the long-term performance or design life of horizontal drains, hydrological data in drained areas were monitored as a means of observing performance during and after project completion. This case study describes observations of groundwater behavior prior to—and after—drain installation, thereafter proposing site planning–level metrics for evaluating the continued function of horizontal drain systems. Drain function is considered through groundwater response to precipitation, but also through a simple evaluation of water storage in the catchment of each landslide. The four paleolandslides—Cougar Creek, Crystal Creek, Eddy A/B, and Eddy C/D—demonstrate different responses to drain installation and long-term performance. Using simple metrics based on monitoring, added indices for evaluating long-term horizontal drain performance at the site scale are proposed. Consistent with the Observational Method, these criteria may serve as additional guidance for a monitoring-based framework for evaluating the life cycle of horizontal drains as a landslide mitigation system and a basis for planning drain maintenance or added mitigation measures.

Agricultural Pressures on the Quality of Ground and Surface Waters in Catchments of Artificial Reservoirs

Changes in nutrient concentrations in groundwater were investigated to determine the impact of agriculture on water quality in artificial lakes. The study covered three reservoirs in an agricultural area of Wielkopolska (central-western part of Poland). Assessing the agricultural impact required a network of piezometers around the reservoirs, used to determine the degree of groundwater pollution from nutrients supplied to the reservoirs. Moreover, the analysis covered the quality of water in streams flowing into the reservoirs, and in the reservoirs themselves. Field research was conducted every month of the growing season from March to November. The analysis covered land inclination, ground permeability, and soil type. Detailed objectives included: (1) assessment of the agricultural impact on the chemical parameters of ground and surface water quality, and (2) evaluation of the impact of different sources of agricultural pollution on water quality in artificial reservoirs in regards to their management. This study revealed high dynamics of nutrient concentrations, particularly for nitrates and phosphates, in groundwater and surface water. A significant effect of maize cultivation on an increase in nitrate concentrations in the groundwater of the catchment of the Przebędowo Reservoir was evidenced, as well as a substantial effect of the functioning of an animal farm on the quality of groundwaters in the catchment of the Lachotka Reservoir. The nutrient load of agricultural origin in the catchment of the Miedzichowo Reservoir was relatively low. Our study revealed elevated amounts of nutrients such as nitrogen and phosphorus, detected more frequently in groundwater than in running waters, which confirms our hypothesis of the importance of groundwater analysis in detecting the source of pollution of the studied lakes. High nutrient concentrations recorded in groundwater leached from arable fields were also observed in the summer period, failing to confirm the hypothesis that the greatest effect of factors would be related to the spring effect of arable fields on water quality (lack of compact vegetation cover, high water level, etc.). Our study also indicated a greater importance of the type of land use than lithology or permeability of deposits.

Estimating solute travel times from time series of nitrate concentration in groundwater: Application to a small agricultural catchment in Brittany, France

Stream flow and concentration dynamics are usually supposed to integrate the diverse hydrological and biogeochemical processes occurring within catchments and their variability in space and time. Proxies like transit times and young water fractions are often used to understand this variability. However, this procedure might not be suitable in catchments with ephemeral streams. The objective of this paper is to test the hypothesis that in catchments where groundwater flow is the main source of water output, solute travel times can be inferred from the monitored groundwater levels and solute concentration time series of piezometer networks. We used data from a well-studied small agricultural catchment in Brittany, belonging to the French network of Critical Zone Observatories. The data set includes long-term nitrate concentration time-series measured both at the stream outlet and the network of piezometers. We applied a parsimonious, conceptual dual-permeability mixing modelto calibrate our dataset and found that the nitrate travel times estimated in mid to upslope piezometers were consistently higher than the one at the stream outlet. We further observed an asynchronicity in seasonal concentration-discharge dynamics between the piezometers and the stream. We hypothesized that either due to riparian denitrification and uptake by vegetation, a pronounced seasonality is being generated which is making our model underestimate the nitrate travel times at the stream, or the piezometers are acting as proxies to the slower conceptual store of our mixing model, and shallow subsurface flow or some hydrologically significant heterogeneities are contributing to the faster route which is not tapped into by the piezometer network. Latter hypothesis is further supported by the fact that nitrate travel velocity along two different transects are in agreement with the slower conceptual store of our model. Nevertheless, we established that to specifically estimate the groundwater travel time of a catchment, a piezometer free from riparian influence alongside a stream is very beneficial.

High‐resolution spatiotemporal analysis of hydrologic connectivity in the historical floodplain of straightened lowland agricultural streams

AbstractIn agricultural watersheds, human interventions such as channel straightening have disrupted the hydrologic connectivity between headwater streams and their riparian environment and have thus undermined the ecological services provided by these small streams. Knowledge of the hydrologic connectivity between these streams and their immediate environment (shallow riparian groundwater in the historical floodplain and on adjacent hillslopes) in human‐impacted settings is critical for understanding and restoring these hydrological systems but remains largely incomplete. The objective of this research is to investigate the hydrogeomorphological conditions controlling hydrologic connectivity in the historical floodplain of straightened lowland streams. Detailed measurements on the spatiotemporal variability of groundwater‐surface water interactions between straightened reaches, historical floodplain including abandoned meanders, and the adjacent hillslopes were obtained using a dense network of piezometers at two sites in the St. Lawrence Lowlands (Quebec, Canada). Results show that the complex mechanisms controlling hydrologic connectivity in naturally meandering lowland rivers also operate in highly disturbed straightened reaches, despite backfilling and agricultural practices. The pre‐straightening hydrogeomorphological configuration of the floodplain partly explains the complex patterns of piezometric fluctuations observed at the sites. The apex of the abandoned meanders stands out as a focal area of hydrologic connectivity as water levels indicate pressure transfer that may reflect flows from the stream, the hillslopes, and the surrounding historical floodplain. These unique field observations suggest that abandoned meanders should be promoted as key elements of restoration strategies in lowland agricultural straightened headwater streams.

Groundwater salinity and isotope characterization: a case study from South-West Punjab, India

Increasing demand of the irrigation water led to improper surface water irrigation policies resulting in water logging problems in southwest Punjab coupled with apprehension of saline zones formation by salinity ingression towards central Punjab due to excessive groundwater abstraction. A network of piezometers exploring 4 upper aquifers was constructed at 6 sites in Sri Muktsar Sahib district of south-west Punjab. Groundwater samples were collected from these piezometers, TDS was measured and analysed for stable isotopes (ẟ18O and ẟD). Based on isotope characterization 4 zones were identified as: (1) zone A: source as fresh water or precipitation (2) zone B evaporation either during precipitation or infiltration (3) zone C intermediate of evaporated and recycled water (4) recycled water. This study can be useful in proper management of the water resources in this region by identifying the fresh water and saline groundwater zones in the area.

Groundwater overuse in arid areas: case study of syncline Bouguirat-Mostaganem, Algeria

Most Algerian agricultural areas are facing groundwater depletion under the combined effects of climate change and big consumption due to irrigation and urban needs. This is exactly the case of syncline Bouguirat located in North Algeria, the topic of this investigation. This region has an agricultural vocation with a dominant market gardening and arid Mediterranean climate characterized by recurrent drought events. During the early twentieth century, the average annual rainfall was estimated between 400 and 500 mm; however, between the years 1990 and 2015, it declined to around 280 mm. During the same period, the water level of water wells and boreholes decreased to 10 and 30 m, while several observation wells of the piezometric network have dried up. The volume of water extracted is estimated at 87.184 hm3 per year while the contribution of water table is only 22.51 hm3 per year, resulting in a deficit of about 65 hm3 per year. Climate, hydrogeological, and piezometry studies show that the syncline of Bouguirat is indeed prone to inordinate overexploitation that generates substantial drawdowns. The comparison between the water demand and groundwater resources allowed an operating assessment of groundwater resources. In this article, the problem of overexploitation of groundwater in Bouguirat synclinal has been well studied by the accurate monitoring of groundwater retreat; this retreat has been determined by a two-part in-depth study. In the Materials and Methods section, a detailed piezometric study of the study area was conducted to confirm the groundwater retreat. The Results and Discussions section was devoted to the study of the variation of the piezometric level as a function of precipitation, which confirms that the retreat is caused by drought and overexploitation of groundwater, then to study the fluctuation of the groundwater by making an overall balance of the exploited underground resources which gave a huge deficit with a significant reduction of up to 30 m. At the end of the study, solutions for the good management of this resource were proposed to remedy this critical situation.

GROUNDWATER STORAGE CHANGE ESTIMATION USING GRACE SATELLITE DATA IN INDUS BASIN

Over exploitation of Ground Water (GW) has resulted in lowering of water table in the Indus Basin. While waterlogging, salinity and seawater intrusion has resulted in rising of water table in Indus Basin. The sparse piezometer network cannot provide sufficient data to map groundwater changes spatially. To estimate groundwater change in this region, data from Gravity Recovery and Climate Experiment (GRACE) satellite was used. GRACE measures (Total Water Storage) TWS and used to estimate groundwater storage change. Net change in storage of groundwater was estimated from the change in TWS by including the additional components such as Soil Moisture (SM), Surface water storage (Qs) and snowpack equivalent water (SWE). For the estimation of these components Global Land Data Assimilation system (GLDAS) Land Surface Models (LSMs) was used. Both GRACE and GLDAS produce results for the Indus Basin for the period of April 2010 to January 2017. The monitoring well water-level records from the Scarp Monitoring Organization (SMO) and the Punjab Irrigation and Drainage Authority (PIDA) from April 2009 to December 2016 were used. The groundwater results from different combinations of GRACE products GFZ (GeoforschungsZentrum Potsdam) CSR (Center for Space Research at University of Texas, Austin) JPL (Jet Propulsion Laboratory) and GLDAS LSMs (CLM, NOAH and VIC) are calibrated (April 2009-2014) and validated (April 2015-April 2016) with in-situ measurements. For yearly scale, their correlation coefficient reaches 0.71 with Nash-Sutcliffe Efficiency (NSE) 0.82. It was estimated that net loss in groundwater storage is at mean rate of 85.01 mm per year and 118,668.16 Km3 in the 7 year of study period (April 2010-Jan 2017). GRACE TWS data were also able to pick up the signals from the large-scale flooding events observed in 2010 and 2014. These flooding events played a significant role in the replenishment of the groundwater system in the Indus Basin. Our study indicates that the GRACE based estimation of groundwater storage changes is skillful enough to provide monthly updates on the trend of the groundwater storage changes for resource managers and policy makers of Indus Basin.

Evaluating Landslide Remediation Methods Used in the Carpathian Mountains, Poland

ABSTRACT The aim of this study was to evaluate the results of landslide remediation in the Polish Carpathians. The research for safeguarding the roads and infrastructure was conducted in the years 2005–2018 in nine landslide areas. The interpretation of engineering geology conditions was complex due to the soil-rock nature of the flysch sediment. Movements were activated after heavy rainfalls. In two cases, triggers were connected with the undercutting of the slope or external loading. The research methods included mapping, drilling, index, oedometer, direct shear tests, ground-penetrating radar scanning, and numerical modeling. To date, 15–59 series of inclinometer and piezometer network readings in 30 locations have been taken. Three online stations have been delivering continuous, nearly real-time data since May 2010. Displacements before the remediation ranged from a few millimeters to several centimeters. The proposed remediation methods included piles, micropiles, anchors, retaining walls, and drainage systems. Six stabilization projects were prepared and checked using the limit equilibrium method and finite element method modeling. The research shows that in five landslide areas, the proposed remedial works were effective. Two other partial stabilization works limited the scope of the movements but did not eliminate the risk. At two locations, only temporary repairs were conducted. Proper identification of the landslide triggers and activity is standard for the recognition of counteraction possibilities and could lower stabilization costs. The selected methods delivered data for remedial decisions. However, effective remediation of an active Carpathian landslide is difficult. It requires individually calibrated investigations, representative monitoring, and careful design of stabilization.

Repairing earth dam drainage systems

Introduction: when reconstructing or overhauling dams, great attention should be paid to drainage systems as the most critical components of the installations. The article describes the typical malfunctions of earth dam pipe drainages. The research considers geological and hydrogeological features that were not taken into account when developing projects.
 Materials and methods: control and measuring instrumentation (piezometer network), full-scale experiments on disabling pipe drainage and mathematical modelling were used as the filtration regime research methods.
 Results: analysis of the hydrogeological features of the base of the right-bank floodplain dam of the Nizhegorodskaya hydroelectric power plant and field filtration observations revealed a strong drainage effect of the base on the filtration flow at several areas of the dam body. At the other areas, a high groundwater level position at the dam downstream and its outlet into the pipe drainage at the downstream were recorded. Substantiated by filtration calculations, the proposed repair of the drainage system consisted in designing open drainage along the dam axis and backfilling the territory at the downstream by 2.0 m that excludes impoundment of the territory without the pipe drainage.
 Conclusions: the following engineering solutions can be recommended for repairing earth dam drainage systems: construction of backfill drainage trenches in the dam downstream, new pipe drainage at higher elevations or an open drainage channel in solid reinforced concrete arranged along the axis of the dam. The proposed version of the pipe drainage repair provides for constructing an open drainage channel in solid reinforced concrete on a reverse filter with an arrangement of gravel-filled asbestos-cement pipes in the dam slopes and bottom. Such a design solution allows repairing the drainage system without dewatering and, if necessary, completely refusing the existing pipe drainage.

Application of a remote sensing-based soil water balance for the accounting of groundwater abstractions in large irrigation areas

The sustainability of groundwater abstractions for irrigation practices must be monitored to achieve a long-term equilibrium in aquifers. The accounting of irrigation water requirements in river basin management plans is commonly and mainly calculated by combining the average multiannual irrigated surface estimates and the unitary crop water requirements. However, remote sensing approaches allow water managers to incorporate more dynamic knowledge of a territory by monitoring irrigated crops. Hence, time series of biophysical products processed from Earth Observation data for 4 years (2010–2013) were incorporated into a remote sensing-based soil water balance to estimate spatially distributed irrigation water requirements on a monthly time scale over a semiarid environment, where agricultural practices greatly depend on groundwater resources. The simulated monthly water abstractions were then evaluated regarding monthly groundwater level changes recorded from a piezometric network. The results indicated that groundwater level changes on a monthly scale could be explained in more than 75% of the cases. Therefore, a simple remote sensing-based approach brings temporally and spatially distributed information of great practical value to river basin water managers according to their management necessities.

Improvement of water table interpolation and groundwater storage volume using fuzzy computations.

The water table is an important piece of data for hydrogeological studies, particularly as input data to groundwater simulation models. Since the accuracy of groundwater simulation models significantly depends on input data, this study highlights the application of fuzzy kriging to improve the accuracy of water table interpolation. The results of the fuzzy kriging approach are compared with common methods in water table interpolation like ordinary kriging, inverse distance weighting (IDW), and Thiessen polygon methods to justify the suitability of the fuzzy kriging. The Gilan and Zanjan plains, located in the northwest of Iran, are used as case study areas. The Gilan Plain is characterized by a dense and regular piezometric network and gentle hydraulic gradient. The longitudinal plain of Zanjan has a sparse and irregular piezometric network and steep hydraulic gradient. Since these plains have different piezometric network configurations, the sensitivity of the interpolation methods to the monitoring point configuration is analyzed. The cross-validation method is employed to validate the accuracy of interpolation methods in water table interpolation. In control points, the average of root-mean-square errors associated with groundwater water table values estimated using fuzzy kriging, ordinary kriging, IDW, and Thiessen polygon methods are obtained to be respectively 1.36, 1.93, 3.49, and 9.10 in the Gilan Plain and 13.60, 22.86, 32.30, and 59.81 in the Zanjan Plain. The results indicate that the fuzzy kriging technique has greater precision in comparison with other methods, especially under the conditions of the sparse piezometric network and steep hydraulic gradient. The results also demonstrate that the used methods generally have higher accuracy in the Gilan Plain with a regular piezometric network than in the Zanjan Plain. Furthermore, Thiessen polygon, IDW, and ordinary kriging methods overestimated water table in comparison with the fuzzy kriging method in our cases. This overestimation may cause large error values in subsequent calculations such as water budget and aquifer storage which play a major role in the appropriate management of water resources.

Proposed changes for post-closure monitoring of Etueffont landfill (France) from a 9-year survey

Environmental monitoring must be continued following landfill closure for at least 30 years according French Waste Disposal Law. The goal of this investigation was to verify whether measures taken with respect to surveillance and control of leachates, surface and ground water originated from closed landfill site in France are sufficient to ensure reliable long-term environmental monitoring. This study is based on the first nine years of the Etueffont landfill's post-closure phase, from 2002 to 2010. In 2007, the site's piezometric network has 17 piezometers. Four supplementary sampling points were also added in up- and downstream of Gros Près and Mont Bonnet Brooks. No raw leachate was discharged directly into the natural environment. Piezometric monitoring has been undertaken monthly. Groundwater and effluent discharges were sampled twice per year, in January and July, while surface water was sampled three times annually. By taking into account all of the monitoring parameters imposed by the Decree of 9 September 1997 amended, the recorded values were all lower than the strictest standards (non-applicable) at the end of monitoring (2005–2010). The discharge is therefore of a much higher quality than required. Several parameters were undetected in the surface waters since their levels were below analytical detection limits. The average purification efficiency observed between upstream (the source) and downstream (MB Brook), observed to be between 72 and 91%, shows just how well the receiving environment can purify contaminated waters by natural attenuation. The groundwater present throughout the monitoring period to be at concentrations below the standards for the following parameters: Total phosphorus, Total nitrogen, Escherichia coli (E. coli), As, Zn, Cd and Cr. In contrast, some excesses are occasionally observed for the organic parameters (TOC, COD and BOD). Thus, this study shows the flaws inherent in the environmental monitoring program imposed by the Decree of 9 September 1997. Consequently, the program has indeed been adapted to the monitoring of effluent discharges and surface water quality since the decree does set quality standards.

Where does infiltrated stormwater go? Interactions with vegetation and subsurface anthropogenic features

The practice of stormwater infiltration is widely used to reduce the amount of urban stormwater runoff delivered to drainage systems and receiving waters. In theory, the practice recharges groundwater, leading to increased urban stream baseflow. In reality, however, little is known about the fate of infiltrated stormwater. Because urban groundwater pathways are numerous and the interactions with subsurface infrastructure (e.g. trenches, pipes, etc.) are highly complex, the spatial and temporal variability of the contribution of infiltrated stormwater to baseflow is difficult to predict. We tracked the fate of infiltrated stormwater out of an 1800 m2 infiltration basin (3.5% of its 5-ha impervious catchment) using a network of piezometers for over three years. We found that groundwater levels downslope of the basin were increased (up to 4 m) while water levels in an array of reference piezometers lateral to the basin showed no change (dry at depths ranging 2–4 m). Monthly water balance calculations indicated that in summer, most of the infiltrated stormwater was evapotranspired by the vegetation downslope of the basin, and thus did not reach the receiving stream. In the colder months, some infiltrated stormwater did reach the stream as plant water use declined. Anthropogenic disturbances (a sewer pipe and stream re-alignment) interacted with the upper part of the plume of infiltrated stormwater, locally lowering the water table. The study provides evidence that the fate of infiltrated stormwater is complex, and that infiltrated stormwater does not always reach receiving streams as baseflow as is often assumed.

Monitoring induced denitrification during managed aquifer recharge in an infiltration pond

Managed aquifer recharge (MAR) is a well-known technique for improving water quality and increasing groundwater resources. Denitrification (i.e. removal of nitrate) can be enhanced during MAR by coupling an artificial recharge pond with a permeable reactive layer (PRL). In this study, we examined the suitability of a multi-isotope approach for assessing the long-term effectiveness of enhancing denitrification in a PRL containing vegetal compost. Batch laboratory experiments confirmed that the PRL was still able to enhance denitrification two years after its installation in the infiltration pond. At the field scale, changes in redox indicators along a flow path and below the MAR-PRL system were monitored over 21 months during recharge and non-recharge periods. Results showed that the PRL was still releasing non-purgeable dissolved organic carbon five years after its installation. Nitrate concentration coupled with isotopic data collected from the piezometer network at the MAR system indicated that denitrification was occurring in the saturated zone immediately beneath the infiltration pond, where recharged water and native groundwater mix. Furthermore, longer operational periods of the MAR-PRL system increased denitrification extent. Multi-isotope analyses are therefore proved to be useful tools in identifying and quantifying denitrification in MAR-PRL systems.

The effect of plant-soil treatment plant on the groundwater quality

The paper presents the impact assessment of the plant-soil treatment plant on the groundwater quality. The physicochemical composition of groundwater was analysed. The samples were collected form the piezometer network located in the irrigated area and around it. Water quality tests were carried out in 2014 with the frequency of the month. Changes in the physicochemical composition of groundwater were determined with reference to quality of domestic wastewater used for irrigation. The obtained results were also referred to groundwater parameters limits before the facility’s operation started. As a result of many years of exploitation the groundwater quality under the irrigated area has changed. The boundary of individual segments of wastewater treatment plant is clearly marked by the change in concentrations of the observed pollution indicators. The highest values of organic matter expressed by BOD and COD were observed in the groundwater the I segment (respectively 6.9 gO2·m-3 and 66.2 gO2·m-3). This was the results of a change in the irrigation regime. As the result of irrigation, an increase of nitrate (V) and nitrate (III) was also observed in comparison to their pre-operational values. Plant-soil treatment plant prove high effectiveness of work. However, due to their significant impact on the groundwater quality their operating should be gradually reduced.

Limitations on the role of the hyporheic zone in chromium natural attenuation in a contaminated urban stream

The urban hyporheic zone may offer natural attenuation potential for contaminants. This potential is contaminant-specific and may be spatially and temporally variable. The aim of this study was the assessment of the natural attenuation potential of the hyporheic zone of an urban stream receiving hexavalent chromium (Cr)-rich effluents from the historical land disposal of chromite ore processing residue (COPR) in Glasgow, Scotland. The evidence based approach involved the use of a network of multilevel piezometers for best capturing potential anoxic field conditions and fine-scale spatial gradients in solute concentrations of surface water and porewater. In-situ porewater sampling was integrated with sediment sampling and reach-scale monitoring of stream water quality. The results show a sharp decrease of total dissolved (filtered <0.45 μm) Cr concentrations at the surface water – sediment boundary in all profiles, from Cr mean values of 1100 μg l−1 in surface water to 5 μg l−1 in porewater. Chromium speciation analysis indicates that no Cr(VI) was detectable in the neutral pH, moderately reducing porewater, while it was the dominant species in surface water. Evidence of historical COPR detrital grains contributed to the total Cr concentrations (size fraction <150 μm) up to 8800 mg kg−1 in the streambed sediment. The abundance in the porewater of Fe (mean value = 1700 μg l−1), mainly as Fe(II), a natural electron donor for Cr(VI) reduction to Cr(III), indicates a high natural attenuation potential of the hyporheic zone for downwelling dissolved Cr, through Cr(VI) reduction to Cr(III) and the formation of Cr(III) solids of low solubility. Authigenic Cr-rich rims on particles also documented active Cr precipitation from solution in the fine sediments. Large short-term changes of stream stage and stream water composition were not reflected in the hyporheic conservative (chloride) and reactive solute composition. This result indicates only limited surface water infiltration and suggests that small advective exchange might limit the effectiveness of the hyporheic zone for enhancing Cr surface water quality at the reach-scale. This is supported by further evidence from preliminary surface water quality synoptic sampling which shows only moderate to low downstream decrease in surface water Cr concentrations. The surface water investigation needs to be supported by combined water quality-flow monitoring and to be extended to a wider range of temporal and spatial scales to corroborate the reach-scale findings.

EVALUATION OF STRESS-STRAIN STATE OF ROCK MASS

Abstract. A new method of determining the stress-strain state of the rocks without dropping its individual parts on the basis of combination of observations of the dynamics of piezometric level in special hydrogeological wells of pre-planned network and by the change in the diameter of wells measured by photo elastic sensors is proposed. With the beginning of the formation of the stress-strain state of the geological environment, the chaotic structure of hydro-geodynamic field(HGD-field) goes into the abnormal condition of a certain form, in accordance with the geometric shape and sizes of the geological structure. Closed lines of equal abnormal values of piezometric levels form geometric circular structures in the Central parts of which are observed their most anomalous values corresponding to the greatest extent of stressstrain state of rock massif. Within abnormal (disturbed) HGD-field is carried out the measurement of the diameters of the wells, fixed by photoelastic sensors which clarify the concrete stress-strain plot (voltages source) of the rock massif. Well drilled for measuring by photoelastic sensors of changes in their diameters, are arranged in the rock massif in a staggered manner, and the special hydrogeological well, drilled up to an isolated water system for the registration of anomalous (perturbed) HGD-field are locatedin two mutually perpendicular profiles, taking into account the geometric shape of the monitored rock mass. The combination of observations according to a pre-planned network of piezometers and wells with photoelastic sensors will allow to get a more accurate picture of the stress-strain state of the investigated deposits of rock without pass of its separate parts.

Abnormal trace element concentrations in a shallow aquifer belonging to saline reclaimed environments, Codigoro (Italy)

Geogenic trace element (TE) contamination is an upcoming concern. The present study reports the temporal and spatial variation of major ions and TEs in a shallow unconfined aquifer belonging to a complex marsh saline environment reclaimed in modern age and intensively cultivated. The use of intensive depth profiles in five different locations gave insights into groundwater and sediment matrix interactions. Data indicate that the dominant factor involved in determining the spatial variability of TE is the sediment–water interaction, while the temporal variation of TE is due to the organic matter content and to the water table oscillation, which in turn drive the groundwater redox status and the mobilization of some inorganic microconstituents, such as Fe and Mn. Despite that the anthropogenic input of TEs in groundwater from fertilizer sources cannot be undoubtedly ruled out, given the elevated TE background concentrations, the combined use of high-resolution sediment profiles, seasonal groundwater sampling and end-member analyses is a promising procedure to distinguish between anthropogenic metal contamination and geogenic contribution in reclaimed deltaic environments. Finally, this study underlines the need of having a dense piezometer network and to perform several monitoring campaigns to ensure that the temporal and spatial variability could be correctly represented and background values of TE confidently determined.

Groundwater salinization in arid coastal wetlands: a study case from Playa Fracasso, Patagonia, Argentina

The origin of the high salinity in the groundwater of a coastal wetland in an arid climate was studied in the Playa Fracasso marsh, located on the northwest coast of the extra-Andean Patagonia. Research was carried out by means of the design of a network of soil pits and short piezometers in the marsh and the surrounding landforms. Continuous fluctuations of the water table, in situ physical and chemical properties, major ions (Ca2+, Mg2+, Na+, K+, Cl−, SO4 2−, HCO3 −) and stable isotopes (18O and 2H) in groundwater, as well as soil salinity, were measured. The combined analysis of the hydrodynamics, the ion ratios rCa2+/rCl− and rMg2+/rCa2+ vs. rCl− and the isotopic composition made it possible to recognize an area within the high marsh in which the origin of groundwater is mainly marine and another in which the contributions are of mixed origin. By means of the analysis of rCl− vs. δ18O, a salinization process with no change in isotopic composition was identified. Its interpretation, together with those of the soil salinity profiles and the records of the fluctuations in electrical conductivity associated with extraordinary tides, was used to define a conceptual model of salinization which could be useful to understand other coastal wetlands under similar arid climatic conditions. It consists in a cyclical mechanism of evapotranspiration, precipitation, dissolution and transport of salts during tides.

Evaluation of river–aquifer interaction in the north part of Dezful–Andimeshk district, SW of Iran

The river and groundwater are significant components of hydrological cycle, and the interaction between these two water resources attracted a great attention recently. Over the years, several methods have been used for the study of the water exchanges between these resources. In this research, a combined approach including hydraulic head measurements, hydrochemistry, and water balance calculations is applied to the assessment of the river–aquifer interactions. The study area is located in the north part of the Dezful–Andimeshk district in the southwest of Iran. The Dez River is the major surface water body that interacts with groundwater in this area. The Dez dam has been constructed on this river in the northern part of the study area. In this study, a series of water measurements including river water stages and discharge monitoring at Dez dam site and Dezful hydrometric station, groundwater table measurement in the piezometric network, and chemical analysis of river and groundwater were carried out for the evaluation of river–aquifer interaction. In order to monitor river and groundwater in the study area, a monitoring network including a hydrometric station (near the Dezful city), 38 piezometers, and 23 water quality monitoring wells have been established by the Khuzestan Water and Power Authority (KWPA). Data of the monitoring network were used for the evaluation of temporal variation of river and groundwater interaction in this research. The discharge measurements of the Dez dam site and Dezful hydrometric station in a 47-year period (1964–2011) shows that the water volume is decreased between these two stations. In addition, examining the time series of river stage and groundwater fluctuations in the study area shows that the groundwater table and river water stage variations have similar patterns. This similar pattern is an observant indication of groundwater and surface water interactions that is confirmed by the interpretation of groundwater potentiometric map of the study area. Following these conclusions, the hydrochemical measurements also were used for the assessment of the Dez River and groundwater connectivity. The surveys showed the similar patterns in the temporal variation trends of chemical characteristics (especially chloride ion) of the Dez River and groundwater as a base for connectivity of these resources. For better assessment of the river–aquifer interaction, 69 groundwater samples were collected from the abstraction wells in August 2012. The physicochemical analysis results show the river influences the groundwater quality. That is, the amounts of electrical conductivity (EC), temperature, and anions such as chloride, sulfate, and nitrate show a notable decrease in river-adjacent wells. Finally, for the quantifying of river–aquifer exchange rate, a simple water balance was formulated. This water budget also confirmed the Dez River role in the hydrologic balance of the study area, and according to calculation, the water infiltration from the riverbed was estimated to be more than 8 % of the aquifer recharge. This research shows the losing nature of the Dez River and its influence on the underlying groundwater quality in the study area.