Search Results (15)

Basalt with columnar jointing can act as a good groundwater conductor. In areas with limited water resources in sedimentary rock, such as the Deccan Traps in India and the Columbia River basalt formations in Washington State (USA), large quantities of groundwater are abstracted from such basalt formations for drinking water supply and irrigation. The hydraulic properties of basaltic formations are difficult to quantify. To obtain a better understanding of their hydraulic properties, intensive field campaigns in Iceland were combined with a conceptual groundwater model in MODFLOW. The field experiments enabled us to derive the upper boundary conditions, like precipitation surplus, and obtain reliable ranges for the k_h (0.01–0.3 m d⁻¹) and k_v (0.01–10 m d⁻¹) of the basalt formations. The main objective was to test the concept of representative elementary volumes (REVs) for such basaltic regions. Precipitation excess for the Vestragil and Eystragil catchments was calculated by taking into account the orographic effect of precipitation. It was found that at higher elevations (600 m + msl) the precipitation was twice the amount compared to the base camp rain gauge at 100 m + msl. Calculated evapotranspiration (1–2 mm d⁻¹) is in line with the literature. In the MODFLOW model, best results were obtained when the top layer (organic soil, peat, and regolith) was considered to be most conductive (up to 10 m d⁻¹), with a gradual reduction in hydraulic conductivity with depth in the basaltic aquifers. This study shows that, when larger elementary volumes are used, a good model representation of basaltic regions can be created. Full article

Groundwater heat pump (GWHP) systems are acknowledged as renewable and sustainable energy sources that can effectively fulfill the heating and cooling requirements of buildings on a district level. These systems harness geothermal sources available at shallow depths. To ensure the long-term sustainability of the system, the thermally used water is generally reinjected into the aquifer, creating a thermal plume starting from the injection well. Over time, this thermal plume may reach the abstraction well in the long term, potentially leading to a reduction in system efficiency. The operation types have a significant impact on this matter, and their effects have not been extensively studied in the existing literature. Therefore, this study aims to determine the optimal operating configurations for the Northern Gateway Heat Network, a GWHP system established in Colchester, UK. In this study, four distinct operation types are considered: (1) continuous heating (actual system), (2) heating and recovery, (3) heating and cooling, and (4) aquifer thermal energy storage (ATES). The results indicate that ATES operation yields the highest thermal energy output due to its ability to benefit from stored energy from the previous operation. However, implementing the ATES system may encounter challenges due to factors such as well development, hydraulic conductivity, and hydraulic gradient. On the other hand, implementing heating and cooling operations does not require additional considerations and offers not only free cooling to buildings but also a delay in thermal feedback time. Full article

In the contemporary era, the exploitation of aquifers in the agricultural sector has become increasingly important. In response, researchers have directed their efforts towards the formulation of effective methodologies, with geophysical prospecting emerging as a fundamental tool in locating the best underground deposits. The magnetic prospecting technique can discriminate between different categories of rocks, which facilitates the localisation of geological contacts—an essential factor in determining the strategic location of boreholes, while electromagnetic time-domain prospecting helps in the definition of sedimentary strata. In particular, this process reveals the important influence of tertiary and metamorphic formations on the regional hydrogeological framework of the studied area. The variable yields recorded in the wells in the area that have yielded good results are a clear indication of the presence of aquifers. However, it is important to note that numerous wells have been drilled in this region that have yielded negligible or even zero flow rates. Prudent selection of the location and depth of boreholes is essential to ensure proper management of this resource. The use of drones equipped with magnetometers is essential to speed up the spatial mapping process. Empirical results corroborate the accurate classification of lithological units, thus facilitating the selection of sites for groundwater abstraction. These studies serve to validate initial hypotheses and profoundly enrich our understanding of the hydrogeological dynamics of the site, thus providing avenues for optimal and sustainable exploitation and future academic research. Full article

Among the well-known approaches for controlling seawater intrusion during extensive freshwater abstraction from coastal aquifers is the construction of subsurface dams. In the current research, the SEAWAT code is being implemented to examine the impact of groundwater extraction on the effectiveness of a damaged subsurface dam for controlling saltwater intrusion. Simulations were performed numerically to check impact of the subsurface dam height, dam location, well height, well location, abstraction rate, fracture aperture, fracture location, seawater density and fracture dimension on the effectiveness of subsurface dam as a countermeasure to prevent saltwater intrusion in coastal aquifers. Increasing the abstraction rate from 1 × 10⁻⁶ to 5 × 10⁻⁶ m³/s caused the seawater to advance more into the freshwater, and the loss of effectiveness increased. The minimum and maximum value of loss of subsurface dam effectiveness was recorded to be 34.6% to 93%, respectively, for the abstraction rates from the well equal 1 × 10⁻⁶ and 5 × 10⁻⁶ m³/s, consequentially. When the dimensionless value of well height location L_w/L_d is increased from 1.0 to 2.0, the effectiveness of the subsurface dam is reduced by around 20%. The findings demonstrate that the well location, well depth, abstraction rate, location of the dam, fracture aperture, and density of saltwater all affect the effectiveness impairment of the fractured subsurface dam for controlling saltwater intrusion. Decision makers could use findings of this research to better manage groundwater resources in coastal aquifers. Full article

Recent studies observed a correlation between estrogen-related cancers and groundwater atrazine in eastern Nebraska counties. However, the mechanisms of human exposure to atrazine are unclear because low groundwater atrazine concentration was observed in counties with high cancer incidence despite having the highest atrazine usage. We studied groundwater atrazine fate in high atrazine usage Nebraska counties. Data were collected from Quality Assessed Agrichemical Contaminant Nebraska Groundwater, Parameter–Elevation Regressions on Independent Slopes Model (PRISM), and water use databases. Descriptive statistics and cluster analysis were performed. Domestic wells (59%) were the predominant well type. Groundwater atrazine was affected by well depth. Clusters consisting of wells with low atrazine were characterized by excessive groundwater abstraction, reduced precipitation, high population, discharge areas, and metropolitan counties. Hence, low groundwater atrazine may be due to excessive groundwater abstraction accompanied by atrazine. Human exposure to atrazine in abstracted groundwater may be higher than the estimated amount in groundwater. Full article

Recently, groundwater resources in Egypt have become one of the important sources to meet human needs and activities, especially in coastal areas such as the western area of Port Said, where seawater desalination cannot be used due to the problem of oil spill and the reliance upon groundwater resources. Thus, the purpose of the study is the sustainable management of the groundwater resources in the coastal aquifer entailing groundwater abstraction. In this regard, the Visual MODFLOW and SEAWAT codes were used to simulate groundwater flow and seawater intrusion in the study area for 50 years (from 2018 to 2068) to predict the drawdown, as well as the salinity distribution due to the pumping of the wells on the groundwater coastal aquifer based on field investigation data and numerical modelling. Different well scenarios were used, such as the change in well abstraction rate, the different numbers of abstraction wells, the spacing between the abstraction wells and the change in screen depth in abstraction. The recommended scenarios were selected after comparing the predicted drawdown and salinity results for each scenario to minimize the seawater intrusion and preserve these resources from degradation. Full article

This study aims to investigate the impact of using untreated wastewater in irrigation. Different scenarios of management were applied by mixing it with treated wastewater or freshwater on groundwater quality. A hypothetical case study is presented. The numerical model of MODFLOW is used in the simulation by applying four stages (21 scenarios) including: different values of pumping rates, changing wastewater recharge rates, and a combination of the previous scenarios. Additionally, protection scenario for groundwater was applied by using different values of mixing of freshwater with wastewater. The simulation was carried out for the contamination of Chemical Oxygen Demand COD and the concentration reached 48.6 ppm at a depth of 25 m and 19.41 ppm at a depth of 50 m in the base case. The results showed a negative impact on groundwater quality had occurred due to increasing the pumping rates, wastewater recharge rates, and combination between two scenarios, which led to an increase of the contaminants in the aquifers. However, positive protection effects occurred due to mixing the wastewater with treated wastewater. The results of COD concentration in groundwater using treated wastewater reached 81.82, 77.88, 74.03, 70.12, and 66.15 ppm at a depth of 25 m and 53.53, 50.95, 48.43, 45.87, and 43.28 ppm at a depth of 50 m, at concentrations of 93, 88.52, 84.14, 79.7, and 75.19 ppm with constant pumping and recharge rates of 4320 m³/d and 547.5 mm/year, respectively. The using of treated wastewater could improve the groundwater quality to be used in the irrigation process and help to minimize groundwater contamination. Moreover, the abstraction of the groundwater should be optimized, and the qualities of wastewater should be constrained in agriculture to protect the groundwater quality. Full article

Lake Alboraj, located in southeast Spain, was declared natural Microreserve and included into European Natura-2000 Network due to its contribution to environmental heritage. Unfortunately, the ecological status of the lake has changed dramatically, mainly due to the lowering of water table caused by groundwater abstractions for irrigation. It is a permanent small karstic lake whose surface has reduced in the last decades to nearly the third part of its historical water level. The water column shows a marked seasonal oxycline, that splits an aerobic upper layer (epilimnion) from an anaerobic layer below (hypolimnion). Sequencing 16S rRNA gene amplicons and applying chemical tools at epilimnion, hypolimnion and sediment, showed a clear gradient in the bacterial community structure, which support the co-existence of assimilatory and dissimilatory microbial mediated reactions. Results allows to infer that microbial stratification could provide various physical and chemical environments at different depths in the water column related to biogeochemical reactions providing N-S-C- recycling processes. Full article

Since the coverage of piped water is still only 20.1% in Indonesia, many people rely on groundwater for drinking and daily use, although the quality of the groundwater is not well understood. This study evaluated the influence of the topography, well type, groundwater abstraction depth, sanitation facility type, and distance between the well and the sanitation facility on the groundwater quality. In addition, a possible household treatment system was investigated based on microbial removal efficiency and household acceptance. The results showed the groundwater abstraction depth and well type were the most important factors in controlling microbial contamination. The sanitation facility type, except small-scale sewer systems, and the distance from a well were not significantly correlated with E. coli concentration. A high microbial concentration was found in a flat area with predominantly shallow wells, latrines, and septic tanks because the topographic conditions determined the commonly used well types and groundwater abstraction depth. The RO + UV system was the only system that assured microbial safety of treated water. The chlorination and microfiltration systems had difficulty with chlorine-dosage adjustment and microbial removal, respectively. Raising public awareness of water quality problems was found to be important to improve acceptance of household treatment systems. Full article

Production landscapes depend on, but also affect, ecosystem services. In the Rejoso watershed (East Java, Indonesia), uncontrolled groundwater use for paddies reduces flow of lowland pressure-driven artesian springs that supply drinking water to urban stakeholders. Analysis of the water balance suggested that the decline by about 30% in spring discharge in the past decades is attributed for 47 and 53%, respectively, to upland degradation and lowland groundwater abstraction. Consequently, current spring restoration efforts support upland agroforestry development while aiming to reduce lowland groundwater wasting. To clarify spatial and social targeting of lowland interventions five clusters (replicable patterns) of lowland paddy farming were distinguished from spatial data on, among other factors, reliance on river versus artesian wells delivering groundwater, use of crop rotation, rice yield, fertiliser rates and intensity of rodent control. A survey of farming households (461 respondents), complemented and verified through in-depth interviews and group discussions, identified opportunities for interventions and associated risks. Changes in artesian well design, allowing outflow control, can support water-saving, sustainable paddy cultivation methods. With rodents as a major yield-reducing factor, solutions likely depend on more synchronized planting calendars and thus on collective action for effectiveness at scale. Interventions based on this design are currently tested. Full article

Groundwater contamination due to saltwater intrusion (SWI) has an extreme effect on freshwater quality. Analytical and numerical models could be used to investigate SWI. This study aims to develop an analytical solution to investigate SWI into coastal aquifers which was applied to a real case study at the Middle Nile Delta aquifer (MNDA). The study presented a new formula to predict the difference in depth of freshwater to seawater interface due to a change in boundary conditions. A Computer Program for Simulation of Three-Dimensional Variable-Density Ground-Water Flow and Transport (SEAWAT) is used for groundwater flow simulation and SWI and the results compared with the developed analytical solution. Four scenarios are considered in the study, including; the sea-level rise (SLR), reduction in recharge, over abstraction, and combination after 50 years (2070). The analytical solution gave good results compared to the numerical one where Equiline 1 intruded to 103 and 101.66 km respectively at the base case. The results also gave a good agreement between numerical and the analytical solution for SLR due to climate changes by 52.80 cm where the Equiline 1 reached to 105 and 103.45 km. However, the reduction in aquifer recharge by 18.50% resulted in an intrusion for the Equiline-1 to 111 and 108.25 km from the shoreline. Over pumping due to the increase in population by 89% has increased the SWI to reach 121,110.31 km, while it reached 131 and 111.32 km at a combination of the three scenarios, which represents the highest threatening scenario. Also, the difference between the two solutions reached 1.30%, 1.48%, 2.48%, 8.84%, and 15.02%, respectively for the base case and four scenarios. For the current case study, the analytical model gave good results compared to the numerical one, so that the analytical solution is recommended for similar studies, which could save the time and capabilities of computer required for the numerical solutions. Full article

Diffuse nitrogen (N) pollution from agriculture in groundwater and surface water is a major challenge in terms of meeting drinking water targets in many parts of Europe. A bottom-up approach involving local stakeholders may be more effective than national- or European-level approaches for addressing local drinking water issues. Common understanding of the causal relationship between agricultural pressure and water quality state, e.g., nitrate pollution among the stakeholders, is necessary to define realistic goals of drinking water protection plans and to motivate the stakeholders; however, it is often challenging to obtain. Therefore, to link agricultural pressure and water quality state, we analyzed lag times between soil surface N surplus and groundwater chemistry using a cross correlation analysis method of three case study sites with groundwater-based drinking water abstraction: Tunø and Aalborg-Drastrup in Denmark and La Voulzie in France. At these sites, various mitigation measures have been implemented since the 1980s at local to national scales, resulting in a decrease of soil surface N surplus, with long-term monitoring data also being available to reveal the water quality responses. The lag times continuously increased with an increasing distance from the N source in Tunø (from 0 to 20 years between 1.2 and 24 m below the land surface; mbls) and La Voulzie (from 8 to 24 years along downstream), while in Aalborg-Drastrup, the lag times showed a greater variability with depth—for instance, 23-year lag time at 9–17 mbls and 4-year lag time at 21–23 mbls. These spatial patterns were interpreted, finding that in Tunø and La Voulzie, matrix flow is the dominant pathway of nitrate, whereas in Aalborg-Drastrup, both matrix and fracture flows are important pathways. The lag times estimated in this study were comparable to groundwater ages measured by chlorofluorocarbons (CFCs); however, they may provide different information to the stakeholders. The lag time may indicate a wait time for detecting the effects of an implemented protection plan while groundwater age, which is the mean residence time of a water body that is a mixture of significantly different ages, may be useful for planning the time scale of water protection programs. We conclude that the lag time may be a useful indicator to reveal the hydrogeological links between the agricultural pressure and water quality state, which is fundamental for a successful implementation of drinking water protection plans. Full article

Groundwater has supported 70% of the water supply at the Lower Kelantan River Basin (LKRB) since the 1930s and demand for groundwater increases annually. Groundwater has been abstracted from shallow and deep aquifers. However, a comprehensive study on groundwater recharge estimation has never been reported. This study evaluated various methods to quantify recharge rate using chloride mass balance (CMB), water table fluctuation (WTF), temperature–depth profiles (TDP), and groundwater modelling coupled with water balance (GM(WB)). Recharge estimation using CMB, WTF, TDP, and GM(WB) showed high variability within 8% to 68% of annual rainfall. CMB is range from 16% to 68%, WTF 11% to 19%, TDP 8% to 11%, and GM(WB) 7% to 12% of annual rainfall, respectively. At 11%, recharge from GM(WB) was the best method for estimation because the model was constructed and calibrated using locally derived input parameters. GM(WB) is the only method involved with calibration and validation process to reduce the uncertainty. The WTF method based on long-term hydrological records gives a reasonable recharge value, in good agreement with GM(WB) and these methods can be paired to ensure the reliability of recharge value approximation in the same ranges. Applying various methods has given insight into methods selection to quantify recharge at LKRB and it is recommended that a lysimeter is installed as a direct method to estimate recharge. Full article

Historical trends of the annual maximum and minimum depths of groundwater tables (GWTs) that are indicative of sustainability status of groundwater resources still remain inadequately studied in the North-West (NW) hydrological region of Bangladesh. This study aimed at evaluating long-term (1985–2016) trends of GWTs of 350 monitoring wells and their impacts on groundwater development status in that region. The trends of the annual maximum and minimum depths of GWTs were determined and evaluated by using MAKESENS trend model. The functionality of suction-mode pumps was identified based on the annual maximum depth of GWTs. A significant (p ≤ 0.05) falling trend of the annual maximum depths of GWTs in 65.71% of the monitoring wells revealed continuous increase in groundwater abstraction. A significant falling trend of the annual minimum depths of GWTs in 69.71% of the monitoring wells revealed groundwater mining. GWTs remained below the suction limit (≈6 m) for 3 to 6 months in each year in 59.72% of the monitoring wells and for the whole year in 15.14% of the monitoring wells, making suction-mode pumps inoperable and creating domestic water scarcity. Therefore, groundwater extraction in many locations has become unsustainable, and hence, measures such as artificial recharge to the aquifers and water-saving technologies are needed to prevent groundwater mining. Full article

Studies on the recovery of head and total dissolved solids (TDS) in a coastal aquifer system from long-term pressure depressions because of groundwater abstraction (e.g., pumping) is essential for freshwater protection and seawater-intrusion prevention in coastal areas. A 2D numerical model is applied in this paper to investigate the recovery of head and TDS in terms of long-term behavior considering low permeability media. The spatial behavior of the transition zone (TZ), which was chosen as an indicator, was studied in depth with respect to the participant hydraulic and solute-transport characteristics of the aquifer. The sensitivity of the TZ to different aquifer parameters was evaluated. The hydraulic conductivity and rainfall recharge are the two most sensitive factors that affect the location of the TZ in homogeneous cases, and the spatial structure of the hydraulic conductivity field, namely, the correlation length and variance, largely influences the sensitivity of the TZ. The required time for the complete recovery of head in the heterogeneous cases is much shorter than that in the homogeneous cases, but the TDS recovery takes much more time. When the recovery of head is 90%, low porosity and large specific storage play an important role in the location of the TZ compared to other parameters, except for the hydraulic conductivity and recharge rate. The results of this study are meaningful for coastal-aquifer management and may be instructive in the restoration of coastal areas that have experienced seawater intrusion because of the long-term overexploitation of fresh groundwater. Full article