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Mountain headwater streams are important freshwater sources, but they are mostly intermittent and highly susceptible to climate change. This paper examines the sustainability of augmented freshwater availability in mountain headwater streams for water supply under baseline and future climate change scenarios using an integrated modeling approach. The climate change data in the 2040s (2030–2059), under Representative Concentration Pathway 4.5 and 8.5 scenarios, were downscaled for the impact assessment. In the region, climate change raises the average precipitation by 5–7% and the temperature by 13–15% in the 2040s. SWAT–MODFLOW model, integrating Soil and Water Assessment Tool (SWAT2012) and finite-difference Modular Groundwater Flow (MODFLOW) models in a single package, was used to assess the water balance. Results show that extracting a minimum of 16.2 m3/day from the sand storage and 30 m3/day from the aquifer was possible without affecting the groundwater table and water yield. The average annual catchment recharge was 6% of the precipitation under the baseline simulation. Climate change is projected to reduce the average water yield and groundwater recharge by 26% and 19%, respectively. However, the water supply-demand is significantly small compared to the exploitable rate of water in the area. This study was based on limited data, and therefore the findings need to be interpreted with caution, though the model output was validated using satellite products. Construction of a series of sand dams is suggested to maximize the benefit under the potential climate change and water supply-demand increase.

Alpine wetlands are hotspots of carbon (C) storage and methane emission, and they could be key contributors to global warming. In recent years, rapid warming has lowered the water table in alpine wetlands on the Tibetan Plateau, concurrent with intensified nitrogen (N) deposition via anthropogenic activities. We carried out a field experiment to investigate the ecological impacts of these two factors on soil bacterial and functional communities, which are essential drivers of greenhouse gas emissions. Nitrogen amendment alone decreased the phylogenetic alpha-diversity of bacterial communities which could be offset by lowered water table. In contrast, microbial functional alpha-diversity, revealed by a high-throughput microarray, remained unchanged. Both bacterial and functional beta-diversity responded to lowered water table, but only bacterial community responded to N amendment. The alpha-Proteobacteria, beta-Proteobacteria, and Bacteroidetes were the major responsive bacterial lineages, and C degradation, methanogenesis, alkaline shock, and phosphorus oxidation were the major responsive functional processes. Partitioning analysis revealed that N amendment changed bacterial community structure mainly via species loss processes but did not affect bacterial functional communities, with soil pH and ammonium as the key factors influencing changes in bacterial community structure. Conversely, lowered water table altered bacterial and functional communities through species substitution processes linked to soil pH and soil moisture. According to our results, the response mechanisms of microbial communities to lowered water table and N amendment are fundamentally different in alpine wetlands.

Since 2016 we have studied the largest interdunal wetlands/slack lying within a deflated parabolic dune east of Lake Michigan. Geologic cross-sections show ∼ 15 m of sand and gravel beneath the dunes, creating an aquifer hydraulically connecting Lake Michigan-Huron (MH) with the water table/shallow groundwater influencing the slack. Lake Michigan-Huron (MH) water levels have risen ∼ 1 m from 2016 to 2020, increasing water levels within and around the slack ∼ 1 m. Color-infrared images and vegetation quadrat sampling show water appearing, then significantly expanding with the main slack and upland/dune vegetation transitioning to wetland vegetation in response to this rise. Monitoring well data show slack water levels rise in spring as Lake MH rises. Levels drop as the growing season begins while Lake MH continues to rise through summer. Short-term slack water level increases occur due to local rain events, but significant water level declines follow due to evapotranspiration. Slack water levels begin to rise again in late summer and into fall as the end of the growing season arrives, evapotranspiration decreases, and heavier, more frequent rain events occur. Together, these factors push slack water levels to their highest point of the year while Lake MH levels are decreasing. In late fall–winter, slack water levels drop in concert with Lake MH levels. Climate change effects, increased transpiration from higher temperatures, summer drought, and greater variability in lake level fluctuations, may make it more difficult to maintain wet growing conditions for hydrophytic vegetation. Hence, climate change poses risks to the existence of this imperiled ecosystem.

We address the significant knowledge gap for groundwater pollution in Africa methods by assessing groundwater pollution risk at the African scale. To do so, we compiled the most recent continental-scale information on soil, land use, geology, hydrogeology, and topography in a Geographical Information System at the resolution of 15 × 15 km and the 1:60 000 000 scale. We produced a vulnerability map by using the generic DRASTIC vulnerability indicator. This map revealed that groundwater is highly vulnerable in Central and West Africa groundwater basins, where the water table is shallow. In addition, very low vulnerability classes are found in the large sedimentary basins of Africa deserts where groundwater is situated in very deep aquifers. The generic groundwater pollution risk map is obtained by overlaying the DRASTIC vulnerability indicator with current land use. The northern, central, and western parts of the African continent are dominated by high vulnerability classes and very strongly related to water table depths and the development of agricultural activities. Given the availability of data, we concentrate first on nitrate vulnerability mapping. To this end, groundwater nitrate contamination data are compiled in literature using meta-analysis technic and used to calibrate as well linear and nonlinear statistical models; the latter performing much better as compared to simple linear statistical models. This study will help to raise awareness of the manager's International Basin Authorities or Transboundary Basin Organizations in Africa and in particular on transboundary groundwater pollution issues.

Forested wetlands with high water tables are sensitive to disruption from harvesting yet support commercially desired tree species like northern white-cedar. Winter harvest was conducted in Maine, ...

Floodplains cover only 6% of the Earth’s surface. Connectivity occurs in multidirectional patterns in riverbeds, throughout both the drainage paths of the tributaries and the areas contiguous to the riverbed. This study discusses the variations in the levels of the water table as a component of a spatiotemporal representation for evaluating the importance of floodplains as hydric regulatory elements, and the application of this knowledge for developing techniques for the renaturalization of water functions to produce ecosystem services. We measured the variation in the water table level in a floodplain of the Paraiba do Sul River (southeastern Brazil), whose 77 floodplains occupy only 3.87% of the basin and present a high potential for the renaturalization of their water functions. The litho-structural control point (LSCP) is situated in the river channel and mark the end of the floodplain. Areas near the LSCP remain continually saturated, storing water and contributing to dry-season hydrographs. Areas up to 4400 m away from the LSCP perform hydric regulation, storing water from floods of the riverbed and reducing its flow downstream. Areas up to 7500 m away from the LSCP have an increased absorption potential. These three areas operate differently and integrally in absorbing floodwaters and recharging the water table, influencing the increase in minimum flows in the riverbed. The understanding of the functions of these sectors enables the design of objective measures that safeguard and increase the likelihood of the renaturalization of the hydrological functions of floodplains.

Run-off water and groundwater carried out the most important cycle between flora and fauna. The Rushikulya river basin is a particular region where one can study the profound behaviour of groundwater, river run-off and seawater. The river system influences the population in Ganjam District. The flow system of the river basin is profoundly affected by its topography and regional tectonics scenario. Understanding the topographical influence, morphometry tools subsequently play vital role and provide knowledge about river basin. Here in this study, the depleting groundwater condition in Rushikulya river basin is correlated with morphometric indices and used to assert its influence. Periodic groundwater level data set is used to assert the condition in the region from 1995 to 2015. The condition of groundwater table and recharge zone is traced with the help of GIS tools. Further recharge zones and depleting zones for groundwater are taken into consideration in the study. The influence of salty water of the Bay of Bengal is also considered in the study to state the contamination in groundwater. This study shows huge depletion in groundwater conditions during 1995–2015 in the western and northern regions of the basin. The eastern part shows depletion in groundwater during 1995–2005 but enhancement during 2010–2015, which may have influence of transgressing seawater. The pre-monsoon and post-monsoon groundwater conditions show Rushikulya river channels are influencing groundwater recharge. Due to this Aska region gets a better groundwater recharge condition as it is situated near the tri-junction of tributaries. Besides, the impact of land use and land cover also played a vital role with the inducements of groundwater depletion within the basin.

Groundwater is one of the most valuable water resources in the world in terms of quantity and quality. Therefore, their protection as an important issue should be considered by the operating managers. Among the types of existing groundwater aquifers, the coastal aquifers need more protection because they could be contaminated by salt in the result of seawater intrusion. Their protection is a priority based on an optimal and comprehensive management model. Increasement of demands in these areas, especially in recent years, requires sustainable and optimal management as one of the main objectives for long-term operation in the future. In order to meet this purpose, a simulation-optimization model of Bandargaz-Nokandeh coastal groundwater system that located in the north of Iran was proposed by the employment of the Groundwater Modeling System (GMS) numerical model and the Non-Dominate Sorting Genetic Algorithm-II (NSGA-II) multi-objective evolutionary optimization algorithm. In this study based on the quantitative simulated groundwater model; two managerial issues have been examined; including the control of water-table drawdown and sustainability of extraction from the wells in this aquifer. By combining these two models and implementing them, optimal withdrawal scenarios which examines different aspects of the study objectives, have been extracted. Regarding the decision-making methods of Simple Additive Weighting (SAW), Gray Relational Analysis (GRA), and Berda Aggregation method (BAM), the best scenario was determined among the points located on the optimal trade-off curve. The results show that implementations of management strategies to create a sustainable development of the Bandargaz-Nokandeh coastal aquifer, has led to a 48.45 percent decrease in water withdrawal. Also, the comparison of the groundwater table level (GWTL) under the two existing and optimal operating conditions shows a 29.54% reduction (monthly average) in the area of aquifer that contain drawdown in the GWTL. This reduction varies from 1.43% in October 2011 to 59.22% in September 2012. Based on this optimal operation policy, the consequences of excessive withdrawal, and more than the natural capacity of the aquifer, could be compensated. Besides that, in order to the sustainable development of the aquifer can be controlled the amount of water extracted from operation wells.

A combined survey including infrared thermography (IRT) and field-laboratory tests were conducted to analyze the thermal responses and thermal properties of loess on a landslide-prone loess slope in the Heifangtai terrace in Northwest China aiming at preliminarily demonstrating the potential of IRT as a complementary technique to the investigation of irrigation-induced loess landslides. Multitemporal thermographic surveys corresponding to various solar radiation intensities during the afternoon were carried out on the landslide-prone loess slope. Accordingly, the spatiotemporal distribution of the thermal responses within the observed slope surface was analyzed qualitatively and quantitatively. Meanwhile, field and laboratory investigations were also performed on the thermal properties of different landslide materials. The results indicate that loess, a landslide-prone deposit that usually has a relatively high water content, exhibits different thermal properties and anomalies, including a lower surface temperature and greater thermal inertia, compared to surrounding zones without landslides. The groundwater table and corresponding seepage line could also be obtained by determining the potential boundary between the thermal response distribution of landslide scarps and that of saturated deposits in the presence of landslides. The results of these investigations are expected to provide insight for future endeavors combining infrared thermography with other efficient survey methodologies (e.g., InSAR, which can monitor the active displacement of a loess slope) to evaluate the activity of this kind of excessive irrigation-induced loess landslide.

The area around the town of Mangalia in Southern Dobrogea (Romania) hosts a unique karst landscape represented mostly by large collapse dolines. Around one of these collapse dolines, named Obanul Mare, there is a peculiar morphology of hillocks that resemble the tropical labyrinth-cone karst but on a much-reduced scale. This peculiar relief was hypothesized to be residual, resulting from the ceiling collapse of a two-dimensional maze cave. This type of maze caves form when the water table remains stable for long periods of time, allowing groundwater to dissolve the carbonate host rock along all available discontinuities. The Obanul Mare structure contains a 200 m long cave (Movile cave), whereas a few kilometers away we can find Limanu maze cave, whose passages sum up to more than 3,500 m. Because the existence of a former maze cave is difficult to demonstrate, in this study we took an indirect approach to this issue. We hypothesize that if there was a maze cave and its ceiling collapsed, then the inner walls would be left standing as pillars. Subsequent subaerial evolution of these pillars would create slopes that would incline towards the former cave passages. By quantifying the slope aspect from a high-resolution digital surface model, we would be able to identify the direction of the original passages, hence the main hypothetical fracture lines along which those passages formed. By comparing these orientations to those of local fractures (deduced from the nearby valley and doline axes), as well as with the orientations of the Movile Cave passages, we found that they are well correlated. This strengthens the hypothesis that the hillocky terrain is tectonically conditioned and that it might be the result of cave ceiling collapse, bringing more information on the existence of maze caves in the region. La zone autour de la ville de Mangalia dans le sud de la Dobrogea (Roumanie) abrite un paysage karstique unique représenté principalement par de grandes dolines effondrées. Autour de l'une de ces dolines d'effondrement, appelée Obanul Mare, il existe une morphologie particulière de buttes qui ressemble aux karsts à cône labyrinthiques tropicaux, mais à une échelle très réduite. Au sein de ce travail, nous proposons l'hypothèse que ce relief particulier était résiduel, résultant de l'effondrement du plafond d'une grotte labyrinthe bidimensionnelle. Ce type de grottes labyrinthiques se forme lorsque la nappe phréatique reste stable pendant de longues périodes, permettant aux eaux souterraines de dissoudre la roche carbonatée hôte le long de toutes les discontinuités disponibles. La structure Obanul Mare contient une grotte de 200 m de long (grotte Movile), tandis qu'à quelques kilomètres de là se trouve la grotte Limanu, dont les passages totalisent plus de 3 500 m. Parce qu'il est difficile de démontrer l'existence d’une ancienne grotte-labyrinthe, dans cette étude, nous avons adopté une approche indirecte de la question. Nous émettons l'hypothèse que s'il y avait une grotte-labyrinthe et que son plafond s'effondrait, alors les murs intérieurs resteraient debout tels des piliers. Les phases d’érosion subaérienne postérieures de ces piliers créeraient des pentes qui s'inclineraient vers les anciens passages de la grotte. En quantifiant l'aspect de la pente à partir d'un modèle de surface numérique à haute résolution, nous pourrions identifier la direction des passages d'origine, d'où les principales lignes de fracture hypothétiques le long desquelles ces passages se sont formés. En comparant ces orientations à celles des fractures locales (déduites des axes de vallées voisines et dolines), ainsi qu'avec les orientations des passages de Movile Cave, nous avons trouvé qu'elles sont bien corrélées. Cela renforce l'hypothèse selon laquelle le terrain vallonné est conditionné tectoniquement et qu'il pourrait être le résultat de l'effondrement du plafond de la grotte, apportant plus d'informations sur l'existence de grottes labyrinthiques dans la région.

Stream restoration, such as channel reconfiguration and riparian zone revegetation, is increasing in response to aquatic impairment in agroecosystems. Though riparian zones effectively remove nitrogen (N), conditions that foster nitrate (NO3−) removal (e.g., soil saturation, low oxygen, available carbon) may facilitate the release of soluble reactive phosphorus (SRP) and greenhouse gases (GHGs—carbon dioxide [CO2], methane [CH4], and nitrous oxide [N2O]). In this study, water quality and GHG fluxes were quantified seasonally at agricultural restored, unrestored, and forested riparian zones via networks of wells and static chambers. Carbon dioxide comprised the majority of GHG emissions, and CO2 fluxes were lower at the restored site than the forested site (medians: 0.71 g C m−2 day−1 and 1.29 g C m−2 day−1, respectively). The restored site was a net CH4 source (median: 1.20 mg C m−2 day−1), while the other sites were net CH4 sinks (medians: − 1.00 to − 1.76 mg C m−2 day−1). Sites had comparable N2O emissions. Subsurface SRP was lower at the restored than unrestored agricultural sites, while median NO3− removal efficiency was higher (restored: 91%, unrestored: 35–66%). Over time, NO3− removal and CO2 fluxes increased post-restoration. Methane emissions were elevated when the restored riparian zone was a CO2 and N2O sink and NO3− removal was high. Despite variability within and between sites, seasonal conditions (temperature, water table height, precipitation) and site characteristics (geomorphology, soils) remained key explanatory variables for riparian N removal and GHG release. Overall, riparian restoration may promote N removal without increasing total GHG emissions.

Due to financial wherewithal, only shallow wells, which are extremely prone to seasonal groundwater decline, are constructed in the study area. Generally, new groundwater wells are designed to follow the criteria of the old wells, which may be vulnerable to substantial groundwater depletion through water-level decline. Going by this, newer groundwater wells constructed near older ones are 100% susceptible to the uninvestigated depletion associated with the older ones. The method used integrates vertical electrical sounding (VES) technique employing the Schlumberger electrode configuration, which measured the resistivity of geologic layers, depths and thickness with hydrogeological information, which constrained the VES interpretation. The aim was to check the spread of groundwater depth–water table ratios for the shallow aquifers. The 1-D resistivity analysis shows that the topsoil/motley topsoil has resistivity ranging from 71.8 to 1964.1 $$\Omega m$$ and mean 586.9 $$\Omega m$$ , while its depth ranges between 0.5 and 11.3 m with mean value of 2.8 m. In layer 2, while the resistivity spans between 71.3 and 1488.6 $$\Omega m$$ with mean value 444.6 $$\Omega m$$ , the depth and thickness, respectively, have a range and mean value of 2.0–170.4 m and 41.9 m and 3.4–112.2 m and 41.0 m. The third layer resistivity ranges from 7.5 to 2332.5 $$\Omega m$$ with mean value of 797.2 m. The depth of burial and the thickness of the third layer, respectively, have mean of 63.0 m and 74.6 m and range of 40.3–106.3 m and 50.1–115.6 m. The fourth layer penetrated by current at 150 m half of current electrode separation has undefined thickness and depth with respective resistivity range and mean of 25.3–2385.3 $$\Omega m$$ and 508.4 $$\Omega m$$ . Based on the resistivity results and nearby borehole data, sizeable numbers of borehole in the area have depths (between 40 and 80 m) that are remarkably greater than the water table depths (1.4–37.6 m). A few boreholes have depths that are sparingly greater than water levels and by the present climate change; they are not likely to be depleted by virtue of water-level declines as the well depth–water table depth ratios are still sustainable to ward off the depletion associated with water-level decline. The results indicate the spatial spread of shallow hydrogeological units as well as the water-level architecture, which is believed to provide useful information that will complement lithological logs while planning for newer groundwater well development in the area.

Groundwater samples from Kapurthala (45), Jalandhar (70), and Hoshiarpur (70) districts from northern Punjab, India, were studied for seasonal variation (pre-monsoon and post-monsoon) of uranium distribution and physicochemical parameters, quality and suitability for drinking purposes, source apportionment, and health risks. The average uranium concentration (in μg L−1) in Kapurthala, Jalandhar, and Hoshiarpur districts was 12.7, 18.8, and 7.0, respectively, in pre-monsoon and 8.0, 17.3, and 5.6, respectively, in post-monsoon. In both seasons, uranium concentration was below WHO limit (30 μg L−1) in more than 90% of groundwater samples, and it was found to exhibit positive correlation majorly with TDS, EC, and total alkalinity. Principal component analysis revealed dissolution of rocks/minerals contributing to mineralization of associated aquifers in addition to some anthropogenic activities such as excessive application of fertilizers/pesticides and dumping of domestic waste followed by their seepage into the groundwater table. All groundwater samples fall in very good to good drinking groundwater quality and its quality is more improved in post-monsoon season owing to dilution of various inorganic salts during groundwater recharge in monsoon season. Average Hazard Index (HI) values due to ingestion of U, F−, and NO3− via drinking water for both adults and children were found to be marginally greater than safe limit of 1 with major contribution from F−. It is advisable to local government/public that regular monitoring of groundwater and proper management policies or strategies should be adopted followed by their implementation to control groundwater pollution in three districts.

To improve the accuracy of hydrological simulations in the groundwater overexploitation zone of North China, it is necessary to study the characteristics of shallow aquifer recharge on daily scale. Three shallow aquifer recharge indices were used to quantify shallow aquifer recharge in two ways. The recharge coefficient was used to quantify the amount of shallow aquifer recharge. The recharge duration and water table rise coefficient were used to quantify the recharge temporal process. The Spearman rank correlation coefficient and regression analysis were used to determine the relationships between aquifer water table depth (WTD), rainfall, and shallow aquifer recharge. The Jiangjiang River Basin, a tributary of the Haihe River, was selected as the study area. The results showed that the recharge coefficient first increased, then decreased, and finally leveled off as WTD increased. When WTD was between 5 and 6 m, the recharge coefficient reached its maximum (approximately 0.3). When WTD was greater than 10 m, the recharge coefficient remained stable (around 0.12). With regard to the sources and forms of recharge, preferential flow was dominant in the areas near the extraction wells. In contrast, plug flow became dominant in the areas distant from the wells. With the reduction of rainfall duration, the proportion of preferential flow contributing to aquifer recharge increased. With the increase of rainfall amount, the duration of aquifer recharge lengthened.

An improved understanding of the relationships among vegetation, groundwater level, and microtopography is crucial for making well-informed management decisions in areas with shallow groundwater resources. We measured plant species abundance/composition and richness in relation to depth to groundwater (DTW) and microtopography in Owens Valley, California, particularly in areas where DTW ranged from 0 to 4 m. Sampling occurred along 67 vegetation transects across three community types. Relationships between DTW and community composition were evaluated using non-metric multidimensional scaling (NMS), while non-parametric multiplicative regression was used to relate DTW and microtopography to species abundance. The dominant gradient in species composition (NMS Axis 1) explained ~51% of variation in our distance matrix and was most strongly associated (r = 0.55) with DTW. The graminoids Juncus arcticus, Leymus triticoides, and Distichlis spicata had strong affinities toward areas with the shallowest DTW ( 2.0 m). Variation in microtopography affected species abundance and increased species richness for vegetation communities at either extreme of the water table gradient, shallow, and deep DTW but not the intermediate DTW. Findings indicate that desert plant communities from shallow aquifers have adapted to different DTW and microtopography conditions and that considering those adaptations may be important to manage groundwater and vegetation resources in these areas.

Artificial groundwater recharge is an important component of water resources management in arid areas. Knowledge of the surface-water/groundwater interaction in a stream–aquifer system is important for sustainably managing the aquifer and obtaining the expected environmental benefits. In this study, an analytical solution of the linearized one-dimensional Boussinesq equation was obtained by using the Laplace transform; then, improved analytical models of multistage recharge were constructed on the basis of the spreading effect and delay effect to model the multiyear water-table fluctuations in a homogeneous, isotropic, unconfined aquifer under intermittent artificial recharge conditions. In addition, sensitivity analyses were performed to assess the responses of the water-table fluctuations to changes in each controlling hydrogeological parameter. To further validate the proposed method, the analytical models were applied to estimate the multiyear water-table fluctuations in the intermittent artificial groundwater recharge basin of the downstream of Tarim River, northwestern China. The results indicated that the analytical solutions and improved analytical models, which utilize the variation in the water table as a boundary condition, can explain the rise and fall of the water table within the unconfined aquifer. The accuracy of the simulation results was tested through a comparison with observations, and the results demonstrated that the models can effectively reflect the water-table fluctuations under transient recharge, spreading recharge and multistage recharge conditions. These findings can provide a theoretical basis and references for studying and modeling the water-table fluctuations under intermittent artificial recharge conditions spanning multiple years.

Wetland CH4 emissions have been demonstrated to be more sensitive than wetland CO2 emissions to increasing temperatures, which may result in a greater relative contribution of CH4 to total GHG emissions under climate warming. However, it is not clear whether this greater sensitivity occurs globally across diverse hydrologic regimes. Here, we evaluate the temperature dependence of CO2 and CH4 emissions on water table depth using a global database and show similarities in the temperature dependence of CO2 and CH4 emissions. A lower water table is associated with a decrease in the temperature dependence of CH4 emissions and a higher water table has the opposite effect. Water table depth does not affect the temperature dependence of CO2 emissions. Our findings suggest the stimulatory effect of increasing temperature on wetland CH4 emissions may not always be stronger than that on CO2 emissions and depends on the wetland water table. Climate change may result in larger releases of CH4 than CO2 from wetlands as CH4 emissions seem to be more sensitive to temperature. Globally, CO2 and CH4 emissions show a similar temperature dependence but this is modulated by wetland water table depth, which affects CH4 (but not CO2) emissions.

There are numerous valley farmlands on the Chinese Loess Plateau (CLP), where suffers from low soil quality and high risk of soil salinization due to the shallow groundwater table and poor drainage system. Currently, research on the evolution processes and mechanisms of soil quality and salinization in these dammed-valley farmlands on the CLP is still inadequately understood. In this study, three kinds of dammed-valley farmlands in the hilly-gully areas of the northern CLP were selected, and the status of soil quality and the impact factors of soil salinization were examined. The dammed-valley farmlands include the new farmland created by the project of Gully Land Consolidation, the 60-a farmland created by sedimentation from check dam, and the 400-a farmland created by sedimentation from an ancient landslide-dammed lake. Results showed that (1) the newly created farmland had the lowest soil quality in terms of soil bulk density, porosity, soil organic carbon and total nitrogen among the three kinds of dammed-valley farmlands; (2) soil salinization occurred in the middle and upper reaches of the new and 60-a valley farmlands, whereas no soil salinization was found in the 400-a valley farmland; and (3) soil salinization and low soil nutrient were determined to be the two important factors that impacted the soil quality of the valley farmlands in the hilly-gully mountain areas of the CLP. We conclude that the dammed-valley farmlands on the CLP have a high risk of soil salinization due to the shallow groundwater table, alkalinity of the loessial soil and local landform feature, thus resulting in the low soil quality of the valley farmlands. Therefore, strengthening drainage and decreasing groundwater table are extremely important to improve the soil quality of the valley farmlands and guarantee the sustainable development of the valley agriculture on the CLP.

Water Phase Inclination is an innovative theory for hydraulic conductivity and determination of vadose zone overlying shallow water table systems. It was originated and analytically derived from Darcy's Law and based on some physio-mechanical properties of soil. Al-Musayab area of 176 Km2 at Mesopotamian region, mid-Iraq was undertaken as a case study. It consists of unconsolidated quaternary deposits and is usually finer-grained than the underlying pebbly sandstone with Mediterranean weather. The Experimental part was divided into field tests which include double ring infiltrometer tests, water table depth measurements and sampling of 32 undisturbed soil samples of surface layers scattered over the study area Whereas lab tests include; the falling and constant head permeability, grain size distribution (sieve and hydrometer analysis), soil specific gravity, direct shear tests and the measuring of Water Phase Inclinations. Angle \emptyset a glassy infiltration box is an experimental device that was manufactured to measure the Water Phase Inclination angle and aquifer simulation. It is found a generalized linear relationship between  and the angle of internal friction which is valid for   23.37 with correlation factor R² = 0.99 and both angles depend on soil texture. The k values estimated by WPI theory and that measured by traditional techniques offer a linear relationship with acceptable Root Mean Square Error equals 0.0642 < 0.1 the max allowable limit and correlation factor R² = 0.96, pointing out to the reliability and stability of the Water Phase Inclination results.

Electrical conductivity (EC) and temperature logging were carried out in twenty-five borewells/piezometers in a hard rock region of Telangana, India at an interval of 1 and 2 m right from the water table till the bottom of the borewell to study the fracture zones at different depths and to recognize temperature variation with depths. The temperature and EC profiles of the groundwater were recorded at regular intervals along the depths of the borewells, the sensitivity of the sensor of the logger being limited to 0.1 K An attempt was made to calculate the vertical component of the water flux in 25 borewells using the temperature profile measurements in these borewells by applying the heat convection and conduction equation and taking into account the volumetric heat capacity of water and the thermal conductivity of rocks (in the present study, granite). The temperature data was first linearly fitted. The dispersion that would exist in thermal conductivity under the assumption as uniform flux for 22 of the borewell’s is unlikely, and data was fitted to the exponential trend of the temperature profile, considered to a non-zero water flux. This approach resulted in a comparatively better fit than the linear variation. Thus the water flux was calculated for 22 sites using the exponential variation relationship. It was found that the water flux ranges from 4 to 30 mm/year, which shows significant large variation from one location to other. It was also observed using the temperature measurements at the surface (from the temperature recorded at the meteorological station) that the temperature at depths is not affected by the variations at the surface, which confirms the reliability of vertical velocity/flow rate determination.

The current study evaluated the hydrogeological conditions and hydraulic properties of the groundwater aquifers in Qaraqosh, Karamless and Bartella areas within Al-Hamdaniya district east Mosul. The depths and water tables of groundwater for 48 well were measured in October 2019, were ranged between 5 - 45 meters and 234 - 278.5 meters, respectively. The highest water table reaches in the center of the studied area north Qaraqosh and decreases gradually in all directions. A map of the flow net was drawn, and it was found that the general direction of water movement is from north to south, with local directions resulting by pumping from the aquifer, or due to the heterogeneity of the porous media. The results of the pumping test in Karamless area shows that the transmissivity was 107.671 m2/day and 100.682 m2/day according to Theis and Cooper-Jacob methods, respectively. The hydraulic conductivity of 157.65 m saturated thickness was found to be 0.683 m/day and 0.639 m/day using Theis and Cooper-Jacob methods, respectively. While the storage coefficient using Theis and Cooper-Jacob methods was 0.0023 and 0.0020، respectively. In Qaraqosh, the transmissivity was 87.1685 m2/day and 88.1004 m2/day according to the mentioned methods, respectively. While the hydraulic conductivity of saturated thickness of 71.07 m was found to be 1.24 m/day and 1.23 m/day using Theis and Cooper-Jacob methods, respectively. The values of storage coefficient using these methods was 0.00135 and 0.00115 respectively. The total dissolved solids (TDS) measured to conclude the hydrogeological system according to the quality of the groundwater aquifers, it was found that the concentrations of total dissolved solids are more than 3500 ppm in the mid of the study area and decreased towards all directions to the limits of 250 ppm. This wide variation in salinity may be because the wells in the central area penetrate the groundwater aquifers, represented by the layers of gypsum in Al-Fat'ha formation, which is hydraulically connected with the main aquifer of the Injana formation.

In this study Aeromagnetic, ground-based magnetic and satellite imagery data have been processed and analyzed to delineate surface and subsurface structures to clarify its impacts on groundwater flow direction, and to detect the thickness of groundwater aquifer’s (accumulation) in the study area. To achieve this target, an interpretation of satellite digital elevation data is processed to generate the main drainage pattern in the area to delineate the Watersheds basins and where the surface water can be accumulated. Moreover, Aeromagnetic data have been used to detect the sedimentary cover in the area, and to assess the thickness distribution of the Nubian aquifer to detect the most eligible aquifer with the largest thickness, consequently the largest amount of groundwater reserve. Also, the ground magnetic survey was conducted in Wadi El Amal to reassure the results obtained from the airborne data. Two main approach techniques were applied to the data. Firstly, the trend analysis applied to the first vertical derivative map to detect main trend analysis and faults. The second approach is to calculate the depth to the basement, which represents the base of the Nubian aquifer in the area under consideration. The final results of the main trend found as follow, the ENE-WSW, NW-SE, and NE-SW trend which found to be is the main trend. The water table in this area is about 100 m, the calculated depth to the basement in the deepest parts study area is ranging between −300 and −700 below ground surface. The integration between satellite techniques and geophysical tools can give us the whole picture of groundwater distribution and its recharge sources.

During the Early Islamic period, groundwater-harvesting agroecosystems in sand appeared along the southeastern Mediterranean coast in the form of plot and berm (P&B) agroecosystems. P&B agroecosystems are agricultural utilizations of shallow, perched rainfall-fed groundwater tables within loose aeolian sand sheets of agricultural hinterlands. These systems involve man-made sand berms that delimit sunken agricultural plots in which refuse-enriched sand transformed into distinct anthrosols. Groundwater table is easily accessible to crop roots and/or humans for water extraction and can support several annual crop cycles. P&B agroecosystems demonstrate innovative adaptations to aeolian and fluvial erosion. Despite the lack of written records, these agroecosystems apparently developed in response to religio-administrative calls for a type of mawāt (Arabic: “dead”) land reclamation. Mawāt are unowned wastelands, which were an important religion-based matter in Islamic economic history. Contemporary mawasi agroecosystems along the northeastern Sinai Peninsula and Southern Gaza Strip Mediterranean coast are similar to the Early Islamic systems. They are reclaimed today by sedentary Bedouins using mechanized water drilling and modification of plot and soil surface levels to compensate for fluctuating groundwater levels. Prior to the mid-twentieth century, Arab peasants cultivated grapes and fruit trees in interdune plantations along the Gaza Strip and southern Israeli coast where the groundwater table was several meters beneath the surface. These three groundwater harvesting agroecosystems in sand are resourceful rainfall-fed agrotechnologies that are independent of the physical and juridical constraints of surficial water supply systems. The unique concentration of these agroecosystems along the southeastern Mediterranean coastal strip implies that biocultural memories were probably transmitted by Islamic culture since their hypothesized inception in coastal Israel. Preservation of these sustainable agroecosystems is a matter of geoethical responsibility and should be treated like other endangered archaeo-landscape elements of the Mediterranean past.

For two years, we quantified the exchange of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) at two different large-scale Sphagnum farming sites. At both, peat extraction left a shallow layer of highly decomposed peat and low hydraulic conductivities. One site was characterized by preceding multi-annual inundation and irrigated by ditches, while the other one was inoculated directly after peat extraction and irrigated by ditches and drip irrigation. Further, GHG emissions from an irrigation polder and the effect of harvesting Sphagnum donor material at a near-natural reference site were determined. GHG mitigation potentials lag behind the results of less decomposed sites, although our results were also affected by the extraordinary hot and dry summer 2018. CO2 exchanges ranged between -0.6 and 2.2 t CO2-C ha−1 y−1 and were mainly influenced by low water table depths. CH4 emissions were low with the exception of plots with higher Eriophorum covers, while fluctuating water tables and poorly developing plant covers led to considerable N2O emissions at the ditch irrigation site. The removal of the upper vegetation at the near-natural site resulted in increased CH4 emissions and, on average, lowered CO2 emissions. Overall, best plant growth and lowest GHG emissions were measured at the previously inundated site. At the other site, drip irrigation provided more favourable conditions than ditch irrigation. The size of the area needed for water management (ditches, polders) strongly affected the areal GHG balances. We conclude that Sphagnum farming on highly decomposed peat is possible but requires elaborate water management.

Geological structures such as faults play a critical role in the flow of fluids in a reservoir by affecting itspermeability. This study explores the role of the Chaman Fault in the distribution of hydrological division, groundwaterseparation of the aquifer systems of Khojak and Chaman basins. The Chaman Fault is a left-lateral strike-slip transformplate boundary located at the border city of Chaman, District Killa Abdullah, Balochistan. The Chaman fault plays animportant role in the division of groundwater in the subsurface, accommodating the structural compartment of theaquifer system. The studies showed that the strike-slip movement of the fault made the aquifer impervious along thefault line. This assertion may also be confirmed by the drastic change in the water table across the fault. Sharp changesin the groundwater table and Total Dissolved Solids (TDS) were observed during the study. The Karazes which are anindigenous method of irrigation is present in the eastern foothills of Khojak mountains called Khojak basin. Here thewater table is as shallow as ≈ 6 meters in comparison to the western side of the fault, where the water table drops to≈274 meters towards the valley of Chaman basin. The average TDS level on the eastern side of the fault line is 773mg/L and 1361 mg/L on the western side. Therefore, the Chaman fault is acting as a groundwater barrier which isfeeding the Karezes for centuries.

This paper studies, through the principles of fuzzy set theory, groundwater response to meteorological drought in the case of an aquifer system located in the plains at the southeast of Xanthi, NE Greece. Meteorological drought is expressed through standardized Reconnaissance Drought Index (RDISt) and Standardized Precipitation Index (SPI), which are calculated for various reference periods. These drought indices are considered as independent variables in multiple fuzzy linear regression based on Tanaka's model, while the observed water table regarding two areas is used as a dependent variable. The fuzzy linear regression of Tanaka is characterized by the inclusion constraints where all the observed data must be included in the produced fuzzy band. Hence, each fuzzy output can get an interval of values where a membership degree corresponds to each of them. A modification of the Tanaka model by adding constraints is proposed in order to avoid irrational behavior. The results show that there was a significant influence of the meteorological drought of the previous hydrological year, while geology plays an important role. Furthermore, the use of RDISt improves the results of fuzzy linear regressions in all cases. Two suitability measures and a measure of comparison between fuzzy numbers are used. HIGHLIGHTS The Fuzzy linear regression of Tanaka is applied between meteorological drought indices and groundwater level in an aquifer system of Xanthi plain.; Two suitability measures are used. The first one includes the objective function of Tanaka's model, while the second one is a fuzzified measure.; A ranking measure is used in order to compare the fuzzified measures of suitability.

In this study, a new 3-stage approach that consists of clustering, simulation, and optimization stages is proposed for the simulation of groundwater level (GWL) in an arid region of eastern Iran. In the first stage, K-means clustering was used to divide the study aquifer into five different clusters based on precipitation, water recharge, water discharge, transmissivity, earth level, and water table. In the second stage, to simulate GWL in each cluster, several input variables, such as water level at the previous month, aquifer discharge, aquifer recharge, evaporation, temperature, and precipitation, were used in the form of various input patterns that were fed to an artificial neural network (ANN). Finally, in the third stage, two advanced optimization methods, i.e., particle swarm optimization (PSO) and whale optimization algorithm (WOA), were utilized to optimize the ANN results. Various patterns were identified as suitable clusters based on the studied models. A pattern including water level at the previous month, aquifer discharge, aquifer recharge, and precipitation was identified as the best model for four clusters, except for cluster 3. The validation with root mean squared error (RMSE), mean absolute percentage error (MAPE), and Nash Sutcliffe index (NSE) revealed RMSE = 0.01, NSE = 0.97, and MAPE = 0.13 for the first cluster, RMSE = 0.011, NSE = 0.99, and MAPE = 0.22 for the second cluster, RMSE = 0.003, NSE = 0.99, and MAPE = 0.30 for the fourth cluster, and RMSE = 0.001, NSE = 0.98, and MAPE = 0.05 for the fifth cluster. For the third cluster, a pattern including water level at the previous month, aquifer discharge, and aquifer recharge was identified as the best model resulting in RMSE = 0.006, NSE = 0.99, and MAPE = 0.05. Finally, according to the results, the ANN–PSO model was applied to three clusters, while the ANN–WOA model was applied to the remaining clusters. In general, this study showed that optimization algorithms can improve the simulation accuracy of ANN, and the efficient use of each method depends on the clustering type. The application of the approach proposed here can be extended to other aquifers that have a relatively large area and limited data availability.

To maintain the balance in the water table, artificial recharge is being adopted in many regions. For this, numerous studies have been carried out. In the present study, vertical electric soundings have been carried out in the different locations of surrounding Atal Nagar, Naya Raipur at 09 random sites to understand the nature and extent of the aquifer and to find out the groundwater potential zone for rainwater harvesting sites. The main objective of this study is to identify the possibility of an appropriate recharge structure at a suitable location. From the interpretation of the VES curve, the evaluation of layer parameters has been done depicting the actual depth of aquifers and high yielding fracture zones. The VES curve has been made to interpret the subsurface geological layers which indicate the 3 to 4 subsurface layers having different resistivity and thickness. When this VES data is correlated with the lithology data of the area, the actual groundwater bearing zone and potential zone can be identified.

Mining activity is often responsible for the drainage of acid or metal-enriched waters to fluvial systems. The release of metals is especially disturbing due to the toxicity and persistence of these products and their accumulation in the biosphere. Hence, a systematic detection and delimitation of highly polluted floodplains and linkages between pollution and high-flow stages would likely assist the improvement of land management and ease the design of mitigation or rehabilitation measures. Here we test how trees growing in different geomorphic positions along a fluvial system uptake metal during floods and how these uptakes can be documented “a posteriori”. To this end, we apply dendrogeochemical analyses to twenty Pinus pinaster Ait. trees growing on the banks of Odiel River (south-western Spain) as well as to five reference trees growing outside the river channel. In the field, trees were sampled with a large-diameter (1 cm) increment borer. In the lab, tree-ring series were dendrochronologically cross dated and separated into 5-yr blocks, so that wood blocks contained the dates of major floods. Then, Inductively Coupled Plasma Mass Spectrometry (ICPM) was employed to evaluate toxic metal concentrations in trees. Results point to clear correlations between the accumulation of toxic metals and the geomorphic position of trees within the fluvial network. We show that morphological units along a river exert control on toxic metal concentrations in trees, with uptake being much higher in trees located on meander cut banks than in trees growing on point-bar structures. Besides, we detect chemical signatures in trees located farthest away from the main river channel after the largest floods, but not in the aftermath of smaller events. We conclude that tree position is the single-most important determinant for metallic pollution in an environment controlled by fluvial processes, but also find that more studies are still needed to determine linkages with individual floods and interactions of metal uptake in roots via the water table in the river corridor.

Rainfall and deep percolation of irrigation are the most important sources of recharge in Khatoon-Abad plain, Kerman province, Iran. Artificial recharge is a practical strategy to increase the storage capacity of groundwater in drought condition. Modeling of groundwater flow for a steady-state period (April 2017 to October 2017) and an unsteady state period from October 2012 to August 2019 was simulated in monthly stress steps. In this study, root mean square error and coefficient of residual mass have been used to evaluate the results of calibration and verification process obtained by PMWIN software. Moreover, two strategies of artificial recharge were incorporated for considering the water table fluctuations. The results show that artificial recharge by direct injection of water into the aquifer prevents evaporation, runoff and outflow as runoff from the plain and increases the aquifer water availability. In different scenarios, the different amounts of recharge were applied to the aquifer, and the simulation results showed that the effect of recharge in the study period varies from 3 km to more than 7 km.

The focus of current water management in drained peatlands is to facilitate optimal drainage, which has led to soil subsidence and a strong increase in greenhouse gas (GHG) emissions. The Dutch land and water authorities proposed the application of subsoil irrigation (SSI) system on a large scale to potentially reduce GHG emissions, while maintaining high biomass production. Based on model results, the expectation was that SSI would reduce peat decomposition in summer by preventing groundwater tables (GWTs) from dropping below −60 cm. In 2017–2018, we evaluated the effects of SSI on GHG emissions (CO2, CH4, N2O) for four dairy farms on drained peat meadows in the Netherlands. Each farm had a treatment site with SSI installation and a control site drained only by ditches (ditch water level −60 / −90 cm, 100 m distance between ditches). The SSI system consisted of perforated pipes −70 cm from surface level with spacing of 5–6 m to improve drainage during winter–spring and irrigation in summer. GHG emissions were measured using closed chambers every 2–4 weeks for CO2, CH4 and N2O. Measured ecosystem respiration (Reco) only showed a small difference between SSI and control sites when the GWT of SSI sites were substantially higher than the control site (> 20 cm difference). Over all years and locations, however, there was no significant difference found, despite the 6–18 cm higher GWT in summer and 1–20 cm lower GWT in wet conditions at SSI sites. Differences in mean annual GWT remained low (< 5 cm). Direct comparison of measured N2O and CH4 fluxes between SSI and control sites did not show any significant differences. CO2 fluxes varied according to temperature and management events, while differences between control and SSI sites remained small. Therefore, there was no difference between the annual gap-filled net ecosystem exchange (NEE) of the SSI and control sites. The net ecosystem carbon balance (NECB) was on average 40 and 30 t CO2 ha−1 yr−1 in 2017 and 2018 on the SSI sites and 38 and 34 t CO2 ha−1 yr−1 in 2017 and 2018 on the control sites. This lack of SSI effect is probably because the GWT increase remains limited to deeper soil layers (60–120 cm depth), which contribute little to peat oxidation. We conclude that SSI modulates water table dynamics but fails to lower annual carbon emission. SSI seems unsuitable as a climate mitigation strategy. Future research should focus on potential effects of GWT manipulation in the uppermost organic layers (−30 cm and higher) on GHG emissions from drained peatlands.

Sedimentary architecture and genesis of residual dune ridges in a temperate climate are presented and implications for their use as archive of changes in long-term precipitation and wind climate are discussed. Residual dunes are common features of wet aeolian systems, where they form sets of shallow ridges, oriented perpendicular to the prevailing wind direction. Residual dune ridges of the study area are vegetated and typically elevate 0.6 to 2.5 m above the surrounding interdune flats. They develop on the lower stoss side of active transgressive dunes, triggered by periods of elevated groundwater table and hence colonization of the foot of the dune by rapid growing pioneer vegetation. Stabilized by plants, the growing ridge detaches from the active transgressive dune and gets abandoned within years in the course of the downwind-migration of the transgressive dune. Grain-size data suggest a main sediment supply from the transgressive dune and only minor input from other sources. Ground-penetrating radar reveals that the residual dune ridges are composed of windward-dipping as well as leeward-dipping sedimentary beds. Leeward-dipping strata reflect sediment supply from the parental dune, whereas windward-dipping beds are seen to result from sediment redistribution along the ridge and sediment supply from the adjacent swales during the ridge growth period. Multi-annual to multi-decadal variability in precipitation leads to the development of sequences composed of tens of ridges, spanning time periods of several centuries. Spacing of individual ridges in these sequences is controlled not by long-term variability in precipitation alone, but probably also reflects variable wind intensity which affects the migration rate of the parental dune. The important role of vegetation in ridge construction makes these landforms a demonstrative example of landscape development by geo-biosphere interacting processes.

Extensive change in land use, climate, and over-exploitation of groundwater has increased pressure on aquifers, especially in the case of crystalline rocks throughout the world. To support sustainability in groundwater management require proper understating of groundwater dynamics and recharge potential. GIS based studies have gained immense popularity in groundwater exploration in recent years because they are fast and provide recent information on the resource for future growth. Thus, the present study utilized a GIS-based Weighted Overlay Index (WOI) model to identify the potential recharge zones and to gain deep knowledge of groundwater dynamics. The in situ infiltration tests have been carried out, which is the key process in groundwater recharge and is neglected in many cases for WOI. In the WOI, ten thematic layers from the parameters influencing and involved in the recharge process are considered to identify potential recharge zones. The results suggested a significant underestimation of recharge potential without considering site-specific infiltration rates that one needs to be considered. The present WOI model considered in situ infiltration information and classified the entire area into four recharge zones, good, moderate, poor, and very poor. The final integrated map compared with the real-time field data like water level fluctuation and infiltration to analyse occurrence and quantification of recharge. The estimated average groundwater draft is 21.9 mcm, while annual renewable recharge is only 5.7 mcm that causing a continuous fall of the groundwater table. The study is useful in selecting regions with more focussed recharge studies and suggested the need of reducing groundwater demand by changing cropping patterns through a predictive decision support tool.

Background. In recent years, mitigation of groundwater contamination resulting from the limited availability of freshwater for domestic use has become an important issue. The presence of heavy metals in water could have adverse effects on both plant and animal life. Objectives. The main objective of the present study was to determine possible heavy metal contamination in groundwater around Al-Buraihi sewage station in Taiz, Yemen and to understand possible sources of contamination and their relationships with groundwater. Methods. Wastewater samples were collected from a wastewater stabilization pond from Al-Buraihi sewage station and borewell water samples were collected from the vicinity. The presence of heavy metals was quantified using inductively coupled plasma-optical emission spectrometry (ICP-OES). Pearson correlation test was performed to understand the relationship between wastewater and groundwater samples. Results. Physical variables including pH, electrical conductivity (EC), dissolved oxygen (DO) and temperature and elements such as silver (Ag), arsenic (As), aluminum (Al), barium (Ba), boron (B), cadmium (Cd), chromium (Cr), iron (Fe), molybdenum, nickel (Ni), selenium (Se) and zinc (Zn) exceeded the permissible limits recommended by international standards in wastewater samples. Conclusions. Treated sewage wastewater in the study area is not suitable for irrigation as the elements/heavy metals are accumulated in soil and plants and may be accumulated in humans and animals through bio-accumulation. In addition, these heavy metals reach the water table and aquifers through percolation, thereby polluting groundwater. Competing Interests. The authors declare no competing financial interests.

In this article, the GMS finite difference simulation of “No Bandegan (NB) Plain” aquifer has been studied. The groundwater flow path and intensity in the plain have been simulated by modeling input to and output from the aquifer. Spatial distributions of four major pollutants have been determined by groundwater sampling at different piezometers and wells throughout the plain. Discharge withdrawal from wells, water quality parameters, and water table drop were simulated repeatedly pursuant to the constraints defined by an (artificial neural network) ANN. The validated ANN was then linked to a multi-objective optimization model to find a Pareto optimal front among the three objectives of enhancing water quality, increasing equity in withdrawal allocation, and reducing water table drawdown. Results were optimized in an agent-based (A-B) approach seeking quantitative and qualitative management of water allocation in the plain. The optimization process caused a reduction in annual water table decline by up to 68% compared to observed drawdowns in the plain. Similarly, the proposed method improved groundwater quality as indexed by pH, TH, TDS, and EC parameters by 8.8, 27.7, 28.4, 25.5%, relative to their observed values, respectively.

Here we present results of digital modelling of a specific setting of hypogenic carbonic acid speleogenesis (CAS). We study an unconfined aquifer where meteoric water seeps through the vadose zone and becomes saturated with respect to calcite when it arrives at the water table. From below, deep-seated water with high p CO 2 and saturated with respect to calcite invades the limestone formation by forced flow. Two flow domains arise that host exclusively water from the meteoric or deep-seated source. They are separated by a water divide. There by dispersion of flow, a fringe of mixing arises and widening of the fractures is caused by mixing corrosion (MC). The evolution of the cave system is determined by its early state. At sites with high rates of fracture widening, regions of higher hydraulic conductivity are created. They attract flow and support one-by-one mixing with maximal dissolution rates. Therefore, the early evolution is determined by karstification originating close to the input of the upwelling water and at the output at a seepage face. In between these regions, a wide fringe of moderate dissolution is present. In the later stage of evolution, this region is divided by constrictions that originate from statistical variations of fracture aperture widths that favour high dissolution rates and focus flow into this region. This MC-fringe instability is an intrinsic property of cave evolution and is present in all scenarios studied. We have investigated the influence of defined regions with higher fracture aperture widths. These determine the cave patterns and suppress MC-fringe instabilities. We have discussed the influence of the ratio of upwelling water flux rates on the rates of meteoric water. This ratio specifies the position of the mixing fringe and consequently that of the cave system. In a further step, we have explored the influence of time-dependent meteoric recharge. Furthermore, we have modelled scenarios where waters are undersaturated with respect to calcite. These findings give important insight into mechanisms of CAS in a special setting of unconfined aquifers. They also have implications for the understanding of corresponding sulfuric acid speleogenesis (SAS).

Numerical modeling for the variations of water table fluctuation in response to subsurface seepage and downwards recharge is an important aspect in the estimation of surface-groundwater interaction. In this work, a numerical model is developed for the approximation of water table variation in an unconfined sloping aquifer subjected to the multiple localized recharge and seepage from the adjacent water body. The Boussinesq equation characterizing the flow of groundwater in unconfined sloping porous media is solved numerically using Du Fort Frankel finite difference method. The application of the result is demonstrated with illustrative examples using varying aquifer parameters. The results indicated that the water table form groundwater mound beneath recharge basins due to continuous recharge.

The effect of waste dumps on groundwater quality on perched aquifers in Nsukka and environs was investigated by applying multivariate statistical analyses using Statgraphics Centurion XVII, ArcGIS ...

Excessive sand mining to meet the growing demands of the construction industry has resulted in the degradation of rivers, lowering of groundwater table, saltwater intrusion into coastal aquifers, a...

Tambakbayan is one of the watersheds in Yogyakarta, Indonesia that is experiencing changes in land use. The research aims to analyze the distribution of intrinsic and specific groundwater vulnerability in the watershed that was influenced by land-use changes from 2006 to 2017. The data used are the RBI maps (containinh topographic and land-use information, 2006 and 2017), SRTM imagery, rainfall recorded at the Kambil, Prumpung, Bronggang, Santan, Gemawang, and Karang Ploso stations (2006-2017), soil map, and aquifer map. Land-use change was analyzed by comparing the RBI maps of 2006 and 2017; while the groundwater vulnerability was assessed with the Susceptibility Index a development of the DRASTIC method. The intrinsic groundwater vulnerability was generated based on physical conditions, including depth to the water table, aquifer media, groundwater recharge, and topography, while the specific groundwater vulnerability was a function of these attributes added with one anthropogenic parameter : land-use. Then, all of these parameters were analyzed with map ovelay. The results showed two levels of intrinsic vulnerability : low (2.18% of the watershed area) and medium (97.8%); and three classes of specific vulnerability : low (0.02%), medium (5.06%), and high (94.92%)in 2006. From 2006 through 2017, the areal percentage of the medium vulnerability increased, while that of the high vulnerability decreased due to the conversion of agricultural land to a reservoir in 2009.

Understanding the processes that mobilize and transport dissolved phosphorus (P) during storms is critical to managing P in flat landscapes with open ditch drainage and legacy soil P. In this study, we used routine baseflow monitoring and intensive storm sampling at a ditch-drained site on Maryland's Lower Eastern Shore (July 2017-September 2018) to assess whether concentration-discharge (C-Q) relationships and chemical and isotopic hydrograph separation could provide insight into the processes that mobilize and transport dissolved P in ditch drainage. Using a segmented regression model, we determined that long-term C-Q relationships for dissolved P differed above and below a discharge threshold of 6.4 L s-1 . Intensive storm sampling revealed that small storms (n = 3) occurring at or below the discharge threshold generally exhibited complex hysteresis and dissolved P dilution patterns that were consistent with deeper (>122 cm) groundwater inputs with low dissolved P concentrations (0.04 mg L-1 ). In contrast, large storms occurring well above the discharge threshold (n = 4) induced rising water tables and preferential flow pathways that most likely tapped dissolved P-enriched shallow (

Groundwater is a vital water resource in arid and semi-arid areas. Diurnal groundwater table fluctuations are widely used to quantify rainfall recharge and groundwater evapotranspiration (ETg). To assess groundwater resources for sustainable use, groundwater recharge and ETg were estimated using the diurnal water table fluctuations at three sites along a section with different depths to water table (DWT) within a wetland of the Mukai Lake in the Ordos Plateau, Northwest China. The water table level was monitored at an hourly resolution using a Keller DCX-22A data logger that measured both the total pressure and barometric pressure, so that the effect of barometric pressure could be removed. At this study site, a rapid water table response to rainfall was observed in two shallow wells (i.e., Obs1 and Obs2), at which diurnal water table fluctuations were also observed over the study period during rainless days, indicating that the main factors influencing water table variation are rainfall and ETg. However, at the deep-water table site (Obs3), the groundwater level only reacted to the heaviest rainfalls and showed no diurnal variations. Groundwater recharge and ETg were quantified for the entire hydrological year (June 2017–June 2018) using the water table fluctuation method and the Loheide method, respectively, with depth-dependent specific yields. The results show that the total annual groundwater recharge was approximately 207 mm, accounting for 52% of rainfall at Obs1, while groundwater recharge was approximately 250 and 21 mm at Obs2 and Obs3, accounting for 63% and 5% of rainfall, respectively. In addition, the rates of groundwater recharge were mainly determined by rainfall intensity and DWT. The daily mean ETg at Obs1 and Obs2 over the study period was 4.3 and 2.5 mm, respectively, and the main determining factors were DWT and net radiation.

Daerah Sambirejo, Kecamatan Prambanan, Kabupaten Sleman merupakan salah satu daerah sulit air berdasarkan kenampakan morfologi berupa perbukitan. Berdasarkan kejadian geologi disuatu daerah memiliki produk yang berbeda satu dengan yang lain. Produk geologi tersebut berupa morfologi, litologi dan genesis, sehingga berdampak pada pengaruh air tanah. Bertambahnya jumlah penduduk sangat berpengaruh pada kebutuhan air secara besar perhari. Daerah yang terindentifikasi kekurangan air, sehingga penting diketahui sebagai dasar untuk mengetahui daerah yang perlu dikaji lebih detail sebagai dasar eksploitasi air tanah dalam dan air bawah permukaan. Penelitian ini bertujuan untuk mengidentifikasi potensi air tanah di daerah Sambirejo. Masalah dalam penelitian ini adalah bagaimana menetukan daerah potensi air tanah yang berkwalitas dan bermafaat untuk memenuhi kebutuhan air baku pada masyarakat.Pemanfaatan air bawah permukaan sangat di perlukan untuk mendapatkan potensi yang besar dan dapat segera dimanfaatkan oleh masyarakat. Penelitian ini dilakukan dengan metode berupa pemetaan geologi untuk menentukan sebaran litologi dan pengukuran geofisika berupa pengukuran geolistrik untuk menentukan daerah potensi air tanah yang berada pada morfologi lereng dan pungungan. Berdasarkan dari hasil geolistrik keberadaan air tanah terdapat pada kedalaman 20-40 meter yang dikatagorikan dangkal sedangkan pada kedalaman 98-142 meter yang di katagorikan sebagai akuifer hampir dalam. Jenis akuifer yang berkembang pada daerah Sambirejo yaitu akuifer setengah tertekan (leaky unconfined aquifer) dimana batuan breksi pumice pada bagian bawahnya terdapat lapisan kedap air berupa tuff. Kata kunci: Aquifer, litologi, Air bersih, Sambirejo

In recent years, the area of Dali Lake has shrunk significantly, resulting in extremely serious ecological and environmental problems. Combining records from lake sediments and ancient shorelines is effective for investigating paleolake evolution and predicating the lake life trend. This study explored the lake area evolution of Dali Lake using remote sensing images and optical stimulated luminescence (OSL) dating. The results suggest the following: 1) on the century time scale, there has been a significant linear relationship between age and elevation from ca. 1.8 cal ka BP to the present (R2 = 0.99) and a potential quadratic polynomial relationship since ca. 4.2 cal ka BP (R2 = 0.99). 2) According to the δ2H and δ18O composition, monthly changes in the lake area, and water balance analysis, the groundwater was the main water source to recharge Dali Lake which originated from an external source, whereby the water may be from the Xar Moron Fault or has been transported by a volcanic conduit. 3) Since ca. 1.3 cal ka BP, the clear differences between lake levels and local precipitation indicated that the changes of the lake level are predominantly determined by groundwater. We conclude that the East Asian summer monsoon intensity and groundwater table variations in this area have jointly controlled the lake level evolution since the late Holocene.

In the aftermath of the January 2010 Haiti Earthquake, the streets of downtown Leogane were paved to mitigate waterborne disease using humanitarian relief funds. After paving, many of the shallow water wells in Leogane dried up. It was believed that the new pavement disrupted groundwater recharge and negatively impacted the wells. Therefore, a project was performed to assess groundwater conditions in a cost-effective manner using a rapid, inexpensive, non-intrusive geophysical approach. The scope of the project included 1) surveying the new pavement system, 2) surveying water wells in Leogane, 3) testing the well water for coliforms, 4) performing geophysical DC resistivity testing to map groundwater depth and 5) developing a groundwater map to assess the impact of the pavement on the water table. As a result of this project, it could not be concluded that the new pavement was a factor in the groundwater fluctuations observed in the water wells in Leogane. It is more likely that some of the drop in the water table was due to the earthquake itself and some of it was caused by seasonal fluctuations in the water table. It was also observed that all the water wells that extract water from shallow (less than 6 m deep) aquifers in Leogane contain coliforms due to their proximity to household latrines, although a second deeper aquifer was identified and found to be coliform-free. With respect to broader impact, this methodology represents a relatively simple approach to mapping groundwater and assessing water quality that can be easily applied to other communities in the developing world to guide their efforts to develop and manage groundwater.

A hybrid model of two multi-criteria decision making techniques specifically, the analytical hierarchy process method and the technique for order preference by similarity to an ideal solution method was proposed to select the best site for constructing an underground dam to control the groundwater table rising or water-logging in the center of Al-Zubair city, southern Iraq. Six influencing factors were selected and prepared depending on the nature of the problem to be resolved the siting of the underground dam, and data availability. These are elevation, slope, curvature, aquifer transmissivity and specific yield, and distance to the water-logging body. Applying the hybrid system proved that approximately 50% of the study area is suitable for constructing the underground dam. Due to the expected high cost of constructing an underground dam in the study area as well as the technical challenges in implementing the project, the proposed design is digging a trench with limited width (meter or half a meter) and shallow depth (not more than 5 m) and fill the hole with an impermeable material (clay for example). It is preferred to drill wells in the headwater of the dam for pumping excess water and used it for another usage.

Groundwater represents the primary source of freshwater for more than 35% of world people, and its contamination became a worldwide challenge. Egypt is suffering from water quantity and quality, especially in desert areas. El Obour city and environs Northeast Cairo face waterlogging owing to the elevated-shallow groundwater table. In the present research work, the water quality of the shallow groundwater aquifer was studied. The remediation efficiency of polluted water using photocatalytic treatment technique in the presence of modified nano-titania and solar radiation has also been investigated. Twenty-eight representative samples have been collected from different locations, and their microbial, physical, and chemical characteristics were determined. The average contents of Pb (214.96 µg/L), As (1517 µg/L), Cd (8.79 µg/L), total bacterial count (2.22 × 105 CFU/ml), and bacterial indicators (MPN-index/100 ml): total coliform (497.4), fecal coliform (358.3), and fecal streptococci (115.9) were higher than WHO permissible limits for drinking water, possibly due to higher industrialization, agricultural, and urbanization rates. The organic pollutants reached critical concentrations (chemical oxygen demand up to 960.8 mg O2/L). Most of the studied samples contained acceptable concentrations of the major ions, (e.g., K+, Mg2+, HCO3−), for drinking and irrigation purposes. The statistical analyses (e.g., principal component analysis and cluster analysis) pointed out the control of water–rock interaction and anthropogenic activities in water composition. The hydrochemical data show that most of the water samples (96.4%) are Na2SO4 and NaHCO3 type, indicating its meteoric origin. The contamination with human and animal fecal substances, NO3¯, and NH4+ was identified in all samples, which pointed out the control of anthropogenic activities in water pollution. The photocatalytic technique efficiently eliminated more than 82–95% of organic contents and microbial pollutants, respectively, but it was inefficient in reducing heavy metal levels. According to the current results, shallow groundwater injection into the deep aquifer must be constrained and reusable after treatment. Finally, more studies are imperative to disseminate the applied treatment techniques to elude bacteria and organic pollutants from water at a pilot scale.

When your well runs dryGroundwater provides nearly half of the water used for agricultural irrigation and most of the drinking water for billions of people. It is essential, then, for this resource to remain secure. Jasechko and Perrone examined data from approximately 39 million wells in 40 countries worldwide to investigate their vulnerability to declining water levels (see the Perspective by Famiglietti and Ferguson). The authors found that construction of deeper wells is not occurring in some areas that are experiencing groundwater decline, a disconnect that poses risks for people who rely on well water.Science, this issue p.418; see also p.344