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Understanding the hydrologic connectivity between kettle holes and shallow groundwater, particularly in reaction to the highly variable local meteorological conditions, is of paramount importance for tracing water in a hydro(geo)logically complex landscape and thus for integrated water resource management. This article is aimed at identifying the dominant hydrological processes affecting the kettle holes' water balance and their interactions with the shallow groundwater domain in the Uckermark region, located in the north-east of Germany. For this reason, based on the stable isotopes of oxygen (δ 18 O) and hydrogen (δ 2 H), an isotopic mass balance model was employed to compute the evaporative loss of water from the kettle holes from February to August 2017.Results demonstrated that shallow groundwater inflow may play the pivotal role in the processes taking part in the hydrology of the kettle holes in the Uckermark region.Based on the calculated evaporation/inflow (E/I) ratios, most of the kettle holes (86.7%) were ascertained to have a partially open, flow-through-dominated system. Moreover, we identified an inverse correlation between E/I ratios and the altitudes of the kettle holes. The same holds for electrical conductivity (EC) and the altitudes of the kettle holes. In accordance with the findings obtained from this study, a conceptual model explaining the interaction between the shallow groundwater and the kettle holes of Uckermark was developed. The model exhibited that across the highest altitudes, the recharge kettle holes are dominant, where a lower ratio of E/I and a lower EC was detected. By contrast, the lowest topographical depressions represent the discharge kettle holes, where a higher ratio of E/I and EC could be identified. The kettle holes existing in between were categorized as flow-through kettle holes through which the recharge takes place from one side and discharge from the other side. K E Y W O R D S evaporation, groundwater inflow, kettle hole, stable water isotope, surface-groundwater interactions

Projections of potential impacts of climate change and groundwater abstraction on gaining and losing streams, particularly in ephemeral river basins exhibiting sporadic and intricate flux exchanges, have remained largely unexplored. To fill this gap, we propose a promising modeling scheme based on the new fully integrated hydrological model SWAT-MODFLOW-NWT, calibrated and validated for 1978-2012, to quantify the intertwined surface-groundwater interactions under a conjuncture of three climatic emission scenarios (RCP 2.6, 4.5 and 8.5) and two groundwater pumping variants: "pumping" (extending current groundwater utilization into the future) and "nonpumping" (assuming a complete cease of pumping in the future). By forcing the integrated model with future downscaled climate predictors of CanESM2 under the aforementioned RCPs for three time slices up to year 2100, projections of various water resources components for the Gharehsoo River Basin (GRB), in northwestern Iran were made. Results demonstrate that because of a general decrease of future precipitation, though with ups and downs across the total projection period, most of the surface and-subsurface budget quantities and fluxes are substantially affected. In particular, future groundwater discharge (baseflow) to the gaining streams will be more influenced by the "pumping" variant (increasing and decreasing for "nonpumping" and "pumping", respectively) than the concentrated groundwater recharge from the losing streams (decreasing and increasing for "nonpumping" and "pumping", respectively). Future water yield and groundwater storage will also diminish and, surprisingly, this cannot be alleviated by future "nonpumping", indicating the groundwater overutilization is the compelling reason for the future water scarcity in the GRB, rather than climate change alone. Plain Language Summary Understanding climate change impacts on surface-groundwater interactions, accommodating nearly all of water resources components of a watershed, is of paramount importance in devising effective strategies to alleviate the adverse impacts of climate change. This is particularly important in semiarid regions where the surface water scarcity has markedly increased the dependency on groundwater resources which, in turn, has highly affected the interaction between these two. We have provided an innovative scheme to assess and project climate change impacts on water resources of a basin and, in particularly, on gaining and losing streams at different temporal and spatial scales. In addition, the net impacts of climate change impacts on the quantity of the water resources, compared with the groundwater overutilization, can be quantified using the proposed methodological approach. Our findings importantly highlight that the groundwater overutilization is the major reason, rather than climate change impacts, for extreme groundwater storage depletion in the Gharehsoo River Basin, in northwestern Iran. As a result, groundwater discharge to the river network will diminish tremendously under the...

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Drawing a distinction between the suspended solid size and concentration impacts on physical clogging process in the Managed Aquifer Recharge (MAR) systems has been fraught with difficulties. Therefore, the current study was then aimed to statistically investigate and differentiate the impacts of clay-, silt- and sand-sized suspended solids at three concentration levels including 2, 5 and 10 g/L, compared with the clean water (0 g/L), on infiltration rate reducibility. The treatments were compared by virtue of Cohen’s d effect size measure. Furthermore, the competency of Singular Spectrum Analysis (SSA) was evaluated in reconstruction of infiltration rate. Results showed that clay-sized suspended solids were found to be the most important determining factor in physical clogging occurrence. The effect size measure highlighted that a lower concentration level of clay-sized suspended solids, that is, 2 g/L could be more important in trigging the physical clogging than a higher concentration level of silt-sized suspended solids namely 5 g/L. Also, we recognized that concentration level of clay-sized suspended sediments could non-linearly decrease the infiltrability. Also, findings revealed that SSA represented a high level of competency in reconstruction of the infiltration rate under all treatments. Hence, SSA can be quite beneficial to MAR systems for forecasting applications.

Little research attention has been given to validating clusters obtained from the groundwater geochemistry of the waterworks' capture zone with a prevailing lake-groundwater exchange. To address this knowledge gap, we proposed a new scheme whereby Gaussian finite mixture modeling (GFMM) and Spike-and-Slab Bayesian (SSB) algorithms were utilized to cluster the groundwater geochemistry while quantifying the probability of the resulting cluster membership against each other. We applied GFMM and SSB to 13 geochemical parameters collected during different sampling periods at 13 observation points across the Barnim Highlands plateau located in the northeast of Berlin, Germany; this included 10 observation wells, two lakes, and a gallery of drinking production wells. The cluster analysis of GFMM yielded nine clusters, either with a probability ≥0.8, while the SSB produced three hierarchical clusters with a probability of cluster membership varying from <0.2 to >0.8. The findings demonstrated that the clustering results of GFMM were in good agreement with the classification as per the principal component analysis and Piper diagram. By superimposing the parameter clustering onto the observation clustering, we could identify discrepancies that exist among the parameters of a certain cluster. This enables the identification of different factors that may control the geochemistry of a certain cluster, although parameters of that cluster share a strong similarity. The GFMM results have shown that from 2002, there has been active groundwater inflow from the lakes towards the capture zone. This means that it is necessary to adopt appropriate measures to reverse the inflow towards the lakes.

Dental and skeletal fluorosis caused by consuming high-fluoride groundwater has been reported over several decades globally. Prediction maps to estimate the fluoride contaminated area rely on interpolation methods. This study presents a comparison of the accuracy of nine spatial interpolation methods in predicting the fluoride in groundwater. Leave-one-out cross-validation (LOOCV), hold-out validation and validation with an independent dataset were used to assess the precision of the interpolation methods. This is the first study on fluoride with a large dataset (N = 13,585) applied at the regional level in India. Our findings showed that the inverse distance weighted (IDW) algorithm outperformed other methods in terms of less discrepancy between measured and predicted fluoride. IDW and local polynomial interpolation (LPI) were the only methods to predict contaminated areas (fluoride > 1.5 mg/L). However, the area estimated by the typical assessment of the percentage of unsuitable samples was much higher (6.1%) compared to that estimated by IDW (0.2%) and LPI (0.2%). LOOCV provided viable results than the other two validation methods. Interpolation methods are accompanied with uncertainty which are regulated by the sample size, sample density, sample distribution, minimum and maximum measured concentrations, smoothing and border effects. Drawing a comparison among variegated interpolation methods capturing a wide range of prediction uncertainty is suggested rather than relying on one method exclusively. The high-fluoride areas identified in this study can be used by the Government in planning remediation actions.