Sustainable groundwater management requires, among other factors, reliable monitoring of groundwater levels (GWLs) and their spatiotemporal evolution in an aquifer with meaningfully quantified uncertainty. Geostatistical methods can estimate GWL surfaces directly from available groundwater monitoring data. This contrasts with groundwater flow modeling, which requires much more detailed data. This study estimates spatiotemporal GWL maps and quantifies associated uncertainties by spatiotemporal kriging, which combines spatial interpolation with temporal gap filling and noise filtering. The central hypothesis is that including hydrogeological information in kriging improves GWL predictions. To test this hypothesis, spatiotemporal trends and soft information inspired by hydrological understanding are included. These include digital elevation models, river exchange components, and the confinement status of aquifers. To test the necessity of full statistical involvement through Bayesian hyperparameter inference, universal kriging is operated in a fully Bayesian framework and then compared to simpler approaches like non-Bayesian and residual space–time kriging. The approach is demonstrated for the Wairau Plain aquifer, New Zealand, where the spatiotemporal GWL estimates can be compared with transient simulation results from a numerical groundwater flow model. The results indicate that space–time kriging is a valuable tool to estimate transient GWL maps, where auxiliary hydrogeological information is highly useful, that the fully Bayesian treatment of universal kriging is worth the effort, but that a posterior (Bayesian) uncertainty of geostatistical hyperparameters is close to irrelevant.
Groundwater resources in hyper-arid regions are stressed by limited recharge and agricultural water demands. Qatar exemplifies these challenges, where groundwater abstraction exceeds sustainable levels and saltwater intrusion threatens coastal aquifers. This study presents an integrated MODFLOW 6 modeling framework for Qatar combining a steady-state calibration, transient performance evaluation, and future scenario analysis of the karstic carbonate aquifer system of the Dammam, Rus, and Umm er Radhuma formations. The model was calibrated using the PEST++ with Tikhonov regularization under steady-state conditions for 1958 and evaluated under transient conditions for 1985–1987. Model calibration yielded a root mean square error of 0.49 m and a Nash–Sutcliffe efficiency of 0.95. Transient evaluation indicated stable model behavior, with Nash–Sutcliffe values of 0.96 for 1986 and 0.93 for 1987. Five scenarios assessed the effects of climate change and groundwater management interventions, including demand reduction, managed aquifer recharge (MAR), and their combined implementation. Under the baseline scenario, continued abstraction produced a mean 2050 drawdown of 12.5 m, with a storage-sensitivity range of 10.4–16.0 m. Climate change increased mean drawdown by approximately 25
Groundwater quality is increasingly threatened by nitrate (NO3−) contamination from agricultural activities. In many aquifers, NO3− is attenuated through microbially mediated reduction coupled to the oxidation of reduced constituents in the aquifer matrix. However, predicting NO3− turnover at the aquifer scale remains difficult because electron donors such as organic carbon and reduced sulfur species are heterogeneously distributed and reliable proxies for NO3− reduction potential are lacking. To address this challenge, batch experiments were conducted using eight facies types from a previously characterized tufaceous Holocene aquifer in southwestern Germany. The facies exhibited a wide range of solid-phase organic carbon contents (SOC 0.5–40.1 wt.
Temporal variability of stable isotopes in groundwater has been addressed by a relatively limited number of studies. Indeed, groundwater exhibits a narrower temporal range of isotopic variability compared with precipitation and surface water. The aim of this study was to characterize the temporal distribution of multi-year seasonal δ18O and δ2H measurements collected from the shallow aquifer of the Alessandria Po Plain (NW Italy) over the 2020–2025 period. This assessment involves: (1) applying statistical tests to characterize temporal variability, (2) analyzing the relationship between rainfall and groundwater levels (GW levels); and (3) examining the relationship between GW levels and groundwater stable isotopes, to better understand aquifer recharge dynamics and influences on groundwater isotopic signatures, and the effect of the 2022 drought. The results reveal temporal variability in stable isotopes that correlates with GW levels, exhibiting a time lag of 18–23 months. This delay reflects the influence of cumulative precipitation over the preceding 24 months on GW levels. This condition explains the lack of a synchronous isotopic response to infiltrating precipitation, due to mixing processes occurring within the aquifer. The general pattern of less enriched heavy-isotope compositions observed alongside declining GW levels is detected, confirming the influence of dry periods on groundwater isotopic compositions during which reduced local rainfall limits recharge in the plain area. In these conditions, groundwater isotopic compositions tend to converge toward less enriched values, indicative of recharge from the mountain front.
Groundwater in the North China coal mining region serves not only as a critical source of industrial and domestic water supply but also poses a potential threat of mine water inrush during deep mining operations. In this study, an investigation was conducted on the hydrochemical characteristics and groundwater mixing processes within the multi-aquifer system of the Yangliu coal mine. Hierarchical clustering analysis (HCA) and principal component analysis (PCA) revealed that groundwater hydrochemistry could be classified into six clusters, with the dominant processes being the dissolution of silicate, carbonate, and sulfate minerals and cation exchange. Hydrogeological analysis and end-member mixing analysis (EMMA) indicated that, in the shallow aquifer zone, the Ordovician aquifer is the major recharge source for the Quaternary aquifer, contributing approximately 67
