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Müller, M., Alaoui, A., Külls, C., Leistert, H., Meusburger, K., Stumpp, C., et al. (2014). Tracking water pathways in steep hillslopes by δ18O depth profiles of soil water. Journal of hydrology, 519, 340–352.
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Musy, S., Meyzonnat, G., Barbecot, F., Hunkeler, D., Sültenfuss, J., Solomon, D. K., et al. (2021). In-situ sampling for krypton-85 groundwater dating. Journal of Hydrology X, 11, 100075.
Abstract: Krypton-85 and other radioactive noble gases are widely used for groundwater dating purposes. 85Kr analysis require large volumes of water to reach the analytical requirements. Conventionally, this water is pumped to the surface to be degassed with a gas extraction system. The large pumping rate may disturb the natural flow field and requires substantial field logistics. Hence, we propose a new in-situ degassing method, in which membrane contactors are used to degas the groundwater directly in the well and gas is collected at the surface. This way, field work is facilitated, groundwater system disturbance is minimized, and the gas sample is collected at a specific depth. We demonstrate the tightness of the system regarding atmospheric air contamination for a collection times of 24 h, which is sufficient for both low-level counting and laser-based counting methods for 85Kr. The minimal borehole diameter is 7.5 cm for the prototype presented in this research but can easily be reduced to smaller diameters. In a case study, we compare the results obtained with the new passive method with those from a conventional packer setup sampling. Additionally, 3H/3He samples were collected for both sampling regimes and the dating results were compared with those from 85Kr. A good agreement between tracer ages is demonstrated and the age stratigraphy is consistent with the expected age distribution for a porous unconfined aquifer. In addition, our study emphasizes the differences between the age information sampled with various methods. In conclusion, we demonstrate that the new in situ quasi-passive method provides a more representative age stratigraphy with depth in most cases.
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Bresinsky, L., Kordilla, J., Hector, T., Engelhardt, I., Livshitz, Y., & Sauter, M. (2023). Managing climate change impacts on the Western Mountain Aquifer: Implications for Mediterranean karst groundwater resources. Journal of Hydrology X, 20, 100153.
Abstract: Many studies highlight the decrease in precipitation due to climate change in the Mediterranean region, making it a prominent hotspot. This study examines the combined impacts of climate change and three groundwater demand scenarios on the water resources of the Western Mountain Aquifer (WMA) in Israel and the West Bank. While commonly used methods for quantifying groundwater recharge and water resources rely on regression models, it is important to acknowledge their limitations when assessing climate change impacts. Regression models and other data-driven approaches are effective within observed variability but may lack predictive power when extrapolated to conditions beyond historical fluctuations. A comprehensive assessment requires distributed process-based numerical models incorporating a broader range of relevant physical flow processes and, ideally, ensemble model projections. In this study, we simulate the dynamics of dual-domain infiltration and precipitation partitioning using a HydroGeoSphere (HGS) model for variably saturated water flow coupled to a soil-epikarst water balance model in the WMA. The model input includes downscaled high-resolution climate projections until 2070 based on the IPCC RCP4.5 scenario. The results reveal a 5% to 10% decrease in long-term average groundwater recharge compared to a 30% reduction in average precipitation. The heterogeneity of karstic flow and increased intensity of individual rainfall events contribute to this mitigated impact on groundwater recharge, underscoring the importance of spatiotemporally resolved climate models with daily precipitation data. However, despite the moderate decrease in recharge, the study highlights the increasing length and severity of consecutive drought years with low recharge values. It emphasizes the need to adjust current management practices to climate change, as freshwater demand is expected to rise during these periods. Additionally, the study examines the emergence of hydrogeological droughts and their propagation from the surface to the groundwater. The results suggest that the 48-month standardized precipitation index (SPI-48) is a suitable indicator for hydrogeological drought emergence due to reduced groundwater recharge.
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Ollivier, C. C., Carrière, S. D., Heath, T., Olioso, A., Rabefitia, Z., Rakoto, H., et al. (2023). Ensemble precipitation estimates based on an assessment of 21 gridded precipitation datasets to improve precipitation estimations across Madagascar. Journal of Hydrology: Regional Studies, 47, 101400.
Abstract: Study region this study focuses on Madagascar. This island is characterized by a great diversity of climate, due to trade winds and the varying topography. This country is also undergoing extreme rainfall events such as droughts and cyclones. Study focus the rain gauge network of Madagascar is limited (about 30 stations). Consequently, we consider relevant satellite-based precipitation datasets to fill gaps in ground-based datasets. We assessed the reliability of 21 satellite-based and reanalysis precipitation products (P-datasets) through a direct comparison with 24 rain gauge station measurements at the monthly time step, using four statistical indicators: Kling-Gupta Efficiency (KGE), Correlation Coefficient (CC), Root Mean Square Error (RMSE), and Bias. Based on this first analysis, we produced a merged dataset based on a weighted average of the 21 products. New hydrological insights for the region based on the KGE and the CC scores, WFDEI (WATCH Forcing Data methodology applied to ERA-Interim), CMORPH-BLD (Climate Prediction Center MORPHing satellite-gauge merged) and MSWEP (Multi-Source Weighted Ensemble Precipitation) are the most accurate for estimating rainfall at the national scale. Additionally, the results reveal a high discrepancy between bio-climatic regions. The merged dataset reveals higher performance than the other products in all situations. These results demonstrate the usefulness of a merging approach in an area with a deficit of rainfall data and a climatic and topographic diversity.
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Zaeri, A., Mohammadi, Z., & Rezanezhad, F. (2023). Determining the source and mechanism of river salinity: An integrated regional study. Journal of Hydrology: Regional Studies, 47, 101411.
Abstract: Study region Zohreh River Basin, Southwest Iran Study focus The salinity of Zohreh River sharply increases in three salinity zones (SZs) along the river named SZ1, SZ2 (the focus of this study), and SZ3. Determining the salinity sources and salinization mechanism using an integrated approach including geological, hydrochemical, isotopic, geophysical, river sinuosity and hydrocarbon analysis are the main objectives of this study. The study focuses on the combination of evidence of regional-scale (i.e., river sinuosity and seismic data) and small-scale (i.e., drilling core analysis). New hydrologic insights for the region Among several known sources of river salinity, it was found that the water quality of the Zohreh River is mainly threatened by the salt-bearing Gachsaran Formation and oil-field brine. It is concluded that halite brine and oil-field brine simultaneously cause the salinization in SZ2, and their contributions were delineated to be 95% and 5%, respectively. The lack of reliable geological evidence to support halite dissolution in surficial layers by circulating waters suggests the possibility of a deep source of halite brine in SZ2. The results revealed that deep halite brine of the salt layers of Gachsaran Formation is mainly responsible for the salinization of SZ2. The mechanism of deep brine penetration to the river through the hidden fault failures detected by the combination of river sinuosity analysis and geophysical data for the first time.
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