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Kisi, O., Heddam, S., Parmar, K. S., Petroselli, A., Külls, C., & Zounemat-Kermani, M. (2025). Integration of Gaussian process regression and K means clustering for enhanced short term rainfall runoff modeling. Scientific Reports, 15(1), 7444.
Abstract: Accurate rainfall-runoff modeling is crucial for effective watershed management, hydraulic infrastructure safety, and flood mitigation. However, predicting rainfall-runoff remains challenging due to the nonlinear interplay between hydro-meteorological and topographical variables. This study introduces a hybrid Gaussian process regression (GPR) model integrated with K-means clustering (GPR-K-means) for short-term rainfall-runoff forecasting. The Orgeval watershed in France serves as the study area, providing hourly precipitation and streamflow data spanning 1970–2012. The performance of the GPR-K-means model is compared with standalone GPR and principal component regression (PCR) models across four forecasting horizons: 1-hour, 6-hour, 12-hour, and 24-hour ahead. The results reveal that the GPR-K-means model significantly improves forecasting accuracy across all lead times, with a Nash-Sutcliffe Efficiency (NSE) of approximately 0.999, 0.942, 0.891, and 0.859 for 1-hour, 6-hour, 12-hour, and 24-hour forecasts, respectively. These results outperform other ML models, such as Long Short-Term Memory, Support Vector Machines, and Random Forest, reported in the literature. The GPR-K-means model demonstrates enhanced reliability and robustness in hourly streamflow forecasting, emphasizing its potential for broader application in hydrological modeling. Furthermore, this study provides a novel methodology for combining clustering and Bayesian regression techniques in surface hydrology, contributing to more accurate and timely flood prediction.
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Fidelibus, M. D., Balacco, G., Alfio, M. R., Arfaoui, M., Bassukas, D., Güler, C., et al. (2025). A chloride threshold to identify the onset of seawater/saltwater intrusion and a novel categorization of groundwater in coastal aquifers. Journal of Hydrology, 653, 132775.
Abstract: Seawater intrusion is the primary cause of groundwater salinisation in coastal aquifers. However, attributing salinisation solely to seawater intrusion may not always be accurate, given the likely presence of other sources. To understand if salinisation comes from seawater intrusion and its onset is crucial for groundwater management, but there are no definite threshold values for common indicators such as chlorides. Based on 1662 groundwater analyses from five Mediterranean coastal aquifers, the study aimed to distinguish the effects of mixing with present-day seawater from those caused by other sources. The trend analysis of cumulative probability plots of chloride (and total dissolved solids) is a key method for discriminating different groundwater salinisation sources and processes. Results establish that chloride, as a non-reactive tracer, is a more reliable indicator of seawater intrusion than total dissolved solids, a reactive indicator. A chloride concentration threshold of 200 mg/L identifies the seawater intrusion onset. The threshold validation comes from groundwater salinisation facies, as provided by groundwater-type codification. Fresh groundwater (Cl < 200 mg/L) anomalous total dissolved solids highlight the input of non-chloride salts and pollutants, providing caution regarding using total dissolved solids to recognise seawater intrusion. Beyond the threshold (Cl > 200 mg/L), data disclose emergent signals of salinisation sources and water–rock interaction processes overlapping seawater intrusion or the involvement of saline fluids different from present-day seawater. The threshold and a new categorisation of groundwater in coastal aquifers according to salinisation processes provide a benchmark for identifying and managing seawater intrusion in the Mediterranean area.
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Krüger, N., & Külls, C. (2025). Partitioning of flows in the unsaturated zone. Journal of Hydrology, 652, 132643.
Abstract: Water transport in the unsaturated zone results from nonlinear relationships between soil moisture state, suction gradients, and conductivity, leading to complex flow processes. This study presents an innovative approach for discretizing the pore spectrum and partitioning capillary-dominated flows into an arbitrary number of pore spaces. While preserving Richards’ equation and soil physical Van Genuchten and Mualem relationships, pore spaces are discretized into fine, medium, and macropores to quantify their individual states and flow contributions to total percolation. The approach has been applied to a continuously monitored soil profile with a depth of 1800 mm over a period of two years. The results reveal that the medium pore space, with a pore diameter of 10 µm < d ≤ 63 µm, plays a significant role, accounting for 80–90 % of the total percolation, controlling most of the transport process. The fine pore space (d ≤ 10 µm) remains consistently active throughout the entire period, contributing only 2–10 % to total percolation, being primarily defined by their interactions with larger pores. Macropores (d > 63 µm) emerge as particularly active during winter, enabling rapid vertical water displacement with contributions of up to 13 % through distinct fast flow events. Flow partitioning further illustrates the development of the critical zone during summer.
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Henke, J. - M. (2021). Ηραίον Σάμου. Αρχαιολογία & Τέχνες. 136.2021, , 118–145.
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Heiden, J. 1955-. (2019). Das Heraion von Samos – Traditionsgrabung mit Perspektiven. Athenea, 2018/2019, , 20–22.
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