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Author Gimeno, M.J.; Tullborg, E.-L.; Nilsson, A.-C.; Auqué, L.F.; Nilsson, L. url  openurl
  Title Hydrogeochemical characterisation of the groundwater in the crystalline basement of Forsmark, the selected area for the geological nuclear repositories in Sweden Type Journal Article
  Year 2023 Publication Journal of Hydrology Abbreviated Journal  
  Volume 624 Issue Pages 129818  
  Keywords Crystalline bedrock, Deep geological repository, Glacial meltwater intrusion, Groundwater mixing, Hydrogeochemical model, Nuclear waste disposal  
  Abstract (up) Numerous groundwater analyses from the crystalline bedrock in the Forsmark area have been performed between 2002 and 2019, together with thorough geological, geophysical, and hydrogeological studies, within the site investigations carried out by the Swedish Nuclear Fuel and Waste Management Company. The groundwater samples have been taken from boreholes down to ≈ 1000 m and the analysis include major- and trace-elements, stable and radiogenic isotopes, gases and microbes. The chemical and isotopic composition of these groundwaters evidences the presence of non-marine brackish to saline groundwaters with very long residence times (many hundreds of thousands of years) and a series of complex mixing events resulting from the recharge of different waters over time: glacial meltwaters, probably from different glaciations of which the latest culminated some 20,000 years ago, and marine waters from the Baltic starting some 7000 years ago. Later, meteoric water and present Baltic Sea water have recharged in different parts of the upper 100 m. These mixing events have also triggered chemical and microbial reactions that have conditioned some of the important groundwater parameters and, together with the structural complexity of the area, they have promoted a heterogeneous distribution of groundwater compositions in the bedrock. Due to these evident differences in chemistry, residence time and origin of the groundwater, several groundwater types were defined in order to facilitate the visualisation and communication. The differentiation (linked to the paleohydrological history of the area) was based on Cl concentration, Cl/Mg ratio (marine component), and δ18O value (glacial component). The work presented in this paper increases the understanding of the groundwater evolution in fractured and compartmentalised aquifers where mixing processes are the most important mechanisms. The model proposed to characterise the present groundwater system of the Forsmark area will also help to predict the future hydrogeochemical behaviour of the groundwater system after the construction of the repositories for the nuclear wastes.  
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  ISSN 0022-1694 ISBN Medium  
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  Notes Approved no  
  Call Number THL @ christoph.kuells @ gimeno_hydrogeochemical_2023 Serial 137  
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Author Gasse, F. url  openurl
  Title Hydrological changes in the African tropics since the Last Glacial Maximum Type Journal Article
  Year 2000 Publication Quaternary Science Reviews Abbreviated Journal  
  Volume 19 Issue 1 Pages 189-211  
  Keywords  
  Abstract (up) Paleohydrological data from the African tropics and subtropics, including lake, groundwater and speleothem records, are reviewed to show how environments and climates from both hemispheres are inter-related. Although orbitally induced changes in the monsoon strength account for a large part of long-term climatic changes in tropical Africa, the Late Pleistocene–Holocene hydrological fluctuations rather appear to have been a series of abrupt events that reflect complex interactions between orbital forcing, atmosphere, ocean and land surface conditions. During the Last Glacial Maximum (23–18ka BP), most records indicate that generally dry conditions have prevailed in both hemispheres, associated with lower tropical land- and sea-surface temperatures. This agrees with simulations using coupled ocean–atmosphere models, which predict cooling and reduced summer precipitation in tropical Africa; the global hydrological cycle was weaker than today when the extent of large polar ice-sheets and sea-ice was a prominent forcing factor of the Earth’s climate. Glacial-interglacial climatic changes started early: a first wetting/warming phase at ca. 17–16ka BP took place during a period of rapid temperature increase in Antarctica. Next, two drastic arid-humid transitions in equatorial and northern Africa occurred around 15–14.5ka BP and 11.5–11ka BP. Both are thought to match the major Greenland warming events, in concert with the switching of the oceanic thermohaline circulation to modern mode. However, part of the climatic signal after 15 ka BP also seems related to the Antarctica climate. During the Holocene, Africa has also experienced rapid hydrological fluctuations of dramatic magnitude compared to the climatic changes at high latitudes. In particular, major dry spells occurred around 8.4–8ka and 4.2–4ka BP in the northern monsoon domain. Comparison with other parts of the world indicates that these events have a worldwide distribution but different regional expressions. In the absence of large polar ice sheets, changes in the continental hydrological cycles in the tropics may have a significant impact on the global climate system. Climate information gathered here allows to identify geographical and methodological gaps, and raise some scientific questions that remain to be solved to better understand how the tropics respond to changes in major climate-forcing factors, and how they influence climate globally.  
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  ISSN 0277-3791 ISBN Medium  
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  Notes Approved no  
  Call Number THL @ christoph.kuells @ gasse_hydrological_2000 Serial 96  
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Author Lawrinenko, M.; Kurwadkar, S.; Wilkin, R.T. url  openurl
  Title Long-term performance evaluation of zero-valent iron amended permeable reactive barriers for groundwater remediation – A mechanistic approach Type Journal Article
  Year 2023 Publication Geoscience Frontiers Abbreviated Journal  
  Volume 14 Issue 2 Pages 101494  
  Keywords Geochemistry, Iron, Permeable reactive barrier, Plating reactions, Reduction potential, Surface passivation  
  Abstract (up) Permeable reactive barriers (PRBs) are used for groundwater remediation at contaminated sites worldwide. This technology has been efficient at appropriate sites for treating organic and inorganic contaminants using zero-valent iron (ZVI) as a reductant and as a reactive material. Continued development of the technology over the years suggests that a robust understanding of PRB performance and the mechanisms involved is still lacking. Conflicting information in the scientific literature downplays the critical role of ZVI corrosion in the remediation of various organic and inorganic pollutants. Additionally, there is a lack of information on how different mechanisms act in tandem to affect ZVI-groundwater systems through time. In this review paper, we describe the underlying mechanisms of PRB performance and remove isolated misconceptions. We discuss the primary mechanisms of ZVI transformation and aging in PRBs and the role of iron corrosion products. We review numerous sites to reinforce our understanding of the interactions between groundwater contaminants and ZVI and the authigenic minerals that form within PRBs. Our findings show that ZVI corrosion products and mineral precipitates play critical roles in the long-term performance of PRBs by influencing the reactivity of ZVI. Pore occlusion by mineral precipitates occurs at the influent side of PRBs and is enhanced by dissolved oxygen and groundwater rich in dissolved solids and high alkalinity, which negatively impacts hydraulic conductivity, allowing contaminants to potentially bypass the treatment zone. Further development of site characterization tools and models is needed to support effective PRB designs for groundwater remediation.  
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  ISSN 1674-9871 ISBN Medium  
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  Notes Approved no  
  Call Number THL @ christoph.kuells @ lawrinenko_long-term_2023 Serial 143  
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Author Custódio, D.A.; Ghisi, E. url  openurl
  Title Impact of residential rainwater harvesting on stormwater runoff Type Journal Article
  Year 2023 Publication Journal of Environmental Management Abbreviated Journal  
  Volume 326 Issue Pages 116814  
  Keywords Rainwater harvesting, Residential buildings, Stormwater runoff, Floods, Computer simulation  
  Abstract (up) Population increase, climate change and soil impermeability are factors causing floods in large urban centres. Such places also always have water shortage problems. This research aims to evaluate the influence of rainwater harvesting in residential buildings on stormwater in a basin located in southern Brazil (Rio Cachoeira Basin). Urbanised and non-urbanised areas, soil types, curve numbers and time of concentration of each sub-basin were taken into account. Through the HEC-HMS programme, it was possible to calculate hydrographs for the base scenario (when there is no rainwater harvesting). Then, rainwater tanks for the residential buildings were sized using the computer programme Netuno. In the second scenario, there is rainwater harvesting in all residential buildings. Thus, the hydrographs for the second scenario were also calculated. The peak flow reduction potentials for the sub-basins ranged from 2.7% to 14.3%. The highest percentage (14.3%) did not occur in the sub-basin with the most extensive roof area; such highest peak flow reduction occurred in Bom Retiro sub-basin. In Bom Retiro sub-basin, there are more houses than multi-storey residential buildings. Even when considering the full potential of rainwater harvesting for roof areas of all existing buildings in the Rio Cachoeira Basin, the average potential reduction in peak flow was 7.2%. The conclusion is that rainwater tanks in residential buildings have little influence on stormwater runoff, and the stormwater runoff will be less affected when the area of the hydrographic basin is larger. Thus, the reduction in peak flows is insignificant when considering the flooding in the region.  
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  ISSN 0301-4797 ISBN Medium  
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  Notes Approved no  
  Call Number THL @ christoph.kuells @ Custodio2023116814 Serial 231  
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Author Singh, A.; Patel, S.; Bhadani, V.; Kumar, V.; Gaurav, K. url  openurl
  Title AutoML-GWL: Automated machine learning model for the prediction of groundwater level Type Journal Article
  Year 2024 Publication Engineering Applications of Artificial Intelligence Abbreviated Journal  
  Volume 127 Issue Pages 107405  
  Keywords AutoML, Bayesian optimisation, Groundwater, Machine learning  
  Abstract (up) Predicting groundwater levels is pivotal in curbing overexploitation and ensuring effective water resource governance. However, groundwater level prediction is intricate, driven by dynamic nonlinear factors. To comprehend the dynamic interaction among these drivers, leveraging machine learning models can provide valuable insights. The drastic increase in computational capabilities has catalysed a substantial surge in the utilisation of machine learning-based solutions for effective groundwater management. The performance of these models highly depends on the selection of hyperparameters. The optimisation of hyperparameters is a complex process that often requires application-specific expertise for a skillful prediction. To mitigate the challenge posed by hyperparameter tuning’s problem-specific nature, we present an innovative approach by introducing the automated machine learning (AutoML-GWL) framework. This framework is specifically designed for precise groundwater level mapping. It seamlessly integrates the selection of best machine learning model and adeptly fine-tunes its hyperparameters by using Bayesian optimisation. We used long time series (1997-2018) data of precipitation, temperature, evaporation, soil type, relative humidity, and lag of groundwater level as input features to train the AutoML-GWL model while considering the influence of Land Use Land Cover (LULC) as a contextual factor. Among these input features, the lag of groundwater level emerged as the most relevant input feature. Once the model is trained, it performs well over the unseen data with a strong correlation of coefficient (R = 0.90), low root mean square error (RMSE = 1.22), and minimal bias = 0.23. Further, we compared the performance of the proposed AutoML-GWL with sixteen benchmark algorithms comprising baseline and novel algorithms. The AutoML-GWL outperforms all the benchmark algorithms. Furthermore, the proposed algorithm ranked first in Friedman’s statistical test, confirming its reliability. Moreover, we conducted a spatial distribution and uncertainty analysis for the proposed algorithm. The outcomes of this analysis affirmed that the AutoML-GWL can effectively manage data with spatial variations and demonstrates remarkable stability when faced with small uncertainties in the input parameters. This study holds significant promise in revolutionising groundwater management practices by establishing an automated framework for simulating groundwater levels for sustainable water resource management.  
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  ISSN 0952-1976 ISBN Medium  
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  Notes Approved no  
  Call Number THL @ christoph.kuells @ singh_automl-gwl_2024 Serial 168  
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Author Brook, G.A.; Railsback, L.B.; Marais, E. url  openurl
  Title Reassessment of carbonate ages by dating both carbonate and organic material from an Etosha Pan (Namibia) stromatolite: Evidence of humid phases during the last 20ka Type Journal Article
  Year 2011 Publication Quaternary International Abbreviated Journal  
  Volume 229 Issue 1 Pages 24-37  
  Keywords  
  Abstract (up) Previous research on lacustrine stromatolites from Etosha Pan in Namibia obtained ages on carbonate close to or beyond the limits of radiocarbon dating. These ages suggested that the basin was likely not subject to extensive flooding during the last ca. 40ka. This study shows that AMS radiocarbon ages for the carbonate of a stromatolite from Poacher’s Point are 15–21ka older than ages for organic material in the stromatolite structure. Calibrated ages range from 30 to 40ka for carbonate and 3–19ka for the organic residue. The new ages, together with petrographic and isotopic data for the stromatolite, have provided important new information on past flooding of Etosha Pan including evidence of prolonged lacustrine conditions during the Holocene Climatic Optimum.  
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  ISSN 1040-6182 ISBN Medium  
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  Notes Approved no  
  Call Number THL @ christoph.kuells @ brook_reassessment_2011 Serial 110  
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Author Lach, P.; Cathelineau, M.; Brouand, M.; Fiet, N. url  openurl
  Title In-situ Isotopic and Chemical Study of Pyrite from Chu-Sarysu (Kazakhstan) Roll-front Uranium Deposit Type Journal Article
  Year 2015 Publication Procedia Earth and Planetary Science Abbreviated Journal  
  Volume 13 Issue Pages 207-210  
  Keywords LA-ICP-MS, pyrite, roll-front, SIMS, sulfur isotopy, traces elements, uranium  
  Abstract (up) Pyrite is common in roll-front type uranium deposit in Chu-sarysu basin, Kazakhstan. Combined in-situ microstructural, isotopic and chemical analysis of pyrite indicates variation in precipitation conditions and in fluid composition. Broad-scale δ34S heterogeneity indicates a complex multi-facet evolution. First generation authigenic framboïdal aggregates are biogenic as demonstrated by the lowest δ34S values of -48‰ to -28‰. The latest generation pyrites are probably hydrothermal with greater δ34S variation (-30‰ to +12‰). This hydrothermal pyrite commonly displays variable enrichment of several trace elements especially As, Co and Ni. Strong variation in δ34S values and variable trace element enrichment is interpreted in terms of continuous variations in fluid composition.  
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  Series Volume Series Issue Edition  
  ISSN 1878-5220 ISBN Medium  
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  Notes Approved no  
  Call Number THL @ christoph.kuells @ lach_-situ_2015 Serial 182  
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Author Sedghi, M.M.; Zhan, H. url  openurl
  Title On the discharge variation of a qanat in an alluvial fan aquifer Type Journal Article
  Year 2022 Publication Journal of Hydrology Abbreviated Journal  
  Volume 610 Issue Pages 127922  
  Keywords Analytical solution, Wedge-shaped aquifer, Image well, Areal recharge  
  Abstract (up) Qanat is a passive (unpumped) horizontal well (or a slant well with a very mild inclined angle) that is capable of extracting water from aquifers by gravity. Many qanats are constructed along the radius of the alluvial fan wedge-shaped aquifers. Analytical modeling of such a qanat-aquifer system provides great benefit for quickly screening different designs of qanats and accessing the performance of qanat discharge in the field. The previous analytical modeling of discharge of qanats, however, did not consider the wedge-shaped aquifers. Thus, the goal of this research is to obtain semi-analytical solutions of discharge variations of qanats in alluvial fan aquifers with nearby pumping wells, subjected to areal recharges due to rainfall. The uniform head boundary is considered inside the qanat (because of its enormous permeability in respect to the background aquifer). The influences of the aquifer lateral boundaries on discharge of qanat and its sensitivity to hydraulic and geometric parameters are explored. The influences of the lateral boundaries on the discharge of qanat due to areal recharge and nearby pumping wells discharge are also explored. The results of this study can be utilized for multiple purposes: 1) to predict the discharge of qanat in an alluvial fan aquifer and explore the influences of the areal recharge and nearby pumping well discharge; 2) to estimate the hydraulic parameters of the alluvial fan aquifer depleted by a qanat; 3) to determine the location of the nearby pumping well to minimize its influences on the discharge of a qanat; 4) to calculate the water budgets of aquifers depleted by qanats and pumping wells and replenished by areal recharge among other applications. This paper is an extension to the work presented by Sedghi and Zhan (2020) (which concerns an infinite unconfined aquifer) for an unconfined alluvial fan aquifer setting.  
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  Series Volume Series Issue Edition  
  ISSN 0022-1694 ISBN Medium  
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  Notes Approved no  
  Call Number THL @ christoph.kuells @ Sedghi2022127922 Serial 267  
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Author Sedghi, M.M.; Zhan, H. url  openurl
  Title Semi-analytical solutions of discharge variation of a qanat in an unconfined aquifer subjected to general areal recharge and nearby pumping well discharge Type Journal Article
  Year 2020 Publication Journal of Hydrology Abbreviated Journal  
  Volume 584 Issue Pages 124691  
  Keywords Analytical solution, Laplace domain, Screen segmentation, Qanat, Areal recharge, Constant head  
  Abstract (up) Qanat is a type of drain that extract water from aquifers by gravity. Significant amount of fresh water used in Middle East and other parts of the world are supplied by qanats. Despite their importance, discharge variation of these type of wells received almost no attention. The aim of this research is to obtain a Laplace domain solution of discharge variation of a qanat installed in an anisotropic unconfined aquifer subjected to arbitrary areal recharge and nearby pumping well(s) discharge. A new semi-analytical solution of drawdown is obtained first to implement the effects of arbitrary areal recharge and nearby pumping well(s) using the principle of superposition. Then, the discharge variation solution of the qanat is obtained from the drawdown solution. To establish a constant-head boundary condition at the qanat periphery, the qanat is discretized into several segments. The results of this study are presented in dimensionless discharge-dimensionless time curves. The effects of hydraulic as well as geometric parameters on the discharge variation of the qanat due to arbitrary areal recharge, falling of water table from its initial position and discharge of nearby wells are explored. We also investigate the influences of distance and screen depth and location of the nearby well on the discharge variation of the qanat. The results of this study can be utilized for multiple purposes: 1) to predict discharge of qanat in response to rainfall and nearby pumping well(s); 2) to estimate the aquifer parameters using hydrograph of the qanat; 3) to determine optimal location and pumping pattern of the nearby wells to minimize their influences on the discharge of the qanat; 4) to calculate water budget of aquifers drained by a qanat. The equation presented in this work can also be used to estimate discharge of a horizontal drain installed in cropland subjected to arbitrary irrigation pattern.  
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  ISSN 0022-1694 ISBN Medium  
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  Notes Approved no  
  Call Number THL @ christoph.kuells @ Sedghi2020124691 Serial 261  
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Author Hdeib, R.; Aouad, M. url  openurl
  Title Rainwater harvesting systems: An urban flood risk mitigation measure in arid areas Type Journal Article
  Year 2023 Publication Water Science and Engineering Abbreviated Journal  
  Volume 16 Issue 3 Pages 219-225  
  Keywords Rainwater harvesting, Urban floods, Flood map, Hydrodynamic model, Built environment, Arid areas  
  Abstract (up) Rainwater harvesting (RWH) systems have been developed to compensate for shortage in the water supply worldwide. Such systems are not very common in arid areas, particularly in the Gulf Region, due to the scarcity of rainfall and their reduced efficiency in covering water demand and reducing water consumption rates. In spite of this, RWH systems have the potential to reduce urban flood risks, particularly in densely populated areas. This study aimed to assess the potential use of RWH systems as urban flood mitigation measures in arid areas. Their utility in the retention of stormwater runoff and the reduction of water depth and extent were evaluated. The study was conducted in a residential area in Bahrain that experienced waterlogging after heavy rainfall events. The water demand patterns of housing units were analyzed, and the daily water balance for RWH tanks was evaluated. The effect of the implementation of RWH systems on the flood volume was evaluated with a two-dimensional hydrodynamic model. Flood simulations were conducted in several rainfall scenarios with different probabilities of occurrence. The results showed significant reductions in the flood depth and flood extent, but these effects were highly dependent on the rainfall intensity of the event. RWH systems are effective flood mitigation measures, particularly in urban arid regions short of proper stormwater control infrastructure, and they enhance the resilience of the built environment to urban floods.  
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  ISSN 1674-2370 ISBN Medium  
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  Notes Approved no  
  Call Number THL @ christoph.kuells @ Hdeib2023219 Serial 242  
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