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Keywords = hydrogeology of volcanic systems

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25 pages, 6044 KiB  
Article
Application of Pumping Tests to Estimate Hydraulic Parameters of Volcanic Aquifers in Lake Tana Basin, Ethiopia
by Fenta Nigate, Alemu Yenehun, Ashebir Sewale Belay, Desale Kidane Asmamaw and Kristine Walraevens
Water 2025, 17(1), 9; https://doi.org/10.3390/w17010009 - 24 Dec 2024
Viewed by 436
Abstract
The purpose of this study was to enhance the understanding and sustainable groundwater management of volcanic aquifer systems by estimating key hydrogeological parameters. The transmissivity of a volcanic aquifer system was estimated using analytical solutions based on 68 constant rate and recovery data [...] Read more.
The purpose of this study was to enhance the understanding and sustainable groundwater management of volcanic aquifer systems by estimating key hydrogeological parameters. The transmissivity of a volcanic aquifer system was estimated using analytical solutions based on 68 constant rate and recovery data sets collected from various sources. A combination of hydro-lithostratigraphy and diagnostic plots was employed to identify the aquifer types and flow conditions, which facilitated model selection. Transmissivity of the confined aquifer was modeled using both Theis and Cooper–Jacob methods, with the Theis residual drawdown solution utilized for estimation. For the unconfined aquifer, the Neuman method was used, and the Hantush/Jacob method was employed for leaky aquifers. The results showed that the transmissivity of the Tertiary basalt varied from 0.38 m2/d to 860 m2/d, while the Quaternary aquifer system ranged from 2.33 m2/d to 1.8 × 104 m2/d, indicating an increase in transmissivity with younger volcanic flows. Specific capacity (SC) was estimated for 74 wells and the values ranged from 0.62 to 5860 m2/d. This wide variation of specific capacity and transmissivity showed significant heterogeneity within the volcanic aquifers. This study introduces the innovative application of derivative diagnostic plots in groundwater research, offering an efficient approach for analyzing and interpreting pumping test data to characterize aquifer systems in various hydrogeologic units. This study focuses on aquifer characterization in hard rock formation, demonstrating methods that can be applied to similar geological environments globally. For the Blue Nile basin in general and for the Lake Tana basin in particular, the study result of aquifer characterization will contribute to exploration, development, and improved groundwater management in the region. Full article
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13 pages, 5166 KiB  
Article
Quality and Influences of Natural and Anthropogenic Factors on Drinking Water in Rural Areas of Southern Chile
by Norka Fuentes, Aldo Arriagada, Claudio Pareja and Mauricio Molina-Roco
Water 2024, 16(19), 2830; https://doi.org/10.3390/w16192830 - 6 Oct 2024
Viewed by 669
Abstract
Water quality is a fundamental aspect of public health and environmental sustainability. In rural areas, the physicochemical and microbiological quality of drinking water depends not only on hydrogeological conditions but also on anthropogenic activities carried out on the surface of the basin. This [...] Read more.
Water quality is a fundamental aspect of public health and environmental sustainability. In rural areas, the physicochemical and microbiological quality of drinking water depends not only on hydrogeological conditions but also on anthropogenic activities carried out on the surface of the basin. This study aimed to identify natural and anthropogenic influences related to the quality of drinking water in rural areas of southern Chile. In order to perform this, six rural drinking water systems were evaluated. A total of two types of catchment sources (groundwater and surface water) that were located in a longitudinal gradient were used, where coverage and sequences of rocks and soils could be differentiated. The results show that the water delivered by the majority of rural drinking water systems studied was of good quality, meeting the standards of Chilean and international regulations. No fecal coliforms or Escherichia coli were recorded. In addition, we recorded that turbidity, color, pH, concentration of total dissolved solids and fecal coliforms showed significant differences between groundwater and surface water. We also recorded that in two groundwater systems, iron and manganese levels slightly exceeded the regulations, endangering the acceptability of the water. These increases can be related to the natural origins of the metals, linked to the presence of oxides in Andisol- and Utisol-type volcanic soils. Full article
(This article belongs to the Section Water Quality and Contamination)
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27 pages, 13685 KiB  
Article
Using an Open-Source Tool to Develop a Three-Dimensional Hydrogeologic Framework of the Kobo Valley, Ethiopia
by Sisay S. Mekonen, Scott E. Boyce, Abdella K. Mohammed and Markus Disse
Geosciences 2024, 14(1), 3; https://doi.org/10.3390/geosciences14010003 - 20 Dec 2023
Viewed by 2585
Abstract
Groundwater resource management requires understanding the groundwater basin’s hydrogeology and would be improved with the development of a three-dimensional hydrogeologic framework model (HFM). A wide range of methods and software exist to quantify the extent, structure, and properties of geologic systems. However, most [...] Read more.
Groundwater resource management requires understanding the groundwater basin’s hydrogeology and would be improved with the development of a three-dimensional hydrogeologic framework model (HFM). A wide range of methods and software exist to quantify the extent, structure, and properties of geologic systems. However, most geologic software is proprietary and cost-prohibitive for use in developing countries. GemPy is a Python-based, open-source (no-cost) tool for generating three-dimensional geological models. This study uses available data and GemPy to develop the Kobo Valley Hydrogeologic Framework Model (KV-HFM), a three-dimensional HFM for Kobo Valley in northern Ethiopia, which is part of the East African Rift System. The KV-HFM is a conceptual model that comprises the hydrostratigraphy, structural features, and hydraulic properties of the Kobo Valley groundwater system. The limited data described the extent and altitude of the hydrostratigraphic units using the GemPy implicit potential–field interpolation. The KV-HFM showed the existence of an east-to-west, structural-based groundwater divide composed of volcanic rock and clay. This divide splits the catchment into two groundwater systems with limited interconnected flow. This study illustrates the use of open-source software for developing an HFM using sparse, existing geologic data. Full article
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16 pages, 9268 KiB  
Article
Geochemical and Isotopic Evidence for Investigating the Impacts of Landfills on Groundwater: A Case Study in the Campania Region (Southern Italy)
by Stefania Stevenazzi, Elena Del Gaudio, Domenico Ruggiero, Ciro D’Aniso, Anna Maria Patelli and Daniela Ducci
Sustainability 2023, 15(22), 15822; https://doi.org/10.3390/su152215822 - 10 Nov 2023
Cited by 3 | Viewed by 870
Abstract
In this study, we present the hydrogeological, hydrogeochemical and isotopic characterisation and monitoring activity of a closed landfill located in the northern sector of the Phlegrean Fields groundwater body in the Campania Region (Southern Italy). The aim of the study is to distinguish [...] Read more.
In this study, we present the hydrogeological, hydrogeochemical and isotopic characterisation and monitoring activity of a closed landfill located in the northern sector of the Phlegrean Fields groundwater body in the Campania Region (Southern Italy). The aim of the study is to distinguish between natural enrichments (e.g., geogenic sources) and anthropogenic pressures (e.g., leakages from the landfill body) causing anomalously high concentrations of some metals (As, F, Fe, Mn) in groundwater. Major anions, cations, metals, water-stable isotopes, carbon isotopes and tritium were analysed. The results show that high As, F and Fe concentrations are due to adsorption–desorption processes occurring in the aquifer hosted in the volcanic rocks/deposits or the occurrence of upwelling hydrothermal fluids related to the volcanic activity of the Phlegrean Fields, which may cause metal mobilisation. High localised Mn concentrations cannot be solely related to natural processes or to groundwater contamination due to leachate leakage from the landfill body. Instead, we hypothesise a leakage from the landfill gas system. The outcomes of this study show the advantages of the coupled use of physico-chemical and isotopic analyses in improving the comprehension of geochemical processes in areas characterised by the presence of municipal landfills. Full article
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21 pages, 3274 KiB  
Article
Uranium Geochemistry of Italian Travertines and Calcareous Tufas: Exploring the Relationship between Carbonate Deposition, Groundwater Circulation and Subsurface Geology
by Francesca Giustini and Mauro Brilli
Minerals 2023, 13(6), 782; https://doi.org/10.3390/min13060782 - 8 Jun 2023
Viewed by 1520
Abstract
A database consisting of 163 data on the uranium content and 234U/238U initial activity ratio of 15 Italian travertine and calcareous tufa sites was created using data from the relevant literature. Using a graphical method, data were interpreted considering the [...] Read more.
A database consisting of 163 data on the uranium content and 234U/238U initial activity ratio of 15 Italian travertine and calcareous tufa sites was created using data from the relevant literature. Using a graphical method, data were interpreted considering the U geochemistry in natural environments as well as the geological, hydrogeological and hydrogeochemical settings of each site. The U content and 234U/238U initial activity ratio in travertine and tufa appear to be affected by different factors, such as the availability of U in the aquifer rocks, the redox state of the waters, and the alpha-active radionuclide recoil phenomenon. The data allow the identification of four groups of travertines/tufas: (i) those precipitated from circulating groundwater, with a short/fast flow path, in volcanic rocks with a high radionuclide content; (ii) those precipitated from circulating groundwater, with a long, deep flow path in carbonate/evaporite formations with a relatively low radionuclide content; and (iii) those precipitated from cold waters associated with riverine systems, which are characterized by oxidizing conditions and fed by high-discharge springs recharged by carbonate aquifers. The fourth group represents the intermediate situations frequently occurring due to the mixing of waters from different aquifers. The results suggest an interpretative model that might contribute to the paleo-environmental reconstruction of fossil travertine and calcareous tufa depositing systems. Full article
(This article belongs to the Special Issue Geochemistry of Travertines and Calcareous Tufas)
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17 pages, 2858 KiB  
Article
Hydrogeochemistry and Strontium Isotopic Signatures of Mineral Waters from Furnas and Fogo Volcanoes (São Miguel, Azores)
by Letícia Ferreira, José Virgílio Cruz, Fatima Viveiros, Nuno Durães, Rui Coutinho, César Andrade, José Francisco Santos and Maria Helena Acciaioli
Water 2023, 15(2), 245; https://doi.org/10.3390/w15020245 - 5 Jan 2023
Cited by 3 | Viewed by 1839
Abstract
This study focused on 13 water samples collected from two of the main active volcanoes (Furnas and Fogo) at São Miguel, Azores. Based on the major element composition, the waters are classified into Na-HCO3 and Na-Cl types. While the concentrations of chloride [...] Read more.
This study focused on 13 water samples collected from two of the main active volcanoes (Furnas and Fogo) at São Miguel, Azores. Based on the major element composition, the waters are classified into Na-HCO3 and Na-Cl types. While the concentrations of chloride seem to reflect the contribution of sea salt aerosols, the behavior of the main cationic species and Sr in the analyzed waters appear to have been largely controlled by the interaction between meteoric waters and the underlying bedrock. The temperature and input of CO2 from the secondary volcanic activity are enhancing the silicate leaching. The stable isotopic data show that these waters have a meteoric origin (δ18O = −2.03 to −4.29‰; δ2H = −7.6 to −17.4‰) and are influenced by a deep hydrothermal/volcanic carbon source (δ13C = −4.36 to −7.04‰). The values of δ34S (0.13 to 12.76‰) reflects a juvenile sulfur source derived from the leaching of volcanic rocks. The Sr isotopic ratios show a slight difference between the values from Furnas (87Sr/86Sr = 0.705235–0.705432) and Fogo (87Sr/86Sr = 0.705509–0.707307) whereas the Furnas waters are less radiogenic. The Sr isotope also shows that the hydrochemical signatures of the groundwater was controlled by the rock leaching, and the samples Furnas reached water-rock isotopic equilibrium. Full article
(This article belongs to the Special Issue Contribution of Carbon Dioxide from Water Bodies to the Atmosphere)
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21 pages, 2683 KiB  
Review
Not All Rivers Are Created Equal: The Importance of Spring-Fed Rivers under a Changing Climate
by Robert A. Lusardi, Andrew L. Nichols, Ann D. Willis, Carson A. Jeffres, A. Haven Kiers, Erwin E. Van Nieuwenhuyse and Randy A. Dahlgren
Water 2021, 13(12), 1652; https://doi.org/10.3390/w13121652 - 12 Jun 2021
Cited by 11 | Viewed by 5014
Abstract
In the Western United States, volcanic spring-fed rivers are anticipated to become increasingly more important for salmonids and other native fishes, as these rivers will retain coldwater habitats as the climate warms. Despite this, little is known about the hydro-biogeochemical interactions within these [...] Read more.
In the Western United States, volcanic spring-fed rivers are anticipated to become increasingly more important for salmonids and other native fishes, as these rivers will retain coldwater habitats as the climate warms. Despite this, little is known about the hydro-biogeochemical interactions within these ecosystems. A review of existing literature on spring-fed rivers, coupled with a decade of research on volcanic spring-fed rivers of northern California, finds that these systems are exceptionally productive and exhibit stable environmental conditions. These unique conditions stem from hydrogeologic processes typical of young volcanic terrains. Aquatic macrophytes, common to some nutrient-rich spring-fed systems, play a disproportionate role in hydrologic and geomorphic processes by facilitating ecological interactions and velocity conditions that improve juvenile salmonid growth. We find that volcanic spring-fed rivers are also resilient to climate change, due not only to their ability to dampen water temperature changes through deep groundwater flow but also because of their nutrient-driven high ecosystem productivity, which may enable coldwater species to metabolically compensate for marginal increases in water temperature. Understanding the fundamental geomorphic and ecological differences between these rare ecosystems and their numerically dominant runoff rivers is essential for developing long-term conservation strategies for coldwater species under a rapidly changing climate. Full article
(This article belongs to the Special Issue Endangered Freshwater Ecosystems: Threats and Conservation Needs)
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28 pages, 40687 KiB  
Review
Water Resources Studies in Headwaters of the Blue Nile Basin: A Review with Emphasis on Lake Water Balance and Hydrogeological Characterization
by Alemu Yenehun, Mekete Dessie, Mulugeta Azeze, Fenta Nigate, Ashebir Sewale Belay, Jan Nyssen, Enyew Adgo, Ann Van Griensven, Marc Van Camp and Kristine Walraevens
Water 2021, 13(11), 1469; https://doi.org/10.3390/w13111469 - 24 May 2021
Cited by 8 | Viewed by 4721
Abstract
The Lake Tana Basin, comprising the largest natural lake in Ethiopia, is the source and the uppermost part of the Upper Blue Nile Basin. In this review paper, research papers, mainly on the rainfall-runoff modeling and lake water balance, and on the hydrogeology, [...] Read more.
The Lake Tana Basin, comprising the largest natural lake in Ethiopia, is the source and the uppermost part of the Upper Blue Nile Basin. In this review paper, research papers, mainly on the rainfall-runoff modeling and lake water balance, and on the hydrogeology, have been reviewed. The earlier water balance estimation attempts used simple conceptual and statistical approaches and calculate on a monthly timescale. More recent research has been using advanced semi-physically or physically based distributed hydrological models. Accordingly, mean annual precipitation over the lake was estimated in the range 36.1–53.1%; lake evaporation at 45.3–57.5%; river inflow (all gauged and estimated ungauged) at 43.6–63.9%; and river (lake) water outflow at 0–9.2%. With the few isotope studies, groundwater inflow and outflow are found insignificant. Different studies had estimated groundwater recharge, ranging from 57 mm to 850 mm. The basin has a heterogenous aquifer system consisting of different volcanic rocks and alluvio-lacustrine sediments. Generally, groundwater with low TDS, Ca–Mg–HCO3 type, isotopically relatively enriched, and high TDS, Na–HCO3 type, isotopically relatively depleted, water types have been identified. In this paper, major research gaps such as aquifer hydraulic characterization, surface-groundwater interaction, groundwater flow and groundwater balance have been identified. Hence, future research shall focus on the groundwater resources, so that existing surface water studies are updated and future water usage options are explored. Full article
(This article belongs to the Section Hydrology)
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15 pages, 9688 KiB  
Article
Critical Tectonic Limits for Geothermal Aquifer Use: Case Study from the East Slovakian Basin Rim
by Stanislav Jacko, Roman Farkašovský, Igor Ďuriška, Barbora Ščerbáková and Kristína Bátorová
Resources 2021, 10(4), 31; https://doi.org/10.3390/resources10040031 - 2 Apr 2021
Cited by 7 | Viewed by 2892
Abstract
The Pannonian basin is a major geothermal heat system in Central Europe. Its peripheral basin, the East Slovakian basin, is an example of a geothermal structure with a linear, directed heat flow ranging from 90 to 100 mW/m2 from west to east. [...] Read more.
The Pannonian basin is a major geothermal heat system in Central Europe. Its peripheral basin, the East Slovakian basin, is an example of a geothermal structure with a linear, directed heat flow ranging from 90 to 100 mW/m2 from west to east. However, the use of the geothermal source is limited by several critical tectono-geologic factors: (a) Tectonics, and the associated disintegration of the aquifer block by multiple deformations during the pre-Paleogene, mainly Miocene, period. The main discontinuities of NW-SE and N-S direction negatively affect the permeability of the aquifer environment. For utilization, minor NE-SW dilatation open fractures are important, which have been developed by sinistral transtension on N–S faults and accelerated normal movements to the southeast. (b) Hydrogeologically, the geothermal structure is accommodated by three water types, namely, Na-HCO3 with 10.9 g·L−1 mineralization (in the north), the Ca-Mg-HCO3 with 0.5–4.5 g·L−1 mineralization (in the west), and Na-Cl water type containing 26.8–33.4 g·L−1 mineralization (in the southwest). The chemical composition of the water is influenced by the Middle Triassic dolomite aquifer, as well as by infiltration of saline solutions and meteoric waters along with open fractures/faults. (c) Geothermally anomalous heat flow of 123–129 °C with 170 L/s total flow near the Slanské vchy volcanic chain seems to be the perspective for heat production. Full article
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24 pages, 11060 KiB  
Article
Natural and Anthropogenic Groundwater Contamination in a Coastal Volcanic-Sedimentary Aquifer: The Case of the Archaeological Site of Cumae (Phlegraean Fields, Southern Italy)
by Luisa Stellato, Silvio Coda, Michele Arienzo, Pantaleone De Vita, Brunella Di Rienzo, Antonio D’Onofrio, Luciano Ferrara, Fabio Marzaioli, Marco Trifuoggi and Vincenzo Allocca
Water 2020, 12(12), 3463; https://doi.org/10.3390/w12123463 - 9 Dec 2020
Cited by 16 | Viewed by 4201
Abstract
Archeological sites close to coastal volcanic-sedimentary aquifers are threatened by groundwater contaminated by natural and anthropogenic processes. The paper reports on a hydrogeological, chemical (major, minor and trace elements) and isotopic (δD-H2O, δ18O-H2O, δ15N-NO3 [...] Read more.
Archeological sites close to coastal volcanic-sedimentary aquifers are threatened by groundwater contaminated by natural and anthropogenic processes. The paper reports on a hydrogeological, chemical (major, minor and trace elements) and isotopic (δD-H2O, δ18O-H2O, δ15N-NO3, δ18O-NO3, δ11B, 222Rn) survey of groundwater at the Cumae archaeological site, which is located in the coastal north-western sector of the volcanic district of Phlegraean Fields (southern Italy), where groundwater flooding phenomena occur. Results show the presence of a complex coastal volcanic-sedimentary aquifer system where groundwater quality is influenced mainly by: (i) aquifer lithology and localized ascent of magmatic fluids along buried volcano-tectonic discontinuities, (ii) mixing of groundwater, deep mineralized fluids and seawater during groundwater pumping, and (iii) nitrate contamination >50 mg/L from non-point agricultural sources. Moreover, δD and δ18O point toward fast recharge from seasonal precipitations, while the isotopic ratios of N and O in nitrate reveal the contribution of mineral and organic fertilizers as well as leakage from septic tanks. Results can assist the local archaeological authority for the safeguarding and management of the archaeological heritage of the Cumae site. Full article
(This article belongs to the Special Issue Focus on the Salinization Issue in the Mediterranean Area)
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22 pages, 4234 KiB  
Article
Hydrochemical and Isotopic Assessment of Groundwater in the Goda Mountains Range System. Republic of Djibouti (Horn of Africa)
by Ibrahim M. Ahmed, Mohamed Jalludin and Moumtaz Razack
Water 2020, 12(7), 2004; https://doi.org/10.3390/w12072004 - 15 Jul 2020
Cited by 11 | Viewed by 3368
Abstract
The hydrogeological system of the Goda Mountains Range (GMR) in the Republic of Djibouti (Horn of Africa), hosted by volcanic and sedimentary formations, is the only water resource in the Tadjourah region for more than 85,000 inhabitants. Water needs are expected to drastically [...] Read more.
The hydrogeological system of the Goda Mountains Range (GMR) in the Republic of Djibouti (Horn of Africa), hosted by volcanic and sedimentary formations, is the only water resource in the Tadjourah region for more than 85,000 inhabitants. Water needs are expected to drastically increase in the coming years, due to fast socio-economic development of the region. Accordingly, this system is under high pressure and should sustainably be exploited. However, little is known about the hydrogeology of this system. This study aims to improve the understanding of the hydrochemistry and the recharge processes of this system. The study is based on the combined interpretation of major ions, stable isotopes (18O, 2H), and radiogenic isotopes (3H, 14C). The interpretation of major ions contents using classical hydrochemical methods and principal component analysis highlighted that alteration of volcanic rocks minerals, coastal rainfall infiltration, and evaporation are the main processes from which groundwater acquires mineralization. Stable isotopes revealed that groundwater is of meteoric origin and has undergone high evaporation during infiltration. Radiogenic isotopes showed that groundwater in the basalts is mostly submodern to old, in relation with low hydraulic conductivity of the rocks and/or longer pathways through fissures from outcrop to subsurface. Groundwater in the rhyolites is much younger compared to the basalts due to faster infiltration. The sedimentary part, in connection with the rhyolites, has younger waters compared to the basalts, but older compared to the rhyolites. The overall results show that GMR is a fairly complex hydrogeological system, containing a resource made up of a mixture of waters of different ages. This study has made significant progress in understanding this system and is an initial step towards the sustainable exploitation of resources. Full article
(This article belongs to the Special Issue Groundwater Resilience to Climate Change and High Pressure)
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18 pages, 8514 KiB  
Article
Recharge–Discharge Relations of Groundwater in Volcanic Terrain of Semi-Humid Tropical Highlands of Ethiopia: The Case of Infranz Springs, in the Upper Blue Nile
by Fenta Nigate, Marc Van Camp, Alemu Yenehun, Ashebir Sewale Belay and Kristine Walraevens
Water 2020, 12(3), 853; https://doi.org/10.3390/w12030853 - 18 Mar 2020
Cited by 20 | Viewed by 5027
Abstract
The major springs in the Infranz catchment are a significant source of water for Bahir Dar City and nearby villages, while sustaining the Infranz River and the downstream wetlands. The aim of the research was to understand the hydrogeological conditions of these high-discharge [...] Read more.
The major springs in the Infranz catchment are a significant source of water for Bahir Dar City and nearby villages, while sustaining the Infranz River and the downstream wetlands. The aim of the research was to understand the hydrogeological conditions of these high-discharge springs and the recharge–discharge relations in the Infranz catchment. The Infranz catchment is covered by highly pervious and young quaternary volcanic rocks, consisting of blocky, fractured, and strongly vesicular scoriaceous basalt. At the surface, these rocks crop out as lineaments forming ridges, delimiting closed depressions in which water accumulates during the rainy season without causing surface runoff. Geology and geomorphology thus combine to produce very favorable conditions for groundwater recharge. Three groundwater recharge methods were applied to estimate groundwater recharge and the results were compared. Groundwater recharge was calculated to be 30% to 51% of rainfall. Rapid replenishment raises the groundwater level during the rainfall period, followed by a rapid decline during the dry season. Shallow local flow paths discharge at seasonal springs and streams, while more regional and deeper flow systems downstream sustain the high-discharge springs and perennial Infranz River. The uptake of 75% of spring water for the water supply of Bahir Dar City, local extraction for domestic and small-scale irrigation use from springs, rivers and hand-dug wells, encroaching farming, and overgrazing are exacerbating wetland degradation. Full article
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22 pages, 12248 KiB  
Article
Evaluation of a Weathered Rock Aquifer Using ERT Method in South Guangdong, China
by Qiang Gao, Yanjun Shang, Muhammad Hasan, Weijun Jin and Peng Yang
Water 2018, 10(3), 293; https://doi.org/10.3390/w10030293 - 8 Mar 2018
Cited by 55 | Viewed by 6774
Abstract
In areas where weathering has hydrogeological significance, geophysical methods can assist to map the subsurface characteristics for groundwater occurrence. In this study, electrical resistivity tomography (ERT) survey in combination with joint profile method (JPM), magnetic method and borehole data was conducted to investigate [...] Read more.
In areas where weathering has hydrogeological significance, geophysical methods can assist to map the subsurface characteristics for groundwater occurrence. In this study, electrical resistivity tomography (ERT) survey in combination with joint profile method (JPM), magnetic method and borehole data was conducted to investigate the aquifer potential in strongly weathered volcanic rocks. The aim was to assess the geological units related to the water-bearing formation of aquifer systems in South Guangdong, China. The resistivities were measured along four profiles each with a total of 81 electrodes, a spread length of 400 m and an electrode spacing of 5 m insuring continuous coverage. The data from a borehole survey revealed three different layers i.e., highly weathered layer, partly weathered layer and fresh basement rock, whose respective thickness were integrated into ERT images to get more useful results about the real resistivity ranges of the these layers (i.e., 22 Ωm–345 Ωm for highly weathered layer, 324 Ωm–926 Ωm for partly weathered and 913 Ωm–2579 Ωm for fresh bedrock). The electrical resistivity imaging including the surface topography provides spatial variations in electrical properties of the weathered/unweathered layers since resistivity depends on the properties of a material rather than its thickness. ERT sections were integrated with JPM and magnetic method to delineate the main faults (F1, F2 and F3). ERT sections show a geometric relationship between different layered boundaries, particularly those of the aquifers with fresh basement and surface topographies. These layers comprise an overburden of 50 m thickness revealed by ERT sections. The results show that weathered and partly weathered layers between the topographic surface and bed rock yield maximum aquifer potential in the study area. ERT imaging method provides promising input to groundwater evaluation in the areas of weathered environment with complex geology. Full article
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15200 KiB  
Article
Regional Mapping of Groundwater Resources in Data-Scarce Regions: The Case of Laos
by Mathieu Viossanges, Paul Pavelic, Lisa-Maria Rebelo, Guillaume Lacombe and Touleelor Sotoukee
Hydrology 2018, 5(1), 2; https://doi.org/10.3390/hydrology5010002 - 23 Dec 2017
Cited by 21 | Viewed by 10469
Abstract
This study focuses on Laos, a landlocked nation located in South-East Asia with sub-tropical climate and highly seasonal rainfall distribution. Laos is one of the world’s least developed countries, and currently witnesses an unprecedented level of development that is highly reliant on its [...] Read more.
This study focuses on Laos, a landlocked nation located in South-East Asia with sub-tropical climate and highly seasonal rainfall distribution. Laos is one of the world’s least developed countries, and currently witnesses an unprecedented level of development that is highly reliant on its natural resources, including groundwater. There is currently very limited data and no nationwide assessment of shallow (<30 m) groundwater resources to support sustainable management. This study provides a first step towards addressing this issue by (i) identifying the major aquifer units of the country; (ii) integrating localized data and regional maps into an assessment of the groundwater potential; and (iii) producing quantitative maps of key hydrogeological indicators. Eight aquifer units have been described and evaluated: (i) Basement aquifers, (ii) Volcanic aquifers, (iii) Schists, (iv) Paleozoic sedimentary, (v) Karsts, (vi) Limestones, (vii) Mesozoic sedimentary and (viii) Alluvial sediments. The Mesozoic sandstones and the Alluvial aquifers are the most extensive and productive hydrogeological systems in the country. The Volcanic and Karstic aquifers, although poorly known, might also have important potential. This assessment, along with the maps of quantitative aquifer indicators, provide a significant improvement in both spatial resolution and accuracy compared to previously available information. It will likely support improved management plans and the identification of areas with higher potential for groundwater development. Full article
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