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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.
Alemu Yenehun; Mekete Dessie; Mulugeta Azeze; Fenta Nigate; Ashebir Belay; Jan Nyssen; Enyew Adgo; Ann Van Griensven; Marc Van Camp; Kristine Walraevens. Water Resources Studies in Headwaters of the Blue Nile Basin: A Review with Emphasis on Lake Water Balance and Hydrogeological Characterization. Water 2021, 13, 1469 .
AMA StyleAlemu Yenehun, Mekete Dessie, Mulugeta Azeze, Fenta Nigate, Ashebir Belay, Jan Nyssen, Enyew Adgo, Ann Van Griensven, Marc Van Camp, Kristine Walraevens. Water Resources Studies in Headwaters of the Blue Nile Basin: A Review with Emphasis on Lake Water Balance and Hydrogeological Characterization. Water. 2021; 13 (11):1469.
Chicago/Turabian StyleAlemu Yenehun; Mekete Dessie; Mulugeta Azeze; Fenta Nigate; Ashebir Belay; Jan Nyssen; Enyew Adgo; Ann Van Griensven; Marc Van Camp; Kristine Walraevens. 2021. "Water Resources Studies in Headwaters of the Blue Nile Basin: A Review with Emphasis on Lake Water Balance and Hydrogeological Characterization." Water 13, no. 11: 1469.
Dhaka city has emerged as the fastest-growing megacity, having more than 20 million inhabitants, with a growth rate of 3.62%. Unplanned and rapid urbanization, coupled with exponential population growth, has significantly altered the groundwater dynamics in Dhaka city. This study concentrates on the evolution of long-term piezometric heads of the Upper Dupi Tila aquifer (UDA) and the Middle Dupi Tila aquifer (MDA) based on long-term hydrographs, piezometric maps and synthetic graphical overviews of piezometric trends. Due to over-exploitation, the piezometric level (PL) has declined deeper than −85 and −65 m PWD (Public Works Department reference datum) in UDA and MDA, respectively. The highest rate of decline was observed in the south-central to southeastern parts of the city both in UDA (4.0 m/year) and MDA (5.74 m/year). The results clearly show that the rates of decline in PL vary from 2.25 to 5.74 m/year in both aquifers of the city, and urban expansion has greatly affected the shape and extent of the depression cone over the past four decades. The magnitudes of the depression cones in both aquifers seem to pose a considerable threat to groundwater resources, indicating that the current exploitation is not sustainable at all.
Mazeda Islam; Marc Van Camp; Delwar Hossain; Mizanur Rahman Sarker; Shahina Khatun; Kristine Walraevens. Impacts of Large-Scale Groundwater Exploitation Based on Long-Term Evolution of Hydraulic Heads in Dhaka City, Bangladesh. Water 2021, 13, 1357 .
AMA StyleMazeda Islam, Marc Van Camp, Delwar Hossain, Mizanur Rahman Sarker, Shahina Khatun, Kristine Walraevens. Impacts of Large-Scale Groundwater Exploitation Based on Long-Term Evolution of Hydraulic Heads in Dhaka City, Bangladesh. Water. 2021; 13 (10):1357.
Chicago/Turabian StyleMazeda Islam; Marc Van Camp; Delwar Hossain; Mizanur Rahman Sarker; Shahina Khatun; Kristine Walraevens. 2021. "Impacts of Large-Scale Groundwater Exploitation Based on Long-Term Evolution of Hydraulic Heads in Dhaka City, Bangladesh." Water 13, no. 10: 1357.
Diffuse groundwater contamination by intense fertilizer use is a widespread problem in most of the agricultural regions in West-Europe and in many other countries worldwide. As a result elevated nitrate concentrations in groundwater are found, and as groundwater is the source of baseflow into rivers and streams, also surface waters show increased nitrate levels. Flanders in the north of Belgium is no exception and despite restrictions on the fertilizer use and remediation practices initiated in the mid-1990s, and still ongoing, in many stream monitoring points, peak concentrations are measured above the 50 mg/l criterium. In many monitoring stations there is apparently a long delay between the start of the restrictions and effect on water quality. Often this delay is related to high concentrations in the groundwater inflow and long residence and travel times of groundwater feeding the streams. To better understand this behavior and estimate response times a tool was developed that incorporates the main water flows in a typical catchment and considers the effects of varying groundwater ages. This tool is conceived as a parsimonious lumped parameter model, simple and easy enough to be used by many people but still capturing the main mechanisms end processes. In this paper the tool is explained and it is applied on two testcases in Flanders to show its performance.
Marc Van Camp; Jeroen De Waele; Stefaan De Neve; Kristine Walraevens. Groundwater inflow in rivers as a controlling factor to surface water nitrate concentrations and impact of groundwater age distribution on response times for remediation strategies. Journal of Contaminant Hydrology 2021, 241, 103820 .
AMA StyleMarc Van Camp, Jeroen De Waele, Stefaan De Neve, Kristine Walraevens. Groundwater inflow in rivers as a controlling factor to surface water nitrate concentrations and impact of groundwater age distribution on response times for remediation strategies. Journal of Contaminant Hydrology. 2021; 241 ():103820.
Chicago/Turabian StyleMarc Van Camp; Jeroen De Waele; Stefaan De Neve; Kristine Walraevens. 2021. "Groundwater inflow in rivers as a controlling factor to surface water nitrate concentrations and impact of groundwater age distribution on response times for remediation strategies." Journal of Contaminant Hydrology 241, no. : 103820.
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.
Fenta Nigate; Marc Van Camp; Alemu Yenehun; Ashebir Sewale Belay; Kristine Walraevens. 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. Water 2020, 12, 853 .
AMA StyleFenta Nigate, Marc Van Camp, Alemu Yenehun, Ashebir Sewale Belay, Kristine Walraevens. 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. Water. 2020; 12 (3):853.
Chicago/Turabian StyleFenta Nigate; Marc Van Camp; Alemu Yenehun; Ashebir Sewale Belay; Kristine Walraevens. 2020. "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." Water 12, no. 3: 853.
The sustainable development of water resources includes retaining some amount of the natural flow regime in water bodies to protect and maintain aquatic ecosystem health and the human livelihoods and wellbeing dependent upon them. Although assessment of environmental flows is now occurring globally, limited studies have been carried out in the Ethiopian highlands, especially studies to understand flow-ecological response relationships. This paper establishes a hydrological foundation of Gumara River from an ecological perspective. The data analysis followed three steps: first, determination of the current flow regime—flow indices and ecologically relevant flow regime; second, naturalization of the current flow regime—looking at how flow regime is changing; and, finally, an initial exploration of flow linkages with ecological processes. Flow data of Gumara River from 1973 to 2018 are used for the analysis. Monthly low flow occurred from December to June; the lowest being in March, with a median flow of 4.0 m3 s−1. Monthly high flow occurred from July to November; the highest being in August, with a median flow of 236 m3 s−1. 1-Day low flows decreased from 1.55 m3 s−1 in 1973 to 0.16 m3 s−1 in 2018, and 90-Day (seasonal) low flow decreased from 4.9 m3 s−1 in 1973 to 2.04 m3 s−1 in 2018. The Mann–Kendall trend test indicated that the decrease in low flow was significant for both durations at α = 0.05. A similar trend is indicated for both durations of high flow. The decrease in both low flows and high flows is attributed to the expansion of pump irrigation by 29 km2 and expansion of plantations, which resulted in an increase of NDVI from 0.25 in 2000 to 0.29 in 2019. In addition, an analysis of environmental flow components revealed that only four “large floods” appeared in the last 46 years; no “large flood” occurred after 1988. Lacking “large floods” which inundate floodplain wetlands has resulted in early disconnection of floodplain wetlands from the river and the lake; which has impacts on breeding and nursery habitat shrinkage for migratory fish species in Lake Tana. On the other hand, the extreme decrease in “low flow” components has impacts on predators, reducing their mobility and ability to access prey concentrated in smaller pools. These results serve as the hydrological foundation for continued studies in the Gumara catchment, with the eventual goal of quantifying environmental flow requirements.
Wubneh B. Abebe; Seifu A. Tilahun; Michael M. Moges; Ayalew Wondie; Minychl G. Derseh; Teshager A. Nigatu; Demesew A. Mhiret; Tammo S. Steenhuis; Marc Van Camp; Kristine Walraevens; Michael E. McClain. Hydrological Foundation as a Basis for a Holistic Environmental Flow Assessment of Tropical Highland Rivers in Ethiopia. Water 2020, 12, 547 .
AMA StyleWubneh B. Abebe, Seifu A. Tilahun, Michael M. Moges, Ayalew Wondie, Minychl G. Derseh, Teshager A. Nigatu, Demesew A. Mhiret, Tammo S. Steenhuis, Marc Van Camp, Kristine Walraevens, Michael E. McClain. Hydrological Foundation as a Basis for a Holistic Environmental Flow Assessment of Tropical Highland Rivers in Ethiopia. Water. 2020; 12 (2):547.
Chicago/Turabian StyleWubneh B. Abebe; Seifu A. Tilahun; Michael M. Moges; Ayalew Wondie; Minychl G. Derseh; Teshager A. Nigatu; Demesew A. Mhiret; Tammo S. Steenhuis; Marc Van Camp; Kristine Walraevens; Michael E. McClain. 2020. "Hydrological Foundation as a Basis for a Holistic Environmental Flow Assessment of Tropical Highland Rivers in Ethiopia." Water 12, no. 2: 547.
The Gaza Strip forms a transition zone between the semi-humid coastal zone in the north, the semi-arid zone in the east, and the Sinai desert in the south. Groundwater is the only water source for 1.94 million inhabitants, where the only fresh replenishment water for the aquifer comes from rainfall. This study focuses on testing a newly developed GIS tool to estimate the spatial and temporal distribution of runoff and recharge from rainfall. The estimation of surface runoff was made using the Soil Conservation Services Curve Number Method, while groundwater recharge was estimated using Thornthwaite and Mather’s Soil Moisture Balance approach. The new tool was applied to the Gaza aquifer for the year 1935 and for the period from 1973 to 2016. A comparison was made between the results obtained with the developed GIS tool and the frequently used Thiessen polygon method for rainfall distribution. Runoff and recharge were estimated for the year 1935 (prior to development) to compare with the current developed conditions. It was found that the built-up and sand dune areas stand in an inverse relationship, where the former is replacing the latter (built-up area expanded from 30.1 km2 in 1982 to 92.1 km2 in 2010). Recharge takes place in the sand dune area, whereas runoff increases in the built-up area. Due to development, runoff almost tripled from 9 million m3 in 1982 to 22.9 million m3 in 2010, while groundwater recharge was reduced from 27.3 million m3 in 1982 to 23 million m3 in 2010, even though the rainfall increased between 1982 and 2010 by 11%. Comparison between the newly developed GIS tool and the Thiessen polygon-based estimation shows that the former leads to higher values of runoff and recharge for dry years.
Ashraf M. Mushtaha; Marc Van Camp; Kristine Walraevens. Quantification of Recharge and Runoff from Rainfall Using New GIS Tool: Example of the Gaza Strip Aquifer. Water 2019, 11, 84 .
AMA StyleAshraf M. Mushtaha, Marc Van Camp, Kristine Walraevens. Quantification of Recharge and Runoff from Rainfall Using New GIS Tool: Example of the Gaza Strip Aquifer. Water. 2019; 11 (1):84.
Chicago/Turabian StyleAshraf M. Mushtaha; Marc Van Camp; Kristine Walraevens. 2019. "Quantification of Recharge and Runoff from Rainfall Using New GIS Tool: Example of the Gaza Strip Aquifer." Water 11, no. 1: 84.
Gaza Strip is experiencing a severe water crisis caused mainly by overexploitation of the groundwater source. Rainfall is the only source of freshwater replenishment for the Gaza coastal aquifer. Groundwater level has dropped to more than 10 m below mean sea level as a result of aquifer exploitation and imbalance between recharge and abstraction in the past decades, which exposes the groundwater to seawater intrusion. As the only fresh water source recharging the aquifer is from rainfall, it is essential to estimate the annual recharge volume from rainfall. This paper is focusing on recharge estimation based on historical daily rainfall data for the past 41 years (1973–2014). An estimation of surface runoff was made using soil conservation services curve number method. An estimation of groundwater recharge has been calculated using two different methods: Thornthwaite and Mather soil moisture balance approach and chloride mass balance. Four land use maps and data have been used for the entire calculation period, three of them based on actual surveys carried out in 1994, 2004 and 2010, while the fourth map was developed based on the population expansion trend to cover the period before 1993. It was found that the proportion of built-up area has expanded from 8.25% in 1982 to 25.23% in 2010, while the sand dune area has shrunk from 31.46% in 1982 to 8.64% in 2010. Runoff has doubled from 6.9 million m3 in 1982 to 13.7 million m3 in 2010, while groundwater recharge was reduced from 24.4 million m3 in 1982 to 18.1 million m3 in 2010.
Ashraf M. Mushtaha; Marc Van Camp; Kristine Walraevens. Evolution of runoff and groundwater recharge in the Gaza Strip over the last four decades. Environmental Earth Sciences 2019, 78, 32 .
AMA StyleAshraf M. Mushtaha, Marc Van Camp, Kristine Walraevens. Evolution of runoff and groundwater recharge in the Gaza Strip over the last four decades. Environmental Earth Sciences. 2019; 78 (1):32.
Chicago/Turabian StyleAshraf M. Mushtaha; Marc Van Camp; Kristine Walraevens. 2019. "Evolution of runoff and groundwater recharge in the Gaza Strip over the last four decades." Environmental Earth Sciences 78, no. 1: 32.
In the European TOPSOIL project, countries around the North Sea are searching for solutions for climate related threats. They explore the possibilities of using the topsoil layer to solve current and future water challenges. The main objective is to improve the climate resilience of the water management of the topsoil and shallow aquifers in the North Sea region. TOPSOIL is supported by the Interreg VB North Sea Region program in line with priority 3 of the program: ‘Sustainable North Sea Region, protecting against climate change and preserving the environment’. The Belgian part of this project, called FRESHEM for GO-FRESH Vlaanderen (‘FREsh Salt groundwater distribution by Helicopter ElectroMagnetic survey for Geohydrological Opportunities FRESH water supply’), focuses on mapping the salinity distribution of groundwater using airborne electromagnetics and aims to look into a number of measures that could increase the availability of freshwater for agriculture in the polder area. Two pilot projects will evaluate the possibilities for freshwater storage and aims to specify what measures can be taken to achieve this. Together with the other water users and water managers, The Flanders Environment Agency wants to prepare a plan for the realization of one or more pilot projects that can improve the availability of freshwater.
Dieter Vandevelde; Esther Van Baaren; Joost Delsman; Marios Karaoulis; Gualbert Oude Essink; Perry De Louw; Tommer Vermaas; Pieter Pauw; Marco De Kleine; Sara Thofte; Rasmus Teilmann; Kristine Walraevens; Marc Van Camp; Huits Dominique; Willem Dabekaussen; Jan Gunnink; Alexander Vandenbohede. Groundwater salinity mapping of the Belgian coastal zone to improve local freshwater storage availability. E3S Web of Conferences 2018, 54, 00040 .
AMA StyleDieter Vandevelde, Esther Van Baaren, Joost Delsman, Marios Karaoulis, Gualbert Oude Essink, Perry De Louw, Tommer Vermaas, Pieter Pauw, Marco De Kleine, Sara Thofte, Rasmus Teilmann, Kristine Walraevens, Marc Van Camp, Huits Dominique, Willem Dabekaussen, Jan Gunnink, Alexander Vandenbohede. Groundwater salinity mapping of the Belgian coastal zone to improve local freshwater storage availability. E3S Web of Conferences. 2018; 54 ():00040.
Chicago/Turabian StyleDieter Vandevelde; Esther Van Baaren; Joost Delsman; Marios Karaoulis; Gualbert Oude Essink; Perry De Louw; Tommer Vermaas; Pieter Pauw; Marco De Kleine; Sara Thofte; Rasmus Teilmann; Kristine Walraevens; Marc Van Camp; Huits Dominique; Willem Dabekaussen; Jan Gunnink; Alexander Vandenbohede. 2018. "Groundwater salinity mapping of the Belgian coastal zone to improve local freshwater storage availability." E3S Web of Conferences 54, no. : 00040.
Kristine Walraevens; Charles Bakundukize; Yohana Enock Mtoni; Marc Van Camp. Understanding the hydrogeochemical evolution of groundwater in Precambrian basement aquifers: A case study of Bugesera region in Burundi. Journal of Geochemical Exploration 2018, 188, 24 -42.
AMA StyleKristine Walraevens, Charles Bakundukize, Yohana Enock Mtoni, Marc Van Camp. Understanding the hydrogeochemical evolution of groundwater in Precambrian basement aquifers: A case study of Bugesera region in Burundi. Journal of Geochemical Exploration. 2018; 188 ():24-42.
Chicago/Turabian StyleKristine Walraevens; Charles Bakundukize; Yohana Enock Mtoni; Marc Van Camp. 2018. "Understanding the hydrogeochemical evolution of groundwater in Precambrian basement aquifers: A case study of Bugesera region in Burundi." Journal of Geochemical Exploration 188, no. : 24-42.
Several studies conducted on occurrences of evaporitic salts in various parts of the world often interpret the formation of such salts as the result of the evaporation of subsurface brines, saline lake waters and sea water-contaminated groundwater, on one hand, and the deposition of sea sprays and wind-transported salts, on the other hand. This study seeks to understand processes governing the formation of evaporitic salts in a humid tropical context and to establish a link between the occurrence of these salts and the different processes controlling the hydrogeochemical evolution of groundwater in Bugesera region, in north-eastern Burundi. Unlike previous studies, salt occurrences in the study area occur in a continental and humid tropical environment where chemical analyses of water samples from several small lakes reveal rather fresh water. While salt incrustations reported in the western Burundi occur in a sedimentary basin which is made up of a mixture of lacustrine and fluviatile sediments, the evaporitic salts in the depression of Bugesera appear in the upper layers of the weathered overburden developed on Precambrian basement rocks. These facts suggest that the lithological nature and setting of the area may not be the key factor controlling the formation of these salt deposits. X-ray diffraction (XRD) analyses performed on saline soils from two quarries in Bugesera region confirm the presence of salt minerals including particularly gypsum (CaSO4·2H2O), halite (NaCl) and thenardite (Na2SO4). Other minerals identified such as goethite, kaolinite, muscovite and quartz may be part of the soil matrix. Chemical analyses on leachates of soil samples from the 2 quarries in Bugesera region confirm their saline nature as evidenced by high TDS (1826–17,679 mg/l) and pH values (8.3–8.5). The predominance of Na+, Mg2+, Ca2+, K+, SO42−, Cl− in the chemical composition of the dissolved salts clearly reflects their mineralogical composition. This study clearly demonstrates that these evaporitic salts originate from the combination of three processes, namely the dissolution of aluminosilicate minerals which enrich groundwater in different salt-forming ions, the capillary rise which lifts the shallow groundwater and the dissolved ions up to the reach of evaporation and ultimately the evapoconcentration which precipitates the salts following well-established pathways. These findings are well supported by the results of the simulation of the evapoconcentration process with the PHREEQC hydrochemical model.
Charles Bakundukize; Yohana Enock Mtoni; Marc Van Camp; Kristine Walraevens. Occurrences of evaporitic salts in Bugesera region (Burundi) and relation to hydrogeochemical evolution of groundwater. Environmental Earth Sciences 2018, 77, 223 .
AMA StyleCharles Bakundukize, Yohana Enock Mtoni, Marc Van Camp, Kristine Walraevens. Occurrences of evaporitic salts in Bugesera region (Burundi) and relation to hydrogeochemical evolution of groundwater. Environmental Earth Sciences. 2018; 77 (6):223.
Chicago/Turabian StyleCharles Bakundukize; Yohana Enock Mtoni; Marc Van Camp; Kristine Walraevens. 2018. "Occurrences of evaporitic salts in Bugesera region (Burundi) and relation to hydrogeochemical evolution of groundwater." Environmental Earth Sciences 77, no. 6: 223.
In the coastal region of Bangladesh, groundwater is mainly used for domestic and agricultural purposes, but salinization of many groundwater resources limits its suitability for human consumption and practical application. This paper reports the results of a study that has mapped the salinity distribution in different aquifer layers up to a depth of 300 m in a region bordering the Bay of Bengal based on the main hydrochemistry and has investigated the origin of the salinity using Cl/Br ratios of the samples. The subsurface consists of a sequence of deltaic sediments with an alternation of more sandy and clayey sections in which several aquifer layers can be recognized. The main hydrochemistry shows different main water types in the different aquifers, indicating varying stages of freshening or salinization processes. The most freshwater, soft NaHCO3-type water with Cl concentrations mostly below 100 mg/l, is found in the deepest aquifer at 200–300 m below ground level (b.g.l.), in which the fresh/saltwater interface is pushed far to the south. Salinity is a main problem in the shallow aquifer systems, where Cl concentrations rise to nearly 8000 mg/l and the groundwater is mostly brackish NaCl water. Investigation of the Cl/Br ratios has shown that the source of the salinity in the deep aquifer is mixing with old connate seawater and that the saline waters in the more shallow aquifers do not originate from old connate water or direct seawater intrusion, but are derived from the dissolution of evaporite salts. These must have been formed in a tidal flat under influence of a strong seasonal precipitation pattern. Long dry seasons with high evaporation rates have evaporated seawater from inundated gullies and depressions, leading to salt precipitation, while subsequent heavy monsoon rains have dissolved the formed salts, and the solution has infiltrated in the subsoil, recharging groundwater.
Mizanur Rahman Sarker; Marc Van Camp; Mazeda Islam; Nasir Ahmed; Kristine Walraevens. Hydrochemistry in coastal aquifer of southwest Bangladesh: origin of salinity. Environmental Earth Sciences 2018, 77, 39 .
AMA StyleMizanur Rahman Sarker, Marc Van Camp, Mazeda Islam, Nasir Ahmed, Kristine Walraevens. Hydrochemistry in coastal aquifer of southwest Bangladesh: origin of salinity. Environmental Earth Sciences. 2018; 77 (2):39.
Chicago/Turabian StyleMizanur Rahman Sarker; Marc Van Camp; Mazeda Islam; Nasir Ahmed; Kristine Walraevens. 2018. "Hydrochemistry in coastal aquifer of southwest Bangladesh: origin of salinity." Environmental Earth Sciences 77, no. 2: 39.
The biological value of natural and protected areas like nature reserves is often reflected in the diversity and combination of different vegetation associations. In settings where the vegetation is strongly groundwater dependent, the specific interrelation between groundwater flow characteristics (hydrodynamics) and groundwater composition (hydrochemistry) is usually the most important factor for controlling the ecological value and occurrence of site-specific vegetation. Consequently, small-scale variations in ecological gradients within the site rather than its overall size are the key features that control the biodiversity of groundwater-dependent ecosystems. This is demonstrated for a small nature reserve called “Gulke Putten” in the northwest of Belgium which is only a few km2 large, but shows an interesting variety in groundwater types the occurrence and genesis of which are due to local and highly seasonal flow conditions. As a result, the site has a high ecological value which is rare in this part of the country. This paper shows how multi-year daily water level measurements were used to quantify seasonal and inter-yearly variation in water levels and flow situations and how these are related to the condition in groundwater chemistry. Different hydrochemical facies are found, ranging from evaporated rainwater and waters influenced in varying degree by calcite dissolution, pyrite oxidation, cation exchange and some marine influence originating from the marine sediments of Tertiary age in the phreatic aquifer. This paper relates the variations in flow conditions and groundwater seepage intensity to the groundwater chemistry and helps to understand the origin of the abiotic ecological gradients that are related to the specific eco-hydrological value of the site.
Marc Van Camp; Daan Lams; Kristine Walraevens. Hydrodynamical and hydrochemical groundwater controls on abiotic environmental gradients in a nature reserve in Flanders (Belgium). Environmental Earth Sciences 2017, 76, 101 .
AMA StyleMarc Van Camp, Daan Lams, Kristine Walraevens. Hydrodynamical and hydrochemical groundwater controls on abiotic environmental gradients in a nature reserve in Flanders (Belgium). Environmental Earth Sciences. 2017; 76 (3):101.
Chicago/Turabian StyleMarc Van Camp; Daan Lams; Kristine Walraevens. 2017. "Hydrodynamical and hydrochemical groundwater controls on abiotic environmental gradients in a nature reserve in Flanders (Belgium)." Environmental Earth Sciences 76, no. 3: 101.
Highlights•VES reveal the hydrogeological structure of Precambrian basement rocks.•Fresh basement, fractured/weathered basement and weathered overburden on top.•Aquifer potential for hand-dug wells depends on upper few meters of saturated zone.•Favourable: 1) thin weathered cover; 2) thick weathered cover with deep water table.•Unfavourable: thick weathered cover with shallow water table. AbstractThis study investigates a Precambrian basement aquifer in Bugesera region, a typical African rural area in northeastern Burundi. Domestic water supply relies on groundwater which is tapped through hand-dug wells. Despite several attempts to increase the number of water points in the area, the water demand is still far from being met as a result of the high rate of well failure. This paper seeks to understand whether the hydrogeological structure and the spatial distribution of hydraulic parameters can explain the low productivity and the high failure rate of hand-dug wells. The hydrogeological structure inferred from the interpretation of a large number of vertical electrical soundings (VES) reveals a typical sequence of geoelectrical layers, which is characterized by an overall upwards fining from the fresh basement, over the fractured/weathered basement, to the overburden or saprolite with a clay-rich layer on top. Whereas the overall aquifer potential mainly depends on the thickness of the weathered overburden, the aquifer potential for shallow hand-dug wells is determined by the hydraulic conductivity of the upper few meters of the saturated zone. This upper zone was investigated in the pumping tests. The spatial distribution of the specific capacity reveals a wide variation of hydraulic parameters, depending on the well's position in the depth profile of the aquifer's hydraulic conductivity. The thickness of the potential aquifer is highest in the central part of the study area (pegmatitic and granitic intrusions) which has the highest overall aquifer potential compared to the surrounding metasedimentary formations. However, a thick weathered overburden will increase the groundwater potential of an aquifer for deep boreholes, whereas for hand-dug wells, the productivity can only be high if the thickness of the weathered overburden is small enough, or the water table is deep enough, to allow to tap the coarse part at the base of the overburden and/or part of the weathered/fractured basement. This study reveals that the main cause of low productivity and failure of many hand-dug wells in Bugesera region is not to be linked to poor groundwater resource potential but rather stems from the inappropriate random siting of wells and from poor well construction expertise which does not take into account the hydrogeological conditions. The results of the investigation indicate that in the typical weathering profile of the Precambrian basement in Sub-saharan Africa, the coarse lower part of the weathered overburden and the fractured/weathered basement, offer(s) good prospects for water resource. Depending on the depth at which this layer is encountered, either shallow hand-dug wells or deep drilled wells are most appropriate.
Charles Bakundukize; Yohana Mtoni; Kristine Martens; Marc Van Camp; Kristine Walraevens. Poor understanding of the hydrogeological structure is a main cause of hand-dug wells failure in developing countries: A case study of a Precambrian basement aquifer in Bugesera region (Burundi). Journal of African Earth Sciences 2016, 121, 180 -199.
AMA StyleCharles Bakundukize, Yohana Mtoni, Kristine Martens, Marc Van Camp, Kristine Walraevens. Poor understanding of the hydrogeological structure is a main cause of hand-dug wells failure in developing countries: A case study of a Precambrian basement aquifer in Bugesera region (Burundi). Journal of African Earth Sciences. 2016; 121 ():180-199.
Chicago/Turabian StyleCharles Bakundukize; Yohana Mtoni; Kristine Martens; Marc Van Camp; Kristine Walraevens. 2016. "Poor understanding of the hydrogeological structure is a main cause of hand-dug wells failure in developing countries: A case study of a Precambrian basement aquifer in Bugesera region (Burundi)." Journal of African Earth Sciences 121, no. : 180-199.
Hydrochemical and stable isotope (δ18O, δ2H) data were used to identify the recharge sources of major springs and the hydraulic interconnection between the volcanic aquifer and springs in the Gilgel Abay catchment and adjacent areas. The hydrochemical data analysis showed that all water samples of springs and shallow wells have freshwater chemistry, CaHCO3 to CaMgHCO3 types. This is mainly controlled by dissolution/hydrolysis of silicate minerals. The analyzed stable isotope data indicate that springs water, except Dengel Mesk, Kurt Bahir and Bility springs, and well waters, except Dangila well, fall close to the LMWL. This clearly shows that the infiltrated rainwater did not undergo much evaporation and δ18O values for spring water and groundwater are nearly equal to the value of Ethiopian summer rainfall, which is −2.5‰. Therefore, generally both stable isotope and hydrochemical data show the recharge source to springs and shallow groundwater is primarily from precipitation. Furthermore, data suggest that rock-water interaction has remained relatively limited, pointing to relatively short residence times, and local recharge rather than regional recharge.
Fenta Nigate; Marc Van Camp; Seifu Kebede; Kristine Walraevens. Hydrologic interconnection between the volcanic aquifer and springs, Lake Tana basin on the Upper Blue Nile. Journal of African Earth Sciences 2016, 121, 154 -167.
AMA StyleFenta Nigate, Marc Van Camp, Seifu Kebede, Kristine Walraevens. Hydrologic interconnection between the volcanic aquifer and springs, Lake Tana basin on the Upper Blue Nile. Journal of African Earth Sciences. 2016; 121 ():154-167.
Chicago/Turabian StyleFenta Nigate; Marc Van Camp; Seifu Kebede; Kristine Walraevens. 2016. "Hydrologic interconnection between the volcanic aquifer and springs, Lake Tana basin on the Upper Blue Nile." Journal of African Earth Sciences 121, no. : 154-167.
The quality and geochemistry of groundwater are significantly affected by the depositional environment of aquifer sediments. Miocene sediments in Al Wahat area (Jalu, Awjilah and Shakherah Oases) in the Libyan Desert at the north-east of the country have been deposited in fluvial marginal marine and marine environments. The purposes of this paper are to describe the areal distribution of the dominant water quality constituents, to identify the major hydro-geochemical processes that affect the quality of water and to evaluate the relations of sedimentary depositional environments and groundwater flow to the quality and geochemistry of water in aquifer sediments of Post-Eocene. This study is the first investigation in Al Wahat Oasis and also in the whole Sahara, which introduces the importance of considering the end members and the synsedimentary influence for the interpretation of the aquifer hydrochemistry. The area involved in this study is within the boundaries 28°N–30°N and 21°E–23°E. Eighteen wells are selected in the area, including eight piezometers, and ten samples were analysed from wells used for domestic and agricultural purposes. Results show high and significant increase in total dissolved solids, especially Na+, Cl−, SO42− and NO3− compared with the previous years. The chemical results for the groundwater samples in Al Wahat are classified according to the Stuyfzand groundwater classification system; the water type is mostly brackish and brackish-saline NaCl in the downstream direction and fresh-brackish NaHCO3 upstream. These water types indicate that groundwater chemistry is changed by cation exchange reactions during flushing of the diluted saline aquifer by freshwater from the south. The different stages of cation exchange produce a chromatographic sequence of groundwater types. These cation exchange reactions during the freshening process occur mainly in the intercalated clay, resulting in a Na+ increase, and peaks of K+ and Mg2+ in the aquifer. In the north, the synsedimentary marine influence on the groundwater is stronger and the abstraction for irrigation is higher. Upconing of deep saline water and anthropogenic pollution may contribute significantly to the aquifer water quality. Calcite equilibrium and gypsum dissolution are also important hydrochemical processes in the aquifer.
Nawal Alfarrah; Abdelrahim Hweesh; Marc Van Camp; Kristine Walraevens. Groundwater flow and chemistry of the oases of Al Wahat, NE Libya. Environmental Earth Sciences 2016, 75, 985 .
AMA StyleNawal Alfarrah, Abdelrahim Hweesh, Marc Van Camp, Kristine Walraevens. Groundwater flow and chemistry of the oases of Al Wahat, NE Libya. Environmental Earth Sciences. 2016; 75 (12):985.
Chicago/Turabian StyleNawal Alfarrah; Abdelrahim Hweesh; Marc Van Camp; Kristine Walraevens. 2016. "Groundwater flow and chemistry of the oases of Al Wahat, NE Libya." Environmental Earth Sciences 75, no. 12: 985.
Kristine Walraevens; Ibrahimu Chikira Mjemah; Yohana Mtoni; Marc Van Camp. Sources of salinity and urban pollution in the Quaternary sand aquifers of Dar es Salaam, Tanzania. Journal of African Earth Sciences 2015, 102, 149 -165.
AMA StyleKristine Walraevens, Ibrahimu Chikira Mjemah, Yohana Mtoni, Marc Van Camp. Sources of salinity and urban pollution in the Quaternary sand aquifers of Dar es Salaam, Tanzania. Journal of African Earth Sciences. 2015; 102 ():149-165.
Chicago/Turabian StyleKristine Walraevens; Ibrahimu Chikira Mjemah; Yohana Mtoni; Marc Van Camp. 2015. "Sources of salinity and urban pollution in the Quaternary sand aquifers of Dar es Salaam, Tanzania." Journal of African Earth Sciences 102, no. : 149-165.
Quantification of water table dynamics is an essential part of eco-hydrological characterisation as they are a controlling factor for vegetation and groundwater-dependent ecosystems. This is often done using the concept of groundwater depth classes, which are defined based on mean high winter and mean low summer water levels. However, this concept does not consider inter-yearly variability of groundwater levels. Also, groundwater depth classes can depend strongly on local topography, which is specially the case in dune belts in coastal regions. In this paper, the relation between groundwater depth classes and the size of seasonal and inter-yearly variations is investigated in a dune region along the Belgian coast, which has the special hydrological and ecological feature of including a dune river. The spatial pattern of the seasonal fluctuations and inter-yearly variability here is much simpler than the heterogeneous distribution of groundwater depth classes. This may provide additional useful information in relation to the occurrence of vegetation and can be used in the context of nature development programmes.
Kristine Martens; Marc Van Camp; Kristine Walraevens. Quantification of water table dynamics as a reference for impact assessment of ecohydrological enhancement measures in a dune area in Belgium. Environmental Earth Sciences 2014, 73, 2223 -2240.
AMA StyleKristine Martens, Marc Van Camp, Kristine Walraevens. Quantification of water table dynamics as a reference for impact assessment of ecohydrological enhancement measures in a dune area in Belgium. Environmental Earth Sciences. 2014; 73 (5):2223-2240.
Chicago/Turabian StyleKristine Martens; Marc Van Camp; Kristine Walraevens. 2014. "Quantification of water table dynamics as a reference for impact assessment of ecohydrological enhancement measures in a dune area in Belgium." Environmental Earth Sciences 73, no. 5: 2223-2240.
Marc Van Camp; Yohana Mtoni; Ibrahimu C. Mjemah; Charles Bakundukize; Kristine Walraevens. Investigating seawater intrusion due to groundwater pumping with schematic model simulations: The example of the Dar es Salaam coastal aquifer in Tanzania. Journal of African Earth Sciences 2014, 96, 71 -78.
AMA StyleMarc Van Camp, Yohana Mtoni, Ibrahimu C. Mjemah, Charles Bakundukize, Kristine Walraevens. Investigating seawater intrusion due to groundwater pumping with schematic model simulations: The example of the Dar es Salaam coastal aquifer in Tanzania. Journal of African Earth Sciences. 2014; 96 ():71-78.
Chicago/Turabian StyleMarc Van Camp; Yohana Mtoni; Ibrahimu C. Mjemah; Charles Bakundukize; Kristine Walraevens. 2014. "Investigating seawater intrusion due to groundwater pumping with schematic model simulations: The example of the Dar es Salaam coastal aquifer in Tanzania." Journal of African Earth Sciences 96, no. : 71-78.
Kristine Walraevens; Tesfamichael Gebreyohannes Tewolde; Kassa Amare; Abdelwassie Hussein; Gebremedhin Berhane; Ruben Baert; Silke Ronsse; Samuel Kebede; Laure Van Hulle; Jozef Deckers; Kristine Martens; Marc Van Camp. Water Balance Components for Sustainability Assessment of Groundwater‐Dependent Agriculture: Example of the Mendae Plain (Tigray, Ethiopia). Land Degradation & Development 2013, 26, 725 -736.
AMA StyleKristine Walraevens, Tesfamichael Gebreyohannes Tewolde, Kassa Amare, Abdelwassie Hussein, Gebremedhin Berhane, Ruben Baert, Silke Ronsse, Samuel Kebede, Laure Van Hulle, Jozef Deckers, Kristine Martens, Marc Van Camp. Water Balance Components for Sustainability Assessment of Groundwater‐Dependent Agriculture: Example of the Mendae Plain (Tigray, Ethiopia). Land Degradation & Development. 2013; 26 (7):725-736.
Chicago/Turabian StyleKristine Walraevens; Tesfamichael Gebreyohannes Tewolde; Kassa Amare; Abdelwassie Hussein; Gebremedhin Berhane; Ruben Baert; Silke Ronsse; Samuel Kebede; Laure Van Hulle; Jozef Deckers; Kristine Martens; Marc Van Camp. 2013. "Water Balance Components for Sustainability Assessment of Groundwater‐Dependent Agriculture: Example of the Mendae Plain (Tigray, Ethiopia)." Land Degradation & Development 26, no. 7: 725-736.
Nawal Al Farrah; Marc Van Camp; Kristine Walraevens. Deducing transmissivity from specific capacity in the heterogeneous upper aquifer system of Jifarah Plain, NW-Libya. Journal of African Earth Sciences 2013, 85, 12 -21.
AMA StyleNawal Al Farrah, Marc Van Camp, Kristine Walraevens. Deducing transmissivity from specific capacity in the heterogeneous upper aquifer system of Jifarah Plain, NW-Libya. Journal of African Earth Sciences. 2013; 85 ():12-21.
Chicago/Turabian StyleNawal Al Farrah; Marc Van Camp; Kristine Walraevens. 2013. "Deducing transmissivity from specific capacity in the heterogeneous upper aquifer system of Jifarah Plain, NW-Libya." Journal of African Earth Sciences 85, no. : 12-21.