Groundwater mineralisation processes in Mediterranean semi‐arid systems (Cap‐Bon,North east of Tunisia): hydrogeological and geochemical approaches     

Adel Zghibi  Lahcen Zouhri  Jamila Tarhouni  Lamia Kouzana 《水文研究》2013,27(22):3227-3239

The groundwater of the Korba plain represents major water resources in Tunisia. The Plio‐Quaternary unconfined aquifer of the Cap‐Bon (north‐east Tunisia) is subject to the intensive agricultural activities and high groundwater pumping rates due to the increasing of the groundwater extraction. The degradation of the groundwater quality is characterized by the salinization phenomena. Groundwater were sampled and analysed for physic‐chemical parameters: Ca²⁺, Mg²⁺, Na⁺, K⁺, Cl^‐, SO₄^2‐, HCO₃^‐, NO₃^‐, pH, electrical conductivity (EC), and the temperature (T°). The hydrochemical analysis is coupled with the calculation of the saturation indexes (SI gypsum, SI halite, SI calcite and SI dolomite), ionic derivation and with the ion correlations compared to chloride concentrations: Na⁺/ Cl^‐, Ca²⁺/ Cl^‐ and Mg²⁺/ Cl^‐ ratios. Seawater fractions in the groundwater were calculated using the chloride concentration. Those processes can be used as indicators of seawater intrusion progression. EC methods were also conducted to obtain new informations on the spatial scales and dynamics of the fresh water–seawater interface of coastal groundwater exchange. The mixing zone between freshwater and saltwater was clearly observed from the EC profile in the investigated area where a strong increase in EC with depth was observed, corresponding to the freshwater and saltwater interface. Results of hydrochemical study revealed the presence of direct cation exchange linked to seawater intrusion and dissolution processes associated with cations exchange. These results, together with EC investigation, indicated that the groundwater is affected by seawater intrusion and is still major actor as a source of salinization of the groundwater in Korba coastal plain. Further isotopic and hydrological investigations will be necessary to identify and more understood the underlying mechanisms. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Delineation of saltwater intrusion zones using the time domain electromagnetic method: the Nabeul–Hammamet coastal aquifer case study (NE Tunisia)     

Fatma Trabelsi  Abdallah Ben Mammou  Jamila Tarhouni  Carlo Piga  Gaetano Ranieri 《水文研究》2013,27(14):2004-2020

The time domain electromagnetic method (TDEM) is applied to monitor, to delineate and to map the saltwater intrusion zones in the Mediterranean Plio‐Quaternary aquifer. Forty‐two TDEM soundings were carried out in the coastal plain of Nabeul–Hammamet region (NE Tunisia). TDEM resistivity data were correlated with the existing borehole logging data to assign them to a particular lithology and to provide information about the position of the freshwater–seawater transition zone. The geoelectric sections showing the vertical configuration of seawater intrusion, with the brackish‐salty‐saturated zones, have a resistivity ranging from ~0.1 to 5 Ω?m and are detected at a depth lower than 1.5 m. The salinized zones are located at Nabeul (Sidi Moussa, Sidi El Mahrsi, Al Gasba and Mrazgua) and at Hammamet (Touristic zone of Hammamet north and south, Baraket Essahel) and reached a distance of 4 km from the coastline, indicating a severe state for the aquifer in these zones. These TDEM results are confirmed by the increase of chloride concentration content in the analysed water samples of monitoring wells. Moreover, in the northeastern part, the presence of a saltwater front located far from the coast and along the NW–SE major surface fault can be explained by two hypothesis: (i) this fault seems to provide a conduit for seawater to move readily towards the water wells and (ii) the clay and gypsum infiltration of marine Messinian deposits through the fault plane leads to low resistivities. Finally, it comes out from this study that TDEM survey has successfully depicted salinized zones of this coastal aquifer. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Relationship between hydrogeological parameters for data-scarce regions: the case of the Araripe sedimentary basin, Brazil   总被引：1，自引：0，他引：1  

Sávio de Brito Fontenele  Luiz Alberto Ribeiro Mendonça  José Carlos de Araújo  Maria Marlúcia Freitas Santiago  José Yarley de Brito Gonçalves 《Environmental Earth Sciences》2014,71(2):885-894

This paper applies and validates a method for generating spatially distributed hydraulic conductivity (k) based on the specific capacity (Q _s) for data-scarce regions. This method has been applied to the Araripe sedimentary basin, Brazil, and consists of four steps: (1) selection of (32) wells for which both k and Q _s data are available; (2) estimation of k as a function of Q _s for the (128) wells for which only specific capacity data are available; (3) spatial distribution of k using the kriging geostatistical tool; (4) validation of the method, using (17) representative wells with k measured data. The equation relating k and Q _s showed a statistically significant linear relationship (R = 0.93), from which a database has been generated using kriging with the spherical model. The results showed a calibration coefficient of Nash and Sutcliffe (NS) of 0.54 and moderate spatial dependence ratio of 69 %. The validation process provided only a moderate efficiency (NS = 0.22), possibly due to the geological complexity of the focus system. Despite its limitations, the method indicates the possibility of application of ordinary kriging to generate reliable data from auxiliary variables, especially for the water management of data-scarce areas.  相似文献   

Seasonal variability in plankton food web structure and trophodynamics in the neritic area of Sagami Bay,Japan     

Koichi Ara  Juro Hiromi 《Journal of Oceanography》2009,65(6):757-779

The plankton food web structure and trophodynamics in the neritic area of Sagami Bay were investigated from January 2003 to December 2005, based on abundance, biomass, production rate and nutritional requirements of pico- (0.2–2 μm), nano- (2–20 μm), micro- (20–200 μm) and mesoplankton (>200 μm: mainly copepods CI-CVI) at 0–10 m depth. The average carbon biomass of the total plankton community was higher in spring and summer (1.452 and 1.466 g C m⁻², respectively) than in winter and autumn (0.676 and 0.686 g C m⁻², respectively). The average values of primary production and of production rate and food requirement of heterotrophic organisms were higher in summer than in other seasons. During the study period the biomass, production rate and food requirement of small heterotrophs (i.e. bacteria: BA; heterotrophic nanoflagellates: HNF; microzooplankton: MZ) were much higher than those of copepod secondary (CSP) and tertiary producers (CTP), indicating that the microbial food web was the main route of carbon flow from phytoplankton (PP) to CSP and CTP, rather than the grazing food chain. In particular, during summer and autumn the biomass of pico- and nano-size PP plus BA was greater than that of micro-size PP, suggesting the high prevalence of the microbial food web (pico-/nanophytoplankton/BA-HNF/MZ-copepods). During winter and spring, the biomass of micro-size PP was greater than that of pico- and nano-size PP plus BA, suggesting that the indirect route (microphytoplankton-MZ-copepods) probably prevailed, while the microbial food web might be important.  相似文献   

Sources and Distribution of Particulate Organic Matter of a Tropical Estuarine-Lagoon System from NE Brazil as Indicated by Lipid Biomarkers     

Talitha L. F. Costa  Michelle P. Araújo  Bastiaan A. Knoppers  Renato S. Carreira 《Aquatic Geochemistry》2011,17(1):1-19

In the present work, we evaluated the origin of organic matter in the tropical estuarine-lagoon system of Mundaú–Manguaba, NE Brazil, by considering the bulk (organic carbon and chlorophyll-a) and lipidic (n-alcohols and sterols) composition of suspended particles. Water samples were collected in August 2006 from 24 stations covering the salinity gradient from the rivers down to the sea outlet. Chlorophyll-a (Chl-a) varied from 22.7 to 134.1 μg L⁻¹ in the lagoons, indicating eutrophic to hypertrophic conditions at the time of sampling. The high correlation between Chl-a and phytol together with the molar C:N ratio indicated the presence of fresh and recently produced autochthonous particulate organic matter throughout the system, except for the river samples. The elevated concentrations of short-chain n-alcohols and phytosterols, mainly 24-methylcholesta-5,24(28)-dien-3β-ol, also corroborated the predominance of autochthonous organic matter in the lagoons but were generated by distinct sources: cianobacteria in the freshwater Manguaba lagoon and diatoms in the brackish Mundaú lagoon compartments. Input of terrestrial organic matter was only detected in the rivers themselves or at the upper river–lagoon interfaces. Coprostanol indicated contamination by sewage in Mundaú lagoon and in some rivers, but at lower levels when compared to other Brazilian coastal lagoons and estuaries.  相似文献   

Comprehension and hydrogeological conceptualization of aquifer in arid and semi-arid regions using integrated hydrogeological information system: case of the deep aquifer of Zéramdine-Béni Hassen (east-central Tunisia)     

Fethi Lachaal  Ammar Mlayah  Makram Anane  Mourad Bédir  Jamila Tarhouni  Christian Leduc 《Arabian Journal of Geosciences》2013,6(7):2655-2671

In arid and semi-arid regions, the groundwater overexploitation caused drawdown in piezometric levels and a degradation of chemical water quality. That is why the groundwater monitoring needs a good comprehension of the hydrogeological aquifer properties. This is specially the case of Zéramdine–Béni Hassen deep aquifer (east-central Tunisia). Seismic profiles interpretation highlights the existence of the Zéramdine fault corridor, the Boumerdès anticline, the Moknine and Mahdia grabens that represent lateral boundaries for the study aquifer. The outcrop of the aquifer is located in the Zéramdine, Béni Hassen and Ain Ben Jannet regions, where two lithostratigraphic sections were realized. The piezometric study shows that the principal groundwater flow is from west to east. A secondary flow is from NW to SE. The hydrochemical study of 22 sample shows that the aquifer is characterized by freshwater, dominated by Na–Ca–Cl–SO4 facies. The salinity increase is from the west to the east, which coincides with the principal water flow direction. The integration of all results deduced from the hydrogeophysic, hydrodynamic and hydrochemical studies is developed to investigate hydrological processes of Zéramdine–Béni Hassen aquifer and consequently to propose a conceptual model, which will help to propose a rescue plan for the studied aquifer and to implement a spatial hydrogeological database using the global information system and then to characterize the complex aquifer system.  相似文献   

Grid-enabled Monte Carlo analysis of the impacts of uncertain discharge rates on seawater intrusion in the Korba aquifer (Tunisia)     

Jaouher Kerrou  Philippe Renard  Giuditta Lecca  Jamila Tarhouni 《水文科学杂志》2013,58(8):1325-1336

Abstract

The Korba aquifer, located in the north of Tunisia, suffers heavily from salinization due to seawater intrusion. In 2000, the aquifer was exploited from more than 9000 wells. The problem is that no precise information was recorded concerning the current extraction rates, their spatial distribution, or their evolution in time. In this study, a geostatistical model of the exploitation rates was constructed based on a multi-linear regression model combining incomplete direct data and exhaustive secondary information. The impacts of the uncertainty on the spatial distribution of the pumping rates on seawater intrusion were evaluated using a 3-D density-dependent groundwater model. To circumvent the large amount of computing time required to run transient models, the simulations were run in a parallel fashion on the Grid infrastructure provided by the Enabling Grid for E-Science in Europe project. Monte Carlo simulations results showed that 8.3% of the aquifer area is affected by input uncertainty.

Citation Kerrou, J., Renard, P., Lecca, G. & Tarhouni, J. (2010 Kerrou, J., Renard, P. and Tarhouni, J. 2010. Status of the Korba groundwater resources (Tunisia): observations and three-dimensional modelling of seawater intrusion. Hydrogeol. J., 18(5): 1173–1190. doi:10.1007/s10040-010-0573-5[Crossref], [Web of Science ®] , [Google Scholar]) Grid-enabled Monte Carlo analysis of the impacts of uncertain discharge rates on seawater intrusion in the Korba aquifer (Tunisia). Hydrol. Sci. J. 55(8), 1325–1336.  相似文献   

Modelling spatio-temporal patterns of sediment yield and connectivity in a semi-arid catchment with the WASA-SED model     

Pedro H. A. Medeiros  Andreas Güntner  Till Francke  George L. Mamede  José Carlos de Araújo 《水文科学杂志》2013,58(4):636-648

Abstract

Rainfall–runoff induced soil erosion causes important environmental degradation by reducing soil fertility and impacting on water availability as a consequence of sediment deposition in surface reservoirs used for water supply, particularly in semi-arid areas. However, erosion models developed on experimental plots cannot be directly applied to estimate sediment yield at the catchment scale, since sediment redistribution is also controlled by the transport conditions along the landscape. In particular, representation of landscape connectivity relating to sediment transfer from upslope areas to the river network is required. In this study, the WASA-SED model is used to assess the spatial and temporal patterns of water and sediment connectivity for a semi-arid meso-scale catchment (933 km²) in Brazil. It is shown how spatial and temporal patterns of sediment connectivity within the catchment change as a function of landscape and event characteristics. This explains the nonlinear catchment response in terms of sediment yield at the outlet.

Citation Medeiros, P. H. A., Güntner, A., Francke, T., Mamede, G. L. & de Araújo, J. C. (2010) Modelling spatio-temporal patterns of sediment yield and connectivity in a semi-arid catchment with the WASA-SED model. Hydrol. Sci. J. 55(4), 636–648.  相似文献   

Runoff initiation in a preserved semiarid Caatinga small watershed,Northeastern Brazil   总被引：2，自引：0，他引：2       下载免费PDF全文

José Vidal de Figueiredo  José Carlos de Araújo  Pedro Henrique Augusto Medeiros  Alexandre C. Costa 《水文研究》2016,30(13):2390-2400

This study analyses some hydrological driving forces and their interrelation with surface‐flow initiation in a semiarid Caatinga basin (12 km²), Northeastern Brazil. During the analysis period (2005 – 2014), 118 events with precipitation higher than 10 mm were monitored, providing 45 events with runoff, 25 with negligible runoff and 49 without runoff. To verify the dominant processes, 179 on‐site measurements of saturated hydraulic conductivity (Ksat) were conducted. The results showed that annual runoff coefficient lay below 0.5% and discharge at the outlet has only occurred four days per annum on average, providing an insight to the surface‐water scarcity of the Caatinga biome. The most relevant variables to explain runoff initiation were total precipitation and maximum 60‐min rainfall intensity (I₆₀). Runoff always occurred when rainfall surpassed 31 mm, but it never occurred for rainfall below 14 mm or for I₆₀ below 12 mm h^?1. The fact that the duration of the critical intensity is similar to the basin concentration time (65 min) and that the infiltration threshold value approaches the river‐bank saturated hydraulic conductivity support the assumption that Hortonian runoff prevails. However, none of the analysed variables (total or precedent precipitation, soil moisture content, rainfall intensities or rainfall duration) has been able to explain the runoff initiation in all monitored events: the best criteria, e.g. failed to explain 27% of the events. It is possible that surface‐flow initiation in the Caatinga biome is strongly influenced by the root‐system dynamics, which changes macro‐porosity status and, therefore, initial abstraction. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

Improving the determination of reservoir capacities for drought control   总被引：2，自引：2，他引：0  

Aline de Araújo Nunes  Fernando Falco Pruski 《Stochastic Environmental Research and Risk Assessment (SERRA)》2015,29(1):183-191

Reliable methods of determining reservoir capacities are becoming more and more necessary to improve the planning and management of water resources. Due to its easy use and solid technical and scientific basis, the Reservoir Operation Study has been widely utilized by engineers. However, this method is limited by its strong dependence on the available database. This study was undertaken to propose potential modifications to the Reservoir Operation Study to overcome its problems, namely the strong dependence upon the first year of the time series and inability of associating the reservoir storage capacity with a frequency (return period). To make the reservoir capacity independent from the first year of the time series, we created (N ? 1) synthetic series of streamflows (N = the number of years in the time series) and applied the Reservoir Operation Study method to each one. To associate the reservoir capacity with a frequency factor (return period), we applied a Gumbel distribution to the reservoir capacity estimated from each one of the synthetic series. For β-values (proportion of the average streamflow to be regulated) greater than or equal to 0.75, the proposed method efficiently overcame the aforementioned limitation regarding the method’s dependence on the database. The association of storage capacities with return periods greater than the length of the time series, which is presented in this work, also considerably improves the Reservoir Operation Study method.  相似文献