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Runoff and sediment yield modeling using SWAT model: case of Wadi Hatab basin,central Tunisia 总被引：1，自引：0，他引：1
This study presents an application of the model Soil and Water Assessment Tool (SWAT) to simulate daily and monthly water flow and sediment fluxes in the Wadi Hatab watershed (2200 km2) located in central Tunisia. The study basin is characterized by a significant climatic contrast, abrupt topography, and soil fragility, resulting thereby in flash floods and important water erosion rates. This alarming situation requires urgent interventions in order to preserve water and soil resources, implying the need for a decision tool for proper integrated management of the watershed. The model was calibrated and validated based on a comparison of simulated and observed flow rates at the basin outlet (hydrometric station Khanguet Zazia), during the periods 1987–1988 and 1989–1990, respectively. The comparison was based not only on visual inspection of the agreement between observed and simulated time series, but also on statistical parameters. Indeed, for the daily time step application, the Nash—Sutcliffe efficiency (NSE) values were 0.52 and 0.61, and the coefficient of determination (R2) was 0.54 and 0.61 for calibration and validation, respectively. As for the monthly time-step application, the obtained NSE values were 0.67 and 0.89 while R2 values were 0.83 and 0.87 for calibration and validation, respectively. This clearly shows the reasonably good agreement between simulated and observed flow rates. In terms of erosion, the model gave sediment yield values ??of 1.15 and 5.37 t/ha/year during the periods of calibration and validation, respectively. 相似文献
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This study examines spatial and time evolutions of the principal constituents of the
Tunisian background aerosols under Sirocco wind circulations. Aerosols coming from the Sahara
Desert were found to be loaded with particulate matter, especially silicon. The aerosols were
shown to have varying geochemical behaviour along the ``South-North" displacement of the Saharan
plumes, depending on the wind flow characteristics, geomorphologic features and the nature of
soils swept by the wind. In the south and the center part of the country, the transfer of aerosol
constituents to the soil (by gravity and/or impaction) was probably predominated by localized
enrichment phenomena. The latter are reinforced by the effect of turbulent winds over bare soils,
wind wakes and probably selective disintegration, especially in the vicinity of the geomorphologic
features of central Tunisia. These relatively high features, extending over important distances,
appear to be of paramount importance for the phenomena of redistribution of aerosol constituents
even during periods without Sirocco wind circulations. In the northern section of the country,
aerosol constituent concentrations dropped to almost 50%, in spite of the abundance of localized
turbulent winds. This may be explained by the effect of forests and the relatively dense vegetation
cover, which clearly reinforces the transfer phenomena to the soil and the attenuate of dust
entrainment. 相似文献
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Marine intrusion is the most serious problem facing the coastal Jorf shallow aquifer, located in south‐eastern Tunisia on the Mediterranean Sea. Jorf Aquifer is intensively exploited to supply the growing needs of agriculture and domestic sectors. This work proposes a multidisciplinary investigation, involving hydro‐geochemical, geoelectrical survey and geostatistical techniques for modelling the saltwater intrusion. For this purpose, 36 water samples were conducted and analysed. Electric conductivity, pH, total dissolved solids and major ions were measured and analysed. Pie and Durov Diagrams, Q‐mode hierarchical cluster and geostatistical analysis were considered to identify the main groundwater mineralization processes. Results revealed that the Na‐Cl‐Ca‐SO4 is the dominant water type suggesting that dissolution of halite and gypsum was the main mineralization source of groundwater in the central and southern part of study area. However, saltwater intrusion was shown to control groundwater quality essentially in coastal areas. Variographic analyses were used to select the variographic model that best fits the spatial development of apparent resistivity. Kriged apparent resistivity profiles showed an abnormal decrease of resistivity values in the coastal zone, implying highly saline water because of seawater intrusion. Apparent resistivity values also decrease considerably in the faulted areas, suggesting a contribution of faults to seawater intrusion. Finally, saltwater mixing ratio was computed for each sample, and a refined seawater intrusion map was developed. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
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Abstract This paper refers to the quantification and prediction of the sedimentation rate of 26 hillside-dam reservoirs in Central Tunisia. The objectives of the study are to develop a simple and practical methodology to identify controlling factors of sedimentation, and to propose a regionalization from the study sites. Principal component analysis (PCA) and complementary multi-dimensional statistical methods are used to relate highly variable area-specific sediment yield to hydro-morphometric, lithological, geomorphological and anthropogenic characteristics of catchments. It appears that catchment area is not the main controlling factor of sedimentation in the studied area. The overall slope index, drainage network characteristics and runoff parameters are also important in characterizing sediment yield. Applied to the annual sedimentation rate series, PCA resulted in retaining the first three principal axes, explaining 65% of the total variance. Statistical methods showed that the overall slope index, the total drainage length, the compacity index and the runoff parameters are as important for the sedimentation quantification. This allowed a graphical clustering of the study zone into three distinct groups having similar behaviours: (i) watersheds characterized by high sediment transport rates and high runoff coefficients, (ii) basins distinguished by relatively low values of both flow discharge and sediment transport rates, and (iii) watersheds with an intermediate sediment yield, especially characterized by relatively high relief. In a second step, a multiple regression model including the four characteristic catchment properties was developed, presenting a valuable tool to predict area-specific sediment yield from catchments in central Tunisia. This model shows reasonable efficiency with an absolute prediction error of 81%. Citation Ayadi, I., Abida, H., Djebbar, Y. & Mahjoub, M. R. (2010) Sediment yield variability in central Tunisia: a quantitative analysis of its controlling factors. Hydrol. Sci. J. 55(3), 446–458. 相似文献
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Impacts of irrigation with treated wastewater effluents on soils and groundwater aquifer in the vicinity of Sidi Abid Region
(Tunisia) are evaluated. The groundwater aquifer was monitored by several piezometers, where monthly water levels were registered
and groundwater salinity was evaluated. This resulted in characterizing the spatial and temporal evolution of the hydrochemical
and hydrodynamic properties of the aquifer, showing thereby the impact of artificial recharge. Piezometric maps for pre-recharge
and post-recharge situations were developed and a comparison study of both piezometric situations was considered. The piezometric
evolution map showed a generalized rise of the piezometric level in the vicinity of the irrigation zone. The extent of recharge
was shown to increase with time as the groundwater level increase, which was localized in the vicinity of the irrigation area,
reached more extended zones. Several groundwater samples were withdrawn from wells and piezometers and analyzed. Examining
the corresponding physical and chemical parameters showed an increase in the concentrations of nutrients (28 mg/l for NO3 and 3.97 mg/l for NH4) in the groundwater aquifer below the irrigation zone, which confirms again the infiltration of treated wastewater effluents.
The evolution of soil salinity was examined through chemical analysis of soil samples. Electric conductivities of soils were
generally shown to be less than 4 mS/cm while the irrigation water has an electric conductivity that may reach 6.63 mS/cm.
This might be explained by the phenomenon of dilution and the capacity of soils to evacuate salts downward. 相似文献
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Flash floods are among the most severe hazards which have disastrous environmental, human, and economic impacts. This study is interested in the characterization of flood hazard in Gabes Catchment (southeastern Tunisia), considered as an important step for flood management in the region. Analytical hierarchy process (AHP) and geographic information system are applied to delineate and characterize flood areas. A spatial database was developed based on geological map, digital elevation model, land use, and rainfall data in order to evaluate the different factors susceptible to affect flood analysis. However, the uncertainties that are associated with AHP techniques may significantly impact the results. Flood susceptibility is analyzed as a function of weights using Monte Carlo (MC) simulation and Global sensitivity analysis. AHP and MC–AHP models gave similar results. However, compared to AHP approach, MC–AHP confidence intervals (95%) of the overall scores had small overlaps. Results obtained were validated by remote sensing data for the zones that showed very high flood hazard during the extreme rainfall event of June 2014 that hit the study basin. 相似文献
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Hydrochemistry of groundwater and its assessment for irrigation purpose in coastal Jeffara Aquifer, southeastern Tunisia 总被引：1，自引：0，他引：1
Groundwater is of a paramount importance in arid areas, as it represents the main water resource to satisfy the different needs of the various sectors. Nevertheless, coastal aquifers are generally subjected to seawater intrusion and groundwater quality degradation. In this study, the groundwater quality of the coastal Jeffara aquifer (southeastern Tunisia) is evaluated to check its suitability for irrigation purposes. A total of 74 groundwater samples were collected and analyzed for various physical and chemical parameters, such as, electrical conductivity, pH, dissolved solids (TDS), Na, K, Ca, Mg, Cl, HCO3, and SO4. Sodium adsorption ratio, magnesium adsorption ratio, Sodium percentage, and permeability index were calculated based on the analytical results. The analytical results obtained show a strong mineralization of the water in the studied aquifer. TDS concentrations range from 3.40 to 18.84 g?L?1. Groundwater salinity was shown to be mainly controlled by sodium and chloride. The dominant hydrochemical facieses are Na–Cl–Ca–SO4, mainly as a result of mineral dissolution (halite and gypsum), infiltration of saline surface water, and seawater intrusion. Assessment of the groundwater quality of the different samples by various methods indicated that only 7% of the water, in the northwest of the study area, is considered suitable for irrigation purposes while 93% are characterized by fair to poor quality, and are therefore just suitable or unsuitable for irrigation purposes. 相似文献
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