The semi-distributed SWAT (Soil and Water Assessment Tools) model was used in this study to model the sediment yield in the watershed of the Aghien lagoon with an area of 365 km<sup><span style="font-fam...The semi-distributed SWAT (Soil and Water Assessment Tools) model was used in this study to model the sediment yield in the watershed of the Aghien lagoon with an area of 365 km<sup><span style="font-family:Verdana;">2</span></sup><span style="font-family:Verdana;">, located in the north of the district of Abidjan (South-East from</span><span style="font-family:Verdana;"> C<span style="white-space:nowrap;">?</span>te d’Ivoire). A sensitivity and uncertainty analysis, as well as calibration of the SWAT model, was conducted using the Sequential Uncertainty Adjustment Procedure (SUFI-2) which is one of the programs interfaced with SWAT in the SWAT-Cup package (SWAT-Calibration-Uncertainty</span><span style="font-family:Verdana;"> Programs). Five parameters of the SWAT model were found to be more sensitive to sediment fluxes. These have been modified (calibration) sparingly in order to improve the reproduction of observed sediments data. Two measures were used to assess the uncertainty analysis of the model: P-factor and R-factor. The R</span><sup><span style="font-family:Verdana;">2</span></sup><span style="font-family:Verdana;"> and Nash-Sutcliffe (NS) coefficients of determination were used to assess the quality of the calibration. The P-factor obtained is 0.58 and the R-factor is 2.28. The NS and R</span><sup><span style="font-family:Verdana;">2</span></sup><span style="font-family:Verdana;"> coefficients in calibration over the period from June 2014 to January 2015 are 0.51 and 0.86 respectively. These values </span><span style="font-family:Verdana;">indicate correct consideration of uncertainties by the model and satisfactory calibration</span><span style="font-family:Verdana;"> of the SWAT model for solid fluxes. Then, the model was used to simulate the sediment fluxes at the horizons 2040 (2035-2056), 2060 (2057-2078</span><span style="font-family:Verdana;">)</span><span style="font-family:Verdana;"> and 2080 (2079-2100) in order to assess the impact of climate change on sediments in the watershed of the Aghien lagoon. The results indicate that sediment fluxes could increase in the future under the RCP 4.5 and RCP 8.5 scenarios. With RCP 4.5, sediment fluxes would increase on average by 14.42%. They could increase by 17.95% on average under RCP 8.5.</span>展开更多
Faced with the scarcity of surface water accentuated by climate change, particularly in many arid and semi-arid countries, the quality of groundwater used for irrigation is a concern to agronomists and hydrogeologists...Faced with the scarcity of surface water accentuated by climate change, particularly in many arid and semi-arid countries, the quality of groundwater used for irrigation is a concern to agronomists and hydrogeologists. When </span><span style="font-family:Verdana;">these waters are of deep origin, they may have high mineralization and</span><span style="font-family:Verdana;"> chemical compositions unsuitable for irrigation;in particular, they may alter soils and crops. It is therefore important to optimize the spatial estimation of the salinity of these waters and contribute to better knowledge of their quality, through an adapted and robust statistical and geostatistical approach. In the case of north-eastern Algeria, the objective of this study is to characterize the quality of deep waters and to test two interpolation methods (Inverse distance weight and ordinary Kriging) of their electrical conductivity (EC) as an indicator of their salinity and of the risk of damaging irrigated soils. 51 ground</span><span style="font-family:Verdana;">water samples were taken in this region where there are many thermal </span><span style="font-family:Verdana;">springs, the water of which is used for irrigation and often is highly mineralized (EC between 0.6 and 26.6 dS/m). The geology is composed of karstic rocks crossed by large faults that allow deep water to rise. Based on major elements contents, analysis of the hydrochemical facies of these waters shows that the main facies are hyperchlorinated sodium (38%) and sulfated calcium (32%). The RSC (Residual Sodium Carbonate) and SAR (Irrigation water salt) indexes were used to assess the water quality. The results indicate that the majority of the sampled</span><span style="color:red;"> </span><span style="font-family:Verdana;">groundwater present a risk for soils irrigated with these waters (almost 1/3 presents a strong risk). The risk for the soils seems to be explained by the positive value of the residual alkalinity, and the high risks of sodization and alkalinization. The geostatistical analysis reveals strong heterogeneity in electrical conductivity (salinity). The maps based on this analysis allow the identification of risk areas. The comparison of Inverse distance weight and ordinary Kriging methods indicates similar results being obtained through both methods. However, ordinary kriging appears to be more accur</span><span style="font-family:Verdana;">ate, less biased, and seemingly better represents the organization of the </span><span style="font-family:Verdana;">groundw</span><span style="font-family:Verdana;">ater resources, as NE-SW alignments are visible. With the proposed ap</span><span style="font-family:Verdana;">proach, it is possible to calculate the surface areas of the different salinity </span><span style="font-family:Verdana;">thresholds and then optimize the use of deep groundwater for irrigation.展开更多
This work aims to evaluate the impact of climate change on the quantitative availability of the Aghien lagoon located in the north of the Abidjan district in Côte d’Ivoire. In the first step, the semi-distri...This work aims to evaluate the impact of climate change on the quantitative availability of the Aghien lagoon located in the north of the Abidjan district in Côte d’Ivoire. In the first step, the semi-distributed SWAT (Soil and Water Assessment Tools) based physical model (Arnold et al., 1998) was calibrated and validated at the monthly time step over the period 1960-1981, in the Me watershed for which data from flow rates are available. SWAT was then applied on the watershed of the lagoon of Aghien which is ungauged but for which the challenges are considerable for the drinking water supply of the Abidjanese population. In the second step, the gross outputs (precipitation, temperatures) of six climate models of the CORDEX-Africa project under the “Representative Concentration Pathways” (RCP 4.5 and RCP 8.5) scenarios were corrected using the delta method. These corrected outputs were used at the SWAT model input to project the impact of climate change on the flow of the Aghien lagoon to horizons 2040 (2035-2056), 2060 (2057-2078) and 2080 (2079-2100). The projections made on these different horizons were compared with the simulated flow over the period 1960-1981. The results show a sensible decrease in the annual flow of the Aghien lagoon compared to the reference period (1960-1981). Under the medium assumption (RCP 4.5), the models predict a decrease in the annual discharge almost 10% on average. Under the pessimistic hypothesis (RCP 8.5), the average annual discharge should decrease by more than 17%. On a monthly basis, flows in August and September would increase by more than 80% and those in October and November would increase by more than 20% in both RCP scenarios.展开更多
文摘The semi-distributed SWAT (Soil and Water Assessment Tools) model was used in this study to model the sediment yield in the watershed of the Aghien lagoon with an area of 365 km<sup><span style="font-family:Verdana;">2</span></sup><span style="font-family:Verdana;">, located in the north of the district of Abidjan (South-East from</span><span style="font-family:Verdana;"> C<span style="white-space:nowrap;">?</span>te d’Ivoire). A sensitivity and uncertainty analysis, as well as calibration of the SWAT model, was conducted using the Sequential Uncertainty Adjustment Procedure (SUFI-2) which is one of the programs interfaced with SWAT in the SWAT-Cup package (SWAT-Calibration-Uncertainty</span><span style="font-family:Verdana;"> Programs). Five parameters of the SWAT model were found to be more sensitive to sediment fluxes. These have been modified (calibration) sparingly in order to improve the reproduction of observed sediments data. Two measures were used to assess the uncertainty analysis of the model: P-factor and R-factor. The R</span><sup><span style="font-family:Verdana;">2</span></sup><span style="font-family:Verdana;"> and Nash-Sutcliffe (NS) coefficients of determination were used to assess the quality of the calibration. The P-factor obtained is 0.58 and the R-factor is 2.28. The NS and R</span><sup><span style="font-family:Verdana;">2</span></sup><span style="font-family:Verdana;"> coefficients in calibration over the period from June 2014 to January 2015 are 0.51 and 0.86 respectively. These values </span><span style="font-family:Verdana;">indicate correct consideration of uncertainties by the model and satisfactory calibration</span><span style="font-family:Verdana;"> of the SWAT model for solid fluxes. Then, the model was used to simulate the sediment fluxes at the horizons 2040 (2035-2056), 2060 (2057-2078</span><span style="font-family:Verdana;">)</span><span style="font-family:Verdana;"> and 2080 (2079-2100) in order to assess the impact of climate change on sediments in the watershed of the Aghien lagoon. The results indicate that sediment fluxes could increase in the future under the RCP 4.5 and RCP 8.5 scenarios. With RCP 4.5, sediment fluxes would increase on average by 14.42%. They could increase by 17.95% on average under RCP 8.5.</span>
文摘Faced with the scarcity of surface water accentuated by climate change, particularly in many arid and semi-arid countries, the quality of groundwater used for irrigation is a concern to agronomists and hydrogeologists. When </span><span style="font-family:Verdana;">these waters are of deep origin, they may have high mineralization and</span><span style="font-family:Verdana;"> chemical compositions unsuitable for irrigation;in particular, they may alter soils and crops. It is therefore important to optimize the spatial estimation of the salinity of these waters and contribute to better knowledge of their quality, through an adapted and robust statistical and geostatistical approach. In the case of north-eastern Algeria, the objective of this study is to characterize the quality of deep waters and to test two interpolation methods (Inverse distance weight and ordinary Kriging) of their electrical conductivity (EC) as an indicator of their salinity and of the risk of damaging irrigated soils. 51 ground</span><span style="font-family:Verdana;">water samples were taken in this region where there are many thermal </span><span style="font-family:Verdana;">springs, the water of which is used for irrigation and often is highly mineralized (EC between 0.6 and 26.6 dS/m). The geology is composed of karstic rocks crossed by large faults that allow deep water to rise. Based on major elements contents, analysis of the hydrochemical facies of these waters shows that the main facies are hyperchlorinated sodium (38%) and sulfated calcium (32%). The RSC (Residual Sodium Carbonate) and SAR (Irrigation water salt) indexes were used to assess the water quality. The results indicate that the majority of the sampled</span><span style="color:red;"> </span><span style="font-family:Verdana;">groundwater present a risk for soils irrigated with these waters (almost 1/3 presents a strong risk). The risk for the soils seems to be explained by the positive value of the residual alkalinity, and the high risks of sodization and alkalinization. The geostatistical analysis reveals strong heterogeneity in electrical conductivity (salinity). The maps based on this analysis allow the identification of risk areas. The comparison of Inverse distance weight and ordinary Kriging methods indicates similar results being obtained through both methods. However, ordinary kriging appears to be more accur</span><span style="font-family:Verdana;">ate, less biased, and seemingly better represents the organization of the </span><span style="font-family:Verdana;">groundw</span><span style="font-family:Verdana;">ater resources, as NE-SW alignments are visible. With the proposed ap</span><span style="font-family:Verdana;">proach, it is possible to calculate the surface areas of the different salinity </span><span style="font-family:Verdana;">thresholds and then optimize the use of deep groundwater for irrigation.
基金This reflection received financial support from the ERASMUS MUNDUS program through the KITE(Knowledge Integration and Transparency in Education)mobility project.
文摘This work aims to evaluate the impact of climate change on the quantitative availability of the Aghien lagoon located in the north of the Abidjan district in Côte d’Ivoire. In the first step, the semi-distributed SWAT (Soil and Water Assessment Tools) based physical model (Arnold et al., 1998) was calibrated and validated at the monthly time step over the period 1960-1981, in the Me watershed for which data from flow rates are available. SWAT was then applied on the watershed of the lagoon of Aghien which is ungauged but for which the challenges are considerable for the drinking water supply of the Abidjanese population. In the second step, the gross outputs (precipitation, temperatures) of six climate models of the CORDEX-Africa project under the “Representative Concentration Pathways” (RCP 4.5 and RCP 8.5) scenarios were corrected using the delta method. These corrected outputs were used at the SWAT model input to project the impact of climate change on the flow of the Aghien lagoon to horizons 2040 (2035-2056), 2060 (2057-2078) and 2080 (2079-2100). The projections made on these different horizons were compared with the simulated flow over the period 1960-1981. The results show a sensible decrease in the annual flow of the Aghien lagoon compared to the reference period (1960-1981). Under the medium assumption (RCP 4.5), the models predict a decrease in the annual discharge almost 10% on average. Under the pessimistic hypothesis (RCP 8.5), the average annual discharge should decrease by more than 17%. On a monthly basis, flows in August and September would increase by more than 80% and those in October and November would increase by more than 20% in both RCP scenarios.