In the Saloum region of central-western Senegal, water needs are essentially met by tapping an underground aquifer associated with the sandy-clay formations of the Continental Terminal, in contact with both the ocean ...In the Saloum region of central-western Senegal, water needs are essentially met by tapping an underground aquifer associated with the sandy-clay formations of the Continental Terminal, in contact with both the ocean to the west and the highly saline waters of the Saloum River to the north. In this estuarine and deltaic zone with its very low relief, the hydraulic loads in the water tables are generally close to zero or even negative, creating a reversal of the natural flow and encouraging saline intrusion into this system, which makes it very vulnerable. This study concerns the implementation of a numerical model of saline intrusion to provide a better understanding of the vulnerability of the water table by analyzing the variability of the freshwater/saltwater interface. The Modflow-2005 code is used to simulate saline intrusion using the SWI2 module, coupled with the GRASS (Geographic Resources Analysis Support System) software under the Linux operating system with the steep interface approach. The probable expansion of the wedge is studied in three scenarios, taking into account its position relative to the bedrock at 1 m, 5 m and 10 m. Simulations carried out under imposed potential and river conditions, based on variations in groundwater reserves using two effective porosity values, 10−1 and 10−2, show that the water table is highly vulnerable in the northwest sector. The probable expansion of the wedge increases as the storage coefficient decreases and is more marked with river conditions in the areas surrounding the Saloum River, reaching 6 km with a probability of 1. The probability of the wedge reaching a certain degree of expansion decreases from 1 to 0.5, and then cancels out as it moves inland. The probable position of the wedge is limited to 500 m or even 1 km depending on the corner around the coast to the southwest and in the southern zone. This modelling, carried out under natural conditions, will be developed further, taking into account climatic parameters and pumping from wells and boreholes.展开更多
基于1979—2010年中国台站降水、GLDAS(Global Land Data Assimilation System)蒸发数据等,求取地表干湿指数SWI(Soil Water Index),对西北近30年干湿状况进行分析,验证近30年西北气候转型存在和延续的可能性,并通过经验正交分解,对西...基于1979—2010年中国台站降水、GLDAS(Global Land Data Assimilation System)蒸发数据等,求取地表干湿指数SWI(Soil Water Index),对西北近30年干湿状况进行分析,验证近30年西北气候转型存在和延续的可能性,并通过经验正交分解,对西北地区夏季降水和SWI的关系进行研究,探讨热带太平洋海温对西北地区气候变化和气候转型的影响。得出结论:(1)近30年来,以新疆为代表的西北地区SWI呈明显的上升趋势,于1987年发生气候突变,突变后降水量增加,新疆显著变湿,表明西北地区在近30年确实存在由干到湿的转型,且转型仍在延续,关键区范围及位置未发生变化。对西北地区夏季降水、SWI等进行EOF分解,结果进一步验证了该结论。(2)太平洋夏季海温趋势变化与新疆、西北地区降水及SWI变化趋势同步,北太平洋中部、热带太平洋中部、加利福尼亚海流区对西北地区夏季SWI的多年平均变化有显著影响,北太平洋西部和加利福尼亚海流区对西北地区夏季SWI的异常变化有显著影响。展开更多
文摘In the Saloum region of central-western Senegal, water needs are essentially met by tapping an underground aquifer associated with the sandy-clay formations of the Continental Terminal, in contact with both the ocean to the west and the highly saline waters of the Saloum River to the north. In this estuarine and deltaic zone with its very low relief, the hydraulic loads in the water tables are generally close to zero or even negative, creating a reversal of the natural flow and encouraging saline intrusion into this system, which makes it very vulnerable. This study concerns the implementation of a numerical model of saline intrusion to provide a better understanding of the vulnerability of the water table by analyzing the variability of the freshwater/saltwater interface. The Modflow-2005 code is used to simulate saline intrusion using the SWI2 module, coupled with the GRASS (Geographic Resources Analysis Support System) software under the Linux operating system with the steep interface approach. The probable expansion of the wedge is studied in three scenarios, taking into account its position relative to the bedrock at 1 m, 5 m and 10 m. Simulations carried out under imposed potential and river conditions, based on variations in groundwater reserves using two effective porosity values, 10−1 and 10−2, show that the water table is highly vulnerable in the northwest sector. The probable expansion of the wedge increases as the storage coefficient decreases and is more marked with river conditions in the areas surrounding the Saloum River, reaching 6 km with a probability of 1. The probability of the wedge reaching a certain degree of expansion decreases from 1 to 0.5, and then cancels out as it moves inland. The probable position of the wedge is limited to 500 m or even 1 km depending on the corner around the coast to the southwest and in the southern zone. This modelling, carried out under natural conditions, will be developed further, taking into account climatic parameters and pumping from wells and boreholes.
文摘基于1979—2010年中国台站降水、GLDAS(Global Land Data Assimilation System)蒸发数据等,求取地表干湿指数SWI(Soil Water Index),对西北近30年干湿状况进行分析,验证近30年西北气候转型存在和延续的可能性,并通过经验正交分解,对西北地区夏季降水和SWI的关系进行研究,探讨热带太平洋海温对西北地区气候变化和气候转型的影响。得出结论:(1)近30年来,以新疆为代表的西北地区SWI呈明显的上升趋势,于1987年发生气候突变,突变后降水量增加,新疆显著变湿,表明西北地区在近30年确实存在由干到湿的转型,且转型仍在延续,关键区范围及位置未发生变化。对西北地区夏季降水、SWI等进行EOF分解,结果进一步验证了该结论。(2)太平洋夏季海温趋势变化与新疆、西北地区降水及SWI变化趋势同步,北太平洋中部、热带太平洋中部、加利福尼亚海流区对西北地区夏季SWI的多年平均变化有显著影响,北太平洋西部和加利福尼亚海流区对西北地区夏季SWI的异常变化有显著影响。
