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Water transit time and active recharge in the Sahel inferred by bomb-produced 36Cl.
Scientific Reports ( IF 3.8 ) Pub Date : 2019-05-16 , DOI: 10.1038/s41598-019-43514-x
Camille Bouchez 1, 2 , Pierre Deschamps 1 , Julio Goncalves 1 , Bruno Hamelin 1 , Abdallah Mahamat Nour 1, 3 , Christine Vallet-Coulomb 1 , Florence Sylvestre 1
Affiliation  

The lack of data and suitable methods to quantify regional hydrological processes often hinders sustainable water management and adaptation to climate change in semiarid regions, particularly in the Sahel, which is known for its climatic variability. Here we show that 36Cl from nuclear tests is a promising method to estimate water transit times and groundwater recharge rates on the catchment scale, and to distinguish water and chloride cycles. 36Cl was measured in 131 surface and groundwater samples in the Chari-Logone sub-catchment of the emblematic Lake Chad Basin, located in central Sahel. It was found that only 12 ± 8% of the catchment is connected to the main rivers. Groundwater supporting rivers in the upper humid part of the catchment has a mean transit time of 9.5 ± 1 years and a recharge rate of 240 ± 170 mm yr-1. In the lower Sahelian part of the catchment, stream-focused recharge yields recharge rates up to 78 ± 7 mm yr-1 in riparian groundwater against 16 ± 27 mm yr-1 elsewhere. Our estimates suggest that aquifers in the Sahel host a significant amount of renewable water, which could therefore be used as a strategic freshwater resource.

中文翻译:

炸弹生产的36Cl推断出萨赫勒地区的水运时间和有效补给。

缺乏数据和合适的方法来量化区域水文过程常常阻碍可持续干旱管理和半干旱地区,特别是萨赫勒地区的气候变化,因为萨赫勒地区的气候多变。在这里,我们表明,核试验中的36Cl是一种有前途的方法,可以估算集水规模上的水通过时间和地下水补给率,并区分水和氯的循环。在位于萨赫勒中心的标志性乍得湖盆地Chari-Logone子汇水区的131个地表水和地下水样品中测量了36Cl。据发现,只有12±8%的流域与主要河流相连。集水区上部潮湿地区的地下水支撑河流的平均渡越时间为9.5±1年,补给速度为240±170 mm yr-1。在该流域的萨赫勒地区下部,以河流为中心的补给在河岸地下水中的补给率高达78±7 mm yr-1,而在其他地方则为16±27 mm yr-1。我们的估计表明,萨赫勒地区的含水层蕴藏着大量的可再生水,因此可以用作战略淡水资源。
更新日期:2019-05-16
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