In recent years, geochemical and geophysical studies have challenged the commonly held view that the use of fossil Sahara aquifers is completely unsustainable because they have not been recharged since the last wet period of the Holocene. Here, we use gravity data and groundwater flow modeling to provide further evidence of modern recharge of the North-Western Sahara Aquifer System (NWSAS, Algeria, Tunisia, and Libya). The rainfall-recharge relationship previously established using data from the Gravity Recovery and Climate Experiment (GRACE) allows to produce a time series of the cumulated recharge of the NWSAS between 1950 and 2016. This reconstruction yields a mean value of 1.3 km³ year⁻¹ while a near-zero recharge is obtained using GRACE data for the current decade. According to our hydrogeological model, the recharge of the confined aquifer amounts to 0.3 km³ year⁻¹, representing almost 25% of the overall recharge. Comparison with the time evolution of pumping rates reveals that unsustainable exploitation came fully into effect around 1980, causing a tremendous decline in natural outflows. We show here that the natural outflow of the deep aquifer at Gabès (Tunisia), which partly sustains the coastal aquifer of the Djeffara plain, will vanish in the coming decade, highlighting unsustainable aquifer exploitation. Current population growth and climate change projections are both leading to a degree of groundwater over-exploitation which can only become increasingly unsustainable. Only the enforced regulation of irrigation practices supported both by current oasis pilot experiments and future fully integrated hydro-economic models will be effective in limiting this evolution.

中文翻译：

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再次探讨西北撒哈拉蓄水层的补给和可持续性

近年来，地球化学和地球物理研究对普遍持有的观点提出了挑战，即撒哈拉沙漠化石含水层的使用是完全不可持续的，因为自全新世以来的最后一个湿润时期以来一直没有对它们进行补给。在这里，我们使用重力数据和地下水流模型来提供西北撒哈拉含水层系统（NWSAS，阿尔及利亚，突尼斯和利比亚）现代补给的进一步证据。先前使用重力恢复和气候实验（GRACE）的数据建立的降雨-补给关系允许产生1950年至2016年之间NWSAS累积补给的时间序列。此重建产生的平均值为1.3 km ³ 年^-1而使用GRACE数据获得的近十年充值接近零。根据我们的水文地质模型，承压含水层的补给量为0.3 km ³  year ^-1，几乎占总充值额的25％。与抽水速度随时间变化的比较表明，不可持续的开采在1980年左右完全生效，导致自然流出量大大减少。我们在这里表明，加比斯（突尼斯）的深层含水层的自然流出将在未来十年内消失，这部分将维持杰费拉平原的沿海含水层，这将凸显出来。当前的人口增长和气候变化预测都导致一定程度的地下水过度开采，这种开采只会越来越难以为继。只有目前的绿洲试点试验和未来的完全综合的水-经济模型都支持对灌溉措施的强制性规定，才能有效地限制这种演变。