Infiltration and recharge dynamics in the Nubian Sandstone Aquifer System of northern Chad

IF 2.4 3区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY Hydrogeology Journal Pub Date : 2024-01-23 DOI:10.1007/s10040-024-02765-3

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Abstract

The Nubian Sandstone Aquifer System (NSAS) is one of the world’s largest fossil groundwater resources. In northern Chad, notably in the areas of the Tibesti and Ennedi mountains, precipitation occurs seasonally with rates up to 150 mm year^–1. This precipitation could lead to diffuse recharge, as well as concentrated recharge along the episodically flooded wadis. Although it is clear that infiltration occurs under flooded areas, it is unknown if and to what extent the infiltration can recharge groundwater. This study combines remote sensing data on precipitation, evapotranspiration, and the temporal and spatial dynamics of the flooded areas with chemical and stable isotopic data from groundwater and surface water sampled between 2013 and 2016. The combination of these data shows that (1) the only area where diffuse recharge occurs is in the southern area of the Ennedi mountains, where concentrated recharge through the wadis occurs concurrently during the month of August, and (2) southeast of the Tibesti and north of the Ennedi mountains, only concentrated recharge occurs. The length of the flooded areas and thus the spatial extent of concentrated recharge varies significantly from year to year and can last up to 3 months. The study has shown that modern recharge does occur in northern Chad, but to a very limited extent, both in space and time. This means that achieving sustainable management of this renewable resource can only be considered through rigorous quantitative assessments. Furthermore, these findings have important implications for future studies on the regional dynamics of the NSAS.

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乍得北部努比亚砂岩含水层系统的渗透和补给动态

摘要努比亚砂岩含水层系统（NSAS）是世界上最大的化石地下水资源之一。在乍得北部，特别是在提贝斯提山脉和恩内迪山脉地区，季节性降水量高达每年 150 毫米。这种降水可能导致漫流补给，也可能导致沿时常泛滥的河道的集中补给。虽然洪水泛滥地区明显存在渗透现象，但这种渗透是否能补给地下水以及补给的程度如何尚不清楚。本研究将降水量、蒸散量以及洪涝区时空动态的遥感数据与 2013 年至 2016 年间地下水和地表水取样的化学和稳定同位素数据相结合。这些数据的综合显示：(1) 只有恩内迪山脉南部地区会出现漫灌补给，而在 8 月份，通过瓦迪斯的集中补给也会同时出现；(2) 在提贝斯提东南部和恩内迪山脉北部，只有集中补给才会出现。淹没区的长度以及集中补给的空间范围每年都有很大不同，最长可达 3 个月。研究表明，乍得北部确实存在现代补给，但在空间和时间上都非常有限。这意味着，只有通过严格的定量评估，才能考虑实现对这一可再生资源的可持续管理。此外，这些发现对今后研究 NSAS 的区域动态具有重要意义。

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来源期刊

Hydrogeology Journal 地学-地球科学综合

CiteScore

5.40

自引率

7.10%

发文量

128

审稿时长

6 months

期刊介绍： Hydrogeology Journal was founded in 1992 to foster understanding of hydrogeology; to describe worldwide progress in hydrogeology; and to provide an accessible forum for scientists, researchers, engineers, and practitioners in developing and industrialized countries. Since then, the journal has earned a large worldwide readership. Its peer-reviewed research articles integrate subsurface hydrology and geology with supporting disciplines: geochemistry, geophysics, geomorphology, geobiology, surface-water hydrology, tectonics, numerical modeling, economics, and sociology.