New Open access article: The Lake Chad hydrology under current climate change
Lake Chad, in the Sahelian zone of west-central Africa, provides food and water to ~50 million people and supports unique ecosystems and biodiversity. In the past decades, it became a symbol of current climate change, held up by its dramatic shrinkage in the 1980s.
- Using a new multi-satellite approach, the authors show that Lake Chad extent has remained stable during the last two decades, despite a slight decrease of its northern pool.
- Moreover, since the 2000s, groundwater, which contributes to ~70% of Lake Chad’s annual water storage change, is increasing due to water supply provided by its two main tributaries.
The results indicate that in tandem with groundwater and tropical origin of water supply, over the last two decades, Lake Chad is not shrinking and recovers seasonally its surface water extent and volume. This study provides a robust regional understanding of current hydrology and changes in the Lake Chad region, giving a basis for developing future climate adaptation strategies.
Severe and recurrent droughts are the principal weather-related hazards for developing economies throughout sub-Saharan Africa, and the quality of long-term weather prediction is a bottleneck hampering drought mitigation and adaptation in the region. This is aggravated by uncertain impacts of the 21st century anthropogenic climate change on the continent’s rainfall and freshwater resources, due to at best fragmentary understanding on the effects of a warming atmosphere on the hydrological cycle at regional scales.
After severe and prolonged droughts that affected the Sahel in the 1970s–1980s which were considered as one of the first major consequences of global climate change during the 20th century, an increase in the mean annual precipitation was recorded since the beginning of the 1990s.
Despite of this trend, the current climate change seems to impact the Sahelian zone of west-central Africa with higher interannual variability affecting from year to year to the amount of precipitation during rainy seasons, and increasing the vulnerability of the regional economy, mainly based on agropastoral activities.
In this context, Lake Chad, located in the central Sahel sector, at the southern edge of the Sahara, rises up as a symbol of the current global climate change occurring in the region.
- After being ranked at the world’s sixth largest inland water body with an open water area of 25,000 km2 in the 1960s, it shrunk dramatically at the beginning of the 1970s and reduced to less than 2,000 km2 during the 1980s, decreasing by more than 90% its area.
- The consequence of the 1970s and 1980s droughts was the subdivision of the lake into a northern pool and a southern pool, and the regular dryness of the northern pool alerted the international community of a possible lake’s disappearance
- It also illustrated the impact of extreme and rapid climate changes in this area as it was initially thought that water withdrawals for irrigation contributed to the lake decline.
- Yet, recent studies showed that the amount of water extraction in the 1980s and 1990s was probably overestimated as the quantity of water abstracted for human activities was negligible compared to the lake volume change.
Since the 1990s, it has been observed that the lake’s surface water extent has increased due to more favorable rainfall in western Sahel.
- Some studies estimated a peak of water extent in April 2013 with its maximum of 14,000 km2 .
- However, these estimates were usually based on partial observations and thus provided incomplete information and increased misunderstanding of the Lake Chad hydrological cycle.
- Other studies only investigated the southern pool of the lake, during some months in a year, or only focused on groundwater. Only two studies investigated in details the seasonal variations of the Lake Chad, but focusing on the previous decades, the 1980s and the 1990s
Now, in the view of the challenges arisen in the Lake Chad area during the last decades, it is crucial to better characterize the Lake Chad hydrological cycle. Indeed, the Lake Chad region is currently facing multiple security risks, including livelihood and violent conflicts. Even though the current conflict was triggered by violence linked to the armed groups known as Boko Haram, the crisis has deep roots in longstanding challenges. Read further the full text article The Lake Chad hydrology under current climate change