The Lake Chad hydrology under current climate change
Tóm tắt
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. Despites a partial recovery in response to increased Sahelian precipitation in the 1990s, Lake Chad is still facing major threats and its contemporary variability under climate change remains highly uncertain. Here, using a new multi-satellite approach, we 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. Our 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.
Tài liệu tham khảo
Stocker, T. et al. Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA 1535 (2013).
Giorgi, F. Variability and trends of sub-continental scale surface climate in the twentieth century. Part I: observations. Climate Dynamics 18, 675–691 (2002).
Nicholson, S. On the question of the recovery of the rains in the West African Sahel. Journal of Arid Environments 63, 615–641 (2005).
Fontaine, B., Roucou, P., Gaetani, M. & Marteau, R. Recent changes in precipitation, ITCZ convection and northern tropical circulation over North Africa (1979–2007). International Journal of Climatology 31, 633–648 (2011).
Taylor, C. M. et al. Frequency of extreme Sahelian storms tripled since 1982 in satellite observations. Nature 544, 475–478 (2017).
Leblanc, M., Lemoalle, J., Bader, J.-C., Tweed, S. & Mofor, L. Thermal remote sensing of water under flooded vegetation: New observations of inundation patterns for the Small Lake Chad. Journal of Hydrology 404, 87–98 (2011).
NASA. Africa’s disappearing lake chad, https://earthobservatory.nasa.gov/images/1240/africas-disappearing-lake-chad (2001).
Coe, M. T. & Foley, J. A. Human and natural impacts on the water resources of the Lake Chad basin. Journal of Geophysical Research: Atmospheres 106, 3349–3356 (2001).
Lemoalle, J., Bader, J.-C., Leblanc, M. & Sedick, A. Recent changes in Lake Chad: Observations, simulations and management options (1973–2011). Global and Planetary Change 80–81, 247–254 (2012).
Lemoalle, J. et al. (eds.) Le développement du Lac Tchad : situation actuelle et futurs possibles. Expertise Collégiale (IRD, 2014).
Zhu, W., Yan, J. & Jia, S. Monitoring Recent Fluctuations of the Southern Pool of Lake Chad Using Multiple Remote Sensing Data: Implications for Water Balance Analysis. Remote Sensing 9 (2017).
Policelli, F., Hubbard, A., Jung, H. C., Zaitchik, B. & Ichoku, C. Lake Chad total surface water area as derived from land surface temperature and radar remote sensing data. Remote Sensing 10 (2018).
Buma, W. G., Lee, S. I. & Seo, J. Y. Recent surface water extent of Lake Chad from multispectral sensors and GRACE. Sensors 18 (2018).
Birkett, C. Synergistic remote sensing of Lake Chad: Variability of basin inundation. Remote Sensing of Environment 72, 218–236 (2000).
Magrin, G. & Pérouse de Montclos, M.-A. (eds.) Crise et Développement : La région du Lac Tchadà l’épreuve de Boko Haram (AFD, 2018).
Vivekananda, J., Fetzek, S., Mobjorrk, M., Sawas, A. & Wolfmaier, S. Action on climate and security risks. Review of Progress 2017 (2017).
Moran, A. et al. The intersection of global fragility and climate risks. US Agency for International Development (2018).
QGIS Development Team. QGIS Geographic Information System. Open Source Geospatial Foundation, http://qgis.org (2009).
Bouchez, C. et al. Hydrological, chemical, and isotopic budgets of Lake Chad: a quantitative assessment of evaporation, transpiration and infiltration fluxes. Hydrology and Earth System Sciences 20, 1599–1619 (2016).
Olivry, J.-C., Chouret, A., Vuillaume, G., Lemoalle, J. & Bricquet, J.-P. (eds.) Hydrologie du lac Tchad (1996).
Bouchez, C. et al. Water transit time and active recharge in the Sahel inferred by bomb-produced 36Cl. Scientific Reports 9, 1–8 (2019).
Roche, M. Tracage naturel salin et isotopique des eaux du système hydrologique du lac Tchad (ORSTOM Editions, 1980).
Carter, R. C. & Alkali, A. G. Shallow groundwater in the northeast arid zone of Nigeria. Quarterly Journal of Engineering Geology and Hydrogeology 29, 341–355 (1996).
Gao, H., Bohn, T. J., Podest, E., McDonald, K. C. & Lettenmaier, D. P. On the causes of the shrinking of Lake Chad. Environmental Research Letters 6, 034021 (2011).
Martens, B. et al. GLEAM v3: satellite-based land evaporation and root-zone soil moisture. Geoscientific Model Development 10, 1903–1925 (2017).
Cuthbert, M. O. et al. Observed controls on resilience of groundwater to climate variability in sub-Saharan Africa. Nature 572, 230–234 (2019).
Aranyossy, J. & Ndiaye, B. Étude et modélisation de la formation des dépressions piézométriques en Afrique Sahelienne. Revue des sciences de laeau/Journal of Water Science 6, 81–96 (1993).
Edmunds, W. M. et al. Groundwater as an archive of climatic and environmental change: Europe to Africa, 279–306 (Springer Netherlands, Dordrecht, 2004).
Bader, J.-C., Lemoalle, J. & Leblanc, M. Hydrological model of Lake Chad. Hydrological Sciences Journal 56, 411–425 (2011).
Cretaux, J.-F. et al. SOLS: A lake database to monitor in the Near Real Time water level and storage variations from remote sensing data. Advances in Space Research 47, 1497–1507 (2011).
Mahmood, R. & Jia, S. Assessment of hydro-climatic trends and causes of dramatically declining stream flow to Lake Chad, Africa, using a hydrological approach. Science of The Total Environment 675, 122–140 (2019).
Mahmood, R., Jia, S. & Zhu, W. Analysis of climate variability, trends, and prediction in the most active parts of the Lake Chad basin, Africa. Scientific Reports 9 (2019).
Lebel, T. & Ali, A. Recent trends in the Central and Western Sahel rainfall regime (1990–2007). Journal of Hydrology 375, 52–64 (2009).
Nicholson, S. E. The West African Sahel: A Review of Recent Studies on the Rainfall Regime and Its Interannual Variability. ISRN Meteorology 2013, 32 (2013).
Maharana, P., Abdel-Lathif, A. Y. & Pattnayak, K. C. Observed climate variability over Chad using multiple observational and reanalysis datasets. Global and Planetary Change 162, 252–265 (2018).
Zhu, W., Jia, S., Lall, U., Cao, Q. & Mahmood, R. Relative contribution of climate variability and human activities on the water loss of the chari/logone river discharge into lake chad: A conceptual and statistical approach. Journal of Hydrology 569, 519–531 (2019).
Nicholson, S. E., Klotter, D. & Dezfuli, A. K. Spatial reconstruction of semi-quantitative precipitation fields over Africa during the nineteenth century from documentary evidence and gauge data. Quaternary Research 78, 13–23 (2012).
Roehrig, R., Bouniol, D., Guichard, F., Hourdin, F. & Redelsperger, J.-L. The Present and Future of the West African Monsoon: A Process-Oriented Assessment of CMIP5 Simulations along the AMMA Transect. Journal of Climate 26, 6471–6505 (2013).
Cook, K. H. The mysteries of Sahel droughts. Nature Geoscience 1, 647 (2008).
Vizy, E. K., Cook, K. H., Crétat, J. & Neupane, N. Projections of a Wetter Sahel in the Twenty-First Century from Global and Regional Models. Journal of Climate 26, 4664–4687 (2013).
Mahmood, R., Jia, S., Mahmood, T. & Mehmood, A. Predicted and projected water resources changes in the chari catchment, the lake chad basin, africa. Journal of Hydrometeorology 21, 73–91 (2020).
Gasse, F. Hydrological changes in the African tropics since the Last Glacial Maximum. Quaternary Science Reviews 19, 189–211 (2000).
Armitage, S. J., Bristow, C. S. & Drake, N. A. West African monsoon dynamics inferred from abrupt fluctuations of Lake Mega-Chad. Proceedings of the National Academy of Sciences 112, 8543–8548 (2015).
Sylvestre, F. et al. The Lake CHAd Deep DRILLing project (CHADRILL)-targeting ~10 million years of environmental and climate change in Africa. Scientific Drilling 24, 71–78 (2018).
Leblanc, M. et al. Reconstruction of Megalake Chad using Shuttle Radar Topographic Mission data. Palaeogeography, Palaeoclimatology, Palaeoecology 239, 16–27 (2006).
Rodriguez-Fonseca, B. et al. Variability and Predictability of West African Droughts: A Review on the Role of Sea Surface Temperature Anomalies. Journal of Climate 28, 4034–4060 (2015).
Park, J.-Y., Bader, J. & Matei, D. Northern-hemispheric differential warming is the key to understanding the discrepancies in the projected Sahel rainfall. Nature Communications 6, 5985 (2015).
Defrance, D. et al. Consequences of rapid ice sheet melting on the Sahelian population vulnerability. Proceedings of the National Academy of Sciences 114, 6533–6538 (2017).
Sultan, B., Janicot, S. & Diedhiou, A. The West African Monsoon Dynamics. Part I: Documentation of Intraseasonal Variability. Journal of Climate 16, 3389–3406 (2003).
Sultan, B. et al. Assessing climate change impacts on sorghum and millet yields in the Sudanian and Sahelian savannas of West Africa. Environmental Research Letters 8, 014040 (2013).
Sakamoto, T. et al. Detecting temporal changes in the extent of annual flooding within the Cambodia and the Vietnamese Mekong Delta from MODIS time-series imagery. Remote Sensing of Environment 109, 295–313 (2007).
Sun, D., Yu, Y. & Goldberg, M. D. Deriving Water Fraction and Flood Maps From MODIS Images Using a Decision Tree Approach. IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing 4, 814–825 (2011).
Berge-Nguyen, M. & Cretaux, J.-F. Inundations in the inner Niger delta: Monitoring and analysis using MODIS and global precipitation datasets. Remote Sensing 7, 2127–2151 (2015).
Sharma, R. C., Tateishi, R., Hara, K. & Nguyen, L. V. Developing Superfine Water Index (SWI) for Global Water Cover Mapping Using MODIS Data. Remote Sensing 7, 13807–13841 (2015).
Cretaux, J. et al. Hydrological Applications of Satellite Altimetry Rivers, Lakes, Man-Made Reservoirs, Inundated Areas (CRC Press, 2017).
Frappart, F., Calmant, S., Cauhopé, M., Seyler, F. & Cazenave, A. Preliminary results of ENVISAT RA-2-derived water levels validation over the Amazon basin. Remote Sensing of Environment 100, 252–264 (2006).
Ricko, M., Carton, J. A., Birkett, C. M. & Cretaux, J.-F. Intercomparison and validation of continental water level products derived from satellite radar altimetry. Journal of Applied Remote Sensing 6, 1–24 (2012).
Biancamaria, S. et al. Satellite radar altimetry water elevations performance over a 200m wide river: Evaluation over the Garonne River. Advances in Space Research 59, 128–146 (2017).
Biancamaria, S. et al. Validation of Jason-3 tracking modes over French rivers. Remote Sensing of Environment 209, 77–89 (2018).
Normandin, C. et al. Evolution of the Performances of Radar Altimetry Missions from ERS-2 to Sentinel-3A over the Inner Niger Delta. Remote Sensing 10 (2018).
Papa, F., Biancamaria, S., Lion, C. & Rossow, W. B. Uncertainties in Mean River Discharge Estimates Associated With Satellite Altimeter Temporal Sampling Intervals: A Case Study for the Annual Peak Flow in the Context of the Future SWOT Hydrology Mission. IEEE Geoscience and Remote Sensing Letters 9, 569–573 (2012).
Frappart, F. et al. Water volume change in the lower Mekong from satellite altimetry and imagery data. Geophysical Journal International 167, 570–584 (2006).
Frappart, F. et al. Surface freshwater storage and dynamics in the Amazon basin during the 2005 exceptional drought. Environmental Research Letters 7, 044010 (2012).
Frappart, F. & Ramillien, G. Monitoring Groundwater Storage Changes Using the Gravity Recovery and Climate Experiment (GRACE) Satellite Mission: A Review. Remote Sensing 10 (2018).
Normandin, C. et al. Quantification of surface water volume changes in the Mackenzie Delta using satellite multi-mission data. Hydrology and Earth System Sciences 22, 1543–1561 (2018).
Crétaux, J.-F. et al. Lake volume monitoring from space. Surveys in Geophysics 37, 269–305 (2016).
Pham-Duc, B. et al. Variations of Surface and Subsurface Water Storage in the Lower Mekong Basin (Vietnam and Cambodia) from Multisatellite Observations. Water 11 (2019).
Frappart, F. et al. Satellite-based estimates of groundwater storage variations in large drainage basins with extensive floodplains. Remote Sensing of Environment 115, 1588–1594 (2011).
Frappart, F. et al. The spatio-temporal variability of groundwater storage in the amazon river basin. Advances in Water Resources 124, 41–52 (2019).
Papa, F. et al. Satellite-derived surface and sub-surface water storage in the Ganges-Brahmaputra River Basin. Journal of Hydrology: Regional Studies 4, 15–35 (2015).
Ramillien, G., Frappart, F. & Seoane, L. Application of the regional water mass variations from grace satellite gravimetry to large-scale water management in africa. Remote Sensing 6, 7379–7405 (2014).
Martens, B., Miralles, D., Lievens, H., Fernandez-Prieto, D. & Verhoest, N. Improving terrestrial evaporation estimates over continental australia through assimilation of smos soil moisture. International Journal of Applied Earth Observation and Geoinformation 48, 146–162 Advances in the Validation and Application of Remotely Sensed Soil Moisture-Part 2 (2016).