A groundwater model for the Lake Chad basin: integrating data and understanding of water resources at the basin scale

This report is part of the Water Global Practice efforts to support the Lake Chad Basin Commission (LCBC) and its Member States (Cameroon, the Central African Republic, Chad, Niger and Nigeria) fulfill their mandate to better monitor and understand water resources dynamics in the Lake Chad Basin.The initial objectives of the efforts portrayed in this report were to (a) integrate all available groundwater data available in the Lake Chad Basin in an updated database; (b) develop an updated and integrative conceptual groundwater model of the Lake Chad Basin, including all old and new information and reflecting the best current understanding, and (c) develop the equivalent numerical groundwater model of the Lake Chad Basin, with emphasis on two focus areas: the Komadougu-Yobe and Chari-Logone river basins, given their relevance for groundwater recharge and use. Even though the overall conceptual model and the numerical model need to be further improved, the basin-wide perspective presented in this work, integrating multiple sources of available data, provides a foundation to better understand and quantify basin-wide hydrogeological dynamics. This enables future efforts to assess potential impacts of future investments and climate futures.The activity leading to this report was coordinated on the World Bank side by Marie-Laure Lajaunie (Lead Water Resources Management Specialist, SAFW1) and Aleix Serrat Capdevila (Senior Water Resources Management Specialist, SAFW2) under the support and guidance of Yogita Mumssen (Practice Manager, SAFW1). The data gathering and analysis, modeling work and the core of the technical writing of this report was done by L. Candela (IMDEA-UPC), F.J. Elorza (IMDEA-UPM), N. Salehi (IMDEA-UPC), G. Vaquero (IMDEA-UPM), D. García-Martínez (IMDEAUPC). Valuable inputs and reviews during the elaboration of the report were provided by Hubert Machard de Gramont, Yves Barthelemy, Marcus Wijnen and Francois Bertone. We also acknowledge the contributions of internal peer reviewers Nagarajao Harshadep, Lucy Lutton, and Francois Bertone. During the data collection and modeling process, we are grateful for the collaboration of the Lake Chad Basin Commission staff Mohammed Bila, Seidu Abderrahmane, Mana Boubakari, Daïra Djoret and Abderamane Hamit Issa, Sanusi Imran Abdullahi, Rohallati Ndara, as well as of Guinbe Amngar (CDIG) and Mahamat Alifa Moussa (Ministère de l'Elevage et de l'Hydraulique, Chad). Also, this work would not have been possible without the invaluable support from Andreas Haveman and Julian Harbrech (BGR); Alexis Gutierrez (BRGM); Christian Leduc (IRD); Gianluca Guidotti and Ismail Musa Mohamed (Project ResEau); Lucas Cornet, Ivann Milenkovic, Calvin Ndjoh-Messina and Olivier Senegas (UNITARUNOSAT); Moussa Isseini (University of N’Djamena, Chad); Ibrahim Goni (University of Maiduguri, Nigeria), Lee Jejung (University of Missouri-Kansas City, USA); Guillaume Favreau (University of Montpellier, France); Justin Sheffield (University of Southampton, UK) and Hylke Beck, Erik Wood and Colby Fisher (Princeton University, USA), and last but not least, the institutional support of UNESCO’s International Hydrologic Programme Groundwater Section, through Alice Aureli and her team. All contributions are gratefully acknowledged.Preprin