Using numerical modeling

IMDEA Water researchers publish the results of their study “The Lake Chad transboundary aquifer. Estimation of groundwater fluxes through international borders from regional numerical modelling”.

The study is part of a broader research at regional level carried out in collaboration with the Fundación Gómez Pardo, the Technical University of Catalonia, the Universidad Politécnica de Madrid, the Lake Chad Basin Commission, and The World Bank.

Lake Chad Basin is the largest basin in Africa. This endorheic system, shared by Algeria, Cameroon, Central African Republic, Chad, Libya, Niger, Nigeria, and Sudan, covers an area larger than 2 million square meters with a heterogeneously spread population of about 44 million. 

Water resources in the Lake Chad Basin are the source of livelihood and economic development. Agriculture is the main water use, with intensive agriculture in some areas of Nigeria and Cameroon. While water availability is not a limiting factor to development at present, increasing abstractions may cause significant impacts on the ecosystems, especially in sharing countries where transboundary management of water resources becomes more challenging. This is especially relevant with climate change predictions, which foresee rising temperatures, evapotranspiration, and an intensified hydrological cycle. In 2012 the ‘Water Charter’ was adopted, now ratified by four Member States, aimed to promote sustainable development through the integrated, equitable, and coordinated management of surface and groundwater resources. One of the objectives is to understand the dynamics of hydrological processes and to update a groundwater model including all the information available to date. Having an updated model is crucial to understand the groundwater current dynamics, the relationships between surface waters and existing aquifers, and to estimate both recharge and extraction values. Moreover, being a transboundary aquifer, this is particularly relevant.

The study has provided an updated conceptual model of the entire Lake Chad basin by integrating currently available data and it has developed a "3D quasi-stationary" model of groundwater flow of the Chad Formation, based on MODFLOW 2005 with ModelMuse 3.5, which allows the simulation of groundwater dynamics at a regional level. The model also allows the estimation of transboundary groundwater flow between Member States.

No standard approach exists for complex water resource sharing between transboundary basins, which is generally subject to negotiations between involved parties. Transboundary water management towards an equitable distribution poses many challenges, from implementation strategy harmonization to joint monitoring. Identifying sensitive areas of transboundary impacts may help determine which ones are likely to undergo quantitative changes in groundwater level, water quality, or artesian conditions. It is, therefore, necessary to enhance international cooperation and shared management strategies to prevent and mitigate cross-border conflicts and to be able to allocate groundwater resources more efficiently. Modelling is an extremely valuable support tool to achieve this goal.

Author: Lucila Candela Lledó