Abstract
Flood risk in the Sahel has increased markedly over recent decades, driven by the intensification of hydro-climatic hazards and the rapid growth of exposure in urban and peri-urban areas. In this context, FEWSs (FEWSs) are increasingly recognized as a key component of climate services for disaster risk reduction, as emphasized by the United Nations Early Warnings for All initiative. However, in West Africa such systems remain limited, particularly in transboundary river basins, where institutional fragmentation, data-sharing constraints, and asymmetries in technical capacity hinder effective cooperation. This paper analyses the transboundary expansion of the Système Local d'Alerte Précoce contre les Inondations de la Sirba (SLAPIS), initially developed in Niger and currently being extended to the shared Sirba River basin between Niger and Burkina Faso. It investigates the operational adaptations required to implement a co-production framework for flood early warning in transboundary contexts. The implementation of SLAPIS Sahel suggests that the original conceptual structure of the framework remains applicable in transboundary contexts, provided that specific implementation requirements are explicitly embedded within each co-production block. Rather than introducing additional phases, the proposed operational adaptation integrates enabling conditions and implementation tools addressing interoperability, upstream/downstream dependencies, institutional asymmetries, South-South competency development and parallel governance arrangements. The study also provides preliminary evidence that extending co-production across national borders may strengthen institutional cooperation, knowledge exchange, and service scaling, while highlighting the need for dedicated FEWS monitoring, evaluation, and learning frameworks to capture the added value of transboundary co-production processes.