Identification of hot spots using robust Water Security Index in Transboundary Basins: the case of the Upper Lempa River Basin between El Salvador, Honduras, and Guatemala

Abstract

Water-related risks are increasing for resource-based livelihoods in the Southern Hemisphere and tropical regions. Water security as a concept has not been extensively reviewed and assessed for rural and urban livelihoods in this context. Although there are studies related to water security, the evidence and approaches to assess water security in transboundary basins are scarce, and several of these focus on defining levels of water security in terms of water scarcity, but does water availability alone guarantee water security? Historically, transboundary water resources management has been based on discourses of water security as a national security issue rather than a collaborative approach. This nationalistic use of water as a threat or power strategy weakens relations between nations and hinders cooperation. To meet these challenges, studies suggest the consolidation of transboundary institutions responsible for monitoring water conditions and serving as conflict mediators between riparian countries (Brooks & Trottier, 2014). An example of this transboundary framework is the tri-national cooperation process that has been developed for environmental management and sustainable development in the Upper Lempa River basin (ULRB), located in a key part of the Trifinio Region is made up of the countries of El Salvador, Guatemala, and Honduras. The legal framework of the Treaty between these three countries, called “Agua Sin Fronteras – 2006-2024”, recognized the relevance of community participation in landscape management. However, the characterization of the biophysical variables and processes in each country in the ULRB is different in terms of data availability (i.e., space and time) and its homogeneity (i.e., kind of variable), which difficult to assess water security as a transboundary tool. To solve these weaknesses and gaps, we proposed a Water Security Index (WSI) with an approach to measure multiple indicators of hydrological risk relative to context-specific water needs, including water availability, quality and sustainability. We followed the logic of the Pressure-State-Response (PSR) model to select indices that can be spatialized in different time steps. The WSI estimates the level of water security on a scale of 0 to 1, where 0 corresponds to the least favorable condition in terms of adequate quantities of water of acceptable quality for sustaining livelihoods, human well-being, and development socioeconomic; and 1 is the most favorable condition. The WSI was evaluated based on the results of a hydrological model (WEAP) under different climatic conditions (i.e., wet, dry, and normal). This evaluation allowed us to identify critical sub-basins (i.e., hot spots) for each condition and prioritized sub-basins with a high degree of vulnerability in all three conditions combined to support ecosystem services and human well-being. Through the analysis of the WSI index, 25 priority hot spots were identified as priority for intervention considering the resulting WSI in the combined conditions of which 11 are recurrent in the three conditions.   Brooks, D., & Trottier, J. (2014). De-nationalization and de-securitization of transboundary water resources: the Israeli–Palestinian case, International Journal of Water Resources Development, 30:2, 211-223, DOI: 10.1080/07900627.2013.84994