Evaluación económico-financiera y formulación de lineamientos de política pública para el fortalecimiento de la seguridad hídrica en el municipio de Lebrija, Santander: ampliación y optimización del embalse Piedras Negras

Abstract

Water security in Lebrija is, first and foremost, a public challenge with structural roots: demand in urban areas is rising, local supplies rely on sources vulnerable to dry spells, and storage capacity is limited. Addressing this requires the simultaneous coordination of infrastructure, land use, environmental conservation, and financial sustainability. Technical reports on the Piedras Negras reservoir from both 2003 and 2013 established that expanding the facility was technically feasible and recommended increasing storage capacity by raising the dam. The technical report underpinning this project proposes raising the dam height by 1.50 meters, resulting in a flooded area of approximately 11.03 hectares and a volume of 373,880 m³—an increase of up to 148,664 m³ over the baseline capacity. With this as a starting point, the project's overall objective is to analyze the expansion and optimization of the Piedras Negras reservoir from an economic-financial and public finance perspective, in order to derive policy guidelines aimed at strengthening Lebrija’s territorial water security. The study employs an applied pre-feasibility approach, combining document analysis, a territorial assessment, fiscal evaluation, cost estimation, cost-utility analysis, and scenario analysis, alongside a proposal for governance and indicators. A budget of COP 5,820 million has been set for 2026, with a pre-feasibility range of COP 4,950 million to COP 6,980 million, depending on construction conditions, land acquisition, design updates, and potential contingencies. The project should not rely solely on the municipality's own resources; therefore, a co-financing structure is proposed that combines municipal funds, the General System of Participation (SGP) funds for drinking water and basic sanitation, contributions from the department and the national government, sectoral financing mechanisms, and—subject to meeting the necessary requirements—resources from the General Royalties System. Based on assumptions regarding continuity benefits, vulnerability eduction, and avoided costs, the baseline scenario yields a social benefit-cost ratio of 2.67 over a 25-year period using a 9% social discount rate; this ratio remains above one even in the unfavorable scenario. This analysis informs a "Municipal Policy Proposal for Territorial Water Security" structured around five pillars: supply and storage resilience; service efficiency and continuity; micro-watershed protection and environmental management; financial sustainability and public investment; and governance, information, and risk management. The expansion of the Piedras Negras system is proposed here as a priority project within a portfolio strategy—rather than a standalone solution—given that a parallel supply alternative sourcing water from Bucaramanga is simultaneously advancing in Lebrija. Keywords: drinking water, Piedras Negras reservoir, socioeconomic evaluation, public finance, public investment, Lebrija, public policy, water security