Guidelines for Reservoir Evaluation, Applied to the Multipurpose Dam "El Azúcar," Santa Elena - Ecuador

Resumen

The El Azúcar dam, built in the 1960s and managed by SENAGUA, supplies drinking water and irrigation to the provinces of Guayas and Santa Elena, including areas such as Playas de Villamil, Zapotal, and Chanduy. However, the region faces a historical water deficit, with the reservoir filling only twice in 60 years, mainly due to events like El Niño. The operator reduces the flow approximately 265 days a year, keeping the reservoir at minimum levels and requiring transfers from the Chongón dam. Additionally, cracks have been detected, allowing the infiltration of brackish water with a salinity of 90-110 ppm (within the standard <500 ppm). The reservoir operates at 50% of its capacity and could receive more water from Chongón. The research analyzed: (i) volume, area, and height of the dam, (ii) supply-demand, (iii) reservoir operation curve, and (iv) flood control through spillways. It is recommended to raise the emergency spillway level to 46.75 meters above sea level (masl) and install gates in the service spillway to increase the useful volume up to 46.20 masl (maximum historical flood level), minimizing downstream impacts. These measures would optimize the use of the reservoir, improve water management, and reduce vulnerability to extreme events, ensuring a stable water supply. Monitoring salinity and infiltrations is crucial to maintaining water quality.