Restoration of freshwater in the Cano Tiburones area, Puerto Rico

Abstract

Cafio Tiburones on the north coast of Puerto Rico originally was a shallow, coastal lagoon, 9 square miles in area. It accumulated freshwater from adjacent rivers and springs and drained to the ocean through unobserved subterranean conduits. Forced drainage by pumping of Cafio Tiburones for agriculture was begun in 1949, and resulted in lowering the water level to below sea level. The reversed hydraulic gradient permitted seawater to enter the Cafio through the conduits forming seawater "springs". Seawater flooding caused widespread sodium chloride contamination in the canals and laterals and in the soils. Agricultural expectations of the area were not realized. The present investigation into the freshening potential of Cafio Tiburones (1979-1982) determined that groundwater discharge does not contribute to salty conditions. On-site experiments were performed to segregate freshwater from seawater using differences in hydraulic head. Dams were constructed on canals and laterals, forcing accumulated saltwater to the ocean. Ring levees were placed around the discharging seawater conduits until sea level was reached and flow to the system stopped. These efforts have succeeded in reducing the amount of seawater in Cafio Tiburones to one-third of its original concentration. Most of the water presently in Cafio Tiburones is suitable for irrigation.