SINKHOLES RECEIVING URBAN DRAINAGE, NORTH COAST OF PUERTO RICO

摘要

Climate change in the Caribbean is predicted to decrease rainfall in the dry summer months, suggesting that water stored in aquifers will become increasingly important for water supply. This underscores the need to protect ground water quality to insure its sustainable utilization. The karst area on Puerto Rico's north coast delivers approximately 59 MGD into the public distribution system with no treatment beyond chlorination. However, this same area has undergone significant urban and industrial development, including the construction of drainage systems which discharge urban stormwater into the drinking water aquifer. Significant water quality impairment has already been documented due to nitrate contamination from fertilizers and septic tank drainage, plus industrial contamination, resulting in the closure of municipal wells. There is a self-reporting inventory of engineered stormwater drainage systems which discharge to sinkholes or drainage wells, but this inventory is incomplete. A comprehensive inventory of sinkholes subject to significant urban drainage impact, including non-engineered drainage systems, has never been performed. An inventory of 231 sinkholes receiving significant urban drainage was compiled. The resulting watershed limits and sinkhole locations were complied into a searchable database, with mapping organized by topographic quadrangle, and was published as a software application. This database documents the large impact of urban drainage on the north coast karst aquifer. It also serves as a tool for identifying the areas where water quality hazard from urban stormwater runoff will probably be greatest, and can be used to locate sampling locations for water quality monitoring wells.