Impact on groundwater of a karstic aquifer in the informal settlement “Las Fincas” on Cozumel island, Mexico.

Abstract

The Yucatán Peninsula is mainly composed of limestone. Cozumel Island is part of the Yucatec carbonate platform. Dissolution processes in the limestone lead to karstification. Groundwater preferentially flows into karstic cavities. Due to its geological structure the karstic aquifer shows a high vulnerability to anthropogenic impacts. This study investigates the impact on groundwater in the area of the informal settlement “Las Fincas”. Due to the informal urbanization of the settlement there is neither a public water and power supply nor a sewerage nor waste disposal system. Groundwater samples were taken in a number of domestic wells that are in use for local water supply in “Las Fincas” and tested for typical indicators of anthropogenic pollution. Distinct evidence of fecal contamination was found. The evaluation of a reference analysis of wells outside “Las Fincas” also showed a significant fecal contamination. Two aspects were considered as a reason for the fecal pollution. On the one hand there is the pollution of wastewater and feces by the local residents. On the other hand, there is the practice of the grouting of treated wastewater in deeper zones of the aquifer by the local water supplier. For further investigation a long-term monitoring was established in order to take groundwater samples and record groundwater levels frequently. The study documents the hydrodynamic and hydro chemical conditions of the aquifer and gives recommendations for the use of groundwater without any health risk.