Hydrology and Groundwater Movement of Laguna Bacalar and the Cenote Negro, Yucatan Peninsula, Mexico

Abstract

Laguna Bacalar is the second largest freshwater lake in Mexico, located along the southeastern perimeter of the Yucatán Peninsula. This unique ecosystem is maintained via groundwater input and direct rainfall, and is dominated by karst topography, making it known for its water of seven colors and the various cenotes that lie within it. This study expands on the knowledge of the lagoon’s groundwater input, hydrology, and role of the Cenote Negro. Obtaining a greater understanding of Laguna Bacalar’s groundwater hydrology and water quality is crucial in preserving the unique ecosystems health and longevity as anthropogenic contamination and pollution magnifies through the expansion of ecotourism. Transects were performed at central and northern locations. The sampling duration consisted of 4-weeks, between June 1^st -29^th, experiencing heavy rainfall events and tropical storms for a majority of the duration. Transect results gave substantial insight on current groundwater flow throughout the lagoon, as well as displayed distinct stratification and water column mixing. Definite groundwater sources at Xul-Ha, the Cenote Negro, and Buena Vista were indicated by an increase in specific conductivity (SpCond) and pH after rainfall events in comparison to central Laguna Bacalar transects. The Cenote Negro vertical profiles displayed a unique pattern of increased conductivity around 20-30 meters depth, suggesting this to be the zone that receives groundwater input, contributing to the flow of freshwater into Laguna Bacalar.