The Lapa River, located within the Planadas-Yeyesa Natural Reserve between the Salinas and Cayey, Puerto Rico municipalities, was designated as a Heritage River in recognition of its ecological, cultural, and historical importance. This designation, part of the Puerto Rico Heritage Rivers Program managed by the Department of Natural and Environmental Resources (DRNA), aims to protect and preserve rivers of significant ecological and cultural value across the island. In certain sections, the river flows underground before re-emerging at the surface, presenting a unique opportunity for study. This case study evaluates key hydrochemical parameters—pH, electrical conductivity (EC), total dissolved solids (TDS), salinity, temperature, and dissolved oxygen—at three sampling sites along the river. Sampling locations where the water transitions from underground to surface flow were chosen, capturing subsurface and surface water characteristics. The data collected will serve as a foundation for a long-term monitoring program to track changes in water quality and river health over time. The proposed methodology integrates multi-parameter monitoring to assess the dynamic nature of the river's water chemistry across different environmental contexts. This study will contribute valuable baseline data for understanding the river's ecological function and support future conservation efforts to protect this critical waterway, ensuring its long-term sustainability and ecological integrity.