About this map:

This map uses several distinct geospatial datasets to portray the subsurface of the Northern Guam Lens Aquifer (NGLA). Included are the drainage basin divisions (both hard divides and flowline boundaries below the water table) and their coastal discharge boundaries, zones of basal and parabasal groundwater, and the topography and zero elevation of the basement volcanic contact surface with overlying limestone. Together, these elements depict the groundwater flow NGLA. The data sources for GIS files used in this map are indicated on other maps in this atlas that separately showcase the individual elements used in this combination map.