Fresh-water
Moore, Y.; Stoessell, R.; Easley, D.
Ground water 30(3): 343-350
1992
ISSN/ISBN: 0017-467X Document Number: 425930
Ground-water velocities within fractures and boreholes, hydraulic heads, and depth profiles of conductivity were measured along a 70 km section of the northeastern coast of the Yucatan Peninsula, Mexico. Hydraulic heads ranged from 40 to 60 cm above mean sea level between 2 and 4 km from the coast. Fluid velocities estimated from point-dilution tests, in the dual-porosity rock in a borehole several kilometers from the coast, were 0.021 cm/sec in the fresh-water lens and 0.082 cm/sec near a fracture in the underlying sea-water zone. Velocities in large fractures increased from 1 cm/sec 10 kilometers inland to 12 cm/sec near discharge points along the coast. This increase is attributed to the decrease in thickness of the fresh-water lens. The thickness of the fresh-water lens is approximately 40% less than the Ghyben-Herzberg relation predicts for a static system, providing the potential to drive fresh water through fractures into the sea-water zone below the halocline. Overall, the halocline appears to be in a steady-state position due to the rapid flow of fresh water and brackish water towards the coast combined with rising sea water in convectional flow.