Saltwater encroachment into freshwater sources is called?

• A. Oxygen-Depleted Zones
• B. Saltwater Intrusion
• C. Harmful Algal Blooms
• D. Primary Sewage Treatment

Answer: (B)

Saltwater intrusion is the movement of saltwater into freshwater sources, usually coastal aquifers, when freshwater withdrawal lowers the hydraulic pressure and seawater moves inland. This occurs because saltwater is denser than freshwater, so once the inland freshwater head drops, the interface shifts toward the land. The process is a common coastal groundwater problem caused by over-pumping, sea-level rise, and reduced recharge, and it degrades drinking water supplies and irrigation.

Other terms refer to different water quality issues: oxygen-depleted zones are hypoxic areas from excess nutrients, harmful algal blooms are blooms that produce toxins, and primary sewage treatment is a stage in wastewater treatment.