Salt water intrusion near the coast is caused by

• A. Over-pumping of groundwater
• B. Increased rainfall
• C. Lower salinity of groundwater
• D. Desalination

Answer: (A)

Saltwater intrusion happens when coastal freshwater resources are drawn down faster than they are recharged. Coastal aquifers usually keep a freshwater layer that sits above seawater and resists the inland movement of salt water. But when groundwater is pumped heavily, a cone of depression forms and the hydraulic pressure in the aquifer drops. Because seawater is denser, it moves inland to fill the space left by the lowered freshwater, contaminating wells and making the water too salty for use. So, pumping too much groundwater near the coast is the primary cause.

Increased rainfall would recharge the aquifer and help push the interface back toward the sea, not cause intrusion. Lower salinity of groundwater would indicate fresher water, not the cause of intrusion. Desalination is a treatment process and doesn’t cause the inland advance of seawater in the aquifer.