Question

What is Saltwater intrusion ?

What causes this problem ?

What measures could be taken to prevent this?

Answer 1

Saltwater intrusion:

Saltwater intrusion is defined as movement of salty or saline water into freshwater aquifers. This causes contaminated drinking water. As saline water mineral content and water pressure is higher than freshwater which causes saltwater to push beneath the freshwater.

Causes of saltwater intrusion:

Because of human activities such as groundwater pumping allows saline water to flow inland. Water extraction decreases groundwater level that reduces water pressure and allows saltwater intrusion.

Saltwater intrusion also occurs through navigation, agricultural and drainage channels that provides passage for saltwater to move inside, and increases sea level rise.

Certain events such as hurricane storm surges allows saltwater intrusion.

Measures taken to prevent saltwater intrusion:

Saltwater intrusion prevented by well siting. By avoiding drilling in locations which are adjacent
to the coast such as within 50 m.

Well depth also contributes to saltwater intrusion. Thus, avoid drilling within areas which are proximal to the coast.

Well alteration is preventive measure of saltwater intrusion. Thus, avoid certain technologies such as hydrofracturing as they are directly connected with the sea.

Always know the risks of saltwater intrusion. Thus, educate users such as property owners, site managers or water system operators and make them aware that their well can be affected.

Monitor water quality during drilling. If there is increase in the measurements then test the chloride concentration of the groundwater and if a salty zone has been found then seal the well to prevent water from entering freshwater aquifers.

Close wells which are not usable as abandoned or open wells provides pathway for flow of saline groundwater.

You can get advice from qualified professional such as hydrogeologist who help in assessing saltwater intrusion, their risk etc.