Friday, 29 March 2013

Saltwater intrusion


Saltwater intrusion represents the process by which sea water infiltrates coastal groundwater systems, thus combining with the local fresh water supply. Groundwater is stored in the pores and fractures of rock within the surface, and the rock structures containing groundwater are termed as aquifers. Aquifers are naturally replenished by way of precipitation (rain, snow) that penetrates into the ground and eventually reaches to the water table.

The water table is simply the boundary between the upper part of the ground that is only partially soaked with water (unsaturated zone) and the lower part where all the pore spaces and fractures are fully soaked with water. The level of the water table at any point is often referred to as the “hydraulic head.”

Salt water intrusion into coastal aquifers is brought on by two mechanisms:

•             Lateral encroachment from the sea due to excessive water distributions from coastal aquifers,.
•             Upward activity from deeper saline areas due to upconing near coastal discharge/pumping water wells.

How to Prevent Water Intrusion

People in the United States sink have been relying on groundwater aquifers as a source of fresh water for a growing population for over a century. They made effort to prevent continuous salt water intrusion by developing a sequence of injection wells.

These injection wells were tactically placed with the idea that if they included fresh water into the aquifers at a given place, then they might be able to develop barriers to prevent further intrusion of the salt water. These limitations proved to only be partly efficient, and only prevented further salt water encroachment into the fresh water aquifer.

Controlling Saltwater Intrusion

 The key to manage salt water intrusion is to maintain the appropriate balance between water being pumped from an aquifer and the amount of water re-charging it.  Constant monitoring of the salt-water interface is necessary in determining the proper management technique.  In the past, many areas that came across a salt water intrusion problem simply set up new production wells.  This only complicated the issue.