salt water intrusion prevention & contgrol. Sea water intrusion here i mention some info about salt water intrusion in costal areas and its control methods.

1. UNIT-5 SALINE WATER
INTRUSION IN AQUIFER

2. SALINE WATER INTRUSION
 Salt water intrusion is the movement of saline water in to fresh
water aquifers.
 This can lead to ground water quality degradation, including
drinking water sources and other consequences.
 Salt water intrusion can naturally occur in costal aquifers, owing to
the hydraulic connection between ground water and sea water.
 Saline water has a higher mineral content than fresh water, it is
denser and has a higher water pressure. As a result, salt water can
push inland beneath the fresh water.
 In other topologies, submarine ground water discharge can push
fresh water into salt water

3. SALT WATER INTRUSION BY
Human activities:
 Almost two thirds of the world’s population lives with in 400km of
the ocean shoreline, just over half live within 200km an area only
taking up 10% of the earth’s surface.
 Most of the coastal regions rely on groundwater as their main
source of fresh water for domestic, industrial and agricultural
purposes.
 As the World’s population continues to grow at an alarming rate,
fresh water supplies are constantly being depleted, bringing with it
issues such as salt water intrusion and increasing the importance of
the ground water monitoring, management and conservation.

4.  Channels and canals provide conduits for salt water to move inland.
Climate change:
 Sea level rise caused by climate change also contributes to salt
water intrusion.
 Salt water intrusion can also be worsened by extreme events like
hurricane storm surges.

5. Salt Water intrusion into freshwater aquifers is also influenced by
factors such as:
 tidal fluctuations
 Long-term climate and sea level changes
 fractures in coastal rock formations
 Recharge rate can also be lowered in areas with increased
urbanization and thus impervious surfaces.

8.  At the coastal margin, fresh groundwater flowing from inland areas
meets with saline groundwater from the ocean.
 The fresh groundwater flows from inland areas towards the coast
where elevation and groundwater levels are lower.
 Because saltwater has a higher content of dissolved salts and
minerals, it is denser than freshwater, causing it to have
higher hydraulic head than freshwater.
 Hydraulic head refers to the liquid pressure exerted by a water
column: a water column with higher hydraulic head will move into a
water column with lower hydraulic head, if the columns are
connected.

9. GHYBEN–HERZBERG
RELATION
 The first physical formulations of saltwater intrusion were made
by Willem Badon-Ghijben in 1888 and 1889 as well as Alexander
Herzberg in 1901, thus called the Ghyben–Herzberg relation.
 They derived analytical solutions to approximate the intrusion
behavior, which are based on a number of assumptions that do not
hold in all field cases.

11.  Freshwater has a density of about 1.000 grams per cubic centimeter
(g/cm3) at 20 °C, whereas that of seawater is about 1.025 g/cm3. The
equation can be simplified to
 Z=40h
 The Ghyben–Herzberg ratio states that, for every meter of fresh
water in an unconfined aquifer above sea level, there will be forty
meters of fresh water in the aquifer below sea level.

12. SALTWATER INTRUSION CONTROL
METHODS
A number of methods had been adopted to control seawater intrusion
to protect groundwater reserves in coastal aquifers. presented
various methods of preventing seawater from contaminating
groundwater sources including:
1. Reduction of pumping rates
2. Relocation of pumping wells
3. Use of subsurface barriers
4. Natural recharge
5. Artificial recharge
6. Abstraction of saline water

13. 1. REDUCTION OF PUMPING RATES
The natural balance between freshwater and saltwater in coastal aquifers is
disturbed by abstraction and other human activities that lower groundwater
levels, reduce the amount of fresh groundwater flowing to the sea, and
ultimately cause saltwater to intrude coastal aquifer. Increasing pumping
rate is considered the main cause of saltwater intrusion along the coasts.
This can be achieved by a number of measures including:
1. Increase in public awareness of the necessity of water to save water
2. Reduction of losses from the water transportation and distribution
systems
3. Reduction of water requirement in irrigation by changing the crop pattern
and using new methods for irrigation such as drip irrigation, canal lining,
etc.
4. Recycling of water for industrial uses, after appropriate treatment
5. Reuse of treated wastewater in cooling and irrigation and recharge of
groundwater

14. 2. RELOCATION OF PUMPING WELLS
Changing the location of pumping wells by moving the wells to more
inland positions aims to raise the groundwater level and maintain the
groundwater storage. This is because in the inland direction, the
thickness of the freshwater lens increases and the risk of upcoming
of saltwater decreases accordingly.
developed an optimal pumping model to evaluate optimal
groundwater withdrawal and the optimal location of pumping wells in
steady-state condition while minimizing adverse effects such as
water quality in the pumping well, drawdown, saltwater intrusion, and
upcoming.
The study involved experimental verification of the optimal pumping
model to develop sustainable water resources in the coastal areas.

15. 3. SUBSURFACE BARRIERS
This method involves establishment of a subsurface barrier to reduce
the permeability of the aquifer to prevent the inflow of seawater into
the basin. Construction of barriers could be achieved using sheet
piling, cement grout, or chemical grout.
Figure shows a sketch of a subsurface barrier to control saltwater
intrusion.
Barsi developed two methods for optimal design of subsurface
barriers to control seawater intrusion through the development of
implicit and explicit simulation-optimization models.
The main objective was to find the optimal design of subsurface
barrier to minimize the total construction cost through the selection
of the width and location of the barrier.

17. 4. NATURAL RECHARGE
This method aims to feed aquifers with additional surface water by
constructing dams and weirs to prevent the runoff from flowing to
the sea.
This method can also be used for flood protection. The retained water
infiltrates into the soil and increases the volume of groundwater
storage.
Figure 2 shows a sketch of the natural recharge process.
This method could be efficient for unconfined aquifers, but it could
take a long time to recharge the aquifer depending on its properties.

18. Advantages: This method helps to prevent the runoff to flow directly
to the sea and uses it to increase the groundwater storage in the
aquifer and prevent the intrusion of saline water.
Disadvantages: Natural recharge depends on the soil properties and
requires high permeability soil. Depending on the soil permeability,
the recharge process could take a long time.
The cost of construction of dams and weirs and their maintenance is
very high. This solution is unsuitable for confined and deep aquifers.

20. 5. ARTIFICIAL RECHARGE
Artificial recharge aims to increase the groundwater levels, using
surface spread for unconfined aquifers and recharge wells for
confined aquifers.
The potential sources of water for injection may be from surface
water, pumped groundwater, treated wastewater, desalinated
seawater, or desalted brackish water.
Surface water can be taken from rivers or canals through pipelines.
Figure 3 shows a sketch of a recharge well.
A number of researchers used this method to control saltwater
intrusion in coastal aquifers.

22. 6. ABSTRACTION OF SALINE WATER
This method of control aims to reduce the volume of saltwater by
extracting brackish water from the aquifer and returning to the sea.
Figure 3 shows a sketch of an abstraction well.
Johnson and Spery presented different methods to control saltwater
intrusion in different states in the USA. In California they extracted
saline water and desalinated it using RO treatment process.
The treated water was blended with untreated groundwater to
produce water suitable for domestic delivery. In Los Angeles,
injection wells were used to protect the coastal aquifers from
saltwater intrusion. Potable and highly treated wastewater was
injected into the wells.