5 Seawater Intrusion In Coastal Aquifers new.ppt

5 Seawater Intrusion In Coastal Aquifers new

1. Seawater Intrusion In Coastal Aquifers
Seawater intrusion is the movement of seawater into fresh
water aquifers due to natural processes or human activities.
Seawater intrusion is caused by decreases in groundwater
levels or by rises in seawater levels.

1 E

2. When you pump out fresh water rapidly, you lower the height
of the freshwater in the aquifer forming a cone of depression .
The salt water rises 40 meter for every 1 meter of freshwater
depression and forms a cone of ascension (up-coning). See
the following pictures. Intrusion can affect the quality of
water not only at the pumping well sites, but also at other
well sites, and undeveloped portions of the aquifer.
2 E

3. Ghyben-Harzberg relation between fresh and saline waters
3 E
Hydrostatic balance between fresh and saline
water

4. Fresh and saline groundwater in an
unconfined coastal aquifer
4 E

5. •Ρs g hs = Ρf g (hs + hf)
•Where
• Ρs = density of saline water = 1.025 gm\cm
3
•Ρf = density of freshwater = 1 gm\cm
3
•g = acceleration of gravity
•hs = z = shown in above figures
•hf = shown in above figures
•hs = z = (Ρf / Ρs – Ρf) x hf
•Then hs = z = 40 hf
5 E
Hydrostatic balance between fresh and saline water

6. Up coning of saline water
6 E

7. SAFE YIELD IN AREAS WITH SALINE GROUNDWATER
d
d
d
7 E

8. The maximum permissible
pumping rate is
Q
max =2/3 K
x d (Δρ/ρ
f)
8 E

9. Control of saline water intrusion
9 E

10. 10 E

11. 11 E

12. 12 E