MITIGASI INTRUSI AIR LAUT

About 70 % of the world population lives in coastal areas (Bear, 1999)

The addition of as little as 2 % of seawater to freshwater can cause it to be undrinkable (Deming, 2003)

INTRUSI AIRLAUT

Saltwater Intrusion is the migration of saltwater into freshwater aquifers under the influence of groundwater development (Freeze and Cherry, 1979)

DAMPAK INTRUSI AIRLAUT (Notodarmojo, 2005)

1. Penurunan kualitas airtanah: Pengaruh salinitas:

< 600 mg/L khlorida, ambang batas rasa asin manusia

Peraturan Menteri Kesehatan RI No. 46/1990: < 500 mg/L khlorida, batas syarat air bersih

< 250 mg/L khlorida, batas syarat air minum

2. Terganggunya produktivitas beberapa tanaman.

3. Mempengaruhi struktur tanah liat menjadi kurang baik.

TDS OF WATER SOURCE (MARKS, 2004)

Drinking water < 1000 mg/L TDS (WHO, 1984)

Drinking water < 500 mg/L TDS (EPA, 2002)

< 3% salinity content of world’s water safe for human consumption

RECOGNITION OF SEA WATER IN GROUND WATER

Sample number:

(1) Normal good ground water in aquifer

(2) Slightly contaminated ground water

(3) Moderately contaminated ground water

(4) Injuriously contaminated ground water

(5) Highly contaminated ground water

(6) Sea water

(Todd, 1959)

MONITORING TECHNIQUES Conventional Vs Electrical Resistivity Tomography (ERT)

(Antonsson et. al.,2006)

MITIGATION, CONTROL, AND PREVENTION

DEFINISI MITIGASI (1)

• Structural and non-structural measures undertaken to limit the adverse impact of natural hazards, environmental degradation and technological hazards. www.unisdr.org/eng/library/lib-terminology-eng%20home.htm

• With respect to an undertaking, the elimination, reduction or control of the adverse effects or the significant environmental effects of the undertaking, and may include restitution for any damage to the environment caused by such effects through replacement, restoration, compensation or any ... www.gov.ns.ca/enla/ea/glossary.asp

• A process of minimizing or compensating for damages to natural habitats, caused by human developments. These activities are designed to decrease the degree of damage to an ecosystem. They may include restoration, enhancement, or creation. ... www.ag.iastate.edu/centers/iawetlands/Glossary.html

DEFINISI MITIGASI (2)

CEQA Guidelines Definition 15370 states: "Mitigation" includes: (a) avoiding the impact altogether by not taking an action or certain parts of an action; (b) minimizing impacts by limiting the degree or magnitude of the action and its implementation; (c) rectifying the impact by repairing ... buttecreekwatershed.org/ecr/new/glossary.htm

CONTROL OF SEAWATER INTRUSION (Basri, 2001)

1. Hydrodynamic control

Maintain seaward gradient

2. Extraction wells

a) Extract seawater before it reaches production wells

b) Combines extraction wells with injection wells

3. Physical containment

Impermeable or semi-impermeable sub-surface barrier

CONTROL AND REMEDIATION OF SALTWATER INTRUSION

(DEMING, 2003)

• Dependent upon the geologic circumstances in each case geologic study:

To identify the causes of the saltwater intrusion.

To identify the mechanism(s) by which it is occuring.

• Approaches to controlling saltwater intrusion: Construct barierrs

Change the distribution of head

• A monitoring network should be installed

APPROACHES TO PREVENTION OR CONTROL OF SEAWATER INTRUSION

Re-arrangement of pumping pattern Bank and Rictor (1953)

Artificial recharge Todd (1959)

Hydraulic barrier ridge Linsley and Franzini

(1979)

Sub-surface barrier Kashef (1986)

Pumping trough Basri (2001)

Economic incentives and regulations Deming (2003)

Desalination Zekri (2007)

Alternate source of water Sorensen

Dwinanto & Iman, 2007

MODIFICATION OF PUMPING

Effect of pumping position on sea water intrusion into a coastal confined aquifer:

(a) Pumping near coast;

(b) Pumping inland.

(Todd, 1959)

PUMPING TROUGH

Control of sea water intrusion by a pumping trough paralleling the coast

(Todd, 1959)

RECHARGE WELL

Sand model results showing successive positions of a salt water wedge in a confined aquifer after recharging (a) at a small rate and (b) at a large rate through a well intersecting the wedge (after Harder and others)

SUB-SURFACE BARRIER

Disadvantages:

• Very expensive due to construction cost (Rogoshewski, 1983; Hanson and Nilsson, 1986; EPA, 1987; Todd, 1980);

• Procedural difficulties of a political, social, and economic nature (US EPA);

• Resistance to earthquake to chemical corrosion (Todd, 1980);

• Limited availability of advanced technology involved and specialty firms capable in constructing barrier (Rogoshewski, 1983)

An illustration of sub-surface barrier (Aiba, 1983) (a) Seawater intrusion advancing Inland (b) Seawater intrusion impeded by a subsurface barrier

PRESSURE RIDGE

Control of sea water intrusion by a pressure ridge paralleling the coast

DESALINATION

In 1970, over 200 plants throughout the world were producing a total of over 50 mgd (190,000 m3/day).

Methods:

• Distillation

• Freezing

• Demineralization

• Electrodialysis

• Reverse osmosis

Kuwait: flash distillation, 5 mgd (220 liters/sec).

Desalination Cost in 1978 (Linsley & Franzini, 1979)

REVERSE OSMOSIS COST (Marks, et. al., 2004)

Zekri, 2007

ECONOMIC INCENTIVES AND REGULATIONS (Zekri, 2007)

Strategies to control groundwater pumping based on:

• Water quotas,

• Electricity quotas, and

• Electricity pricing.

FRESHWATER INJECTION BARRIER

In South California

(Schwartz & Zhang, 2003)

CONTROLLING INTRUSION AT MANHATTAN BEACH, CALIFORNIA

Top – initial condition

Bottom – two years after recharge

12 inchi recharge wells surronded by 3-in. gravel pack were spaced at 500-ft intervals to form a line 4000 ft long.

The combined total injection rate for the eight wells was about 5 cfs.

5% wasted to the ocean, 95% will flow landward.

(Todd, 1959)

MANAGEMENT OF GROUNDWATER RESOURCES

MANAGEMENT OF GROUNDWATER RESOCURCES

Predictive Modelling of Future Conditions

Monitoring

Measurement of Existing Conditions

Modifications

WHAT CAN HELP REDUCE SEAWATER INTRUSION?

USGS Fact Sheet 057-00, April 2000

Seawater intrusion on Lopez Island can be minimized by water conservation, efficient well construction, and by judicious well-operation practices like these: • Using such water-conserving devices as low-volume plumbing

fixtures and toilets. • Keeping outdoor watering to a minimum. • Reusing or recycling water when possible. • Augmenting fresh ground-water recharge by, for example, using

surface ponds to slow surface runoff and raise infiltration rates. • Constructing wells that do not penetrate deeper below sea level

than necessary. • Sizing pumps for lower pumping rates and minimizing lengths of

pumping cycles. • In multiple-well systems, pumping wells alternately.

US. PATENT

Control and Prevention of Seawater Intrusion

METHOD AND APPARATUS FOR MONITORING THE ADVANCE OF SEAWATER INTO FRESH WATER AQUIFERS NEAR COASTAL CITIES

Inventors:

David J. Rossi, Katy;

Willem A. Wijnberg, Houston;

Peter V. Howard, Belleville;

Jean-Pierrre R. Delhomme, Boulogne-Billancourt;

Kamal Babour, Bures sur Yvette.

MEANS FOR DESALINATION OF WATER THROUGH REVERSE OSMOSIS

Inventor:

Robert A. Uhlinger, Carlsbad, Calif.

SALTWATER INTRUSION PREVENTION SYSTEM

Inventor: Wayne W. Spani, Mission Viejo, CA (US)

SEA WATER DESALINIZATION SYSTEM

Inventor: Lincoln A. Vlasnik, 1422 Beckwith Ave., Los Angeles, Calif. 90049

PUSTAKA Todd, D. K., 1959, Groundwater Hydrology, John Wiley & Sons Freeze, R. A., Cherry, J. A., 1979, GROUNDWATER, Prentice-Hall Linsley, R. K., Franzini, J. B., 1979, Water Resources Engineering 3rd edition,

McGraw-Hill Kashef, A. I., 1986, Groundwater Engineering, McGraw-Hill International

Editions Domenico, P. A., Schwartz, F. W.,1990, Physical and Chemical

Hydrogeology, John Wiley & Sons Soliman, M. M., LaMoreaux, P. E., Memon, B. A., Assaad, F. A., LaMoreaux,

J. W., 1998, Environmental Hydrogeology, Lewis Publishers Orr, L., 2000, Is Seawater Intrusion Affecting Ground Water on Lopez Island,

Washington, USGS Fact Sheet 057-00 Basri, M. H., 2001, The New Methods for Optimal Design of Subsurface

Barrier to Control Seawater Intrusion, Ph.D Thesis in Department of Civil and Geological Engineering University of Manitoba.

Deming, D., 2002, Introduction to Hydrogeology, McGraw-Hill Hendrayana, H., 2002, Intrusi Air Asin ke dalam Akuifer di Daratan, Zaitunah, A., 2002, Kajian Keberadaan Hutan Mangrove: Peran, Dampak

Kerusakan, dan Usaha Konservasi, USU digital library. Schwartz, F. W., Zhang, H., 2003, Fundamentas of Groundwater, Wiley Marks, D. H., et.al, 2004, Review of the Desalination and Water Purification

Technology Roadmap, The National Academic Press Notodarmojo, S., 2005, Pencemaran Tanah dan Airtanah, Penerbit ITB Prieto, C., 2005, Groundwater-Seawater Interactions: Seawater Intrusion,

Submarine Groundwater Discharge, and Temporal Variability and Randomness Effects, Ph.D Thesis in KTH.

Cameo, E. A., 2006, Seawater Intrusion in Complex Geological Environments, Ph.D Thesis in Technical University of Catalonia.

Sherif, M., Kacimov, A., …, Control of Seawater Intrusion in Coastal Aquifers by Pumping Saline Water, College of Engineering.

Mirosoft Student with Encarta 2008 US Patent

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