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Dr. Joanna J. Doummar

American University of Beirut- Geology Department- P.O.Box 11-0236- Riad El-Solh, Beirut 1107 2020, E-mail: jd31@aub.edu.lb; 00961-1-35000, Ext 4165

Karst Groundwater Resources in Lebanon & Formation of Caves

University for Seniors 30-10-2014

Afqa Cave

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The amount of water on the earth’s surface: • 95.96% Ocean water• 2.97% Ice caps and glaciers• 1.05% as Groundwater• 0.009% as Lakes, rivers, and streams.

Importance of Groundwater

Importance of Groundwater

• Groundwater is used as main resource in arid to semi arid regions, given the scarcity of surface water.

• Drinking

• Domestic use

• Agricultural

• Industrial

e.g., Daily consumption (150 l/capita/day)

Therefore it is important to

• Assess the availability of groundwater resources

• Ensure a sustainable protection against contamination.

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The Water Cycle

Spring

Precipitation

Infiltration

Evaporation + Transpiration

Surface runoff

Where does Groundwater come from? Catchment areas or GW basins

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Evaporation + Transpiration

Infiltration

Precipitation

Where does Groundwater come from?

The Water Cycle

Aquifers and Aquicludes

The different types of rocks can be considered aquifers or aquicludes depending on their permeability and porosity = ability to convey water.

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Aquifers

Aquifers

Aquifers are layers of highly permeable rocks/material with relatively high porosity that can store and transmit large quantities of ground water.

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Fractured Aquifers

Porous aquifers like sand (water flow in between the grains in pores), whereas in fractured aquifers water flows in fractures and dissolved cracks highly heterogeneous and unpredictable

Groundwater outlets: Springs and wells

SPRINGS• Springs: natural flow of groundwater and occur when water table intersect the earth’s

surface.

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Groundwater: Springs and wells

WELLS• When drilling water wells, if ground water rises naturally in a well above the level

where it was initially found, it is called artesian well.

• Artesian well can be found in a confined aquifer: aquifer overlain and underlain by two aquicludes that keep water under pressure . Water will rise under its own pressure.

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Groundwater: Springs and wells

WELLS • When the water is pumped from a well, it produces a depression in the water

table known as cone of depression occurring around the well.

• Over-pumping causes depression in the water table at a large area; that sometimes causes nearby wells to become dry.

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Drawdown due to pumping

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Geologic Work of Groundwater= Formation of Caves

• Karst is a term used to describe a special style of landscape containing caves and extensive underground water systems that is developed on especially soluble rocks such as limestone, marble, and gypsum.

• Limestone is a sedimentary rock (composed of CaCO3),

• About 80 % of rock exposure in Lebanon are mostly limestone or dolostone.

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Geologic Work of Groundwater= Formation of Caves

• The primary erosional work of groundwater is the dissolution of soluble rock such as limestone, therefore responsible for the creation of caverns and other related features.

• Limestone (insoluble in pure water) can be dissolved by water containing weak carbonic acid (H2CO3 ) as most natural water dissolves carbon dioxide from the air and from decaying plants.

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Geologic Work of Groundwater

Water containing carbonic acid follows bedding planes, joints and dissolving limestone:

The carbonic acid react with calcite to form calcium bicarbonate and calcium (a soluble material carried away in

solution), forming limestone caverns.

CO2 + H2O → H2CO3

CaCO3 + H2CO3 → 2(HCO3)- + Ca2+

Carbonic acid

Lapiaz

Karst Topography

Karst Topography; an irregular terrain formed due to differential dissolution of calcite • Different types of karst features:

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Solution pits

Rillen karren

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Input Landforms: dolines

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Baloua Baatara- Tannourine

Dolines

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Sinkhole in FloridaLeif Skoogfors/Woodfin Camp.

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Geologic Work of Groundwater: Speleothems

In the vadose zone (unsaturated zone), calcite can precipitate again to form:

• Cave features: Speleothems e.g., Stalactites and Stalagmites

2(HCO3)- + Ca2+→ CaCO3 + H2O + CO2

Geologic Work of Groundwater

Speleothems: 2(HCO3)- + Ca2+→ CaCO3 + H2O+ + CO2

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THE LONGEST CAVES OF LEBANON

( as of 2008, Speleo Club du Liban archives in m)1 JIITA CAVE {10,050}2 ROUEISS CAVE {5,460}3 AFQA CAVE {5,260}4 AL-KASSARAT CAVE {4,648}…6 NABAA AL-SHATAWIE {4,130}

THE DEEPEST CAVES IN LEBANON

( as of 2008, Speleo Club du Liban archives)1 FAOUAR DARA SINKHOLE {-622}2 QATTINE AZAR SINKHOLE {-515}3 BALLOUH BAATARA SINKHOLE {-255}…10 TARCHICH SINKHOLE {-147}

Caves of Lebanon

Groundwater Resources in Lebanon= Water Budget

Precipitation (Snow and Rain; P)

Evapotranspiration (ETP)

Infiltration/Recharge (I)

∆𝑆 = 𝑃 − 𝐸𝑇𝑃 − 𝑅 − 𝐼

Flow in the subsurfaceGroundwater

Surface runoff Rivers (R)

𝐼𝑛𝑓𝑙𝑜𝑤 − 𝑂𝑢𝑡𝑓𝑙𝑜𝑤 = ±∆𝑆

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Water Budget= Precipitation in Lebanon

Precipitation (including snow)= 800- 1800 mm/year; (UNDP, 1970), from coastal zones to high mountains.

Snow is not measured in Lebanon. therefore there is a high uncertainty regarding the precipitation quantities

Water Budget= Infiltration

Main Aquifers in Lebanon= Karst aquifers

Sandstone

Basalt

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Water Budget= Infiltration

Main Aquifers in Lebanon= Karst aquifers

Aquicludes: Impermeable Material

Karst Aquifer: limestone

Water Budget= Precipitation in Lebanon

Infiltration to Groundwater (50-70% depending on the catchment especially high in fractured systems)

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Water Budget= Groundwater outlet

Springs:

Jeita Spring

Afqa Spring

High variability of discharge and fast response to rain event in karst spring

Water Budget= Groundwater outlet

Springs:

Jeita Spring

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High variability of discharge; very low discharge in summer times

Water Budget= Groundwater outlet

Anjar Spring

Assal Spring

Afqa Spring

Laban Spring

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Water Budget= Surface Runoff

Rivers: mostly originating from springs

Major rivers: Litani, Assi, and Hasbani

Minor rivers: Nahr Ibrahim, Nahr El Kalb

Groundwater contamination

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The composition of the raw water often requires processing in a waterworks prior distribution to the customer.

Costly processing methods are involved, hydrogeology helps protecting groundwater at the source

Problematic ingredients in raw water are:

- heavy metals Iron, Manganese - organic micropollutants (PPCP, Chlorinated Hydrocarbons)- Microbial contaminants- Heavy metals - Other: Sodium Chloride, Potassium etc...- Pharmaceuticals

Contamination of the Water at the source Treatment at the supply

Microbial Pollution

Drinking water has to be microbiologically clean (0 CFU (Colonies) of Pathogens)

Microorganisms can reach the groundwater when a protective soil cover is missing.

Contamination from disposal of untreated waste water. E-coli

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Petroleum products and heavy metals

Elevated heavy metal contents in water originating from recharge areas for Petroleum byproducts disposal

Pharmaceuticals: Ibuprofen, Carbamazepine (below toxic limits), cocaine metabolites

Varying concentration and Mass fluxes of Carbamazepine (pharmaceutical) in a spring with time

Agricultural contaminationPesticides, insecticides and manure

High levels of K+, Na+ and nitrates degradation of the soil quality and subsquently of Groundwater

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Salt water Intrusion High levels of salinities in many areas brakish water

Allowed levels of Chlorides: 500 mg/lIn wells in southern Beirut areas:e.g., maximum chloride concentration: 8733 mg/l • due to extensive abstraction

Some Research Investigation related to Groundwater

Jeita: Delineation of catchment area: Tracer tests (funded by BGR: Federal Institute for Geoscience- Germany 2010-2012)Groundwater age on the Jeita catchment to know transit times of water in an aquifers (funded by AUB)

Emerging pollutants in Lebanese springs (transport of pharmaceuticals in groundwater)

Vulnerability studies: Identification of highly vulnerable zones for protection on two pilot areas (funded by USAID, PEER Science 2014-2017):

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Jeita: Delineation of catchment areas

Identification of protection zones

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Sampling for environmental tracers and stable isotopes

Measurement of water levels in the springs and other chemical parameters

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Thank you