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1 Importance of Groundwater The amount of water on the earths - PDF document

Jan 31, 2023 •598 likes •943 views

Karst Groundwater Resources in Lebanon & Formation of Caves 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

  1. Karst Groundwater Resources in Lebanon & Formation of Caves 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 University for Seniors 30-10-2014 Afqa Cave 1

  2. Importance of Groundwater 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 • 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. 2

  3. The Water Cycle Where does Groundwater come from? Catchment areas or GW basins Precipitation Surface runoff Evaporation + Transpiration Infiltration Spring 3

  4. Where does Groundwater come from? The Water Cycle Precipitation Evaporation + Transpiration Infiltration Aquifers and Aquicludes The different types of rocks can be considered aquifers or aquicludes depending on their permeability and porosity = ability to convey water. 4

  5. Aquifers Aquifers Aquifers are layers of highly permeable rocks/material with relatively high porosity that can store and transmit large quantities of ground water. 5

  6. 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. 6

  7. 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. 7

  8. 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. 8

  9. Drawdown due to pumping 9

  10. 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 CaCO 3 ), • About 80 % of rock exposure in Lebanon are mostly limestone or dolostone. 10

  11. 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 (H 2 CO 3 ) as most natural water dissolves carbon dioxide from the air and from decaying plants. 11

  12. 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. Carbonic acid CO 2 + H 2 O → H 2 CO 3 CaCO 3 + H 2 CO 3 → 2(HCO 3 ) - + Ca 2+ Karst Topography Karst Topography; an irregular terrain formed due to differential dissolution of calcite • Different types of karst features: Lapiaz 12

  13. Solution pits Rillen karren 13

  14. Input Landforms: dolines 14

  15. Baloua Baatara- Tannourine Dolines 15

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  17. Sinkhole in Florida Leif Skoogfors/Woodfin Camp. 17

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  20. 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(HCO 3 ) - + Ca 2+ → CaCO 3 + H 2 O + CO 2 Geologic Work of Groundwater 2(HCO 3 ) - + Ca 2+ → CaCO 3 + H 2 O+ + CO 2 Speleothems: 20

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  22. Caves of Lebanon 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} Groundwater Resources in Lebanon= Water Budget Precipitation (Snow and Rain; P) Evapotranspiration (ETP) Infiltration/Recharge (I) Flow in the subsurface  Groundwater Surface runoff  Rivers (R) 𝐽𝑜𝑔𝑚𝑝𝑥 − 𝑃𝑣𝑢𝑔𝑚𝑝𝑥 = ±∆𝑇 ∆𝑇 = 𝑄 − 𝐹𝑈𝑄 − 𝑆 − 𝐽 22

  23. 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 23

  24. 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) 24

  25. Water Budget= Groundwater outlet Springs: Jeita Spring Afqa Spring Water Budget= Groundwater outlet Springs: High variability of discharge and fast response to rain event in karst spring Jeita Spring 25

  26. Water Budget= Groundwater outlet Anjar Spring High variability of discharge; very low discharge in summer times Afqa Spring Assal Spring Laban Spring 26

  27. Water Budget= Surface Runoff Rivers: mostly originating from springs Major rivers: Litani, Assi, and Hasbani Minor rivers: Nahr Ibrahim, Nahr El Kalb Groundwater contamination 27

  28. Contamination of the Water at the source  Treatment at the supply The composition of the raw water often requires processing in a waterworks prior distribution to the customer. 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 Costly processing methods are involved, hydrogeology helps protecting groundwater at the source Microbial Pollution Drinking water has to be microbiologically clean (0 CFU (Colonies) of Pathogens) Contamination from disposal of untreated waste water. E-coli Microorganisms can reach the groundwater when a protective soil cover is missing. 28

  29. 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 contamination Pesticides, insecticides and manure High levels of K+, Na+ and nitrates  degradation of the soil quality and subsquently of Groundwater 29

  30. Salt water Intrusion High levels of salinities in many areas  brakish water Allowed levels of Chlorides: 500 mg/l In 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): 30

  31. Jeita: Delineation of catchment areas Identification of protection zones 31

  32. Sampling for environmental tracers and stable isotopes Measurement of water levels in the springs and other chemical parameters 32

  33. Thank you 33

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