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www.globaloceans.org/globalconferences/2008/pdf/JSundaresan.
 

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    www.globaloceans.org/globalconferences/2008/pdf/JSundaresan. www.globaloceans.org/globalconferences/2008/pdf/JSundaresan. Presentation Transcript

    • Impact of sea level rise on the ground water resources of very small low islands, Lakshdweep Archipaelago – India J Sundaresan Indian Journal of Marine Sciences, National Institute of Science Communication and Information Resources, Council of Scientific and Industrial Research, New Delhi – 110012, India
    • Islands and Islets of India
      • India have 1175 islands & islets
      • Bay of Bengal have 667 islands & islets
      • Arabian Sea have 508 islands & islets
    • Introduction
      • Lakshadweep islands
      • Very small low islands
      • Lattitude 8 o and 13 o N
      • Longitudes 71 o and 74 o E
      • 36 islands
      • 10 inhabited
      • Territorial Waters
      • 20,000 Sq km
      • Exclusive Economic Zone 400,000 Sq km
      • Lagoon Area
      • 4200 Sq km
    • Parameters Studied
      • Coastal elevation Mean Sea Level (MSL)
      • Aquifer
      • Beach Characteristics
      • Coastal Establishment
      • Impact of Sea Level Rise
    • Materials and Methods
      • Islands were divided into small segments
      • Observation wells were fixed
      • Elevation from MSL were surveyed
      • Water-table vatiations were examined
      • Density of ground water was calculated using Lafond Formula
    • Fresh & Saline water interface SLR
      • Ghyben-Herzberg Relation for oceanic island was used
      • For coral islands all the rain water percolates to the ground water
      • Bruun’s Rule was used to calculate Sea Level Rise (SLR)
    • Bruun’s Rule and Hypotheses Mathematically Bruun’s Rule is where s — shore line recession h D — Average height of the sand dunes D — Limiting depth between predominant near shore and offshore material h’ — Sea Level rise L — The active portion of the profile participating in the adjustment
    • Application of Bruun’s Rule in Atoll
      • Reef structure of the lagoon have a role in active portion of the beach profile
      • The texture of the beach material and height of breaking wave were considered
      • The bathymetric chart is used for determining the limiting depth
    • Results and Discussion Kavarathi Atoll
      • Beaches of Kavarathi is steep
      • Height of island varies 2-0.5 m towards south
      • Height reduces to 0.5 m towards southern end
      • It consists regions of height less than MSL
    • Results and Discussion Kavarathi Atoll
      • Intense beach erosion occurs on many regimes
      • Tetrapods are used for Beach protection
      • Stable beaches present in regions having Seaevola taccada
      • Presence of important establishments in vulnerable coast area
    • Results and Discussion Kavarathi Atoll
      • Depth of water-table very small
      • Patches of saline water are located in the northern region
      • Fresh-water potential maximum at 3500 m away from southern tip
      • Water consumption during the year 2030 will be 108% more
      • 11.6% of fresh water will be contaminated due to 20 cm SLR
      Results and Discussion Kavarathi Atoll
    • Results and Discussion Kavarathi Atoll
      • Water consumption during the year 2030 will be 460 million liters
    • Results and Discussion Kavarathi Atoll
      • 20 cm sea level rise
      • Shore line recession at eastern side – 8.2 m
      • Shore line recession at southern side – 30.8 m
      • Shore line recession at northern side – 6.38 m
    • Results and Discussion Kavarathi Atoll Important establishments that would affect due to 50 cm SLR
      • Admn. Bunglow
      • Desalination Unit
      • Wind Mill
      • Helipad
      • Light House
      • All Govt Qtrtrs
      • Helipad
      • Metero Station
    • Results and Discussion Kavarathi Atoll
      • SLR will exacerbate the present water dilemma of this atoll
    • Results and Discussion Bengaram Atoll
      • 40 observation wells
      • Piezometric surface varies from 150-210 cm
      • Maximum water potential at station 37 is 16.22  10 5 M 3
      • 50 cm SLR will contaminate 5.99% of fresh water
    • Results and Discussion Bengaram Atoll
      • A verage height of coastal line is 3 m
      • Beaches are stable
      • Erosion is observed in the western beaches during monsoon
      • Accretion is observed during the post- to pre-monsoon seasons
    • Results and Discussion Agatti island
      • The length of the island is 7.6 km
      • Fifty one observation wells were fixed for water level observations
    • Results and Discussion Agatti island
      • Maximum diurnal variation of tide in the ground water is 15 cm
      • Maximum tidal fluctuation and maximum water level have a time lag of 2 hours
      • Depth of water level varies from 60 cm to 395 cm
      • It reduces to 2 km during monsoon
    • Results and Discussion Agatti island
      • Saline water intrudes up to 4 Km from south during pre monsoon
      • Eastern side of the atoll is affected by salinity intrusion
      • 50 cm SLR will contaminate 26% of available fresh water source through salinity intrusion
      • The acquifer system and beach stability are in stake as on today
      • This will further worsen due to impact of SLR of even 20 cm
      • There are 290 species of plants out of which 230 are angiosperms
      • Fifty six species of fresh and sea water algae
      Conclusion
      • Species
      Conclusion
      • 152 group of Meiofauna
      • 69 ploychaets
      • 17 siphunculids
      • 7 echiurids
      • 13 stomatyopods
      • 79 insects
      • 168 mollusks
      • 72 echinoderms
      • There is an urgent need to protect the ecosystem of the island utilizing the resources and methods available locally
      Conclusion
    • Acknowledgement The author thanks to Director General, CSIR; Director, NISCAIR; Deptt. of Science & Technology, Govt. of India; Ministry of Environment & Forest, Govt. of India; Centre for Earth Science Studies, Kerala; Zoological Survey of India; Deputy Director, Deptt. of Science & Technology, Lakshadweep.
    • Thank you Email: sundaresanj@hotmail.com