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

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

  1. 1. 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
  2. 2. Islands and Islets of India <ul><li>India have 1175 islands & islets </li></ul><ul><li>Bay of Bengal have 667 islands & islets </li></ul><ul><li>Arabian Sea have 508 islands & islets </li></ul>
  3. 3. Introduction <ul><li>Lakshadweep islands </li></ul><ul><li>Very small low islands </li></ul><ul><li>Lattitude 8 o and 13 o N </li></ul><ul><li>Longitudes 71 o and 74 o E </li></ul><ul><li>36 islands </li></ul><ul><li>10 inhabited </li></ul>
  4. 4. <ul><li>Territorial Waters </li></ul><ul><li>20,000 Sq km </li></ul><ul><li>Exclusive Economic Zone 400,000 Sq km </li></ul><ul><li>Lagoon Area </li></ul><ul><li>4200 Sq km </li></ul>
  5. 5. Parameters Studied <ul><li>Coastal elevation Mean Sea Level (MSL) </li></ul><ul><li>Aquifer </li></ul><ul><li>Beach Characteristics </li></ul><ul><li>Coastal Establishment </li></ul><ul><li>Impact of Sea Level Rise </li></ul>
  6. 6. Materials and Methods <ul><li>Islands were divided into small segments </li></ul><ul><li>Observation wells were fixed </li></ul><ul><li>Elevation from MSL were surveyed </li></ul><ul><li>Water-table vatiations were examined </li></ul><ul><li>Density of ground water was calculated using Lafond Formula </li></ul>
  7. 7. Fresh & Saline water interface SLR <ul><li>Ghyben-Herzberg Relation for oceanic island was used </li></ul><ul><li>For coral islands all the rain water percolates to the ground water </li></ul><ul><li>Bruun’s Rule was used to calculate Sea Level Rise (SLR) </li></ul>
  8. 8. 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
  9. 9. Application of Bruun’s Rule in Atoll <ul><li>Reef structure of the lagoon have a role in active portion of the beach profile </li></ul><ul><li>The texture of the beach material and height of breaking wave were considered </li></ul><ul><li>The bathymetric chart is used for determining the limiting depth </li></ul>
  10. 10. Results and Discussion Kavarathi Atoll <ul><li>Beaches of Kavarathi is steep </li></ul><ul><li>Height of island varies 2-0.5 m towards south </li></ul><ul><li>Height reduces to 0.5 m towards southern end </li></ul><ul><li>It consists regions of height less than MSL </li></ul>
  11. 11. Results and Discussion Kavarathi Atoll <ul><li>Intense beach erosion occurs on many regimes </li></ul><ul><li>Tetrapods are used for Beach protection </li></ul><ul><li>Stable beaches present in regions having Seaevola taccada </li></ul><ul><li>Presence of important establishments in vulnerable coast area </li></ul>
  12. 12. Results and Discussion Kavarathi Atoll <ul><li>Depth of water-table very small </li></ul><ul><li>Patches of saline water are located in the northern region </li></ul><ul><li>Fresh-water potential maximum at 3500 m away from southern tip </li></ul>
  13. 13. <ul><li>Water consumption during the year 2030 will be 108% more </li></ul><ul><li>11.6% of fresh water will be contaminated due to 20 cm SLR </li></ul>Results and Discussion Kavarathi Atoll
  14. 14. Results and Discussion Kavarathi Atoll <ul><li>Water consumption during the year 2030 will be 460 million liters </li></ul>
  15. 15. Results and Discussion Kavarathi Atoll <ul><li>20 cm sea level rise </li></ul><ul><li>Shore line recession at eastern side – 8.2 m </li></ul><ul><li>Shore line recession at southern side – 30.8 m </li></ul><ul><li>Shore line recession at northern side – 6.38 m </li></ul>
  16. 16. Results and Discussion Kavarathi Atoll Important establishments that would affect due to 50 cm SLR <ul><li>Admn. Bunglow </li></ul><ul><li>Desalination Unit </li></ul><ul><li>Wind Mill </li></ul><ul><li>Helipad </li></ul><ul><li>Light House </li></ul><ul><li>All Govt Qtrtrs </li></ul><ul><li>Helipad </li></ul><ul><li>Metero Station </li></ul>
  17. 17. Results and Discussion Kavarathi Atoll <ul><li>SLR will exacerbate the present water dilemma of this atoll </li></ul>
  18. 18. Results and Discussion Bengaram Atoll <ul><li>40 observation wells </li></ul><ul><li>Piezometric surface varies from 150-210 cm </li></ul><ul><li>Maximum water potential at station 37 is 16.22  10 5 M 3 </li></ul><ul><li>50 cm SLR will contaminate 5.99% of fresh water </li></ul>
  19. 19. Results and Discussion Bengaram Atoll <ul><li>A verage height of coastal line is 3 m </li></ul><ul><li>Beaches are stable </li></ul><ul><li>Erosion is observed in the western beaches during monsoon </li></ul><ul><li>Accretion is observed during the post- to pre-monsoon seasons </li></ul>
  20. 20. Results and Discussion Agatti island <ul><li>The length of the island is 7.6 km </li></ul><ul><li>Fifty one observation wells were fixed for water level observations </li></ul>
  21. 21. Results and Discussion Agatti island <ul><li>Maximum diurnal variation of tide in the ground water is 15 cm </li></ul><ul><li>Maximum tidal fluctuation and maximum water level have a time lag of 2 hours </li></ul><ul><li>Depth of water level varies from 60 cm to 395 cm </li></ul><ul><li>It reduces to 2 km during monsoon </li></ul>
  22. 22. Results and Discussion Agatti island <ul><li>Saline water intrudes up to 4 Km from south during pre monsoon </li></ul><ul><li>Eastern side of the atoll is affected by salinity intrusion </li></ul><ul><li>50 cm SLR will contaminate 26% of available fresh water source through salinity intrusion </li></ul>
  23. 23. <ul><li>The acquifer system and beach stability are in stake as on today </li></ul><ul><li>This will further worsen due to impact of SLR of even 20 cm </li></ul><ul><li>There are 290 species of plants out of which 230 are angiosperms </li></ul><ul><li>Fifty six species of fresh and sea water algae </li></ul>Conclusion
  24. 24. <ul><li>Species </li></ul>Conclusion <ul><li>152 group of Meiofauna </li></ul><ul><li>69 ploychaets </li></ul><ul><li>17 siphunculids </li></ul><ul><li>7 echiurids </li></ul><ul><li>13 stomatyopods </li></ul><ul><li>79 insects </li></ul><ul><li>168 mollusks </li></ul><ul><li>72 echinoderms </li></ul>
  25. 25. <ul><li>There is an urgent need to protect the ecosystem of the island utilizing the resources and methods available locally </li></ul>Conclusion
  26. 26. 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.
  27. 27. Thank you Email: sundaresanj@hotmail.com

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