Groundwater management: Jaffna, Sri Lanka

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A presentation by Herath Manthrithilake at the Annual Research Meeting at IWMI HQ, Sri Lanka. December 2012. …

A presentation by Herath Manthrithilake at the Annual Research Meeting at IWMI HQ, Sri Lanka. December 2012.

Groundwater management: Jaffna, Sri Lanka

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  • 1. Groundwater Management: Jaffna/ Sri Lanka Herath Manthrithilake Water for a food-secure world www.iwmi.org
  • 2. Jaffna Peninsula Water for a food-secure world www.iwmi.org
  • 3. Main Groundwater Aquifers in Jaffna Peninsula Chunnakam VadamaradchiKayts Thenmaradchi Water for a food-secure world www.iwmi.org
  • 4. Annual average rainfall is 1250 mm, but 900 mm is received between months of October and December • 50% of the northeast monsoonal rainfall is received within a very short time period • 75% probability of rainfall in this district was 510 millimeters (mm) in Maha and 102 mm in Yala • Evaporation of 45-48% of the annual rainfall Water for a food-secure world www.iwmi.org
  • 5. Geology and condition of groundwater in the Jaffna Peninsula permeability hydraulic conductivity Infiltration high to very high 30 to 50 m/d 430 mm/hourSource: Sirimanne 1952(a) Red earth, (b) Jaffna limestone, (c) Granitic genesis, MSL (mean sea level), GWT (groundwater level), FWZ (zone of freshwater saturation), BWZ (probable zone of brackish water);(1) dry well, (2) bottomless well or tidal well (Nilavarai), (3) ordinary successful well, (4) spring of Keerimalai type, (5) solution cavern. Water for a food-secure world www.iwmi.org
  • 6. • Spatial variation of net groundwater recharge was observed to be in the range of 12 to 69% of the total rainfall,• with an average of 37% during the short rainy season (i.e., during October, November and December).• A significant volumes of run-off (43 - 60%)is lost to the sea during monsoon months.
  • 7. Water for a food-secure world www.iwmi.org
  • 8. PROBLEMS ASSOCIATED WITH AVAILABLE WATER Over extractionQUANTITY Rapid rate of extraction Development of salinity Own propertyDigging of Deep wells Wet season water table Excess pumping Dry season water table Wet season lens Excess Dry season lens pumping msl msl Fresh water Salt water Salt water intrusion Water for a food-secure world Salt water up coning www.iwmi.org (Ref. Prof.Y.D. Joshuva)
  • 9. • Abstraction for irrigation varied from 9.4 to 15.7 mm/day with an average of 11.5 mm/day• Daily ET in 2011 varied from 3.4 mm/day in December to 5.6 mm/day in May with an annual average of 4.7 mm/day Water for a food-secure world www.iwmi.org
  • 10. Monthly deficits (i.e., Rainfall - ET) for 2011 Water for a food-secure world www.iwmi.org
  • 11. • Excessive irrigation was 51% over the peak demand of 5.6 mm/day; the major portion of which will eventually return to groundwater• This limits the water availability and promotes saltwater intrusion• Have serious consequences on groundwater pollution as the return flow could carry fertilizer and pesticide residues Water for a food-secure world www.iwmi.org
  • 12. Water for a food-secure world www.iwmi.org
  • 13. Fertilizer useCrop Avg. nitrogen Recommended Excess Applied (kg/ha) nitrogen (kg/ ha) nitrogen (kg/ha)Onion 178.1 70 108.1Carrot 230 150 80.0Cabbage 142.6 150 -7.4Beetroot 246 180 66.0Tobacco 262.9 No recommendation - Water for a food-secure world www.iwmi.org
  • 14. Concentration of nitrate- N during January 2011 Max PerD D+H Public Paddy Banana Highland crops Farm Water for a food-secure world www.iwmi.org
  • 15. Water for a food-secure world www.iwmi.org
  • 16. Water for a food-secure world www.iwmi.org
  • 17. Agro-well densityWater for a food-secure world www.iwmi.org
  • 18. Hot-spots where agro-well density is very high Water for a food-secure world www.iwmi.org
  • 19. Water for a food-secure world www.iwmi.org
  • 20. Water for a food-secure world www.iwmi.org
  • 21. Roof top Count Water for a food-secure world www.iwmi.org
  • 22. ResultsWater for a food-secure world www.iwmi.org
  • 23. Challenges• Establishing caps on abstraction• Prevention of Contamination• Prevention of over irrigation• Increasing recharge & runoff reduction• CC challenges• Stakeholder cooperation Water for a food-secure world www.iwmi.org
  • 24. Recommendations• Awareness creation• Promotion of technologies• Investment on pollution control• Agrochemical use reduction• Rainwater harvesting & recharge• A policy framework for GW mgt. Water for a food-secure world www.iwmi.org
  • 25. Water for a food-secure world www.iwmi.org
  • 26. “There is a sufficiency in the world forman’s need but not for man’s greed.”