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

1. Groundwater Management: Jaffna/ Sri Lanka
Herath Manthrithilake
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3. Jaffna Peninsula
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4. Main Groundwater Aquifers in
Jaffna Peninsula
Chunnakam Vadamaradchi
Kayts
Thenmaradchi
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5. 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
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6. Geology and condition of groundwater
in the Jaffna Peninsula
permeability hydraulic conductivity Infiltration
high to very high 30 to 50 m/d 430 mm/hour
Source: 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
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7. • 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.

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9. PROBLEMS ASSOCIATED WITH AVAILABLE WATER
Over extraction
QUANTITY Rapid rate of extraction
Development
of salinity
Own property
Digging 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
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(Ref. Prof.Y.D. Joshuva)

10. • 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
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11. Monthly deficits (i.e., Rainfall - ET) for 2011
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12. • 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
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14. Fertilizer use
Crop Avg. nitrogen Recommended Excess
Applied (kg/ha) nitrogen (kg/ ha) nitrogen (kg/ha)
Onion 178.1 70 108.1
Carrot 230 150 80.0
Cabbage 142.6 150 -7.4
Beetroot 246 180 66.0
Tobacco 262.9 No recommendation -
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15. Concentration of nitrate- N during January 2011
Max Per
D D+H Public Paddy Banana Highland crops
Farm
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18. Agro-well density
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19. Hot-spots where agro-well density is very high
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22. Roof top Count
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23. Results
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24. Challenges
• Establishing caps on abstraction
• Prevention of Contamination
• Prevention of over irrigation
• Increasing recharge & runoff reduction
• CC challenges
• Stakeholder cooperation
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25. Recommendations
• Awareness creation
• Promotion of technologies
• Investment on pollution control
• Agrochemical use reduction
• Rainwater harvesting & recharge
• A policy framework for GW mgt.
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26. Water for a food-secure world
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27. “There is a sufficiency in the world for
man’s need but not for man’s greed.”