Descibes n cascade system in Sri Lanka and how the man made changes impacts on those as well as aquifer types

1. Impact of unplanned
manmade changes on
subsurface hydrology
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2. What is a cascade system?
• Almost all ancient tanks are inter connected by canals
• Resulting very complex systems
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3. Definition for Cascade system
• A connected series of village irrigation tanks
organized within micro catchments of the dry zone
landscape, storing, conveying and utilizing water from
an ephemeral rivulet.(madduma Bandara, 1985,
Panabokke, 2002)
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5. • Early Sri Lanka community had the control of the
ownership of tanks . It was headed by Velvidane
(irrigation headman), elected who has offered services
in water issues, regulations, control and management.
• Decentralized independent management
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6. Interconnection between surface and
subsurface hydrology
• Process of exchanging water between on
land surface and under the surface
• Moving forces= Thermal energy and
gravitation
• One stage of natural hydrological cycle
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7. • Streams interact with ground water in 3
basic ways
1. Streams gain water from inflow of ground
water through the stream bed.
2. streams loss water by out flow through
the streambed.
3. They do both(depending upon the
location)
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8. Ways of water transfer
• Infiltration through unsaturated zone
• Infiltration through saturated zone
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9. Aquifer
• Regolith aquifer
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10. Seasonal changes and potential of
aquifer
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12. What are the manmade
changes?
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14. Antient and Modern Irrigation
Highland
Village
Paddy
Drainage is collected back to stream
through pick up points
Drainage systems collect water
discharge and dispose them
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15. Problems and Mittigation
Problem Mitigation measures
Degradation of
irrigated land:
- Improve I & D operation to match demand both 'how much &
when'.
Reduced socio-economic
conditions:
- Manage I & D to prevent disease spread.
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16. Continue…
Reduced socio-
economic conditions:
- Manage I & D to prevent disease spread.
Increased incidence of
water related disease
- Educate about causes of disease.
Increased inequity - Improve health facilities.
Weaker community
infrastructure
- Allow sufficient time and money for extensive public participation to
ensure that plans are optimal, that all sections of affected society are
considered and that local institutions are in place to sustain irrigated
agriculture, particularly in respect of land and water rights.
- Consider markets, financial services and agricultural extension in
conjunction with proposed irrigation and drainage changes.
- Ensure that agricultural intensification does not preclude other
economic or subsistence activity, such as household vegetables, fodder or
growing trees for firewood.
- Provide short-term support and/or skills for an alternative livelihood if
irrigation removes existing livelihood
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17. Conclusion
• If we improve the cascade system in the
right manner we can manage the water
resources in sustainable manner.
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18. Thank You
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