Water

1. Water

2. PROBLEMATIC • The water situation is studied since a long time. • Our only resource today is groundwater, fragile quantity wise and quality wise. • No final decision on the way to proceed about water sourcing has been fixed so far. • We still have serious uncertainty about the sources to be used to ensure safe and reliable water supply. • In the frame of a developing city, it is high time to reach decisions. • A lot of uncertainty prevail: • Urban design & urban planning • Population growth • Speed of growth and development • Individual consumption • Safety of groundwater resources

3. Methodology of the study • 1st step: • To define the context • To look at all the potential water resources • To frame the uncertainties within reasonable limits • To define comparison factors • To analyse the potential and implication for each possibility • To compare between all the possibilities • To generate a synthesis to help in the decision making process . • 2nd step • To develop further the most promising solution

4. Context • All the resource today is coming from the groundwater • The upper aquifer (Cuddalore) is not water tight • Bore wells tap multiple aquifers • Groundwater is depleting • Groundwater threatened by seawater intrusion • Runoff water offer a large scope as a resource

5. All the resource today is coming from the groundwater

6. The upper aquifer (Cuddalore) is not water tight

7. Bore wells tap multiple aquifers

8. Groundwater is depleting

9. 5 km Groundwater threatened by seawater intrusion Doctor Aude Vincent: HYDROLOGICAL AND HYDROGEOLOGICAL STUDY OF THE COASTAL SEDIMENTARY BASIN OF KALUVELLI-PONDICHERRY (TAMIL NADU, INDIA) Water level map of the Vanur aquifer N 5 m 10 m 0 15 m N -30 Baie du Bengale -57 2006 1950

10. WATER CYCLE

11. Runoff water offer a large scope as a resource

12. The potential water resources • Groundwater • Rainwater • Wastewater • Seawater desalinization • Groundwater desalinization

13. Potential water resources: main points of evaluation • Groundwater: • Infrastructure already existing • Fragile because of general degradation • Running cost and maintenance easy and cheap • Rainwater: • Yearly available in very large quantity but highly fluctuating • Can be collected using topographic conditions. • Must be part of planning and development issues immediately. • Not depending on any larger territory than Auroville • Running cost and maintenance well- known, Cheapest • Wastewater: • A part only of the water consumption • High risk for cross contamination. • Well adapted to local solution • Running cost and maintenance relatively complex • Seawater desalinization: • Unlimited resource • Social issues to be addressed • Running cost and maintenance complex, costly • Groundwater desalinization: very large resource • Cheaper than seawater • Social issues • Can be integrated at any stage • Running cost and maintenance relatively complex and costly

14. Evaluation Evaluation table: 4 stars best, 1 star worth

15. Conclusion on resources • All resources can be part of the sourcing system. • Multi sourcing is a necessity • Groundwater is already used but very fragile. • Groundwater desalination seems a worthy solution compared to seawater desalination • Rainwater harvesting solution offers best scores. It is hence studied further below.

16. To frame the uncertainties within reasonable limits • Time frame • Population • Water consumption • Runoff • Limit of validity of a resource from the quantitative point of view

17. Time frame • Implementation in accordance with very long term forecasting may lead to technical solutions totally outdated when they would become necessary, because of the fast technological evolution. • Accordingly, it makes a lot of sense to reflect on very long term principles, but to stay on shorter time frame for the technical solutions. • Proposed solutions should fit with • practicality • reasonable time frame • be a sustained asset for the now as well as the long term. • To Invest in long-term related infrastructure may overload the present population with financial demand • Conclusion: By retrospectively looking at the past and learning from it, it seems very reasonable to limit practical horizon to a 20 years time period from now or the year 2030.

18. Population • by 2030 Auroville’s population will reach • 6,100 people for a growth rate of 5% • 22,200 people for a growth rate of 12%

19. Water consumption • Hence, the retained values for this study are : • 160lcd (lowest value) • 215lcd (highest value)

20. Runoff in Auroville’s urbanizing context • Hence, the retained values for this study are : • 35% runoff for low population/ low imperviousness • 54% runoff for high population/ high imperviousness

21. Limit of validity of a resource from the quantitative point of view • The level of complexity requires that the volume is large enough to justify the choice for a particular resource. • Investment for large infrastructure is done • because it is acting on public safety • because it is fulfilling a function on the daily life of the targeted population. • Hence, a water resource system must fulfill 2 criteria: • to run for the longest possible period during the year • to run with the smallest possible interval between standby period. • It is fixed arbitrary that such a limit in the context of this study should be to supply the targeted population for at least half a year (180 days). Below this value investment, maintenance and operation may become too costly to justify such choice.

22. Limits for the study: Synthesis • Conclusion • A 20 years time frame is a reasonable limit for planning • Even by using large fresh water consumption values, rainwater harvesting offers a very large scope as a resource • Auroville as a developing city will offer larger scope for water harvesting through time.

23. Methodology of the study • 1st step: • To define the context • To look at all the potential water resources • To frame the uncertainties within reasonable limits • To define comparison factors • To analyses the potential and implication for each possibility • To compare between all the possibilities • To generate a synthesis to help in the decision making process . • 2nd step • To develop further the most promising solution

24. Potential from rainwater and surface water • Ground water recharge • Roof rainwater harvesting • Catchment in existing Irumbai tank • Catchment in artificial ponds made in canyons • Catchment in Matrimandir Lake

25. Rainwater: main points of evaluation • Ground water recharge • Cost effective in east part of Auroville but limited scope on west part • Recharge potential will drop through development (impervious area) • Already largely practiced but scope for improvement due to future development. • Become then a groundwater resource and will help to maintain it but becomes vulnerable. • Roof rainwater harvesting • Costly because of the rainfall pattern (large storage required to optimize collection) • Connection to municipal supply difficult • Can be developed along the development process • Running cost and maintenance complex • Catchment in existing Irumbai tank • Cheap • Social issue • It is a source of irrigation for agriculture • High losses by evaporation and limited storage • Pollutant from agricultural activities difficult to avoid • Running cost and maintenance relatively complex • Catchment in artificial ponds in canyons • Costly • Large excavation required • Exceeding water mainly lost to the sea • Running cost and maintenance complex • Catchment in Matrimandir Lake • Cheap as only the drainage system is to be considered • Practical value generated for Matrimandir Lake • Exceeding water could be recharged in groundwater table as the best possible location • Social issues cannot be neglected • Becomes a multi-purpose solution: drainage, esthetical, symbolic, supply • Important evaporation losses • Running cost and maintenance relatively complex

26. Rainwater: synthesis Evaluation table: 4 stars best, 1 star worth

27. Rainwater: Conclusion • All solutions can be part of the sourcing system. • Open storage system is generating important losses because of high evaporation rate. • The Catchment in Matrimandir Lake solution offers the best score.

28. Are we able to make choices? • Multi sourcing? • Rain water as a resource? • Matrimandir Lake as major part of the water system? • Integration in planning and development issues?

29. Thanks a lot for A Sustainable and Harmonious Future!