Effective RWH
Systems – Significance of Geology
and Hydrogeology

J.Saravanan
Consulting Hydrogeologist
Thrust Geoconsulta...
Presentation
Structure

•What

is effective RWH System?

•What

is the Geology & Hydrogeology of

Chennai city?
•How

do I...
Effectiveness wrt RWH
Coverage…
Effective wrt RWH
design a RWH system
Designing

(particularly in the case of )
groundwater recharge based on
the hydrogeo...
Besant
Nagar
Coastal Alluvium
•

•Sandy

strata (aquifer)
•Good Porosity and Permeability
•Water table : Shallow

 

 

 
...
Anna Nagar
•Gondwana

- Clay /Shale mainly with
intermittent silt / fine sand
•Highly Porous but poor in permeability
•Wat...
Tambaram
•Hard

rock area
•Weathered / fractured rock ( aquifer)
•Moderate to Poor in Porosity and
Permeability
•Water Tab...
Geology of Chennai
Era

Formation

Hydro

Recent and
Sub-Recent

Alluvium,laterite,
Conglomerate &
Black clay.

Good
Coast...
Chennai’s Aquifer capacity
The total storage capacity of chennai city aquifer works out to 392 mcm.
(1 mcm is 1000 MLt; 2...
Hydrogeology of my locality
Geotechnical Report for foundation
designing
Hydrogeology of my locality…
Hydrogeological Report for
groundwater surveys
Observing BW drilling in
neighbourhoods (hand ...
Hydrogeology of my locality…

16
Public Supply Vs Water Policy Vs RF
Alternate Days Supply

GW Reg. Act

Telugu Ganga Opted

RWH Mandatory for new building...
Source Dependance by Chennai ite’s

Source

% of dependance to meet the daily
water requirement

Metro Water

35 %

Ground...
Status of Public Supply


Present Public System is highly subsidised and
hence lacks economic sustenance



Cost varies ...
Towards Effective Water
Management System


Water Requirement Estimation


Percapita requirement (70.…135….150lpcd)????
...
21
Effective management…
Need

for a comprehensive study on
Chennai’s groundwater resources
Mapping

of Aquifers – Aquifer ...
Effective management ….
Record

on Wells, drilling, well
designing and construction – to record
lithology and decide slot...
Effective management ….
Provision

of space, atleast to drill a
borewell in future in the rest of identified
potential po...
Do’s and Do’nts….
Constant

depletion of water table is
an indication of
Over

exploitation of GW sources
Reduced recha...
Designing effective Rainwater Harvesting systems_Saravanan_2013
Designing effective Rainwater Harvesting systems_Saravanan_2013
Designing effective Rainwater Harvesting systems_Saravanan_2013
Designing effective Rainwater Harvesting systems_Saravanan_2013
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Designing effective Rainwater Harvesting systems_Saravanan_2013

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This presentation gives an overview on how to design effective rainwater harvesting systems based on the underlying rock structure and hydrogeology of an area.

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Designing effective Rainwater Harvesting systems_Saravanan_2013

  1. 1. Effective RWH Systems – Significance of Geology and Hydrogeology J.Saravanan Consulting Hydrogeologist Thrust Geoconsultants P Ltd, Chennai 1
  2. 2. Presentation Structure •What is effective RWH System? •What is the Geology & Hydrogeology of Chennai city? •How do I know the hydrogeology of my locality? •Why effective RWH? •Towards effective water management in Chennai city
  3. 3. Effectiveness wrt RWH Coverage…
  4. 4. Effective wrt RWH design a RWH system Designing (particularly in the case of ) groundwater recharge based on the hydrogeology of an area. • • • • Better functioning of the system Maximum realisation of benefits Cost benefit Case of Besant Nagar, Anna Nagar, Tambaram
  5. 5. Besant Nagar Coastal Alluvium • •Sandy strata (aquifer) •Good Porosity and Permeability •Water table : Shallow               Coastal Alluvium (Sandy)              
  6. 6. Anna Nagar •Gondwana - Clay /Shale mainly with intermittent silt / fine sand •Highly Porous but poor in permeability •Water Table Shallow to moderate Clay             Fine Sand / Silt Clay Shale  
  7. 7. Tambaram •Hard rock area •Weathered / fractured rock ( aquifer) •Moderate to Poor in Porosity and Permeability •Water Table : Shallow? To Deep   Top Soil / Weathered  rock Partly Weathered /  Fractured rock Fr. Rock Hard rock w   
  8. 8. Geology of Chennai Era Formation Hydro Recent and Sub-Recent Alluvium,laterite, Conglomerate & Black clay. Good Coastal, (exl. Clay) central chennai Tertiary(2.6 M yrs) Sand and sandstone mainly Good to North Chennai, very good Ambattur.. Sriperumbudur Clay, Shales, beds (150 M Felspathic yrs) Sandstone. Poor Lower Gondwanas Green Shales and boulders. Poor Archaean (4500 M yrs) Dolerite, Charnockite and Gneiss. Moderate - Poor Type area East Chennai, Porur, Annanagar South Chennai
  9. 9. Chennai’s Aquifer capacity The total storage capacity of chennai city aquifer works out to 392 mcm. (1 mcm is 1000 MLt; 2.74 MLD) The storage capacity reduces drastically with falling water table. The capacity at 10m water level is 259 mcm ie., 66% of the total storage capacity The storage capacity at 20m water table is 126 mcm which is about 32% of the total storage capacity. This may be due to the fact that the major yielding zones are restricted to the top 30m bgl which is mainly alluvium. Beyond 30m depth the porosity and specific yield of the formations such as shale and hard rock is very poor and hence cannot store nor yield sufficient quantity of groundwater. This also corroborates with the reduction of yield in borewells during summer when the water table depletes drastically. 13
  10. 10. Hydrogeology of my locality Geotechnical Report for foundation designing
  11. 11. Hydrogeology of my locality… Hydrogeological Report for groundwater surveys Observing BW drilling in neighbourhoods (hand auger, rotary, DTH) Government Departments – CGWB, CMWSSB, TWAD, PWD Groundwater. http://cgwb.gov.in/District_Profile.html http://www.mdws.gov.in/node/2623
  12. 12. Hydrogeology of my locality… 16
  13. 13. Public Supply Vs Water Policy Vs RF Alternate Days Supply GW Reg. Act Telugu Ganga Opted RWH Mandatory for new buildings Alternate Days Supply Telugu Ganga Realised 100MLD Desal Unit Piped water supply stopped RWH Mandatory for all buildings Veeranam tapped 17
  14. 14. Source Dependance by Chennai ite’s Source % of dependance to meet the daily water requirement Metro Water 35 % Groundwater 62 % 18
  15. 15. Status of Public Supply  Present Public System is highly subsidised and hence lacks economic sustenance  Cost varies from Rs. 10 to Rs. 45 per KL  At present tanker supply costs Rs. 100 per KL  Sources : AK Basin  Surface Water T G Veeranam Neyveli Aquifer Kollidam?? RO Lowest Per capita supply in the country 19
  16. 16. Towards Effective Water Management System  Water Requirement Estimation  Percapita requirement (70.…135….150lpcd)???? Development should be based on resource availability or FSI or Guideline Value?    Case of OMR and other High value projects Aquifer carrying / bearing capacity…. Development based on public water supply system??? Environment Consideration….  Importance to sea facing or sustained fresh water availability?
  17. 17. 21
  18. 18. Effective management… Need for a comprehensive study on Chennai’s groundwater resources Mapping of Aquifers – Aquifer Potential – Recharge sources – Safe Yield estimation – Conservation and Management Conducting Groundwater Studies prior to construction   Geology, Hydrogeology, Geophysical Surveys Part of EIA – (Safe, Critical, Semi Critical, Over Exploited) Identifying potential groundwater sources within the site Selection of suitable drilling technique Borehole diameter
  19. 19. Effective management …. Record on Wells, drilling, well designing and construction – to record lithology and decide slot position Well the development and yield measurement through V notch plate Water level measurement after well drilling / development Selection of suitable pump based on the total working head, yield of the borewell and water level Well completion report containing all the above details
  20. 20. Effective management …. Provision of space, atleast to drill a borewell in future in the rest of identified potential pockets. Dug wells still a viable option at localities – case of Selvaraj Nagar, Urapakkam; Ramapuram Tapping shallow zone during post monsoon by provision of slots in borewell casing Shallow water table zones with clayey Soil Safe disposal of waste water during construction
  21. 21. Do’s and Do’nts…. Constant depletion of water table is an indication of Over exploitation of GW sources Reduced recharge Sustaining the water table fluctuation through RWH and GWR&R to avoid dwindling of water table Periodic water quality analysis

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