Transcript Project Title - Auroville Water harvest

HILDEN PROJECT PRESENTATION
NAME OF THE PROJECT
Restoration of Traditional Rainwater Harvesting Tank
and the Recharge of the Aquifer in the Vanur Taluk,
Villupuram District, Tamil Nadu, INDIA
Funded by
Implemented By
CITY OF HILDEN
AUROVILLE WATER
HARVEST
Phases of Hilden
• First Phase 2006-2007
• Second Phase 2007-2008
Project Area
Parts of the Vanur Aquifer near the
villages of:
1. Vanur
2. Annpakkam
3. Pulichapallam
LOCATION MAP
Aim of Project
• To promote the way their ancestors used
water sustainability.
• To improve groundwater recharge
• To use innovative technologies to recharge
the aquifer.
• To capture more rainwater
• To try and protect the coastal area from
salt water intrusion of our aquifer
Objectives
• To identify where encroachment of communal water harvesting
structures has taken place and to work with the farmers to remove
the encroachment
• To assess the present status of the traditional heritage rain water
harvesting structures and to rehabilitate them.
• To raise awareness amongst the villagers about the need to use
water sustainably like their ancestors did.
• To rehabilitate existing tanks to enlarge holding capacity
• To restore channels to increase holding capacity of tanks
• To design and build new check dams and to capture rainwater and
to recharge the ground water
• To improve the irrigation capacity of dry land farmers by the check
dams and rehabilitated tanks
• To drill some recharge and observations wells so that we can
monitor how successful (or not) the project is.
Rationale of the Project
• Test have found saltwater intrusion in parts of the Aquifer
• It is imperative that urgent action is taken to try and mitigate this
pressing problem.
• The extraction rate is up to 15x more than the annual average
recharge of the region
• Traditionally, Tamils created a network of tanks (dams) and channels
to harvest all the rainwater. This tradition is dying so Harvest is
working to preserve this dying art
• Harvest has been restoring these traditional tanks and with the City
of Hilden is either restoring or building new rainwater harvesting
structures.
• Highly silted tanks contribute to less water holding capacity
• Abusive agricultural irrigation methodologies, the poor state of the
traditional rainwater harvesting structures and inadequate water
conservation practices perpetuate falling water tables
Phase of work
The project work will be carried out in one year. We
will follow the four activities below
i)
ii)
ii)
Social Mobilization
Design
Implementation
iii)
Monitoring
Social Mobilization
• This component is a Key activity, (however not part of
the Hilden project). We received funding from another
NGO to cover this area of the project. We mention it
here just to give Hilden an overview and importance of
the project.
• We work to empower the villagers to be part of the
development process via education, shared decision
making, ownership, etc.
• We have worked with these user groups to take
responsibility for maintaining the tanks and check dams.
Physical implementation
• 2 Check dams
• One Pond and an outlet weir
• Clearing channel of the odai for the Check
dams
• 2 recharge wells
• 2 sand filters
• 2 observation wells
Checkdams
Purpose of the Checkdams
• The purpose of the construction of the
check dams is to retain all rainwater runoff
in the area
• This captured rainwater would percolate
back into the aquifer
Methodology for Checkdams
• Identify Catchment Area and where
checkdams will be situated
• Design structures considering runoff,
Depth of Storage and Type of Soil
• Clear the odai (channel) to enhance water
flow
• Monitoring water levels before and after
monsoon
Specification of Checkdams
Description
Pulichapallam Annpakkam
Length of body wall
Type of Surplus
6.0 M
Weir
9.0 M
Weir
Material Used
Height of body wall
Random
Rubble
1.50 M
Random
Rubble
1.20 M
Width of body wall
0.45M
0.45M
Protection wall
Wing wall
Wing wall
Impact of Check dams
• Increased the ground water recharge and stabilized the
ground water status near the check dams
• This would enhance the agricultural productivity near the
check dam and rehabilitated tanks
• Water level raised in surrounding open wells (depends
on the fillings. Last year both check dams had 10 fillings)
• Soil erosion was controlled by strengthening the side
bunds of the odai
• The larger volumes of water percolating into the aquifer
assist in mitigating salt water intrusion
• Reforestation of tank and check dam walls assist in
reduced runoff and better recharge
Outcomes
• 1.540 cubic meter earthwork was taken at
pulichapallam. 0.05mcft water storage
increased(14.15 Lakhs liters)
• 4.225 cubic meter earthwork was taken thus by
increasing storage by 0.15 mcft (42.460,000
liters)
• 300 meter bund was strengthened both at
Pulichapallam and Anpakkam
• 500 meter of odai was cleared for free flow at
both Pulichapallam and Anpakkam
Recharge Pond - Innovative
• Two Different storage level in One Tank
• Water from the catchments enters into the first pond
which was built to be lower than the second pond. So
most of the silt and sediment are deposited into the first
pond.
• The water reaches a certain height before it starts to fill
the second pond. The second pond due to its ingenious
design doesn’t fill up with sand and silt.
• The water from both tanks discharge into the aquifer
• During the heavy rains most of the water was captured in
all the series of tanks and dams. Less runoff will
overflow from the tank and via channels end up in the
Kaliveli (or sea).
Specification of Recharge Pond
•
•
•
•
•
•
•
•
Length of bund: 330 m
Deepest bed level: + 20.60 m (Above MSL)
Full tank level + 21.30 m (Above MSL)
Maxi. Water level: + 21.90 m
Catchments: 1,95 sqkm.
Nature of catchments: Average
Total annual rainfall 1.250mm.
Yield from the catchments: 0.131m3
Impact of Recharge Pond
• A Recharge pond is an artificially created
structure that captures water. The
subsurface is highly permeable so most
captured water percolates and recharges
the ground water (aquifer);
• Our monitoring of wells has seen a rise in
water table (see graph
below)
Recharge Calculation
Area of the Catchments
= 0.12sq.km
Rainfall infiltration factor
= 0.16
Total recharge in one filling = 0.12*0.16;
= 0.00192 mcum,
= 1920 cum,
= 1920000 liters.
Total no. of fillings in monsoon = 8 fillings
Possible recharge amount
= 8*1920000
= 15.360m3.
Outcomes of Recharge Pond
• 250 meters of bund was strengthened;
• Recharge is ensured;
• Monitoring the recharge of the observation
well on the upstream side was provided;
• Increase of 22.400 cubic meter capacity;
• 8 to 10 surrounding wells have benefited
from the extended capacity of the Vanur
outlet pond ??? From one or dams????
Monitoring
Monitoring Components for RECHARGE
1) Recharge well at Aanpakkam
2) Recharge well at Pulichaplaam
3) Observation well at Vanur recharge pond
(Upstream)
4) Observation Well at Vanur recharge pond
(Down stream)
5) Two Sand Filters for Two Recharge wells
Specification of Wells
Sl. Description
No
Depth of
Well
Earth Dia
Pipe
casing Dia
1
Annpakkam
Recharge well
Pulichapallam
Recharge Well
Vanur
Observation well
(Upstream)
150feet
16 inch
12 inch
150feet
16 inch
12 inch
70 meter
8 inch
4 inch
Vanur
Observation well
(Down stream)
70 meter
8 inch
4 inch
2.
3.
4
Monitoring water level
• At Vanur Recharge pond, post monsoon
Jan 09
35.4
52.65
Mar 09
40.45
58.90
Oct 08 Jan 09
Vanur check dam 1
-5.25
Vanur check dam 2
-22.5
Mar 09
-10.3
-28.8
Vanur check dam 1
Vanur check dam 2
Constraints
• For at least 2000 years Tamil’s have
practiced sustainable water management.
However with the advent of the Green
Revolution and the introduction of bore
wells the aquifers of the Third World have
been decimated. Will farmers change
their irrigation methodologies in time to
save the aquifers that aren’t salinated?
Water Dilemma
Farmers realise that borewells are causing their aquifers
to sink at an alarming rate. Yet their need to produce
crops (and make money and feed their families) makes
them continue to perpetuate the crash (saltwater
intrusion) of their aquifer. Will sanity prevail and they
take steps, initiated by NGOs, to change their course to
save the aquifer? Without rational water management
we will lose our aquifer like other areas of India.
Programs that are able to recharge the aquifer need to
work hand in hand with teaching organic farming which
reduce water consumption. These steps could hopefully
save our aquifer and the livelihood of the villagers in our
bioregion.
Conclusion
• We are happy to report that our data collection
after the (very good) monsoons has risen the
water table
• It is imperative that we restore or build new
check dams and recharge wells in the region to
assist the aquifer and the villagers of the Vanur
Block.
• This project can be a model project to show
others the way forward to save their aquifer if the
program works hand in hand with teaching
organic agriculture.