hilden presentation

8/3/2019 Hilden Presentation

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HILDEN PROJECT PRESENTATION

NAME OF THE PROJECT

Restoration of Traditional Rainwater Harvesting Tankand the Recharge of the Aquifer in the Vanur Taluk,Villupuram District, Tamil Nadu, INDIA

Funded by Implemented By

CITY OF HILDEN AUROVILLE WATERHARVEST


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Phases of Hilden

First Phase 2006-2007

Second Phase 2007-2008


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Project Area

Parts of the Vanur Aquifer near thevillages of:

1. Vanur

2. Annpakkam

3. Pulichapallam


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LOCATION MAP


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Aim of Project

To promote the way their ancestors usedwater sustainability.

To improve groundwater recharge

To use innovative technologies torecharge the aquifer.

To capture more rainwater To try and protect the coastal area from

salt water intrusion of our aquifer


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Objectives

To identify where encroachment of communal water harvestingstructures has taken place and to work with the farmers to removethe encroachment

To assess the present status of the traditional heritage rain waterharvesting structures and to rehabilitate them.

To raise awareness amongst the villagers about the need to usewater 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 checkdams and rehabilitated tanks To drill some recharge and observations wells so that we can

monitor how successful (or not) the project is.


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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) andchannels to harvest all the rainwater. This tradition is dying soHarvest is working to preserve this dying art

Harvest has been restoring these traditional tanks and with the Cityof Hilden is either restoring or building new rainwater harvestingstructures.

Highly silted tanks contribute to less water holding capacity Abusive agricultural irrigation methodologies, the poor state of thetraditional rainwater harvesting structures and inadequate waterconservation practices perpetuate falling water tables


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Phase of work

The project work will be carried out in one year. We

will follow the four activities below

i) Social Mobilizationii) Design

ii) Implementation

iii) Monitoring


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Social Mobilization

This component is a Key activity, (however not part ofthe Hilden project). We received funding from anotherNGO to cover this area of the project. We mention it

here just to give Hilden an overview and importance ofthe project.

We work to empower the villagers to be part of thedevelopment process via education, shared decisionmaking, ownership, etc.

We have worked with these user groups to takeresponsibility for maintaining the tanks and check dams.


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Physical implementation

2 Check dams

One Pond and an outlet weir

Clearing channel of theodai

for the Checkdams

2 recharge wells

2 sand filters 2 observation wells


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Checkdams

Purpose of the Checkdams

The purpose of the construction of thecheck dams is to retain all rainwater runoffin the area

This captured rainwater would percolateback into the aquifer


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Methodology for Checkdams

Identify Catchment Area and wherecheckdams will be situated

Design structures considering runoff,Depth of Storage and Type of Soil

Clear the odai (channel) to enhance waterflow

Monitoring water levels before and aftermonsoon


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Specification of Checkdams

Description Pulichapallam Annpakkam

Length of body wall 6.0 M 9.0 M

Type of Surplus Weir Weir

Material Used RandomRubble

RandomRubble

Height of body wall 1.50 M 1.20 MWidth of body wall 0.45M 0.45M

Protection wall Wing wall Wing wall


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Impact of Check dams

Increased the ground water recharge and stabilized theground water status near the check dams

This would enhance the agricultural productivity near thecheck dam and rehabilitated tanks

Water level raised in surrounding open wells (dependson the fillings. Last year both check dams had 10 fillings)

Soil erosion was controlled by strengthening the sidebunds of the odai

The larger volumes of water percolating into the aquiferassist in mitigating salt water intrusion

Reforestation of tank and check dam walls assist inreduced runoff and better recharge


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Outcomes

1.540 cubic meter earthwork was taken atpulichapallam. 0.05mcft water storageincreased(14.15 Lakhs liters)

4.225 cubic meter earthwork was taken thus byincreasing storage by 0.15 mcft (42.460,000liters)

300 meter bund was strengthened both at

Pulichapallam and Anpakkam 500 meter of odaiwas cleared for free flow at

both Pulichapallam and Anpakkam


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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. Somost of the silt and sediment are deposited into the firstpond.

The water reaches a certain height before it starts to fillthe second pond. The second pond due to its ingeniousdesign doesnt 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 inall the series of tanks and dams. Less runoff willoverflow from the tank and via channels end up in theKaliveli (or sea).


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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


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Impact of Recharge Pond

A Recharge pond is an artificially createdstructure that captures water. Thesubsurface is highly permeable so most

captured water percolates and rechargesthe ground water (aquifer);

Our monitoring of wells has seen a rise in

water table (see graph below)


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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 fillingsPossible recharge amount = 8*1920000

= 15.360m3.


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Outcomes of Recharge Pond

250 meters of bund was strengthened;

Recharge is ensured;

Monitoring the recharge of the observationwell on the upstream side was provided;

Increase of 22.400 cubic meter capacity;

8 to 10 surrounding wells have benefitedfrom the extended capacity of the Vanuroutlet pond ??? From one or dams????


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Monitoring

Monitoring Components for RECHARGE

1) Recharge well at Aanpakkam

2) Recharge well at Pulichaplaam3) Observation well at Vanur recharge pond

(Upstream)

4) Observation Well at Vanur recharge pond(Down stream)

5) Two Sand Filters for Two Recharge wells


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Specification of WellsSl.No

Description Depth ofWell

Earth Dia Pipecasing Dia

1 AnnpakkamRecharge well

150feet 16 inch 12 inch

2. PulichapallamRecharge Well

150feet 16 inch 12 inch

3. VanurObservation well

(Upstream)

70 meter 8 inch 4 inch

4 VanurObservation well(Down stream)

70 meter 8 inch 4 inch


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Monitoring water level

At Vanur Recharge pond, post monsoonJan 09 Mar 09

Vanur check dam 1 35.4 40.45

Vanur check dam 2 52.65 58.90

Oct 08 Jan 09 Mar 09

Vanur check dam 1 -5.25 -10.3

Vanur check dam 2 -22.5 -28.8


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Constraints

For at least 2000 years Tamils have

practiced sustainable water management.However with the advent of the Green

Revolution and the introduction of borewells the aquifers of the Third World havebeen decimated. Will farmers change

their irrigation methodologies in time tosave the aquifers that arent salinated?


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Water Dilemma

Farmers realise that borewells are causing their aquifersto sink at an alarming rate. Yet their need to producecrops (and make money and feed their families) makesthem continue to perpetuate the crash (saltwater

intrusion) of their aquifer. Will sanity prevail and theytake steps, initiated by NGOs, to change their course tosave the aquifer? Without rational water managementwe 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 whichreduce water consumption. These steps could hopefullysave our aquifer and the livelihood of the villagers in ourbioregion.


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Conclusion

We are happy to report that our data collectionafter the (very good) monsoons has risen thewater table

It is imperative that we restore or build newcheck dams and recharge wells in the region toassist the aquifer and the villagers of the VanurBlock.

This project can be a model project to showothers the way forward to save their aquifer if theprogram works hand in hand with teachingorganic agriculture.

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