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) Social Mobilization

ii) Design

ii) 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 6.0 M 9.0 M

Type of Surplus Weir Weir

Material Used Random Rubble

Random Rubble

Height of body wall 1.50 M 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 WellsSl.No

Description Depth of Well

Earth Dia Pipe casing Dia

1 Annpakkam Recharge well

150feet 16 inch 12 inch

2. Pulichapallam Recharge Well

150feet 16 inch 12 inch

3. Vanur Observation well (Upstream)

70 meter 8 inch 4 inch

4 Vanur Observation well (Down stream)

70 meter 8 inch 4 inch

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 09Mar 09

Vanur check dam 1 -5.25 -10.3

Vanur check dam 2 -22.5 -28.8

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.