Rainwater harvestingRainwater harvestingMs Ms KokilKokil Gupta Gupta

Research AssociateResearch Associate

TERITERIKokilgKokilg@@teriteri.res.in.res.in

International training workshop on “Key vulnerabilities in small island developing states: scope for technology cooperation with India”

Session II: Water availability and quality

22nd August, 2005

River water, lakes and ponds, water in wells and below the River water, lakes and ponds, water in wells and below the ground, canal water, tap water, even bottled waterground, canal water, tap water, even bottled water

-- the source of all water is the source of all water is RAINRAINThe principle of collecting and The principle of collecting and using precipitation from a using precipitation from a catchments surface is termed as catchments surface is termed as Rain water harvesting.Rain water harvesting.In ancient Rome, residences were In ancient Rome, residences were built with individual cisterns and built with individual cisterns and paved courtyards to capture rain paved courtyards to capture rain water .water .As early as the third millennium As early as the third millennium BC, farming communities in BC, farming communities in BaluchistanBaluchistan and and KutchKutchimpounded rain water and used it impounded rain water and used it for irrigation dams.for irrigation dams.

Naadis, Rajasthan, TERI 2001

Underground Tankas

Growing Need For Rain Water HarvestingGrowing Need For Rain Water HarvestingWIthWIth piped water supply, the piped water supply, the relevance of this decentralized relevance of this decentralized system has got lost.system has got lost.

Inadequate surface water reserves as Inadequate surface water reserves as well as inequitable water well as inequitable water distribution distribution

growing dependence on ground growing dependence on ground waterwater

Reduction inReduction in nfiltrationnfiltration of rain water of rain water into the subinto the sub--soil soil

Increased surface runoff choking Increased surface runoff choking drains and flooding in urban areas.drains and flooding in urban areas.

To utilize a large amount of high quality water, which otherwiseTo utilize a large amount of high quality water, which otherwise runs off or runs off or gets lost through evaporation.gets lost through evaporation.

Can be used to provide water in times of distress/ supplement muCan be used to provide water in times of distress/ supplement municipal nicipal supplysupply

Recharge the ground water and Improve the quality of Ground wateRecharge the ground water and Improve the quality of Ground water by r by dilution.dilution.

In addition, arrest sea water intrusion in coastal areas.In addition, arrest sea water intrusion in coastal areas.

How can Rain Water Harvesting help??How can Rain Water Harvesting help??

RWH RWH –– Design parametersDesign parametersEnd use/ purposeGround water recharge/ augment available supply/ arrest runoff

Catchment sizeIn urban areas: paved areas, rooftops, open spaces and in countryside: at water shed level

Climatic conditionsRainfall pattern & rate of evaporation

Surface/ Sub Surface Storage: Direct MethodSurface/ Sub Surface Storage: Direct MethodIn this type of rainwater harvesting method, the structures collIn this type of rainwater harvesting method, the structures collect water directly from ect water directly from the rain and use for domestic and irrigation purposes. In all rothe rain and use for domestic and irrigation purposes. In all rooftop rainwateroftop rainwater--harvesting systems, both small and large, the basic components harvesting systems, both small and large, the basic components are:are:

Rainfall(mm) 100 200 300 400

500 600 800 1000 1200 1400 1600 1800 2000Roof top area (sqm)

Harvested water from Roof top (cum)20 1.6 3.2 4.8 6.4 8 9.6 12.8 16 19.2 22.4 25.6 28.8 3230 2.4 4.8 7.2 9.6 12 14.4 19.2 24 28.8 33.6 38.4 43.2 4840 3.2 6.4 9.6 12.

816 19.2 25.6 32 38.4 44.8 51.2 57.6 64

50 4 8 12 16 20 24 32 40 48 56 64 72 8060 4.8 9.6 14.4 19.

224 28.8 38.4 48 57.6 67.2 76.8 86.4 96

70 5.6 11.2 16.8 22.4

28 33.6 44.8 56 67.2 78.4 89.6 100.8 11280 6.4 12.8 19.2 25.

632 38.4 51.2 64 76.8 89.6 102.4 115.2 128

90 7.2 14.4 21.6 28.8

36 43.2 57.6 72 86.4 100.8 115.2 129.6 144100 8 16 24 32 40 48 64 80 96 112 128 144 160150 12 24 36 48 60 72 96 120 144 168 192 216 240200 16 32 48 64 80 96 128 160 192 224 256 288 320250 20 40 60 80 100 120 160 200 240 280 320 360 400300 24 48 72 96 120 144 192 240 288 336 384 432 480400 32 64 96 12

8160 192 256 320 384 448 512 576 640

500 40 80 120 160

200 240 320 400 480 560 640 720 8001000 80 160 240 32

0400 480 640 800 960 1120 1280 1440 1600

2000 160 320 480 640

800 960 1280 1600 1920 2240 2560 2880 32003000 240 480 720 96

01200 1440 1920 2400 2880 3360 3840 4320 4800

Runoff Available for Harvesting from Roof top

Assuming coefficient of run off for roof top as 0.8

Recharge to ground water: Indirect methodRecharge to ground water: Indirect method

1. Recharge pits2. Recharge trenches3. Recharge shaft4. Trench with recharge well5. Shaft with recharge well6. Recharge through abandoned hand pumps7. Recharge through abandoned tube well8. Recharge well9. Injection well10. Percolation tank11. Check dam12. Gabion bund13. Sub-surface dyke14. Recharge wells/ Tidal Regulators to arrest

Salinity Ingress in Coastal Aquifers

While storage of rain water on surface is a traditional techniquWhile storage of rain water on surface is a traditional technique and structures e and structures used were underground tanks, ponds, check dams, weirs, etc. Rechused were underground tanks, ponds, check dams, weirs, etc. Recharge to ground water arge to ground water is relatively a new concept of rain water harvesting and the stris relatively a new concept of rain water harvesting and the structures generally used uctures generally used are:are:--

(CGWB)

Recharge through abandoned bore well. Approximate cost: Rs.1500 – 2500/-

--For recharging the shallow as For recharging the shallow as well as deeper aquifers.well as deeper aquifers.

-- Construction of lateral trench Construction of lateral trench of 1.5 to 3 m wide & 10 to 30 m of 1.5 to 3 m wide & 10 to 30 m ..

-- One or more bore wells.One or more bore wells.

-- lateral trench is back filled with lateral trench is back filled with boulders, gravels & coarse sand. boulders, gravels & coarse sand.

TRENCH WITH RECHARGE WELLTRENCH WITH RECHARGE WELL

-- Approximate cost : Approximate cost : RsRs. 2000 . 2000 ––4000 per m. run of trench4000 per m. run of trenchRsRs. 20000 . 20000 –– 35000 per recharge well35000 per recharge well

SHAFT WITH RECHARGE WELLSHAFT WITH RECHARGE WELL

-If aquifer is available at greater depth say 20 or more than 20 metre.

-Shallow shaft of 2 to 5 m dia and 5 to 3 to 5 m deep depending upon availability of runoff.

-Inside the shaft a recharge well of 100 to 300 mm dia is constructed for recharging the available water to the deeper aquifer.

-At the bottom, filter media is provided to avoid choking of the recharge well.

-Approximate cost: Rs. 50,000

-Constructed across small streams having gentle slopes

-Feasible both in hard rocks as well as in alluvial formations.

-The site selected should have sufficient thickness of permeable bed or weathered formation to facilitate recharge of stored water within short spell of time.

-The water stored in these structures is mostly confined to stream course and height is about 1 to 5 meters.

-Approximate cost:Rs. 50000 –300000/-

RECHARGE THROUGH CHECKDAMSRECHARGE THROUGH CHECKDAMS

LAKSHADWEEP

BAY OF BENGAL

INDIASCALE (km) 0 400 800

KERALA

ARABIANSEA

Rain water harvesting : Selected examples

Lakshadweep islands, a chain of 36 islands Lakshadweep islands, a chain of 36 islands is located 220 to 440 Km from the coastal is located 220 to 440 Km from the coastal city of city of CochiCochi in Kerala state, India.in Kerala state, India.

Though fully surrounded by water, fresh Though fully surrounded by water, fresh water availability both surface and ground water availability both surface and ground water sources is limited.water sources is limited.

There is growing dependence on ground There is growing dependence on ground water with increasing threat of sea water water with increasing threat of sea water intrusion. intrusion.

Considering the growing threat, the Central Water Resources DeveConsidering the growing threat, the Central Water Resources Development and lopment and Management (CWRDM), Management (CWRDM), uderGovtuderGovt. of Kerala initiated the project “Management . of Kerala initiated the project “Management of Fresh water sources in Lakshadweep”, funded by Indo Canada Enof Fresh water sources in Lakshadweep”, funded by Indo Canada Environment vironment Facility (ICEF).Facility (ICEF).

Aim: •GW management through conservation of sub surface flows using sub surface check dams;• reducing over exploitation of ground water sources and •protecting existing tanks and ponds.•rainwater harvesting by the construction of structures of roofs top collection and storage in underground ferro-cement tanks and line ponds.

Salient features of the project

Capacity building through infrastructure development , training and awareness generation etc form an integral part of the project.

Cost of ferrocement tank (10,000 lts) = 18,000 INR

Initiatives in Chennai, India

1,200 mm

One of the largest metros in India, Chennaireceives about 1200 mm rainfall annually.

Water is brought from a distance of 235 km (Veeranam lake) and now planning to go farther 300 Km (Veeranam extension project) at the cost of Rs 300 Crore.

At the same time, 46 to 89 per cent of population depends on groundwater depending on the income levels.

2000 1996 19901972

42 20 3.0Distance from the sea coast in metres

Before After

Rejuvenation of temple tanks• Rain water harvesting made mandatory through law:

1987: the groundwater regulation act restricted commercial explo1987: the groundwater regulation act restricted commercial exploitation itation 2003: RWH compulsory for all the buildings (existing and new) in2003: RWH compulsory for all the buildings (existing and new) in all cities, towns all cities, towns and municipalities.and municipalities.

Direct storage structures constructed all over the city at indiDirect storage structures constructed all over the city at individual and vidual and community level.community level.

One of the initiatives taken up by the Rotary club of Chennai isOne of the initiatives taken up by the Rotary club of Chennai is desilting and desilting and rejuvenation of the traditional temple tanks. This has not only rejuvenation of the traditional temple tanks. This has not only made the area water made the area water secure but is also enabling revival of dug wells in surrounding secure but is also enabling revival of dug wells in surrounding areas.areas.

The cost of desilting tanks ranges between 5,00, 000 to 10,0000The cost of desilting tanks ranges between 5,00, 000 to 10,0000 INR.INR.

Issues Issues wrtwrt to water in SIDSto water in SIDSSmall island developing states continue to face water managementSmall island developing states continue to face water management and and water access challenges, caused in part by deficiencies in waterwater access challenges, caused in part by deficiencies in water availability availability and partially by growing demands. The common issues include:and partially by growing demands. The common issues include:

Limited natural fresh water resources: Antigua& Limited natural fresh water resources: Antigua& barbudabarbuda, Bahamas, Nauru, , Bahamas, Nauru, SingaporeSingaporeGrowing dependence on ground water resource: Maldives, Growing dependence on ground water resource: Maldives, TongoTongoSaline water intrusion: MaldivesSaline water intrusion: MaldivesPollution of water resources ( surface water; ground water and cPollution of water resources ( surface water; ground water and coastal oastal area):Belize, Cuba, Guyana, Jamaica coast, Samoaarea):Belize, Cuba, Guyana, Jamaica coast, SamoaHeavy surface and sub surface runoff: Barbados Heavy surface and sub surface runoff: Barbados

Rainwater harvesting is most critical for islands where there are limited inland streams and rivers, ground water is limited or not potable or there is heavy runoff.

In an number of low-lying islands where rainwater catchments constitute the major part of the water supply , rain water system s are being extensively used.

In St. Lucia,RW collection is done using used oil drums/ plastic tanks/ underground concrete tanks.

Rooftop and purpose-built catchments also are common place in the Bahamas. One settlement (Whale Cay) has a piped distribution system based on rooftop-collected water.

Rain Water Harvesting practices in SIDSRain Water Harvesting practices in SIDS

… Not sufficient wrt growing demands and over all potential

Defined strategic master plan catering to both long term and short term goalsDemand Side managementConserving whatever water we have and harvest more water.Decision support system

Technologically, economically and financially feasible sound planning is required based on - a reliable data base, - modeling tools to describe the regional flow pattern, - proper definition of goals and related criteria and - monitoring network.

Enabling environment - Adoption by Government bodies, institutions such as schools and hospitals to be self –reliant.- Community participation :in terms of involvement as well as financial contribution to develop a sense of ownership.- Appropriate legislative and regulatory tools to be developed and integrated.

WAY AHEAD….WAY AHEAD….

Thanks…Thanks…

For further information:

Kokil Gupta

Water Resources Policy and ManagementPolicy Analysis DivisionTERII HC ComplexLodhi RoadNew Delhi – 110003Mail: Kokilg@ teri.res.in

Scope of experience sharing and technology adoption….Scope of experience sharing and technology adoption….