Outline • What is Rainwater Harvesting (RWH)?

• Historical Development

• Why are they important? • Benefits of RWH

• Limitations and Disadvantages of RWH

• Design of RWH

• Case Studies

• References and Links

• Q&A

What is Rainwater Harvesting?

Historical Development Gansu Province, Central China (4000 BC): Clay pots and

bottle-shaped water cellars to store rooftop rainwater

Baluchistan, India (3000 BC): simple stone-rubble structures for impounding rainwater

India Subcontinent and Thailand (2000 BC): tradition of rainwater harvesting systems

Khadins and ahar (large bunds used to collect surface runoff) or sailabas or kuskabas

Tankas (pits lined with lime) and kundi (concrete saucer shaped catchment to store in cistern) in Thar Desert

Negev Desert, Israel (2000 BC): cisterns for storage of hillside runoff

Historical Development Palace of Knossos, Greece (1700 BC): sophisticated

collection and storage system

Romans took technology from Phoenicians and Carthaginians and improved their cities with it (600 BC)

Large Cisterns found in Northern Egypt still in use (0 AD)

Mexico (300 AD): Chultuns (ground catchment systems)

Istanbul, Turkey (550 AD): Yerebatan Sarayi, the largest cistern in the world

Venice (700 AD-1500 AD): historical records shows rooftop collection and storage was principal water source

Historical Development Bermuda (1628 AD): roof cathment systems (now required

by law)

France (1703 AD): plan presented to Academy of Science included a provision of rainwater cistern with a sand filter in every house

Gibraltar (1869 AD): Rooftop tanks required by public ordinance

Historical Development Iran: abanbars (conical dome shaped structures to house

communical cisterns)

Sub-Saharan Africa: rooftop rainwater catchment systems with storage in jars and pots

Kalahari bushmen stored water in ostrich eggs only to collect them in times of drought

East Coast Africa: djabirs (traditional roof and ground catchment systems) introduced by Arab traders and settlers

Northeastern Brazil: hand dug cisterns made from lime mortar introduced by the Portuguese

South Pacific Island and Hawaii: households are currently required to have rainwater catchment systems built into their homes

Why are they important? Average annual rainfall over land amounts to 119,000 cubic

kilometers per year (or 20% of global-wide rainfall)

All of our water comes from rainfall.

1.4 billion people currently lack access to safe drinking water

2.3 billion people lack basic sanitation

7 million people die each year from disease linked to water

By 2025, the demand for fresh water will be 56% more than is currently available from what current trends shows

Urban water withdrawals typically range from 500-800 liters per day per person for developed nations and 50-100 liters per day per person for developing nations and 10-40 liters per day per person in water scarce regions of developing nations

Why are they important? Effects on Global Warming is changing the rainfall

patterns. Global Warming will produce more water vapor in the air which means more intense storms.

Also means in places where they get little rainfall will get less rainfall but will be in a monsoon way (intense storm followed by longer dry days). Places with high rainfall will get more rainfall also in a monsoon way.

It is predicted that annual average runoff and water availability will decrease by 10-30% over dry regions at mid-latitudes and in the dry tropics while increasing by 10-40% at high latitudes and in wet tropical areas by 2050.

Benefits of RWH Great Water Quality

Contains no hardness and very little dissolved solids (TDS) Is acidic to a pH of 4.5-5.5 because of atmospheric pollutants (sulfuric

and nitric acids) No chance for bacterial contamination until it hits the ground or roof

That means the catchment area must be clean before or during a rainfall event

Reduces Stormwater Runoff Floods can be mitigated in urban areas Decrease in loss of sediments and nonpoint pollution

Free for anyone There is more water than cities can do with it

Greater Awareness to how we use the water Confidence from giving the sense of water security

Construction is Low Tech and can be made of local materials

Costs of RWH Increased monetary cost per unit of water than conventional

sources The tank or cistern is the largest source of the monetary cost (typically

$0.50-2.25 per gallon collected)

Maintenance Rooftop must be cleaned of large debris before major rainfall event

The gutters and downspouts must be cleaned and inspected for repair

Filters must be cleaned before and after major rainfall event

Tanks must be inspected and cleaned (confined space issues) Preferably use pumps to remove sediments from bottom of tank

This only needs to be done rarely (once an decade)

Household members must be educated to perform the basic maintenance work

This effort is to reduce the potential for bacterial contamination

Limitations of RWH Requires land to place tanks (either above or below

ground) and a rooftop or catchment area to catch the rainfall Poor urban areas will have the greatest need for water

but no place or money to build such a project

If the amount of dry days between rainfall events * water usage per day is greater than the amount of water in the tank, then you will have days without water! Solution: Backup system of potable water lines or get a

larger catchment area and tank

Limitations of RWH Rainfall patterns are not an exact science. It is based

from predictions based from data of previous events.

Mosquito and Animal Control

If mosquitos are present, assume leak. Plug the leak and treat the water with kerosene

System must be per household basis giving the responsibility of the household to do the maintenance

Community systems tend to not work because of confusion to who is responsible

People can fall off rooftops cleaning the roof and gutters

8 Principles 1. Begin with long and thoughtful observation

2. Start at the highpoint of your watershed and work your way down

3. Start small and simple

4. Spread and infiltrate the flow of water

8 Principles 5. Always plan for an overflow route, and manage that

overflow water as a resource

6. Maximize living and organic groundcover

7. Maximize beneficial relationships and efficiency by “stacking functions.”

8. Continually reassess your system: the “feedback loop.”

Water Harvesting Ethics 1. Care of the Earth

2. Care of the People

3. Reinvestment of Surplus Time, Money, and Energy

Overview Systems are composed of:

Catchment Area (i.e. roof)

Water Conveyance (i.e. gutters and PVP pipes)

Filtration (i.e. first flush diverters and debris screens)

Optional: Treatment (UV and microfilters)

Storage (i.e. tanks and cisterns)

Outflow (i.e. valves and taps)

Catchment Area Roof catchments

Almost any hard or impervious non-toxic roof surface materials like:

corrugated iron, plastic, tile, asbestos sheet, slate, and thatch (some palms)

cant use wood, lead, zinc, and thatch (all grasses and some palms)

Can only use certain non-toxic coatings

NSF International Protocol P151

Catchment Area Ground Catchments

Cement or Tarmac-covered surfaces

Compacted Sand

Rock Catchments

Rock Dams

Other

Groundwater Dams (sand river storage)

Earth Dams (Hafirs)

Fog and Snow Catchment

Water Conveyance Gutters and Downspouts

Materials: metal, plastic, cement, wood, PVC, and bamboo

Can be 5-15% of total cost of system

Gutters must be sloped to downspout at least 1/16” per 1’

Follow the Uniform Plumbing Code unless local rules and regulations specify otherwise

1 cm^2 crosssectional area per 1 m^2 of roof area

Splash Guards for high rainfall events to curb loss

Filtration Devices for filtering roof debris for sanitary purposes

Guttersnipe

Simple metal screen on entrance of downspout

First Flush Diverters

Rule of Thumb: 1-2 gal for every 1,000 ft^2 of roof area

Purpose: initial volume of water will carry almost all sediments (screen filtrate) on roof

Roof Washer

30-50 gallon tank with external leaf strainer and internal screen or filter

Filtration

Storage Type of Above Ground Tanks

Ferrocement

Brick and Block

Reinforced concrete

Metal (Corrugated Steel or Galvanized Steel)

Plastic

Polyethylene and Polypropylene

Fiberglass

PVC

Wood

Storage Types of Cisterns

Ferrocement hemispherical tanks

Excavated water cellars

Brick and Concrete Blocks

Use of liners

Butyl Rubber and Polythene sheeting

Clay Liners

Storage

Storage Above Ground Tanks

Requires foundation (earthen gravel or concrete) pad and anchoring

Gravity flow (no pumping needed)

Lower cost

Easier to detect leaks

Elevated water temperature

Must be opaque to prevent algae growth

Usually lower volumes than cisterns

Storage Cisterns

Must be far away from septic and wastewater systems to prevent contamination

Higher Cost due to excavation of soil

Requires pumping to access water

Difficult to detect leaks

Cooler and protect water from freezing

Usually higher volumes than above ground tanks

Soil acts as a foundation for water

If groundwater level is high and tank is empty, cistern will float

Storage Other

Dry vs. Wet Conveyance

Overflow

Multiple Tank Connections

Rule of Thumb: 1” of rainfall on 1’ of roof area = 6/10 gal of water

Outflow Best water quality in tank is near the water level of

tank

Use hose with floater connected to tap (inside tank)

Tap or Faucet

Use pump and hose to push water to large distances

Can be used for agricultural uses: drip irrigation

EWB RWH Projects

Plastic Tank

Corrugated Steel Tank

Oil Barrel

Ferrocement Tank

Thai Jar

Sri Lankan Pumpkin Tank

Mud Tank

Plastic Tube Tank

Fabric Tank/Bamboo&Plastic Film Tank

Crate Tank

Tarpaulin Tank

Brazil Brick-Lime Cistern

Brazil Plate Tank

Underground Brick Dome Tank

Partially Below Ground Brick Tank with Ferrocement/Thatch Cover

Stabilized Soil Blocks Tank

Rammed Earth Tanks

Website Links and Literature

Literature Resources Rainwater Harvesting for Drylands and Beyond

Volumes 1 & 2 by Brad Lancaster

Rainwater Catchment Systems for Domestic Supply by John Gould

Water Storage, Tanks, Cisterns, Aquifers, and Ponds by Art Ludwig

ARCSA Level 200 Workshop: Rainwater Harvesting System Planning (1/2010)

Roofwater Harvesting: A handbook for Practitioners by T.H. Thomas and D.B. Martinson

Education http://rainwaterharvesting.tamu.edu/

http://www.harvestingrainwater.com/

http://www.irc.nl/page/37471

http://www.rainwatercollection.com

http://rwhdigest.com/

http://www.harvesth2o.com/

Case Studies http://www.uoregon.edu/~hof/S01havestingrain/i

ndex.html

http://www2.warwick.ac.uk/fac/sci/eng/research/civil/dtu/rwh/

http://www.cd3wd.com/

http://www.oas.org/dsd/publications/Unit/oea59e/begin.htm#Contents

http://www.watercare.org

Other Education http://www.rainwaterharvesting.org/

http://www.rainharvesting.com/

http://rainwaterclub.org/

http://www.oaecwater.org/education/roofwater-harvesting-booklet

http://www.appropedia.org/Rainwater

http://www.wateraid.org/uk/what_we_do/sustainable_technologies/technology_notes/246.asp

Professional Organizations http://www.arcsa.org/

http://www.eng.warwick.ac.uk/ircsa/

http://www.irha-h2o.org/

State and Local Manuals of RWH http://www.twdb.state.tx.us/iwt/rainwater.asp

http://www.hawaiirain.org/downloads/catchment.php

http://www.dca.ga.gov/development/ConstructionCodes/

http://www.cabellbrandcenter.org/

http://www.ci.tucson.az.us/water/harvesting.htm

http://sfwater.org/mto_main.cfm/MC_ID/14/MSC_ID/361/MTO_ID/559

http://www.portlandonline.com/bps/index.cfm?a=bbehfa&c=ecbbd

Miscellaneous http://www.werf.org/livablecommunities/

http://www.win-water.org/

http://www.bcwaternews.com/

http://www.bluegold-worldwaterwars.com/

http://www.pragya.org/water.htm

http://www.iirr.org/

http://knowyourh2o.blogspot.com/

References not listed http://www.unesco.org/water/wwap/wwdr/

http://www.lifewater.org/

http://www.rwsn.ch/

http://practicalaction.org/practicalanswers/

http://www.gdrc.org/uem/water/rainwater/introduction.html

http://cawalup.urbanocean.org

http://www.greywater.com

RWH Local Action http://larainwaterharvesting.org/

http://www.h2o-me.com/

http://www.treepeople.org

http://www.rainthanks.com/

http://www.whollyh2o.org/

http://www.greywateraction.org/

http://www.sandiego.gov/thinkblue/programs/spprojects/rainbarrels.shtml

http://www.victorygardenssandiego.com/