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Unit 1Introduction

What is water harvesting ?

What are the benefits of water harvesting ?

What are the limitations of water harvesting ?

For which areas is water harvesting suitable ?

Where was water harvesting used traditionally ?

Where is water harvesting used at present ?

Introduction

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1.to be directly conveyed to a

cropping area and stored in the soil

profile for immediate uptake by thecrops (i.e. runoff farming systems) or

2.to be stored in a water reservoir for

future productive uses

domestic consumption

livestock watering

irrigation

aquaculture

What is water harvesting?

Run-on area

= cropping area

or storage mediaRunoff area

= catchment area

The principle

A process of collecting runoff from a catchment area

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To secure water supply in dry areas where other water

resources (surface water or ground water) are not

available or are uneconomical to develop, in order to:

increase the productivity of arable and grazing land which suffers frominadequate rainfall

increase yields of rainfed farming

minimize the risk of crop failure in drought- prone areas

combat desertification by afforestation, fruit tree planting or agroforestry supply drinking water for animals

supply domestic water

The main goals of water harvesting

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Storage in thesoil profile

Annual crops/ trees / pasture

Run-on area

Irrigatedcrops

Runoff area

(catchment)

water

water

water

Storagemedia

Storagemedia

The principle of water harvesting

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The principle of water harvesting

Macrocatchment

Floodwater harvesting

Microcatchment

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Roof tops

Courtyards, streets, public squares

Catchment area

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Small ground surfaces

untreated

treated

Catchment area

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Slopes

untreated

treated

Catchment area

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Large, untreated catchment areas which feed

seasonal water courses

Catchment area

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Roof tops

Courtyards,

streets, public

squares

Catchment areas

Slopes

untreated

treated

Large

catchment areas

feeding seasonal

courses

Small groundsurfaces

untreated treated

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Underground storage

Soil

Sediments

Storage media

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Underground storage

Cisterns

Storage media

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Storage above ground

Tanks and jars

Storage media

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Storage above ground

Ponds

Storage media

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Storage above ground

Reservoirs

Storage media

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Underground storage

Soil

Sediments

Cisterns

Storage media

Storage

above

ground

Tanksand jars

Ponds

Reservoirs

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What are the benefits of water harvesting ?

WATERHARVESTING

Water conservation(tapping unused water)

Soil conservation(for macrocatchments

on cropping area only) =less soil erosion

Higher productivity(higher yieldsand less risk)

Pastureimprovement =more livestock[= moredesertification ?]

Improvedre-/afforestation =less desertification

Crop production inareas where it isnormally not feasible

Groundwaterrecharge = morewater available

Suppression of salinityin soil = moreproductive land

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What are the limitations of water harvesting?

Climatic risks still exist

No guarantee for high yields

Methods scientifically not well established

Very often limited experience of extension service

Possible conflicts between people upstream and downstream

Possible harm to fauna and flora

Larger schemes and structures are difficult to implement (need

acceptance by people, political backing and financial support)

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Arid, semi-arid and semi-humid areas

Where water demand of crops is higher than supply because of

low rainfall and / or

uneven seasonal distribution of rainfall and / or

high temperatures (high evapotranspiration)

Where rainfall exceeds 150 mm /year, if rain falls in

the cool season

Where rainfall exceeds 200 mm /year, if rain falls in the hot seasonand if no storage in ponds or reservoirs is provided

For which areas is water harvesting suitable?

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Where was water harvesting

used traditionally?

Asia

Jordan (since 7000 BC)

Mesopotamia (4500 BC)

Palestine (2000 BC-1200 AD)

Yemen (since 1000 BC)

Pakistan

India

Sri Lanka

China

America

Arizona and New Mexico(1000 AD)

Africa Tunisia: `Meskats, Mgoud

and Jessours

Somalia: `Caag and `Gawansystems

Sudan: `Haffire, `Teras etc.

Burkina Faso: Pits

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Examples:

Morocco

Algeria Egypt

Chad

Mali

Niger

Sudan

Ethiopia

Somalia

Kenya

Tanzania

Zambia

Where is water harvesting usedat present in Africa ?

WH welldocumented

WH mostprobablyapplied

Othercountries

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Some examples:

Niger, Ader Doutchi Maggia area (Haussa): rock bunds,

stalks and earth for water diversion in fields

Burkina Faso (Mossi): rock bunds and stone terraces

Mali : stone constructions, macrocatchments

Chad, Ouaddai area: small check dams

Burkina Faso: pitting (Zay), rock bunds

Kenya, Turkana and Baringo area: many types

Many more traditional water harvesting systems exist

In sub-Saharan Africa, water harvesting is

still far below its potential!

Where is water harvesting used

in sub-Saharan Africa?

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Othercountries

WH mostprobablyapplied

WH welldocumented

Where is water harvesting used

at present in Asia? (I)

Yemen

Saudi Arabia

Iran

India

China

Pakistan

AfghanistanSyria

Jordan

Oman

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Where is water harvesting used

at present in Asia ? (II)

China

Thailand

VietnamLaos

MyanmarIndia

CambodiaPhilippines

WH mostprobablyapplied

WH welldocumented

Othercountries

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Water harvesting

Is the collection and concentration of runoff water

Can produce crops in areas with insufficient rain

Can improve pasture and crop yield

Is suited for arid, semi-arid and semi-humid regions

Has positive side effects on: water and soil conservation

Consists of a runoff area and a run-on area

The water is stored in the soil, in cisterns or reservoirs

Has been used traditionally in many (semi-) arid areas of the world

Its use is still far below its potential!

Summary

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