Water Harvesting

Sangati CPR work group

Why is Water Harvesting especially important for India?

• In India, most water reaches the ground through rain. – In contrast, in Western countries (mid-latitude

regions), 50% of water coming down (precipitation) is in the form of snow

• Snow melts slowly and percolates into the ground and recharges ground water

• What about rain water?

Rain Water Pattern in India

• Total annual rainfall in India: 400 million hectare-meters (area x height)

• India’s area: 329 million hectares• If evenly spread, average height: 1.28m• Actual distribution:

– Highly skewed area-wise– Thar desert receives less than 200mm annually, while

Cherrapunji receives 11,400mm– But almost every part of India receives at least

100mm annually• Key: even 100mm annual rainfall sufficient if

harvested properly and where it falls

But….• Temporal distribution of rain in India also skewed• Rainfall in India seasonal (unlike Western countries)• Most of the country receives rainfall only for about 100

hours each year– Rough rule of thumb: #cm of rain = #hours rain received– E.g.: Jodhpur receives 40cm of rain in about 40 hours

• Half of this rainfall is precipitated in just 1/5 th of the total hours– E.g.: Jodhpur receives more than half its annual rain in about 8

hours• Natural implication of such skew:

– Most of the rain water lost due to runoffs– Unlike the west, very little water percolates into the ground– Hence, the importance of harvesting structures for local self-

sufficiency

Importance of Water Harvesting (contd.)

• Ground water exploitation in India is very high– Area irrigated by ground water has increased 5 times since

independence– Tubewells and borewells constructed primarily by larger farmers,

encouraged by cheap electricity drain ground water• Big dam projects have hardly had any positive impact

– Very few surface irrigation initiatives completed since independence

– Too expensive to complete (estimate: Rs. 60000 crore to complete all ongoing major irrigation projects)

– More importantly, displace communities, – Also reduce soil quality, lead to deforestation, all of which is

detrimental to ground water levels• To find out: what is the proportion of land irrigated by

ground water versus dams?

Importance of Water Harvesting (contd.)

• Traditional water harvesting systems have withstood the test of time– Hence, worth taking seriously, of course in the current context

and fully understanding their limitations• Example of the stellar success of traditional water

harvesting systems:– The city of Jodhpur, even though several hundred years old and

right in the middle of a desert, has never been evacuated for lack of water.

– The traditional water harvesting systems worked even in droughts when piped water supply failed

– Om Thanvi, a Rajasthan journalist found over a 45-day survey that

• In villages where traditional water systems were maintained and used, there was no scarcity of drinking water even during times of drought

• In villages which relied purely on piped supply, the drying up of the Rajasthan canal meant an acute water crisis

Water Harvesting Structures in the Thar Desert and Central Highlands• Urban/rural water harvesting structures:

– Tankas, Nadis, Talabs, Bavdis, Tanks, Rapats, Kuis, Virdas

• Rural water harvesting structures:– Kunds, khadins

Tanka

• Tankas (small tank) are underground tanks, found traditionally in most Bikaner houses. • Built in the main house or in the courtyard. • Circular holes made in the ground, lined with fine polished lime, in which raiwater was

collected. • Tankas were often beautifully decorated with tiles, which helped to keep the water cool.

The water was used only for drinking. • If in any year there was less than normal rainfall and the tankas did not get filled, water

from nearby wells and tanks would be obtained to fill the household tankas. • The tanka system is also to be found in the pilgrim town of Dwarka where it has been

in existence for centuries. It continues to be used in residential areas, temples, dharamshalas and hotels.

Bavdi

• Traditional stepwells are called vav or vavadi in Gujarat, or baoris or bavadis in Rajasthan and northern India.

• They were secular structures from which everyone could draw water.

• Most of them are defunct today.• Stepwell locations often suggested the way in which they would be

used. – Within or at the edge of a village - utilitarian purposes and as a cool

place for social gatherings. – Outside the village, on trade routes - resting places.

• When stepwells were used exclusively for irrigation, a sluice was constructed at the rim to receive the lifted water and lead it to a trough or pond, from where it ran through a drainage system and was channeled into the fields.

Nadis, Talabs, Lakes

• Nadis– Natural surface depression which receives rain water

from different directions– They receive their water supply from erratic, torrential

rainfall. – Can lead to heavy sedimentation and siltation

• Trees can prevent some of this• Dredging out the sediment before monsoon can also help

– Can lose water by evaporation• Talabs, lakes are similar• Toba is similar as well – natural depression with

a natural catchment area

Jhalara

• Human-made tanks, found in Rajasthan and Gujarat• Essentially meant for community use and for religious rites. • Often rectangular in design, jhalaras have steps on three or

four sides. The steps are built on a series of levels .• The jhalaras collect subterranean seepage of a talab or a lake

located upstream .

Kunds• Covered underground tank,

developed primarily for tackling drinking water problems.

• Usually constructed with local materials or cement, kunds were more prevalent in regions where groundwater is saline.

• Before the onset of rains every year, meticulous care was taken to clean up the catchment of the kunds.

• Cattle grazing and entry with shoes into the catchment area of the kunds was strictly prohibited.

• The proximity of a kund to the house or village saved time and effort in searching for drinking water.

Kunds• Saucer-shaped catchment area with a gentle slope towards the centre

where a tank is situated. • Openings or inlets for water to go into the tank are usually guarded by a wire

mesh to prevent the entry of floating debris, birds and reptiles. • The top is usually covered with a lid from where water can be drawn out with

a bucket.• Kunds are by and large circular in shape, with little variation between the

depth and diameter which ranges from 3-4.5 m. • Lime plaster or cement is typically used for the construction of the tank • The success of a kund depends on the selection of the site, particularly its

catchment characteristics. An adequately large catchment area has to be selected or artificially prepared to produce adequate runoff to meet the storage requirements of the kund.

• The catchment size of kunds varies from about 20 sq m to 2 ha depending on the runoff needed and the availability of spare land.

• The catchment areas of kunds were made using locally available sealing materials such as pond silt, murrum, charcoal ash, and gravel. After clearing the soil surface of vegetation, the land was given a smooth gradient of 3-4 per cent towards the kund and the cleared surface was lined with pond silt obtained from nearby talabs or nadi beds.

• Rainfall data collected showed that areas with 100 mm of rainfall can use the kund system effectively.

Kui• 10-12 m deep pits dug near tanks to collect

the seepage. Kuis can also be used to harvest rainwater in areas with meagre rainfall.

• The mouth of the pit is usually made very narrow. This prevents the collected water from evaporating.

• The pit gets wider as it burrows under the ground, so that water can seep in into a large surface area.

• The openings of these entirely kuchcha (earthen) structures are generally covered with planks of wood, or put under lock and key.

• The water is used sparingly, as a last resource in crisis situations.

Khadin (or Dhora)• Practiced in Jaisalmer area

– Not enough rain to fulfill crop requirements

• Designed to harvest surface runoff water for agriculture.

• Its main feature is a very long (100-300 m) earthen embankment (khadin bund) built across the lower hill slopes lying below gravelly uplands.

• Sluices and spillways allow excess water to drain off.

• The khadin system is based on the principle of harvesting rainwater on farmland and subsequent use of this water-saturated land for crop production.

Khadin• Requirements:

– Catchment area: shallow, gravelly and rocky uplands with high runoff potential

– Flood plain or gently sloping plain area (khadin area) where soils are suitable for crop production

• Before rainfall: kharif crop– If good rain, half grown kharif crop (e.g. bajra) used for fodder,

and rabi crop grown instead• Khadin area – few salts• But area just outside khadin bund has salt accumulation;

hence khadin farmers better off than non-khadin farmers• Maintenance:

– Grass on catchment, plus restricted cattle grazing– Periodic cleaning of khadin area, including leveling the land plus

possible removal of deposited gravel and sand

Virdas• Shallow wells dug in low depressions called jheels

(tanks). • They are found all over the Banni grasslands, a part

of the Great Rann of Kutch in Gujarat. • They are systems built by the nomadic Maldharis,

who used to roam these grasslands. Now settled, they persist in using virdas.

• These structures harvest rainwater. The topography of the area is undulating, with depressions on the ground. By studying the flow of water during the monsoon, the Maldharis identify these depressions and make their virdas there.

• They separate potable freshwater from unpotable salt water. After rainwater infiltrates the soil, it gets stored at a level above the salty groundwater because of the difference in their density.

• A structure is built to reach down (about 1 m) to this upper layer of accumulated rainwater.

• Between these two layers of sweet and saline water, there exists a zone of brackish water.

• As freshwater is removed, the brackish water moves upwards, and accumulates towards the bottom of the virda.

• There are also tank structures where the rainwater is collected and multiple virdas (wells-in-a-tank) are built

Rapats• A rapat is a percolation tank• There is a bund to impound rainwater flowing through a

watershed and a waste weir to dispose of the surplus flow.

• If the height of the structure is small, the bund may be built of masonary, otherwise earth is used.

• Rajasthan rapats, being small, are all masonry structures.

• Rapats and percolation tanks do not directly irrigate land, but recharges well within a distance of 3-5 km downstream.

• Silting is a serious problem with small rapats and the estimated life of a rapat varies from 5 to 20 years.

Johads• Began in Rajasthan’s Alwar district, which

was a desert. • To solve the water scarcity, the village

collective started rainwater harvesting.• They started by repairing the old

checkdams or Johads. Johads are the traditional way of harvesting rainwater.

• A johad is a crescent-shaped bund which is built across a sloping catchment to capture the surface water before it runs off.

• Water accumulating in the johad percolates in the soil to augment the groundwater. The groundwater then can be used when there is no rainfall.

• Over the next few years, the water table in the ground have been increased through the Johads. The village needs water for drinking, sanitation, cooking, cattle and irrigation.

• Water is distributed based on the needs by the collective. The collective has the following rules:

– All villagers must benefit from the efforts of the collective

– All decisions will be arrived after informal discussions

– All decisions will be strongly enforced– Each person in the collective will be

responsible to carry out the task– Collective will use external help only for

guidance and they will do all the work

Before RWH & reforestation

After RWH &reforestation

Johad Check dam

Johads

• Johad collects water during monsoons

• Later used for cultivation

• Johads became the basis for community participation with general developmental impact – fewer migrations, higher participation by women, micro-credit, etc.

• Decisions on johads taken in local gram sabhas

Health Hazards

• Water quality of traditional water systems often does not satisfy drinking water quality standards– Faecal contamination of tankas– Floating organic debris, weeds, etc. in tankas– Excessive presence of chemicals such as fluorides

and nitrates– Breeding ground for mosquitoes

• WHO estimates that 80% of all sickness and disease in the world is due to inadequate water and sanitation (from both piped and traditional systems)

Strategies for Improvement

• Specifically:– Construction of water sources that cannot be contaminated by

infected persons– Filtration of water– Disinfection through chemicals (such as chlorine)

• Broadly– Community involvement, coupled with health education– Protect the catchment area; fencing it off to keep out cattle and

human beings from polluting the area– Improvements in the design and construction of the catchment

area, storage and withdrawal so as to reduce pollution– Awareness regarding traditional water systems and their health

impact

Points

• Importance of reforestation• Keeping cattle away from catchment• Uthnau – “holes” dug up in the stone quarries

act as water tanks– Soil isn’t very deep, mostly rocky land– No trees – Volunteers from outside very hard to find (remote

area)• Volunteers need to not feel superior to the local tribals

– Too Goria centric

Motivations for water harvesting

• India too diverse for dams

• Working examples

• Modern technology potentially lead to regression

• Water crucial in India (50% people will suffer from lack of drinking water)