PRESENTATION ON

Water Harvesting

Presented by:Baniaraplang Syiemiong(M.Sc.Forestry)

DEPARTMENT OF FORESTRY, MIZORAM UNIVERSITY, AIZAWL

Water HarvestingThe purpose of the stored water, whether for domestic use, stocking weathering, supplementary of full irrigation.

ORThe collection and storing of water on the surface of the soil for subsequent use is known as water harvesting. This include all measures that induce, collect, store and conserve surface runoff in a region. Water harvesting is most essential operation in arid and semi arid region where water is the deficit for most of the season.

Many water harvesting structures and water conveyance systems specific to the eco-regions and culture has been developed into:-

They harvested the rain drop directly. From rooftops, they collected water and stored it in tanks built in their courtyards.

From open community lands, they collected the rain and stored it in artificial wells.

They harvested monsoon runoff by capturing water from swollen streams during the monsoon season and stored it various forms of water bodies.

They harvested water from flooded rivers

History• Water has been harvested in India since antiquity, with our ancestors

perfecting the art of water management. • Around the third century BC, the farming communities in Balochistan (now

located in Pakistan, Afghanistan and Iran), and Kutch, India, used rainwater harvesting for irrigation.

• In ancient Tamil Nadu (India), rainwater harvesting was done by Chola kings.• Rainwater from the Brihadeeswara temple (located in Balaganpathy Nagar,

Thanjavur, India) was collected in Shivaganga tank• There are evidences that, even during Harappan period, there was very good

system of water management as could be seen in the latest excavation at Dholavira in Kachch.

• Many water harvesting structures and water conveyance systems specific to eco-regions and culture has been developed.

TRADITIONAL METHODS OF WATER HARVESTING

Traditional rainwater harvesting, which is still prevalent in rural areas, was done in surface storage bodies like lakes, ponds, irrigation tanks, temple tanks etc.

In urban areas, due to shrinking of open spaces, rainwater will have to necessarily be harvested as ground water, Hence harvesting in such places will depend very much on the nature of the soil viz., clayey, sandy etc.

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Some of the Traditional Techniques

ROOF WATER: Slightly sloping roofs allow water to run into gutters, down

pipes, and into specially prepared drums. Filters of wire mesh, sand, gravel, and charcoal clean the

water. It is funneled into underground sumps or aboveground tanks.

Tanks are sealed to keep out air, sunlight, and organic matter; treatment with alum reduces turbidity; and bleaching powder kills bacteria.

This water can be used for gardening, flushing toilets, washing clothes

NAULAS:Stone walls built across a stream to dam the water. Shady trees planted at the sides cut down

evaporation, and medicinal plants thrown into the small reservoirs purify the water.

PERCOLATION TANKS, RAPATS: Small tanks built on sandy or rocky soil to store

rainwater. Some of the water is used, but the remainder

percolates through to aquifers, which replenish wells.

BHANDARAS: Underground tanks built to intercept water from

springs, channeling it to storage tanks for city use.QANATS: Vertical shafts in hilly areas to catch rainwater.The water is collected in underground channels that

carry it by gravity over long distances to storage wells.INTEGRATED TANKS: Tanks that overflow into a series of lower tanks to

catch the rainwater that is funneled through gutters.

Modern Methods of Water Harvesting

The Modern methods of rainwater harvesting are categorized under two, they are Artificial Recharging and Rain Water Harvesting.

The former is classified into Absorption Pit Method, Absorption Well Method, Well cum Bore Method and Recharge trench cum injection well.

The later is categorized into Individual Houses and Grouped Houses which are further classified into Percolation Pit Method, Bore Well with Settlement Tank, Open Well Method with filter bed Sump and Percolation Pit with Bore Method.

New Techniques

There are two main techniques of Water Harvesting1. Storage of rain water on surface for future use

The storage of rainwater on surface is a traditional technique and structure used in underground tanks, ponds, check dams, weirs etc.

2. Recharge of ground waterRecharge of ground water is a new concept of water harvesting

The General Structure of Recharge Ground Water Are:-

1. Pits Recharge: Pits are constructed for recharging the shallow aquifers.

2. Trenches: These are constructed when the preamble strata is available at shallow depths.

3. Dug wells: Existing dug wells may well be utilized as recharge structure and water should pass through filter media before putting into dug well.

4. Hand Pumps: The existing hand pumps may be used for recharging the shallow / deep aquifers, if the availability of water is limited. Water should pass through filter media before diverting it into hand pumps.

5. Recharge Shafts: With bore wells for recharging the upper as well as deeper aquifers, lateral shafts of 1.5 to 2m wide and 10 to 20m long depending upon availability of water with one or two bore wells is constructed. The lateral shafts are back filled with boulders, gravels and coarse sand.

6. Spreading Techniques: When permeable strata start from top then this technique is used. Spread water in streams by making check dams, cement plugs or a percolation pond may be constructed.

ConclusionWater Harvesting is used for direct usage or for recharging aquifers. It is most important to ensure that the rainwater caught is free from pollutants. These are the following Benefits

1. An ideal solution to water problems in areas having inadequate water resources.

2. The ground water level will rise.3. Mitigates the effects of drought and achieves drought

proofing.4. Reduces the runoff which chokes the storm water drains.5. Flooding of roads is reduced,quality of water improves and

Soil erosion will be reduced.6. Saving of energy per well for lifting of ground water.7. Prevention of sea water ingress.

THANK YOU

Reference

1. Indian forestry- K. Manikandan2. kirtifrm.blogspot.in3. rainwaterharvesting.org4. www-rain.blogspot.in