Rainwater collection in multistory roofs
Rainwater harvesting in small houses.
tank used in rainwater harvesting.
Sunday 2 March 2014
Now we will talk about the rest of the process in this post.
First Flush Pipe
- Debris, dust & dirt collect on the roof during non rainy periods when the first rain arrive.
- A first flush system arrangement is made to avoid the entering unwanted material into the Filter media & storage tank.
- This is a simple manually operated arrangement or semi-automatic system with a valve below the ‘T’ junction. --------------------------------------------------------------------------------------------------------------------
Filter Unit
- The filter unit is a container or chamber filled with filter media such as coarse sand, charcoal, coconut fibre, pebbles & gravels to remove the debris & dirt from water that enters the tank.
- The filter unit is placed over the storage tank or separately.
- It may be of Ferro cement filter unit, Aluminium, Cement rings or Plastic bucket etc.
Storage Tank
- It is used to store the water that is collected from the roof through filter.
- For small scale water storage plastic buckets, jerry cans, clay or cement jars, ceramic jars, drums may be used.
- For larger quantities of water, the system will require a bigger tank with cylindrical or rectangular or square in shape constructed with Ferro cement or cement rings or plain cement concrete or reinforced cement concrete or brick or stone etc.
- The storage tank is provided with a cover on the top to avoid the contamination of water from external sources.
- The storage tank is provided with pipe fixtures at appropriate places to draw the water to clean the tank & to dispose of extra water.
- No. of person in the House hold
- Per capita water requirement
- No. of days for which water is required
Roof catchment
- The roof of the house is used as the catchment for collecting rain water.
- The style construction and material of the roof effect its suitability as a catchment.
- Roofs made of corrugated iron sheet , asbestos sheet, Tiles or Concrete can be utilized for harvesting the rain water.
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Gutters
- Gutters are channels fixed to the edges of roof all around to collect & transport the rainwater from the roof.
- Gutters can be made in semi-circular and rectangular shape with cement pipe, plain galvanized iron sheet, PVC pipes, bamboos etc.
- Use of locally available material reduce the overall cost of the system.
Down Pipe
- It is the pipe which carries the rainwater from the gutters to the filter & storage tank.
- Down pipe is joined with the gutters at one end & the other end is connected to the filter unit of the storage tank.
- PVC or GI pipe of 50mm to 75mm (2 to”) are commonly used for down pipe.
- Bamboo can be also used wherever available and possible.
The roof catchment are selectively cleaner when compared to the ground level catchment.
- Losses from roof catchment are minimum.
- Built & Maintained by local communities.
- No Chemical contamination & only required filtration.
- Available at door step with least cost.
Rain water harvesting system ------
The typical roof top rain water harvesting system comprises:-
The typical roof top rain water harvesting system comprises:-
- Roof catchment
- Gutters
- Down pipe & first flushing pipe
- Filter Unit
- Storage Tank
let's talk about these one by one--
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ATTRIBUTES OF GROUNDWATER
- There is more ground water than surface water.
- Ground water is less expensive and economic resource.
- Ground water is sustainable and reliable source of water supply.
- Ground water is relatively less vulnerable to pollution.
- Ground water has usually high bacteriological purity.
- Ground water is free of pathogenic organisms.
- Ground water needs little treatment before use.
- Ground water has no turbidity and colour.
- Ground water has distinct health advantage as alternative for lower sanitary quality surface water.
- Ground water is usually universally available.
- Ground water resource can be instantly developed and used.There is no conveyance losses in ground water based supplies.
- Ground water has low vulnerability to drought.
- Ground water is key to life in arid and semi-arid regions.
- Ground water is source of dry weather flow in rivers and streams.
Rainwater harvesting – Methodologies
- Roof Rain Water Harvesting
- Land based Rain Water Harvesting
- Watershed based Rain Water harvesting
Roof & Land based Rainwater harvesting.
- Public, Private, Office & Industrial buildings
- Pavements, Lawns, Gardens & other open space
Rain Water Harvesting– Advantages
1.Provides self-sufficiency to water supply.
2.Reduces the cost for pumping of ground water.
3.Provides high quality water, soft and low in minerals.
4.Improves the quality of ground water through dilution when recharged.
5.Reduces soil erosion & flooding in urban areas.
6.The rooftop rain water harvesting is less expensive & easy to construct, operate and maintain.
7. In desert, Rainwater harvesting only relief.
8. In saline or coastal areas & Islands, rain water provides good quality water.
2.Reduces the cost for pumping of ground water.
3.Provides high quality water, soft and low in minerals.
4.Improves the quality of ground water through dilution when recharged.
5.Reduces soil erosion & flooding in urban areas.
6.The rooftop rain water harvesting is less expensive & easy to construct, operate and maintain.
7. In desert, Rainwater harvesting only relief.
8. In saline or coastal areas & Islands, rain water provides good quality water.
What is rain water harvesting ?
It is the activity of direct collection of rain water.
Rain water can be stored for direct use or can be recharged into the ground water aquifer.
Rain water can be stored for direct use or can be recharged into the ground water aquifer.
Rain Water Harvesting - process of collecting, conveying & storing water from rainfall in an area – for beneficial use.
Storage – in tanks, reservoirs, underground storage- groundwater
As Rainwater harvesting- neither energy-intensive nor labour-intensive
It can be a cost-effective alternative to other water-accruing methods. With the water table falling rapidly, & concrete surfaces and landfill dumps taking the place of water bodies, Rainwater harvesting is the most reliable solution for augmenting groundwater level to attain self-sufficiency.
- Rain water is the ultimate source of fresh water
- Potential of rain to meet water demand is tremendous
- Rain water harvesting helps to overcome water scarcity
- To conserve ground water the aquifers must be recharged with rain water
- Rain water harvesting is the ultimate answer
therefore ,we have seen the great benefits of rainwater harvesting.
Why Rain water be harvested????????????
To conserve & augment the storage of ground water
Why Rain water be harvested????????????
To conserve & augment the storage of ground water
- To reduce water depletion
- To improve the quality of ground water
- To arrest sea water intrusion in coastal areas
- To avoid flood & water stagnation in urban areas
Saturday 1 March 2014
Ancient techniques for rainwater harvesting
Talab/ Bandhis
Talabs were reservoirs. They could be natural, such as the ponds (pokhariyan) at Tikamgarh in the Bundelkhand region or could be man-made, such as the lakes in Udaipur. A reservoir area of less than five bighas was called a talai; a medium sized lake was called a bandhi or talab; bigger lakes were called sagar or samand. The pokhariyan served the purpose of irrigation and drinking. When the water in these reservoirs dried up, the pond beds were used for cultivation.
Talabs were reservoirs. They could be natural, such as the ponds (pokhariyan) at Tikamgarh in the Bundelkhand region or could be man-made, such as the lakes in Udaipur. A reservoir area of less than five bighas was called a talai; a medium sized lake was called a bandhi or talab; bigger lakes were called sagar or samand. The pokhariyan served the purpose of irrigation and drinking. When the water in these reservoirs dried up, the pond beds were used for cultivation.
Johads Johads,
in Rajasthan, were small earthen check dams built to capture
and conserve rainwater, thus improving percolation and
recharging ground water
Baoris / Bers
Baoris or bers were community wells, found in Rajasthan, that were used mainly for drinking. Most of them are very old and were built by banjaras for their drinking water needs. They could hold water for a long time because of almost negligible water evaporation.
Baoris or bers were community wells, found in Rajasthan, that were used mainly for drinking. Most of them are very old and were built by banjaras for their drinking water needs. They could hold water for a long time because of almost negligible water evaporation.
Jhalaras
Jhalaras were man-made tanks, found in Rajasthan and Gujarat, essentially meant for community use and for religious rites but not for drinking. Often rectangular in shape, jhalaras have steps on three or four sides. They were ground water bodies which were built to ensure easy and regular supply of water to the surrounding areas.
Jhalaras were man-made tanks, found in Rajasthan and Gujarat, essentially meant for community use and for religious rites but not for drinking. Often rectangular in shape, jhalaras have steps on three or four sides. They were ground water bodies which were built to ensure easy and regular supply of water to the surrounding areas.
Water Temples or ‘Step Wells’
Another most unique example for harvesting rainwater and providing water for drinking purpose in arid parts of our country was the step well.
Another most unique example for harvesting rainwater and providing water for drinking purpose in arid parts of our country was the step well.
Step wells are also called water temples of
India. The idea to construct step wells was initiated due to
the need to ensure water supply during the period of drought.
Some of the step wells were dug very close to tanks to get
drinking water throughout the year.
Step wells are also called Vav, Vavadi, Bawdi, Bawri,
Baoli, and Bavadi and can be found in Gujarat and
Rajasthan.
Adalaj-Vav is a very popular step-well i.e.
about 20 kms from Ahmdabad. It is made in the form of a temple
that ends into a well. The well is about six storeys below ground
level. Picture 6 illustrates the depth of the well. Agrasen ki baoli is one of them which situates in Delhi.
RAIN WATER HARVESTING TECHNIQUES
There are two main techniques of rain water harvestings-
- Storage of rainwater on surface for future use.
- Recharge to ground water.
The storage of rain water on surface is a traditional techniques and structures used were underground tanks, ponds, check dams, weirs etc
Recharge to ground water is a new concept of rain water harvesting and the structures generally used are :-
- Pits :- Recharge pits are constructed for recharging the shallow aquifer. These are constructed 1 to 2 m, wide and to 3 m. deep which are back filled with boulders, gravels, coarse sand.
- Trenches:- These are constructed when the permeable stram is available at shallow depth. Trench may be 0.5 to 1 m. wide, 1 to 1.5m. deep and 10 to 20 m. long depending up availability of water. These are back filled with filter materials.
- Dug wells:- Existing dug wells may be utilised as recharge structure and water should pass through filter media before putting into dug well.
- 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.
- Recharge wells :- Recharge wells of 100 to 300 mm. diameter are generally constructed for recharging the deeper aquifers and water is passed through filter media to avoid choking of recharge wells.
- Recharge Shafts :- For recharging the shallow aquifer which are located below clayey surface, recharge shafts of 0.5 to 3 m. diameter and 10 to 15 m. deep are constructed and back filled with boulders, gravels & coarse sand
- Lateral shafts with bore wells :- For recharging the upper as well as deeper aquifers lateral shafts of 1.5 to 2 m. wide & 10 to 30 m. long depending upon availability of water with one or two bore wells are constructed. The lateral shafts is back filled with boulders, gravels & coarse sand.
- Spreading techniques :- When permeable strata starts from top then this technique is used. Spread the water in streams/Nalas by
making check dams, nala bunds, cement plugs, gabion structures or a percolation pond may be constructed.
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Reasons of Shortage of Water
- Population increase
- Industrialization
- Urbanization
- Increase in per capita utilization
- Less peculation area
- In places where rain fed/ irrigation based crops are cultivated through ground water
- Decrease in surface area of Lakes, talab, tanks etc.
(i) Less precipitation
(ii) Absence of Barriers
(a) Rain drops checked by leaves of tree
(b) Water slowly descends through twigs & trunk
(c) Humus – acts as reservoir
(d) Tiny creatures – helps percolation
Do you know--------
1 hectare of forest-6-7 Lac ton of water(after filtering) top layer can hold 1.2 Lac tons of water.
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