Rainwater Harvesting in Residences

AFTER BEING MADE MANDATORY, RAINWATER HARVESTING IS GAINING PUBLICITY AMONG BANGALOREANS.IS IT NECESSARY FOR US TO INCORPORATE THE SAME IN OUR HOUSES????

"What makes desert a beautiful is the presence of a well somewhere".Therefore water is one of the most important element supporting life on earth. The earth is covered with 74% percent water on her surface with 4% potable water. We need water for all our activities in day-to-day life. Not only for domestic purposes, but also for various other industrial manufacturing.

"Water water everywhere neither a drop to drink".Water supply in urban area is always short against the total demand. Surface water is inadequate to meet our demand and we have to depend on ground water. Due to rapid urbanization, infiltration of rainwater into the subsoil has decreased drastically and recharging of ground water has diminished.Since there is no such legislation that limits the number of bore wells in Bangalore, the bore well tradition has touched the sky in no time. The number is estimated to be 3,40,000.

This scenario requires an alternative source to bridge the gap between demand and supply. Rainwater, which is easily available and is the purest form of water, would be an immediate source to augment the existing water supply by "catching water wherever it falls".

Rainwater Harvesting has emerged as a viable alternative to traditional perennial sources of water in hilly areas, in places where the level of fluoride and arsenic is above permissible limits and in urban areas facing water shortage and flooding during monsoons.

Rainwater Harvesting (RWH) is the process of collecting and storing rainwater in a scientific and controlled manner for reuse. Rainwater Harvesting in urban areas include
1. Roof top rainwater harvesting
2. Rainwater harvesting from surface flow (open fields, parks, pavement landscapes etc.)
3. Rainwater Harvesting in large areas with open ponds, lakes, tanks etc.

Rainwater from the rooftop is drawn through the drain pipes systematically and collected in storage devices such as HDPE (plastic) tanks or underground sumps.

The Bangalore Water Supply and Sewerage Board guideline reads, "the water conserved for 1 sqft of roof area must be 2 litres and 1sqft of open paved area must be 1 litre." Therefore the residents have to calculate their roof area and open areas against the water to be conserved.(That should be the storage capacity of your sump, tank and well)
Residences without enough open space can construct underground sumps depending on the roof yield. Or the other immediate option will be a synthetic tank on the roof or a chejja without disturbing the aesthetics of the building. Or sometimes even a surface tank will serve the purpose.

It is important to note that the water before being collected in the storage tanks, has to be passed through the filters that are exclusively available for filtering rain water. Houses falling under trees are tend to get accumulated with leaves that have to be segregated through a life slide (mesh).

Major portion of rainwater is collected from huge structures such as apartments, commercial complexes, industrial layouts etc. Such places can carry out rainwater harvesting where the rainwater replaces large quantities of fresh surface water and even ground water.


Apart from storing in storage tanks, water can also be diverted to the ground through open wells. The open wells may be constructed in the open area within the premises at the lower gradients to receive water from the roof as well as the open spaces through gravity flow. The water from open wells percolate to the ground slowly. This increases the water table in the long run and the water availability within these cement ring wells proportionally increases.The well should be 10ft deep(min) with a diameter of 3ft(min). This varies according to the plot and roof area.

In residences where space is a constraint, an underground sump within the living area will accommodate for storing rainwater. An overflow outlet can be led to the storm water drain outside.
Houses which have traditional open wells and stone wells can use the same for RWH. But as a precaution, filters have to be incorporated.

If the water is used for gardening solely, then a first flush separator can be used for segregating floating impurities.



Benefits of Rainwater Harvesting
1.Eco friendly and easy approach for water requirements
2.RWH is an ideal solution for water requirements in areas having inadequate water supply
3.Increases ground water level
4.Improves ground water quality(dilutes salts present in groundwater)
5.Mitigates the effects of drought
6.Reduces the runoff, which other wise floods storm water drains
7.Reduces flooding of roads and low-lying areas
8.Reduces soil erosion
9.Cost effective and easy to maintain
10.Reduces water and electricity bills

Traditional Water Harvesting in Karnataka underlines the importance of step wells, lakes, tanks, channels etc., as water storage bodies, the basic purpose of which was to establish a chain of water storage structures. However, a vanishing "Lake Culture" due to urbanization and industrialization has caused these systems to be neglected.

To make Rainwater Harvesting (RWH) a success, we should have a thorough knowledge of the following: geographic location; climate; geology; soil; land use; water requirements; existing water supply system; cost of water; systems & forms of RWH and the potential of harvesting rainwater.

RWH has the following unique advantages
1.Capturing rainwater in-situ and augmenting supply water at a marginal cost
2.Replenishing groundwater through recharging of rainwater by using the soil column
3.Reducing pollution and contamination
4.Reducing the water bill for the state exchequer
5.Providing clean and safe water
6.Least capital investment with maximum benefits to households and the city as a whole

The demerits of RWH
1.It is dependent on the monsoons and intensity of rainfall.
2.It depends on intensive participation from house level to the city level.
3.It is only a supplementary source and cannot replace the existing supply system completely.
4.Quality of rainwater harvested should be tested.

As the primary source of water, rainwater is the purest form of water. Rainwater harvesting not only solves the problem of unavailability of water, but also provides good quality water. However, certain precautions need to be taken to ensure that the stored water is not polluted.

1.Keep the roof or the water collection area clean before the rains.
2.Flush the rainwater collected in the first few minutes.
3.Store the collected rainwater in a closed container (avoid sunlight).
4.The quality of water deteriorates in the presence of sunlight and air.
5.Water can be kept clean over a period of five to six months in a clean container stored in an enclosed area protected from sunlight.
6. If any bacterial contamination is noticed, a small dosage of chlorine is recommended.

Who can harvest rainwater and where?
1. People planning construction of house, modification of house, existing house, etc.
2. From rooftops of Govt. buildings, Institutions, Hospitals, Hotels, shopping malls etc.
3. From rooftops and open areas
4. Farmlands, Public Parks, Playground, etc.
5. Paved and unpaved areas of a    
    layout/city/town/village

 Need for rainwater harvesting
Water harvesting is an activity of collection of rainwater and storing in containers for direct use or can be recharged in to the ground.As water is becoming scarce, it is the need of the day to attain self-sufficiency to fulfill the water needs
As urban water supply system is under tremendous pressure for supplying water to ever increasing population.Groundwater is getting depleted and polluted.
Soil erosion resulting from the unchecked runoff. Health hazards due to consumption of polluted water

Methods of Rainwater Harvesting

1. Rainwater stored for direct use in tanks above ground or underground sumps or overhead tanks and used directly for flushing, gardening, washing etc.
2. Ground water recharge.
3. Recharged to ground through recharge pits, dug wells, bore wells, soak pits, recharge trenches, etc

 Rainwater Harvesting potential

 Rainwater harvesting potential in urban areas is huge. Considering the availability of rainwater in a residential site of 40 x 60 feet (an area of 2400sq.ft./223 sq.mts.), around 2,23,000 lts of rainwater can be harvested in a location where the rainfall is around 1000 mm or 39.4 inches (Bangalore receives around 995 mm of rainfall annually). The amount of rainwater that can be harvested from the available rainwater in the plot depends on potential rainfall, catchment area available, collection methods and its efficiency etc.

Reuse of rainwater
Rainwater can be filtered for bacteria and reused for primary purposes such as drinking and cooking. Reverse Osmosis filters, UV filters, Iodine filters, Silver impregnated carbon filters, etc can be employed to filter rainwater to make it potable.
Rainwater Harvesting for Domestic Applications
Water requirement of a house can be broadly classified into
Drinking, Cooking, Bathing, Washing Vehicles, Utensils, Clothes, Floor cleaning, Gardening and Flushing in toilets. For washing, gardening and flushing toilets, relatively less clean water can be used (secondary use). Rainwater Harvesting (RWH) can meet all these above needs with suitable RWH techniques.Water requirement in a house is throughout the year. However, rainwater availability without having facilities to store is limited to number of rainy days and the quantity of rainwater available during the rainy days. Several interventions can be made to enhance the number of days of use of rainwater from number of rainy days to 365 days a year. Parameters, which support rainwater harvesting, are availability of space, willingness to invest, technical suitability of soil structure and geological parameters.
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