Rain Water Harvesting – Complete Coverage

*Note:- This article provides for a step by step guide on how any individual or a group can go for rain water harvesting and what is the correct way to go about it.All most all of us know what is rain water harvesting is, hence instead of writing an article on rain water harvesting itself, we tried to give it an utilitarian prospect.If you know how to do it , then you know better than the other person who only knows what it is .

What is RWH?

Rain water harvesting is collection and storage of rain water that runs off from roof tops, parks, roads, open grounds, etc. This water run off can be either stored or recharged into the ground water. A rainwater harvesting systems consists of the following components:

  1. catchment from where water is captured and stored or recharged,
  2. conveyance system that carries the water harvested from the catchment to the storage/recharge zone,
  3. first flush that is used to flush out the first spell of rain,
  4. filter used to remove pollutants,
  5. storage tanks and/or various recharge structures.

Why RWH?

Rain may soon be the only source of clean water. Rainwater harvesting systems use the principle of conserving rainwater where it falls and have the following benefits:

1)Helps meet ever increasing demand of water.
2)Improves quality and quantity of groundwater.
3)Reduces flooding.

Where Can it be done ?

1)Individual homes

Everywhere……the potential for rainwater harvesting is huge

How to do it :-

Step 1- Information Collection

A)Types, area and location of catchment:-

Different types of catchments are to be marked on the site plan. The collection efficiency of a particular catchment will be determined by the fact whether the catchment will be paved, unpaved or roof.

Area of the catchments

The amount of rainfall that will be collected will depend directly on the area of the catchment-the larger the area, the more the water. The area from where water would be collected will be arrived at by multiplying the length by the breadth of this space under the roof.

Location of the catchments

The quality of water that will be collected from the catchment will depend on the location of the catchment. Roof catchment provides the best quality of water. In areas where the catchments are open to contamination or are chemically treated then the water must be treated before being used for any purpose. Care must be taken when harvesting water from industrial areas.

Type of catchments Possible contamination
Industrial areas Toxic materials such as oil, grease, heavy metals
Roads, highways, parking areas Oil, grease, dust
Agricultural areas, lawns, gardens Pesticides, fertilisers, silt


There are four types of rainfall information:-

The annual average rainfall: Will give an overall picture of the total amount of water that can be collected.

The pattern of rainfall over different months: Will tell you when the rainfall is available – is it available most of the year or only during a certain part of the year.

Number of rainy days:  Will give an indication to decide whether to store the rainwater or to recharge it. If most of the rainfall comes only in a short span of time, then it is better to recharge the aquifer.

The peak rainfall intensity: Will give an indication to design the size of the storage or recharge structure. The sizing will be based on how much water will need to be stored or recharged during the most intense spell of rain.

C)Geological and hydrogeological data

For systems where the harvested rainwater will be used to recharge the aquifer, selection of site is important. Information must be collected on the following:-

Parameter Type Description
Soil Poor or well sorted sand or gravel, fine sand, silt, loam, layered or unweathered clay Sand, sandy loam and loamy sand soils have high infiltration rates.  Silty loam or loam has moderate infiltration rates and clayey soils or consolidated rocks have low infiltration rates.
Rocks Fractured or massive rocks, sandstone, limestone Hard massive rocks are conducive to recharge
Aquifer Confined or unconfined, perched, thickness of aquifer The aquifer should be unconfined and must have good hydraulic conductivity as well as transmissivity so that the water that is recharged is quickly spread horizontally to prevent a water mound forming below the surface.
Depth of water table Shallow or deep water table zones The aquifer must not be at shallow depths and should be at least 8-10 metres below the ground level.

The size of the water harvesting structure is determined by two factors – how much is needed and how much is available.

  • Quantity of water currently used: This will give the total water demand and an indication of what portion of this total water need can be met from rainwater harvesting.
  • Per capita water demand: In case one cannot find out the exact amount of water used, one can find out the number of persons and multiply this with the per capita norm for water supply to arrive at the total water demand.
  • Water demand during the driest period: This is to estimate the most essential quantum of water needed during the driest period so that plans can be made for rainwater harvesting to meet this minimum need.

E. Legislation and incentives
Today many state governments and city municipalities have passed laws that make it mandatory for existing or new buildings to have rainwater harvesting systems. At the same time, there are also many incentives to motivate people to take up rainwater harvesting.

Step 2 -Study Site Plan

Once all the relevant information has been collected, the next step is to study the site plan:

  • From the site plan find out the space available for water harvesting structures. This will determine the size and location of the structures.
  • Note the number and location of existing rain water pipes, outlets/spouts.
  • Find out if there are any defunct or existing borewells, swimming pool, water storage tanks that can be used for storing the harvested water. In a colony delineate all the open spaces from where water can be harvested as well as stored.
  • Determine the natural drainage, slope and location of storm water drains. This will help to lay out the conveyance pipes along the natural drainage patterns. This is particularly important while planning for a large complex or colony.
  • Mark the location of plumbing (water and sewage) and electrical lines in the site. Care must be taken to avoid plumbing and electrical lines while constructing the water harvesting structures. In case of project in public places this becomes even more important that underground sewer, water supply and other such cables and lines are not inadvertently destroyed.
  • Other information such as the existence and location of generator room, compost pit, waste dump etc also need to be taken into account.
  • The water harvesting structures should be as close as possible to the source and use of water.

Step 3 -Calculate Water harvesting potential and demand

Total volume of water = Area x runoff coefficient x rainfall
There is some loss of water due to evaporation or absorption by catchment surfaces and other kinds of losses. The runoff coefficent of a catchment gives you the proportion of the rainwater that can be harvested from the total rainfall.

Step 4 -Decide number , type and capacity of structure

Storage, recharge or both: The decision about whether to make storage or recharge structures depends on a number of factors as explained in table below:

Parameter Type/condition Recommended structure
Nature of aquifer Impermeable, non-porous, non-homogeneous, hard rock area Storage
Depth of groundwater table More than 8 metres Recharge and storage
Nature of terrain Hilly, rocky or undulating Storage
Uniform or flat, alluvial and sedimentary Recharge and storage
Nature of soil Alluvial, sandy, loamy soils, gravel, silty, with boulders or small stones (kankar) Recharge and storage
Clayey soil Storage
Nature of geological formation Massive rocks (such as the Deccan trap) Storage
Fractured, faulted or folded rocks, or comprises of weathered, jointed or fissured rocks Recharge and storage
Nature of rainfall and monsoon Number of rainy days are more, bimodal monsoon, not intensive, uniformly distributed Storage
Unimodal monsoon, rainfall available only for a few months Recharge and storage

Number of structures: The number of tanks will depend on the site conditions, which includes the position and location of the down pipes, the layout of the building, the size of the storage tank, the slope of the roof, the budget and the space available.

Capacity of storage tanks: Those will depend on the type of monsoon, bi-modal or uni-modal, number of rainy days, total demand and the rainfall intensity. If the rainy days are more, a smaller tank is sufficient as the tank can get frequently filled. The size will also depend on the demand and the total rainfall. Where the rainfall intensity is greater, the size will increase.

Location of structures: The location of structures will depend on the layout, the slope, the presence of other services and pipes and proximity to point of use.

Filtration and treatment: The type of filtration method used will depend on the use of the rainwater. If the harvested rainwater is going to be used for toilet or irrigation, then minimal filtration (with sand, gravel) is required to ensure that the water does not contain solid and toxic contaminants. On the other hand, when the water is to be used for drinking, then the level of treatment or filtration should be of high level.

Step 5-Start the Project

After all the above steps are complete, it is necessary to measure the financial requirement and funding but that differs on a  case by case basis and hence must be dealt at project level.

Defense Procurement Policy,2016 :-

Background :-

The Defence Procurement Policy 2016 made public this week is a step forward in increasing the participation of India’s private sector in military manufacturing. It replaces the last DPP unveiled in 2013, and has several recommendations for improving indigenous procurement. The DPP, the governing manual for all defence procurement, was part of a set of military reforms undertaken to address the many deficiencies noticed during the 1999 Kargil war. Since the first one in 2002, the DPP has been revised periodically.


The new policy places the highest preference to a newly incorporated procurement class called ‘Buy Indian-IDDM’, with IDDM denoting Indigenous Designed Developed and Manufactured. This category refers to procurement from an Indian vendor, products that are indigenously designed, developed and manufactured with a minimum of 40 per cent local content, or products having 60 per cent indigenous content if not designed and developed within the country.

The policy has also liberalised the threshold for offset liabilities for foreign vendors — now the obligation to invest at least 30 per cent of the contract value in India will kick in at Rs.2,000 crore, a significant increase from the previous Rs.300-crore mark. The policy lays stress on micro, small and medium enterprises (MSMEs), and on “Make in India”. A 10 per cent weightage has been introduced for superior technology, instead of selecting the lowest bidder only in financial terms.

New Rules on Bio-medical waste management:-

The key highlights of the new notification:-

  1. The new rule mandates a bar code system for bags and containers containing bio-medical waste, which is a good move as this will restrict the entry of waste in the illegal recycling market. It will also be beneficial to rag-pickers and people dealing with infected solid plastic waste and working in the recycling industries, respectively.

  2. The purview of the new rules has been expanded to include vaccination camps, blood donation camps, surgical camps and other healthcare activities
  3. The new rules have reduced the categorization of waste from 10 to four. This will ease the waste segregation process at the source of generation
  4. A ministry statement said that under the new rules, bedded hospitals will get automatic authorisation while there would be a one-time authorisation for non-bedded hospitals.
  5. New Rules mandate pre-treatment of lab waste, blood samples, laboratory waste, microbiological waste and blood bags through disinfection or sterilisation on-site in the manner as prescribed by WHO or NACO.
  6. Under the new Rules, use of chlorinated plastic bags, gloves and blood bags will be phased out within two years. This will be a good step if implemented within the stipulated time of two years as burning of chlorinated plastics often leads to emission of dioxin-furan, a Persistent Organic Pollutant (PoP) that has the potential to cause reproductive and developmental problems, damage to the immune system, interfere with hormones and also cause cancer.
  7. The new Rules ask for training and regular immunization of all healthcare workers. It needs delineation of proper responsibility of the stakeholders else the issue does not get addressed


Do You Know


1) A newspaper is easily torn vertically but not horizontally. Why is it so?


Paper is either `hand-made’ or `machine-made’. The machine used for making paper could be either a cylinder machine or fourdrinier. Newsprint is invariably made on a Fourdrinier.

Tearing strength (`Internal tearing resistance’) is the average force, in grams, required to tear a single sheet of paper under standardized conditions. The fibre orientation in a sheet of paper determines the tearing strength of the paper. If the orientation is at random, the tearing strength will be almost the same in all the directions. This is the case in `hand-made’ and `cylinder-made’ papers.

On the other hand, if the orientation is in one direction, the tear strength will be a minimum along that direction and a maximum along the cross (perpendicular) direction. This is the case in `fourdrinier-made’ paper.

In the case of a paper made on the fourdrinier — essentially, a long continuous wire screen — the fibre orientation is mainly along the direction of travel on the machine, that is, in the machine direction. Hence, in the machine direction, the tear is obtained just by separating the felted fibres, without any significant cutting of the fibres.

But, in the cross direction, the `tear’ is obtained mainly by cutting the fibres. Therefore, a much greater force, vis-�-vis the first case, would be needed.

Thus, a paper is easily torn `vertically’ (in the machine direction) but not `horizontally’ (in the cross direction). Contrastingly, paper is generally stronger (greater tensile strength) in the machine direction than in the cross direction.

2)  What is the difference between bacteria and virus?


Ans :-

Bacteria Virus
Ribosomes Present Absent
Cell wall Peptidoglycan / Lipopolysaccharide No cell wall. Protein coat present instead.
Living attributes Living organism Opinions differ on whether viruses are a form of life or organic structures that interact with living organisms.
Introduction (from Wikipedia) Bacteria constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a number of shapes, ranging from spheres to rods and spirals. A virus is a small infectious agent that replicates only inside the living cells of other organisms.
Nucleus No No
Reproduction Fission- a form of asexual reproduction Invades a host cell and takes over the cell causing it to make copies of the viral DNA/RNA. Destroys the host cell releasing new viruses.
Number of cells Unicellular; one cell No cells; not living
Structures DNA and RNA floating freely in cytoplasm. Has cell wall and cell membrane. DNA or RNA enclosed inside a coat of protein.
Treatment Antibiotics Vaccines prevent the spread and antiviral medications help to slow reproduction but can not stop it completely.
Enzymes Yes Yes, in some
Virulence Yes Yes
Infection Localized Systemic
Benefits Some bacteria are beneficial (e.g. certain bacteria are required in the gut) Viruses are not beneficial. However, a particular virus may be able to destroy brain tumors (see references). Viruses can be useful in genetic engineering.
Size Larger (1000nm) Smaller (20 – 400nm)




3)Why do eyes produce tears when tear gas is used?


Tear gas, in the form of CN (chlorocetophenone) or CS (chlorobenzylidemalononitrile) is often used for law enforcement. Today, CS has largely replaced CN and is probably the most widely used tear gas internationally. The tear gas is either launched in the form of grenades or aerosol cans so that the liquid becomes an aerosol.

Both CN and CS are skin irritants — they irritate mucous membranes in the eyes, nose, mouth and lungs, and cause tearing, sneezing, coughing. The more moisture on our body, the faster the acid is created and tissues are damaged, causing pain. When it is contacted with moist eyes, it affects mucous membranes which initiates glands to shed more tears.


4)Why is fire hot?


Chemical reactions can be either exothermic (heat liberation or endothermic (heat absorption). Oxidation reactions are exothermic and reduction reactions are endothermic. Combustion is an oxidation reaction and hence is exothermic.

All liquid, solid, and gaseous fuels contain any one of the three combustibles constituents viz. carbon, hydrogen and sulphur. When a fuel is burnt the heat liberated makes the products of combustion hot.

The products of combustion are carbon dioxide, water vapour and sulphur dioxide. Along with these, the unused oxygen in the atmospheric air supplied for combustion and also the entire quantity of nitrogen which is the major constituent in the air are also heated. That is why fire is hot.



5)Why does our hair change its colour as we age ?


Hairs are the appendages of the skin generated from the epidermal layer. Hair is a made up of Keratin a highly insoluble and mechanically stable fibrous protein. This Keratin is not only found in hairs but also in the skin. Actually Keratin is produced from the Keratinisation zone of the epidermis, which is the outer most layer of the skin. In the skin it provides water proofing quality.

The Keratin is generally pigmented. It is intensively pigmented in the hair. The dark black colour of the hair is due to the presence of high concentration of melanin pigments in it. The skin colour is also due to the presence of this pigment in the keratinocytes. The Keratin gets its melanin pigments from melanocytes, which are found in the inner layer of the epidermis, which is found just beneath the keratinizing layer. The melanocytes have long processes which extent between and under the cells of the epidermis. The melanin granules formed in the melanocytes pass along their branches and are secreted at their tips. The granules are subsequently engulfed by the keratinocytes, which make up 90 per cent of the epidermal cells.

Melanin is a protein like polymer of the amino acid tyrocin. In its biosynthesis tyrocin is converted in to dihydroxy phenyl alanine (DHPA) by oxidative enzymes amongst which tyrocin is particularly important. Then a series of reactions take place during which polymerisation occurs to form the final melanoprotein.

The hair grows only from the keratinocytes of the germinal matrix of the hair follicle. This germinal matrix lies in the proximal enlargement of the root hair, called the hair bulb. The hair shaft, which projects from the surface, consists of an inner medulla, an intermediate cortex and an outer cuticle. All these parts are made up of cornified cells. The medulla is composed of polyhedral cells; the cortex consists of elongated cells with inner lumen. These cells are united to form flattened fusiform fibers. The lumens of these cells contain pigmented granules in dark hair and air space in white hair.

The development of white hairs because of the absence of melanin pigments, may be due to the absence of one or more enzymes, necessary for the DHPA path way. It will lead to the failure of melanin accumulation in the keratinocytes, found in the hair bulb, from which hair is growing. Usually such physiological disorder occurs in the old age, which results in the growing of gray and white hairs in the body.


6) Why does a ship sinks more during the day than at night?


The phenomenon of floating is governed by the property known as density. Less dense substances float over more dense liquids. Density of substances is alterable by temperature. It decreases with the increase of temperature. Water has maximum density at 4oC (note that water at 0oC, that is ice, is less dense and hence floats) namely, 1000 kg/m3.

Density of water also changes with the amount of dissolved substances present in it. Density of sea water at 14oC is 1026.00 kg/m3; but it is only 999.27 kg/m3 for pure water. It is well known that bathers can float in “Dead Sea.” This is because of its extreme salinity. The salt content of it is 25 per cent. That means dead sea is seven times as salty as the ocean. Ships will sink to a more depth when they enter from ocean into river water and vice versa.

During the day, temperature of sea water is greater and hence density is lower. Hence ship sinks more in the water in the day.


 7) How can we test the purity of honey? 


A cotton wick dipped in pure honey when lighted with a matchstick burns and shows the purity of honey. If adulterated, the presence of water will not allow the honey to burn, If it does, it will produce a cracking sound. Generally honey is adulterated by adding a syrup of jaggery. Pure honey does not dissolve in water but impure honey dissolves. So to test it mix a spoon of honey in a cup of water and find out whether it dissolves to check its purity.

8) What is artificial blood?

Ans- A blood substitute (also called artificial blood or blood surrogates) is a substance used to mimic and fulfill some functions of biological blood. It aims to provide an alternative to blood transfusion, which is transferring blood or blood-based products from one person into another.While true blood serves many different functions, artificial blood is designed for the sole purpose of transporting oxygen and carbon dioxide throughout the body. Depending on the type of artificial blood, it can be produced in different ways using synthetic production, chemical isolation, or recombinant biochemical technology.


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