Rainwater Harvesting

Presented byShawn Miller, Dip. Eng., B. Eng.

Why is there a water shortage? Deforestation

Population increase

Industrialization

Urbanization - Increase in per capita utilization and less peculation area

In places where rain fed/ irrigation based crops are cultivated through ground water

Decrease in surface area of Lakes, Rivers, Dams etc.

What is the solution? 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

What is Rainwater Harvesting? Rainwater is collected when it falls on the earth, stored and utilized at a later

point. It can be purified to make it into drinking water, used for daily applications and even utilized in large scale industries.

The simplest method for a rainwater harvesting system is storage tanks. In this, a catchment area for the water is directly linked to cisterns, tanks and reservoirs. Water can be stored here until needed or used on a daily basis.

Major Objectives of Rainwater Harvesting1. Meet the increasing demands of water

2. Reduce ground water contamination

3. Reduce soils erosion

4. Supplement domestic water needs

5. Avoid flooding of roads

Major Objectives of Rainwater Harvesting6. Supplement ground water supplies during lean season

7. Reduce run off loss

8. Raise the water table by recharging ground water

9. Reduce the run-off which chokes the drain

10. Reduce groundwater pollution

Benefits of Rainwater Harvesting1. Easy to Maintain: Systems for the collection of rainwater are based on simple

technology. It is important to do so since drinking water is not easily renewable.

2. Reduces Water Bills: For many families and small businesses, rain water harvesting leads to a large reduction in their utilities bills. On an industrial scale, harvesting rainwater can provide water for many operations to take place smoothly without depleting water sources.

Benefits of Rainwater Harvesting1. Suitable for Irrigation: Most rooftops act as a workable catchment area,

which can be linked to the harvesting system.

2. Reduces Floods and Soil Erosion: Rainwater may be collected in storage tanks to reduce floods in low lying areas. This also reduces soil erosion and contamination of surface water with pesticides and fertilizers from rainwater run-off which results in cleaner lakes and ponds.

3. Reduces Demand on Ground Water: With an increasing population, the demand for water is also continuously increasing. Rainwater harvesting reduces the demand on ground water resources.

Methods of Rainwater HarvestingThere are two main methods of harvesting rainwater

1. Surface runoff harvesting

2. Roof top rainwater harvesting

Surface Runoff HarvestingIn urban areas rainwater typically flows away as surface runoff. This runoff could be caught and used for recharging aquifers by adopting appropriate methods.

Roof Top Rainwater HarvestingThe rainwater is collected from the roof of the building in this method. It can either be stored in a tank or diverted to an artificial recharge system. This method is very cost efficient and effective if implemented properly.

Components of the roof top rainwater harvesting The system mainly constitutes of :

Catchments

Transportation

First flush

Filter

Components of the roof top rainwater harvesting • Catchments - The surface that receives rainfall directly is the catchment of

rainwater harvesting system. It may be terrace, courtyard, or paved or unpaved open ground. The terrace may be flat RCC/stone roof or sloping roof. Therefore the catchment is the area, which actually contributes rainwater to the harvesting system.

• Transportation - Rainwater from rooftop should be carried through down take water pipes or drains to storage/harvesting system. Water pipes should be UV resistant (ISI HDPE/PVC pipes) of required capacity. Water from sloping roofs could be caught through gutters and down take pipe. At terraces, mouth of the each drain should have wire mesh to restrict floating material.

Components of the roof top rainwater harvesting First Flush – The first shower of rains needs to be flushed-off to avoid

contaminating storable/rechargeable water by the probable contaminants in the atmosphere and the catchment roof. First rain separators should be made at outlet of each drainpipe.

Filter - After first flushing of rainfall, water should pass through filters to remove turbidity, colour and microorganisms. A gravel, sand and ‘netlon’ mesh filter is designed and placed on top of the storage tank. It removes silt, dust, leaves and other organic matter from entering the storage tank.

Types of Filters

Sand Gravel Filter

These are commonly used filters, constructed by brick masonry and filleted by pebbles, gravel, and sand as shown in the figure. Each layer should be separated by wire mesh.

Charcoal Filter

Charcoal filter can be made in-situ or in a drum. Pebbles, gravel, sand and charcoal as shown in the figure should fill the drum or chamber. Each layer should be separated by wire mesh. Thin layer of charcoal is used to absorb odor if any.

PVC Pipe filter

This filter can be made using PVC pipe. The pipe is divided into three compartments by wire mesh. Each component should be filled with gravel and sand alternatively. A layer of charcoal could also be inserted between two of the layers.

Sponge Filter

It is a simple filter made from PVC drum having a layer of sponge in the middle of drum. It is the easiest and cheapest form filter, suitable for residential units.

Types of Filters

By providing pipe water system with source (electric based)

(a) Surface water

(b) Deep wells

Recharging strata's through rainwater harvesting methods

(No. of villages of lower range concentration can be decreased)

Storing rain water for drinking purpose

(a) In areas where electricity is a problem

(b) In areas where concentration is more

(c) In areas where dependable source is not available

How can the problem be minimized?

A reservoirCreated with pond liner which lasts for over 50 years.

Rainwater harvesting for domestic useThis can be used to generate potable water for drinking purposes, laundry and other household uses.

Use what you havePre-existing depression being assessed for its ability to serve as a rainwater harvesting pond in support of drip irrigation for crop production.

Clear DrainsThis man is clearing a drain to have less debris in waterway.

Getting the rainwater harvesting pond readyRainwater harvesting pond ready to be lined with pond liner.

Lining processThe first layer of pond liner is being laid. Each piece is welded to the other to cover the full surface area of the pond.

Rainwater harvesting pond completedThe next stage will be to install pipes to fill the tank.

Rainwater harvest system under constructionThis will use run-off water from building roof and transport the water in 10-inch PVC pipes to the pond that will in turn supply water through a drip irrigation system to support crop production.

Rainwater harvest pond being lined with water proof lining

Rainwater harvesting from run-off from roof – greenhouse structure

Used for crop productionRainwater harvest pond supporting shade-house crop production – tomatoes, sweet peppers, cucumbers.

Same pond support the production of 2.2 acres of outfield vegetable mulched crop production – sweet pepper, tomato, cabbage, cauliflower.

We use what we sellRainwater harvesting tank sold by Isratech Waterworks being used at Head Office in Manchester.

Use tanks for storageBlack water storage tanks used to store water used in the pipe production process at the factories in Kendal, Manchester.

ConclusionIn the past, farmers could almost predict rain patterns to determine when to plant their crops. But now, we scarcely know when we will be getting rain and still farmers are sticking to their usual patterns of planting thus they are losing crops.

Since we can’t create water, let’s harvest it and use it when needed because every drop counts.

END

THANK YOU