Water harvesting principles and methods

Water harvesting principles and water harvesting methods.Run off methods and Rooftop harvesting methods

1. WATER HARVESTING

2. What is water harvesting? The term ‘water harvesting’ is usually taken to mean the immediate collection of rainwater running off surfaces upon which it has fallen directly. This definition excludes run-off from land watersheds into streams, rivers, lakes, etc. Hence it is the catching of rain water when it falls and storing to use during the non rainy season.

3. Principles of Water Harvesting Studying of Rainfall and suitable Locations Construct small structures which can be constructed by locally available materials Start constructing from high point and gradually come down Stream should be made of water rather than runoff and erode lot of soils.

4. Create a storage so that the harvested water be allowed for percolation to take place Always plan for an overflow route and manage that overflow as a resource Using this harvested water multiple purposes can be served Continually reassess the system such that any shortage can be met with in the next face in 2 nd principle

5. The technology of rain water harvesting Can be divided according to the purpose and the source of collecting water. Methods Roof top harvesting Run off harvesting These methods can be selected considering the purpose, the type and quantity of storage, Catchment state.

6. Roof top harvesting- This method include the catchment area as the roof top in rural and urban area. This include Rooftop of houses,flats,factories,offices,complexes.

7. Runoff harvesting Here the runoff water is collected- Gardens,driveways,landscapes,open fields,parks,roads and pavements and other open areas of the environment can be used to harvest the rain water runoff. Using this method, it is possible to collect water from a larger area. This is particularly advantageous in areas of low rainfall.

8. Components of rain water Harvesting Catchment area- Rain water can be collected from most forms of roofs Tiled roofs, or roofs sheeted with corrugated mild steel etc are preferable, since they are the easiest to use and give the cleanest water.

9. Thatched or palm leafed surfaces are also feasible, although they are difficult to clean and can often taint the run-off. Asbestos sheeting or lead-painted surfaces should be avoided .

10. Gutters and pipes In a roof top system gutters and pipes are used to collect and transport water to the storage tanks. These pipes and gutters can be made of PVC or metal,but PVC is widely used.

11. Filters They are used to filter out the debris that comes with the roof top water and prevent them being added to the storage tank. Mesh filters First-flushing devices sediment discharge tap Mesh filter and first flushing device.

12. Storage facility Storage tank is the structure where the water is stored. This can be varied according to the shape- cylintrical,rectangular,hexangular,square Material of construction- rainforced cement concrete (RCC),Ferro cement,Masonery,Plastic or metal sheets. Position of tank-Above ground,Partly underground,fully underground

13. Storage tanks in different shapes and positions

14. Devices to draw water out This include devices such as hand pumps, motorized pumps or taps. The device depends on the position of the tank and the use of water.

15. Advantages of rain water harvesting Relatively cheap materials can be used for construction of containers and collecting surfaces Construction methods are relatively straight forward Low maintenance costs and requirements Environment friendly Increase the ground water level and quality. Mitigates the effects of drought. Reduces the runoff Reduces the soil erosion Helps in reducing water and electricity bills Provides a supply of safe water close to homes, schools or clinics, encourages increased consumption, reduces the time women and children spend collecting water, reduces back strain or injuries from carrying heavy water containers

16. Disadvantages of rain water harvesting Supplies can be contaminated by bird/animal droppings on catchment surfaces and guttering structures unless they are cleaned/flushed before use Poorly constructed water jars/containers can suffer from algal growth and invasion by insects, lizards and rodents. They can act as a breeding ground for disease vectors if they are not properly maintained Regular maintenance should be needed

17. Importance of rain water harvesting and future Rain water harvesting plays an important role in agriculture Useful for urban areas It is important to save the water for the future. Thus it is important to improve rain water harvesting through technical and financial prospects.