Rainwater Harvesting by Subrata Das.pptx

Rainwater harvesting (RWH) is the collection and storage of rain, rather than allowing it to run off. Rainwater is collected from a roof like surface and redirected to a tank, cistern, deep pit (well, shaft, or borehole), aquifer, or a reservoir with percolation, so that it seeps down and restores the ground water. Dew and fog can also be collected with nets or other tools. Rainwater harvesting differs from stormwater harvesting as the runoff is typically collected from roofs and other area surfaces for storage and subsequent reuse. Its uses include watering gardens, livestock, irrigation, domestic use with proper treatment, and domestic heating. The harvested water can also be committed to longer-term storage or groundwater recharge.

Fig. 1: Rainwater Harvesting

Rainwater harvesting is one of the simplest and oldest methods of self-supply of water for households, having been used in South Asia and other countries for many thousands of years. Installations can be designed for different scales including households, neighbourhoods and communities and can also be designed to serve institutions such as schools, hospitals and other public facilities.

Water is essential for life and place a major role in earth’s climate. By modifying land use, the proportion of the different pathways, evaporation, percolation and run off change. The never-ending exchange of water from the atmosphere to the oceans and back again is known Hydrological Cycle.




Fig. 2: Hydrological Cycle

In the present day world, rapid urbanization coupled with industrialization has become the order of the day. Added to urbanization, scanty and erratic rainfall is often resulting in reduction in water levels indicating depletion in storage in the surface reservoirs. Dependence on ground water is increasing rapidly over the past two decades. The demand is so high that indiscriminate use of groundwater resulting in steep fall of the ground water levels and there is also reduction in yields.
Apart from this, sealing of permeable soil zone is gradually increasing due to construction activities thereby resulting in reduced percolation of rainwater into the sub‐surface and increased surface run‐off. Therefore, an urgent need to take up rain / roof water harvesting / conservation methods in urban and rural areas on a large scale, which subsequently help to recharge and maintain ground water balance, in order to make it a sustainable source.

1. Seminar  ​  On ​ Rainwater Harvesting ​ Submitted By: Subrata Das Roll No. 002230302015 2nd Year, 4th Semester Water Resources and Hydraulic Engineering Department Jadavpur University

2. INDEX Introduction The Water Cycle Rainwater Harvesting- Alternative Water Resource What do you mean by Rainwater Harvesting? Importance of Rainwater Harvesting Objectives of Rainwater Harvesting Methods of Rainwater Harvesting Advantages of Rainwater Harvesting Disadvantages of Rainwater Harvesting References

3. Harvesting Rainwater for saving drinking water has gained enormously in significance as modern water saving sanitary technique.  This can be used for private and public buildings as well as for many industrial areas.  Due to the storage (retention) and the usage of rainwater the water flowing off housing estates in both reduced and delayed.    Introduction

4. The Water Cycle 1- Precipitation 2- Infiltration - contributes Ground water sources   3- Transpiration 4- Surface runoff – contributes to surface water sources   5- Evaporation 6 - Condensation

5. Rainwater harvesting- Alternative water source Technology used for collecting and storing rainwater for human use from rooftops, land surfaces. Decentralised system – Installed in houses, Institutions , community .

6. What do you mean by Rainwater Harvesting? Water is our most precious natural resource and something that most of us take for granted .  We are now increasingly becoming aware of the importance of water to our survival and its limited supply, especially in such a dry continent as Australia.

7. Importance of Rainwater Harvesting? The harvesting of rainwater simply involves the collection of water from surfaces on which rain falls, and subsequently storing this water for later use.  Normally water is collected from the roofs of buildings and stored in rainwater tanks. This is very common in rural Australia.  Water can also be collected in dams from rain falling on the ground and producing runoff.

8. Objectives of Rainwater Harvesting? To meet the increasing demand of water.  To reduce the run-off which chokes the drains?  To avoid the flooding of roads.  To raise the underground water table.  To reduce groundwater pollution.  To reduce soils erosion.  Supplement domestic water needs.  

9. Methods of Rainwater Harvesting Surface runoff harvesting  ​ In urban area rainwater flows away as surface runoff. This runoff could be caught and used for recharging aquifers by adopting appropriate methods.​ Roof Top rainwater harvesting  It is a system of catching rainwater where it falls. In rooftop harvesting, the roof becomes the catchments, and the rainwater is collected from the roof of the house/building. It can either be stored in a tank or diverted to artificial recharge system. This method is less expensive and very effective and if implemented properly helps in augmenting the ground water level of the area.

10. Roof Top Rainwater Harvesting

11. Advantages of Rainwater Harvesting Easy to Maintain  Reducing Water Bills  Suitable for Irrigation  Reduces Demand on Ground Water  Reduces Floods and Soil Erosion  Can be Used for Several Non-drinking Purposes 

12. Disadvantages of Rainwater Harvesting Unpredictable Rainfall  Initial High Cost Regular Maintenance  Certain Roof Types may Seep Chemicals or Animal Droppings  Storage Limits 

13. Harvesting water harnessing life: A case study of Kotla village in Mewat, Rajasthan A case study of good watershed interventions by the Sehgal Foundation that has helped improve the water situation in Kotla village in Mewat, Rajasthan People   Meo Tribals   Geographical Location   Foothills of Aravalis   Average rainfall   336mm-500mm   Occupation of villagers      a) Agriculture & Animal Husbandry   b) Others   58%   42%   Cultivated area   80%   Irrigated area   44%   Source of water for irrigation   Ground water- 95%   Water Quality   Mostly brackish   Ground water depletion rate   Over 25cms a year  

14. Thank You