1. HYDROLOGY AND WATER RESOURCES ENGINEERING PARUL INSTITUTE OF ENGINEERING & TECHNOLOGY. Semester:- 5 th Branch:- Civil Engineering.

2. TOPIC WATER HARVESTING PRESENTED BY:- BRIYAN D PATEL-130370106020

3. INDEX Introduction. Rain Water Harvesting Techniques. Rainwater collection- Rooftop Method. Components of Rooftop Method. Need for Rooftop Rainwater Harvesting. Water Harvesting by Small Dams. Benefits of Small Dams.

4. INTRODUCTION In Semi arid and arid regions, both the surface water and the groundwater are scare. Therefore attempts are made in these regions to collect and preserve rainwater to maximum possible extend. This collection of rainwater is called water harvesting, which is defined as collection of rainwater and runoff primarily for irrigation, human and livestock consumption. Rainwater harvesting is the accumulating and storing, of rainwater for reuse, before it reaches the aquifer. It has been used to provide drinking water, water for livestock, water for irrigation, as well as other typical uses given to water.

5. RAINWATER / WATER HARVESTING TECHNIQUES 1)Rainwater Harvesting – Rooftop rainwater harvesting. 2)Runoff Collection – Surface runoff harvesting. Small dams (check dams) Ponds and Reservoirs 3) Recharge to ground water. 4) Runoff enhancement.

6. RAINWATER COLLECTION – ROOFTOP RAINWATER HARVESTING Rooftop rainwater harvesting is the technique through which rain water is capture from the roof catchment from the roof catchment and stored in surface ground reservoir. The main objective of rooftop rain water harvesting is to make water available for future use. Capturing rainwater for use is particularly important in dry land, hilly, urban and costal areas. The quality of harvested water is usually clean following proper installation and maintenances. The effective roof area and the material used in construction determine the quality o the water collected.

7. COMPONENTS OF ROOF TOP RAINWATER HARVESTING The system mainly constitutes of following sub components: 1) A collection (catchment) area, 2) A conveyance system consisting of pipes and gutters, 3) A storage facility, and 4) A delivery system consisting of a tap or pump.

8. NEED FOR ROOFTOP RAIN WATER HARVESTING 1) To meet the ever increasing demand for water, 2) To reduce the runoff which chokes storm drains, 3) To reduce ground water pollution and exploitation, 4) To reduce soil erosion, 5) To reduce the cost for pumping of ground water at greater depth, 6) To supplement domestic water requirement during summer, 7) To improve quality of ground water.

9. WATER HARVESTING BY SMALL DAMS Small dams or check dams are constructed in natural channels to Impound the runoff water up to certain depth in the channel. The excess water is allowed to flow over dam. The impounded slowly infiltrates into the soil and recharges the ground water aquifer. In regional topography several smalls or large check dams are possible and may be created not so much for surface withdrawal but for recharging the falling ground water table. Small check dams are constructed over the streams bed thereby checking runoff and increasing the contact period of rainwater with underlying formations.

10. BENEFITS OF SMALL DAMS 1) Small dams to slow the movement of water in the stream, 2) They allow increase percolation into the soil, 3) They may also contribute to the increase in fishery, 4) The help in creating a recreational spot, 5) Slit that builds up behind the dam creates good farmland for plants, 6) Water can be use for irrigation purpose.