Domestic and Industrial


     Rainwater harvesting is the gathering, or accumulating and storing, of rainwater. Rainwater harvesting has been used to provide drinking water, water for livestock, water for irrigation or to refill aquifers in a process called groundwater recharge. Rainwater collected from the roofs of houses, tents and local institutions, or from specially prepared areas of ground, can make an important contribution to drinking water. In some cases, rainwater may be the only available, or economical, water source. Rainwater systems are simple to construct from inexpensive local materials, and are potentially successful in most habitable locations. Roof rainwater is usually of good quality and does not require treatment before consumption. Household rainfall catchment systems are appropriate in areas with an average rainfall 1200mm per yearS

     There are a number of types of systems to harvest rainwater ranging from very simple to the complex industrial systems. Generally, rainwater is either harvested from the ground or from a roof. The rate at which water can be collected from either system is dependent on the plan area of the system, its efficiency, and the intensity of rainfall.

  • Ground catchment systems
  • Roof catchment systems
  • Subsurface dyke
  • Groundwater recharge
  • Advantages in urban areas
  • Quality
  • System sizing

1. What is Rain Water Harvesting

     The concept of rain water harvesting lies in tapping the rain water where it falls. A major portion of rainwater that falls on the earth's surface, runs-off from streams to rivers and finally to the sea. An average of 8% of the total rainfall recharges the ground water aquifers. Therefore, most of the rainfall goes waste in the form of surface run-off. The technique of rainwater harvesting involves catching the rain from localized catchment surfaces such as roof of a house, plain and sloping ground surface etc. The rainwater that falls on these catchment is diverted into dugout ponds, vessels or underground tanks to store for long periods. Construction of small barriers across small streams to check and store the running water is also an example of small catchment water harvesting.

     Water harvesting means to understand the value of rain and to make optimum use of rain water at the place where it falls. In scientific terms, water harvesting (broadly) refers to collection and storage of rain water and also other activities such as harvesting surface water, extracting ground water prevention of losses through evaporation and seepage. In general, water harvesting is the activity of direct collection of rain water. The rain water collected can be stored for direct use or can be recharged into the ground water.

2. Why Rainwater Harvesting?

     Rain is the first form of water that we know in the hydrological cycle, hence it is a primary source of water for us. Rivers, lakes and ground water are all secondary sources of water In present times, we depend mainly on such secondary sources of water. In the process, it is forgotten, that rain is the ultimate source that feeds all these secondary sources and remain ignorant of its value. Water crisis situation occurs only because, effective collection and storage of rain water has been ignored. The potential of rain to meet water demand is tremendous. Unless people are involved in conserving rain water from individual households to big industries/institutions, it would be very difficult to meet the looming water crisis.

     We get a lot of rain, yet we do not have water. Why? Because we have not realised the value of each drop of rain. Ironically, even Cherrapunji which receives about 11,000 mm of rainfall annually suffers from acute shortage of drinking water. This is because the rain water is not conserved but allowed to drain away. Thus it does not matter how much rain we get, if we don't capture or harvest it.