Rain water harvesting is compulsory from BWSSB
As per the Bangalore water supply and sewerage act 1964(Karnataka act no 36 of 1964, substitution of section 72A Karnataka Gazette Extraordinary on the fifth day of February, 2011) Every owner or occupier of building having a sital area of not less than 2400 Sqfts(224 Sq mtrs) or every owner who propose to construct a building on sital area of not less than 1200 sqfts (112 sq meters) shall Provide rain water harvesting structure for storage for use or for groundwater recharge in such manner and subject to such conditions as may be provided in the regulations & guidelines issued by the Board.
Explanation For the purpose of this section
- ‘Rainwater harvesting’ means means collection and storage of rainwater from roof top a building or from a vacant land for use or for groundwater recharge
- ”Groundwater recharge means recharging of open well or underground water as the case may be, by use of harvested rainwater.”
Roof based Rainwater harvestingRoof based rainwater shall be harvested from the roof of the buildings such as tiled/slope roof and flat/RCC roof may be collected using appropriate size of gutters or pipe lines respectively and stored either in a collection tank or storage structure of appropriate size placed over the ground or underground after proper filtering and disinfection. for use through a filter into to a storage tank the water shall be used for non potable purpose or for rechargeof an open well.In case of a borewell in the building through artificial recharge structure or pits,irresptive the nature of sub soil conditions.While designig the roof based rain water harvesting the capacity of storage structure or for artificial rechargestructure to ground water,a provition at the rate of 20 ltrs per Sq.mtr or more capacity.
Land based Rain water harvestingLand based rainwater harvesting shall done by using appropriate ground water recharge structure or pits depending on the nature of the sub-soil conditions. The capacity of a storage structure or artificial recharge struture to ground water a provision at the rate of 10 ltrs per Sq.mtr or more capacity.
Storing Rainwater or Recharging Groundwater AquifersRainwater can be stored for direct use or alternatively it can be charged into the groundwater aquifers. This can be done through any suitable structures like dug wells, bore wells, recharge trenches and recharge pits. selection of a recharge location has to be done intelligently so as to ensure maximum collection of the rainwater runoff from the catchment area as well as to facilitate the maximum possible recharge. Scientifically there are various techniques available for geologically determining an ideal recharge location which is usually at the lowest point in the complex nearest to the existing out drainage point that shall facilitate collection of maximum rainwater runoff. Situating a recharge bore next to an existing tube well also enhances the rate of recharge into the ground and helps to sustain the existing ground water withdrawals. However, it is always advisable to maintain a minimum safe distance between the two bores. Subsequent chapters of this book focus on various techniques for aquifer recharging. Generally, only runoff from paved surfaces is used for storing, since it is relatively free of bacteriological contamination. Drainpipes that collect water from the catchment (rooftop) are diverted to the storage container
Contribution of Rainwater Harvesting to a Sustainable Water StrategyMany cities around the world obtain their water from great distances – often over 100 km away. But this practice of increasing dependence on the upper streams of the water resource supply area is not sustainable. Building dams in the upper watershed often means submerging houses, fields and wooded areas. It can also cause significant socio-economic and cultural impacts in the affected communities. In addition, some existing dams.
Restoring the Hydrological Cycle