Technical methods to conserve water
Rainwater Harvesting :
Rainwater harvesting is a simple, economical and eco-friendly technique of preserving every drop of water by guiding the rainwater that falls to borewells, pits and wells through small diameter pipes.The traditional method of rain water harvesting is the most effective and simple way to conserve the water. It means utilization of rain water for the domestic as well as agricultural purposes.
Rainwater Harvesting in urban areas is the process of collecting, filtering and using of rainwater, which falls on the rooftop (terrace or tile roof) and in the portico of the house. Rainwater harvesting can be adopted in three methods. These are:
- recharging of borewells near the house
- recharging of ground water sources and
- collection of rainwater for reuse.
Recharging of borewells should be done to prevent them from drying up and improve their water table. It is usually done by the following method. First, a pit should be dug in the region surrounding the casing pipe and cement rings should be installed in it. The size of the pit should be one meter in diameter and 10 feet in depth. At the bottom of the pit, filter holes should be made and a casing pipe with steel mesh should be fixed tightly to the bore well pipe. This casing pipe will function as a filter. Cement rings matching the borewell’s diameter should be installed till the base of the pit. The pit should be filled with boulders from the base up to a height of two feet. A second layer of two feet height filled with jelly stones of 40 mm should follow this. The third layer of one-foot height should be filled with jelly stones of 20 mm size. The fourth layer should be filled with charcoal. This exercise should be repeated till there is 3 feet of space left from form the ground level. A nylon curtain should be spread on the layers and the remaining space of the pit should be filled with sand until one foot from the ground level. A pipe should be fixed to collect the rainwater from the roof and this pipe should be connected to the pit. A pipe should be fixed to prevent the excess water from running away to roadside drainage.
By following the above method, we can recharge our borewells and keep them alive always. Those having open wells too can adopt this system. By directing the filtered rainwater to the open wells, their water tables could be improved.
Ground water recharging
Ground water recharging in urban areas is done by collecting the rainwater from the rooftops and the portico of the house and by making it easily absorbed within the veranda space
The method: An absorption pit should be constructed in the sloped area of the house veranda. The size of the absorption pit should be a minimum of 5 feet in width and a maximum of 10 feet in depth. Matching cement rings should be installed till the base of the pit. The pit should be filled with boulders (or big jelly stones) and a nylon curtain should be laid at the top. The remaining part of the pit should be filled with sand till one foot of the ground level. The pipe, which is installed for collecting the rainwater from the rooftop and the veranda of the house, should be linked to this absorption pit. Another pipe should be deployed for allowing the excess water to run off into the storm water drainage. Thus, by effectively preventing the rainwater from running off into the drainage and by making it absorbed into the ground, ground water sources can be recharged. All Bangaloreans, by adopting the ground water recharging system, can save the future generations the problem of water shortages.
Reuse of rainwater
Bangalore has an annual average rainfall of about 1,000 mm. It has been estimated that 2,23,000 litres of water can be collected annually from the rooftop of a 40’x60’ house with 1,000 mm rainfall. Assuming that, on an average, a Bangalorean spends 135 litres of water, a family of four would need about 2 lakh litres of water annually. So, water needed by an average family living in a 40’x60’ house could be collected from the rainwater falling on the rooftop.