India makes up to 2.5% of the global land mass; we not only have a good 4% of the global freshwater resource but also are endowed with an average annual rainfall of 925 mm from the Southwest and Northeast monsoons. But we are under a huge demographic stress as we have over 16% of the global population in the 2.5% land mass.
Increase in population density is leading to a shortage of freshwater; we are drawing up the underground water to meet this demand. Urbanization may not be as rapid compared to global standards but the population density is exploiting the underground water causing long-term damages to the water tables. Water tables are depleting, and excess drilling is leading to contamination of underground water.
The hydrological imbalance needs some immediate attention and a sound water management process to be put in place. Few years ago one would have argued that expanding capacity of reservoirs and creating surface water bodies would help to store fresh water, but that argument is not strong enough in the current scenario. Surface water is easily contaminated by pesticides, industrial waste and human waste making it less usable.
With an annual rainfall of 925 mm, rainwater becomes the primary source and the single largest source of fresh water, and a proper harvesting plan both at a macro level and micro levels is critical. Macro may be more as government undertaking the activity but at a micro level, we in our own communities can implement it to address the ever growing demand for fresh water.
Rainwater harvesting in simple terms mean conservation and efficient utilization of rainwater. Harvesting can be done either as collection to storage for immediate use or to recharge back into the groundwater aquifers.
A basic calculation on a house of 100 sq mts, built in a place with 600 mm of annual rainfall, assuming that only 60% of it is getting harvested it would add up to appox 36000 liters of water per annum.
A community based approach to make harvesting part of housing plan and larger constructions like apartments, schools, commercial complexes and office buildings will help in better utilization of the rainwater, which otherwise would flow into the drainages or dry up form the surface water storages.
Rainwater harvesting is definitely not new to India, it is recorded as early as the Indus valley civilization. In many cities responsible citizens have implemented harvesting, even though much needed legislation on making it mandatory for all types of constructions does not really exists.
As a step forward in conservation of our natural resources, at our community level we should make rainwater harvesting a revolution. We need to actively put forward the agenda to the policy makers both at local and state level to make rainwater harvesting a mandatory requirement in all construction and penalize defaulters.
Be a responsible citizen, little effort from your end will go a long way to conserve freshwater for all.