Now that the rains are here, we might as well harvest them for future use. Just like what a senior scientist in India has been doing the past many years. He harvests the rain and stores the same in a huge underground tank below his house.
He is Dr. M. M. Sharma, manager of Visitors, Protocol and Travel Services at the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT) in the Indian state of Hyderabad.
One of the first things we learned from him when we visited ICRISAT was how he harvests rain for his family’s use. In 1995, Dr. Sharma built his house with a flat roof made of concrete measuring about 160 square meters. Underneath, he built an underground storage tank to catch the rain water from the roof.
Before the water reaches the underground tank, it passes through a filter made of gravel. The water for household use is pumped by a 0.25 hp electric pump to a 1,000-liter capacity plastic overhead tank. From this tank water comes down by gravity and is used in the kitchen and toilets.
Dr. Sharma said that since 1995, the rainwater harvested has been used for drinking, cooking, bathing and washing clothes all year round. It is not necessary to boil or treat the water used for drinking and cooking. An ordinary filter is sufficient.
The walls of the underground tank are made of rough granite stones joined by a rich mixture of cement and sand. The floor is made of concrete. There is a concrete staircase to descend into the tank to facilitate cleaning. He explained that cleaning the tank annually ensures water quality. It is very important that the tank is built in such a way that sunlight does not penetrate the structure to prevent algal growth. Because it is soft water, using rainwater in the washing machine saves about 50% of detergent powder.
In late 2003, Dr. Sharma connected his neighbor’s roof to the same rainwater tank and together they have been harvesting about 250,000 liters of rainwater every year.
It cost Dr. Sharma US$1,025 to build his water harvesting system. During the first eight years, the system saved Dr. Sharma about 1 million liters of water worth $1,250. This means that the total construction cost was recovered in seven years.
From 2003 to 2007, the total value of water conserved by Dr. Sharma’s rainwater harvesting system was valued at $1,850
Total savings from 1995 to 2008 amounted to US$4,450. So it really pays to harvest rainwater.