Rain Harvesting in Kerala, India

Rain Harvesting in Kerala, India

Sunday, February 1, 2009



1. Problems addressed

Access to safe clean water is a basic human right for a healthy sustainable life. Unfortunately, still millions of people in Asia have no adequate access to water. New solutions to overcome this fact are constantly being addressed in villages and communities.

In rural areas of India, water is commonly sourced from open wells. In the state of Kerala, with a of population 32 million persons, there are over 250 open wells per square kilometer. This total, estimated at 5.8 million is the highest in the world. But the majority of these wells had become unusable, due to high saline content and a low water table. The average life span of wells providing clean safe water is a mere 5 to 6 years.

In 2004 PLANET Kerala, a local non-government organization that addresses issues related to community development and environmental response, began to take a hard look at this issue. Choosing a small village located in Kadalundi, Calicut district in north Kerala, representatives met with community leaders and families who were faced with a serious water shortage.

Since Kerala lies along the Arabian Sea, it is the first state in India to receive the monsoon rains that fall twice per year, from the southwest and the northeast. The rainy season lasts nearly four months and is particularly abundant, with an annual rainfall of 3000 mm (119 inches), but these rains were never really harvested which often led to flooding and run off. As a result, the water table has been depleted and many wells have become unusable. Many households in some coastal areas of Kerala were faced with no choice but to buy water from outside sources as they watched their wells deteriorate, not knowing how to find a solution.

As the PLANET Kerala representatives presented the concept of backwashing to the community, they explained that lack of water could be solved through the process of diverting water back into their wells, to replenish the water table and rejuvenate their wells back into use as before. 20 households volunteered to be part of this pilot project. PLANET Kerala would provide the expertise in how the process would function and the households would be responsible for covering the cost.

2. Activities

Backwashing is a method to regenerate shallow open wells by harvesting rain water from rooftops. The practice aims to replenish the ground water table as well as reducing flooding due to run off water clogging storm water drains.

The coastal regions of Kerala have an abundant natural water source provided through the annual monsoon season as over 3000 mm of rainwater falls with a period of approximately 120 days. Backwashing provided a solution to utilize this natural source of water.

PLANET Kerala introduced this concept of backwashing in Kadalundi in 2004, selecting 20 households whose well had been rendered useless due to contamination and depleted water tables. They organized meetings to demonstrate the principle and convince the families of the long term benefits. Through continuous follow up visits more households were brought into the program. Currently there are 50 households in Kadalundi alone with 300 in the three districts where the practice was first introduced.

The process of backwashing is quite simple, involving collection of rain water from rooftops using a gutter or other suitable receptacles that feeds directly into open wells located within the household premises(see picture). A filtering device at the end of the pipe or gutter system will catch the debris before it enters the well. Backwashing does not involve any additional storage structures compared to conventional rainwater harvesting units. The cost of this infrastructure varied from tiled roofs (1000-1300 Rs), flat terraced roofs (300-750Rs), slope terraced roofs (200-1000 Rs) and thatched roofs (1000 Rs) (1). The cost of this was covered by the households.

The first rains wash off the roof tops and channels, with subsequent rainwater diverted into the well. As the water is diverted into the well the soft rainwater mixes with the existing water. Gradually the well adjusts with the new influx of water, regenerating itself and the water table below.

(1) The exchange rate in 2004 was approximately US$1=Rs44
3. Key outcomes

The initiative of PLANET Kerala and the involvement of the communities using simple and cost effective methods of collecting rainwater have regenerated wells that were once deemed unusable.

The results of the study and data provided by PLANET Kerala based a sample of 20 households that were monitored during one year period demonstrate the success of using this method of backwashing. It was noted that prior to the project taking effect in December 2004, the wells were providing 5% of their drinking/cooking water, 85% for cleaning and 15% for bathing purposes. One year later, the wells, now rejuvenated by the backwashing process, were able to provide 35% of the drinking/cooking water, 95% for cleaning and 100% for bathing purposes. Not only had the well systems been restored but the reduction in sourcing bulk water from the outside had been greatly reduced.

4. Sustainability and replication

Backwashing is a practical modification of the conventional rainwater harvesting adapted to suit local conditions. Basically the key innovation lies in the modification of the methodology for harvesting water so as to render the practice affordable to a vast number of households, resulting in tangible and quick results. Some of the key factors making the practice attractive include:

Affordability – low cost
Adaptability – any roof top is suitable
No operational costs
Minimum skill required for installation – local talent sufficient
System fabricated from locally available materials
Capitalise on the availability of a large number of open wells
Revival of the investment lost in the wells rendered unusable
The practice has been proven effective in Kerala, an area of consistent annual rainfall, and has a huge potential for upscaling. Assuming a modest collection per household of 100,000 litres, with an average cost of Rs.1,000 and a life expectancy of 5 years, the cost of backwashing works out to a mere Rs.3 per kl of harvested water. Even though the immediate benefits would be more apparent in regions with over 1500 mm per annum of rain fall, adoption of the practice in areas having lower rainfall also will have a positive effect.

5. Contact information

Dr. K.C. Bellarmine
18/952, Waterland Road, Palluruthy
COCHIN – 682006, INDIA
Phone: +91-484-2234368
Mobile: +91-98470-70001
Email: bellarmine.kc@gmail.com