Muriel Kakani takes a trip across five Indian states to learn more about ancient rainwater harvesting techniques
India gets 75% of its rainfall during the four months of monsoon. In the dry season, water needs to be harvested and conserved. In ancient times, Indians built very elaborate and locally adapted rainwater harvesting structures that collected and stored monsoon precipitation. India's civilisation wouldn't have thrived for 5,000 years without this expertise in rainwater harvesting!
Today, however, water harvesting structures are neglected, in spite of government orders and severe water crises looming ahead. You would be shocked to know that due to a lack of proper storage and inappropriate water management, only 18% of monsoon precipitation is utilised!
Let's take a look at how Indian states used to harvest their rainwater!
Kunds are covered underground tanks prevalent in the arid regions on the fringes of the Thar Desert where groundwater is brackish. Kunds are sometimes the only source of clean drinking water in these areas.
A Kund is a circular pit with a diameter of roughly 2mts. The sides of the pit are plastered with lime mixed with ash. Each pit has a dome-shaped cover made from local wood and plastered with mud. On top of the kund is a lid that can be locked. Water is drawn out with a bucket. Each kund has several openings or inlets to let rainwater enter. The openings are covered with a wire mesh to prevent the entry of debris.
The catchment area of the kund has to be perfectly smooth and is given a gentle slope with a gradient of 3 to 4% towards the centre where the tank is situated. The catchment is plastered with local materials to make it waterproof. The success of the kund depends on the size of the catchment area.
Before the onset of the monsoon, the catchment area of the kund has to be cleaned and then cattle and people should avoid entering this area. Kunds are situated close to villages and are usually privately owned.
Most of West Bengal lies in the Indo-Gangetic Plains where the Ganga, Damodar, Padma, Brahmaputra and Meghna rivers flow. The area is the largest alluvial delta and one of the most fertile regions in the world.
During the monsoons, the flat, low-lying plains are inundated by the overflowing rivers. In the past, Bengal had an absolutely extraordinary system of flood or overflow irrigation. People used the inundation canals and the overflow of rivers to supply water to the fields. The overflow carried rich silt and an abundance of fish. The overflowing muddy waters of the rivers fertilised the land and brought fish that fed on the mosquitoes. The fish killed all the mosquitoes that would have caused malaria, making the area extremely healthy.
The flood irrigation system lasted for many years till it was uprooted by the British for the construction of railways. Today, most of the rivers of Bengal have been embanked, thus reducing fertility of the soil and increasing mortality to malaria and famine. The rivers that were once a boon have become a nuisance!
In South India, especially Tamil Nadu, temples had one or two tanks in their premises, usually one tank inside and one outside. Temples and tanks were inseparable.
In the past, these temple tanks were centres of cultural activity where people bathed on auspicious days of the Hindu calendar, held festivals and performed age-old religious rites. In the centre of the tank was a small shrine that housed the deity of the temple during festivals.
These temple tanks were a place for water storage and insurance against droughts. They were usually built in a square or rectangular shape with steps on all sides. They had wells located in their beds. The purpose of these wells was to recharge the Aquifer. Most temples tanks were rain-fed or fed through inlets connecting the temple tank to a catchment area. Today, most tanks are dry due to total negligence.
Ladakh is a high-altitude, cold desert where agriculture is almost impossible.
In the valleys, the growing season is restricted to the few summer months and the only sources of water are the melting snow and glaciers that feed streams rolling down the mountains. The water from streams that are fed by glaciers is diverted with the help of channels and collected in tanks called zings.
Each village has a large network of channels and tanks and thus lots of zings, which are maintained by village communities. The water harvested in the zings is the main source of water for irrigation. To ensure the fair distribution of the precious resource, a churpun or water Official is appointed. His duty is to see that each field gets irrigated.
The Khasi farmers of Meghalaya have a 200-year-old system of tapping streams using bamboo pipes. Bamboo pipes are used to divert several hundred metres of perennial spring water from hilltops to the fields in the lower valleys. What is most remarkable is that the water is distributed without any leakage on the way.
The flow of water is controlled by manipulating the size, diameter and position of the pipes. Pipes are adjusted perfectly at every stage of diversion to enable the water to be supplied at the rate of 20 to 80 drops per minute.
It takes 15 days, with two workers working all day, to install the bamboo pipes on a hectare of land. Once installed, the bamboo drop irrigation system is quite permanent. Maintenance is done by the farmers themselves.
Muriel Kakani is an author and illustrator of a book series called 'Ecological Tales from India'