WATER HARVESTING SYSTEM - AVAILABLE ALTERNATIVE

WATER HARVESTING SYSTEM -  AVAILABLE ALTERNATIVE

Many thought that given the disadvantages and rising resistance against the multi-purpose projects, a water harvesting system was a viable alternative, both socio-economically and environmentally. In ancient India, along with the sophisticated hydraulic structures, there existed an extraordinary tradition of water-harvesting systems. People had in-depth knowledge of rainfall regimes and soil types and developed wide-ranging techniques to harvest rainwater, groundwater, river water, and floodwater in keeping with the local ecological conditions and their water needs. In hill and mountainous regions, people built diversion channels like the ‘guls’ or ‘kuls’ of the Western Himalayas for agriculture. ‘Rooftop rainwater harvesting’ was commonly practised to store drinking water, particularly in Rajasthan. In the flood plains of Bengal, people developed inundation channels to irrigate their fields. In arid and semi-arid regions, agricultural fields were converted into rain-fed storage structures that allowed the water to stand and moisten the soil like the ‘khadins’ in Jaisalmer and ‘Johads’ in other parts of Rajasthan.

Figure:  Collect information about flood-prone areas of the country

Source: This topic is taken from NCERT TEXTBOOK

TANKAS

TANKAS

In the semi-arid and arid regions of Rajasthan, particularly in Bikaner, Phalodi and Barmer, almost all the houses traditionally had underground tanks or tankas for storing drinking water. The tanks could be as large as a big room; one household in Phalodi had a tank that was metres deep, 4.27 metres long and 2.44 metres wide. The tankas were part of the well-developed rooftop rainwater harvesting system and were built inside the main house or the courtyard. They were connected to the sloping roofs of the houses through a pipe. Rain falling on the rooftops would travel down the pipe and was stored in these underground ‘tankas’. The first spell of rain was usually not collected as this would clean the roofs and the pipes. The rainwater from the subsequent showers was then collected.

Rooftop Rainwater Harvesting steps

* Rooftop rainwater is collected using a PVC pipe

* Filtered using sand and bricks

* Underground pipe takes water to sump for immediate usage

* Excess water from the sump is taken to the well

* Water from the well recharges the underground

* Take water from the well (later)

(a) Recharge through Hand Pump

(b) Recharge through Abandoned Dugwell

Figure 3.3: (a),(b) - Rooftop Rainwater Harvesting

The rainwater can be stored in the tankas till the next rainfall making it an extremely reliable source of drinking water when all other sources are dried up particularly in the summers. Rainwater, or palar pani, as commonly referred to in these parts, is considered the purest form of natural water. Many houses constructed underground rooms adjoining the ‘tanka’ to beat the summer heat as it would keep the room cool. 

Today,  in western  Rajasthan,  sadly the practice of rooftop rainwater harvesting is on the decline as plenty of water is available due to the perennial Indira Gandhi Canal, though some houses still maintain the tankas since they do not like the taste of tap water.

Figure 3.4: 

Fortunately, in many parts of rural and urban India, rooftop rainwater harvesting is being successfully adapted to store and conserve water. In Gendathur, a remote backward village in Mysuru, Karnataka, villagers have installed, in their households’ rooftop, rainwater harvesting system to meet their water needs. Nearly 200 households have installed this system and the village has earned the rare distinction of being rich in rainwater. See Fig. 3.6 for a better understanding of the rooftop rainwater harvesting system which is adapted here. Gendathur receives annual precipitation of 1,000 mm, and with 80 percent of collection efficiency and of about 10 fillings, every house can collect and use about 50,000 litres of water annually. From the 200 houses, the net amount of rainwater harvested annually amounts to 1,00,000 litres.

Figure 3.5: Traditional method of rainwater harvesting

​(A kul leads to a circular village tank, as the above in the Kaza village, from which water is released as and when required.)

Figure 3.6: (Rooftop harvesting was common across the towns and villages of the Thar. Rainwater that falls on the sloping roofs of houses is taken through a pipe into an underground tanka (circular holes in the ground). Built-in the main house or in the courtyard. The picture above shows water being taken from a neighbour’s roof through a long pipe. Here the neighbours’  rooftop has been used for the collection of rainwater. The picture shows a hole through which rainwater flows down into an underground tanka)
 

More to know

1. Rooftop rainwater harvesting is the most common practice in Shillong, Meghalaya. It is interesting because Cherapunjee and Mawsynram situated at a distance of 55 km. from Shillong receive the highest rainfall in the world, yet the state capital Shillong faces an acute shortage of water. Nearly every household in the city has a rooftop rainwater harvesting structure. Nearly 15-25 percent of the total water requirement of the household comes from rooftop water harvesting.

2. Tamil Nadu is the first state in India which has made rooftop rainwater harvesting structure compulsory to all the houses across the state. There are legal provisions to punish the defaulters.

Activity:

1. Find out other rainwater harvesting systems existing in and around your locality.

2. Collect information on how industries are polluting our water resources.

3. Enact with your classmates a scene of water dispute in your locality

Source: This topic is taken from NCERT TEXTBOOK

BAMBOO DRIP IRRIGATION SYSTEM

BAMBOO DRIP IRRIGATION SYSTEM

In Meghalaya, a 200-year-old system of tapping stream and spring water by using bamboo pipes, is prevalent. About 18-20 litres of water enters the bamboo pipe system, gets transported over hundreds of metres, and finally reduces to 20-80 drops per minute at the site of the plant.

Picture 1: Bamboo pipes are used to divert perennial springs on the hilltops to the lower reaches by gravity.

Picture 2,3: The channel sections, made of bamboo, divert

Picture 4:  If the pipes pass a road, water to the plant site where it is distributed into branches, again they are taken high above the land. made and laid out with different forms of bamboo pipes. The flow of water into the pipes is controlled by manipulating the pipe positions.

Picture 5,6:  Reduced channel sections and diversion units are used at the last stage of water application. The last channel section enables water to be dropped near the roots of the plant.

Source: This topic is taken from NCERT TEXTBOOK