Villagers captured rainwater wherever it fell. A hectare of desert land in Barmer, for example, can capture 1 million litres with a rainfall of just 100 mm
Over the last around 100 years, the world has witnessed two major shifts in water management:
One, individuals and communities steadily handed over their role to the State despite the fact that more than 150 years ago no government anywhere in the world provided water.
Second, the use of simple technologies of harvesting and using rainwater declined. And, exploitation of rivers and groundwater through dams and tube wells became the key source of water.
Water in rivers and aquifers was only a small portion of the total rainwater. So, there was an inevitable, growing and, in many cases, unbearable stress on them.
Dependence on the State also meant that costs of water supply were high. Poor cost of recovery drove financial sustainability of water schemes aground and repairs and maintenance were in an abysmal state.
With nobody interested in carefully using water, sustainability of water resources became doubtful — a problem India witnessed recently. This meant there were serious problems with government drinking water supply schemes.
Every year for seven years 0.14 million habitations slipped out of the government's rural drinking water programmes, according to a report presented in the Lok Sabha in 2016. So despite the government pumping in crores to take drinking water to nearly 1.7 million habitations during 2007-2014, 58 per cent of them slipped to 'not covered' status or needed fresh investments through new projects to supply water. This is the reason the government had to deploy hundreds of tankers to supply water to villages during drought.
But how did communities access water before the government? Imagine you had a hectare of land in Barmer, one of the driest places in India. You would receive just 100 millimetres of water a year. This is as much as 1 million litres (Ml) of water — enough to meet the drinking and cooking water needs of 182 people for a year at a liberal 15 litres per day.
Even if you were not able to capture all that water — depending on the rainfall and the type of run-off surface — you could still capture at least 0.5 Ml a year, even with rudimentary technology.
It was, in fact, only with this rudimentary technology that people came to inhabit the Thar desert and made it the most densely populated desert in the world.
Now, assume that one could capture the 2,000 mm annual rainfall that eastern India usually receives. One would need only 500 square metres of land (21 m x 21 m plot) to capture 1 million litre of rainwater.
The rural population density follows the intensity of annual rainfall. Barmer, which receives less rainfall, is sparsely populated. Here, a lot of land is available per person. On the contrary, 24 Parganas in West Bengal, which receives a copious amount of rainfall, is densely populated.
In fact, there is no village in India that cannot meet its basic drinking and cooking needs through rainwater harvesting.
Census 2011 showed that India had 0.64 million inhabited villages with a total population of 833 million. This means every village has an average population of 1,300. India’s average annual rainfall is about 1,088 mm.
It varies from about 200 mm in the deserts of western India to more than 25,000 mm in the hills of the North East. Nearly 12 per cent of the country receives an average rainfall of less than 610 mm per annum while 8 per cent receives more than 2,500 mm. But more than 50 per cent of this rain falls in about 15 days and in less than 100 hours, of the total 8,760 hours in a year.
The total number of rainy days in a year can range from as less as five in desert regions of Gujarat and Rajasthan — though some of these days can record high-intensity rainstorms — to 150 days in the North East.
Given that an individual consumes eight litres of water a day, an average village requires almost 3.8 Ml water a year for drinking and cooking. This means an average village would require 0.17 ha to catch this rainfall even if half the average rainfall was captured.
If there was a drought and the rainfall amount halved, the land requirement would increase to 0.7 ha. In Rajasthan, the land required would vary from 0.98-2.29 ha in different meteorological regions and, in Gujarat it would be between 1.22 and 2.39 ha even, if there was a 50 per cent deficit of rainfall.
The amount of land needed to meet the drinking water needs of an average village would vary from 0.10 ha in Arunachal Pradesh, where villages are small and rainfall is high, to 8.46 ha in Delhi, where villages are big and rainfall is low. And, of course, people can use the surplus amount of harvested rainwater for irrigation. This is precisely what the “dream catcher” villages did.
Is there any village that does not have this much of land available? India’s total land area is more than 288 million ha. Assuming that India’s villages could harvest surface run-off from 144 million ha, excluding the inaccessible forest areas, high mountains and other uninhabited terrains, it still gives every village access to about 224 ha, or a rainfall endowment of 2.44 billion litres.
These calculations show that the potential of rainwater harvesting is enormous and undeniable.
Recognising the fact that almost all the rain came down in a few days, ancient Indians learnt to harvest rainwater in a variety of ways. In Rajasthan, people collected water flowing down from rooftops and stored it in tanks built in their courtyards. They stored the rain falling on open community lands in artificial wells, called kundis.
In water-surplus areas, people harvested monsoon run-off by capturing water from swollen streams and stored it in zings in Ladakh, ahars in Bihar, johads in Rajasthan and Eris in Tamil Nadu, to name a few. Even in north Bihar and West Bengal, people harvested water from flooded rivers.
So, it is possible to drought-proof the entire country. It is possible to provide not just drinking water to all but also irrigation water to most of the agricultural fields — of course for growing crops that are less water-intensive.
The strategy is to ensure that every village captures all the run-off resulting from the rain falling over its entire land and the associated government revenue and forest lands, especially during years when the rain is normal. Then the villages should store it in tanks or ponds or use it to recharge the depleting groundwater.
Only then the country can have enough water in its tanks and wells to irrigate lands in every single village.
(This is based on a briefing for parliamentarians done by late environmentalist and founder editor of Down To Earth Anil Agarwal. Download the complete paper here: http://www.rainwaterharvesting.org/downloads/drought_english.pdf)
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