Rainwater harvesting is the best way forward for irrigation
As intensive agriculture spreads across India, there is an urgent need to encourage rainwater harvesting to irrigate multiple crops instead of the current unsustainable practice of groundwater extraction
There’s increasing concern about the growing demand for irrigation and emerging unsustainable practices of groundwater exploitation. This has been my major preoccupation for the past three decades. It was in 1990, when I started exploring problems of farming in Purulia and Bankura districts of West Bengal and adjoining areas of Jharkhand, that I realised unless farmers are encouraged to conserve rainwater in their own field, it would be difficult to meet the demand of irrigation to save their crops from dry spells.
My engagement with farmers on irrigation infrastructure development was guided by the understanding that, so long we are not taking best possible care of rainwater that we receive on our land, we should not think of exploiting other water resources. At that time I proposed that at least five percent of each piece of land or each farmer’s holding should be converted into small water harvesting structures.
That was in context when farmers were primarily worried about saving their Kharif (summer) paddy from dry spells during flowering. The idea emerged through interaction with several village communities in Purulia. If a patch of land, say of 100 hectares, is treated for rainwater harvesting, this area would have five hectare of water bodies and each farmer would have free access and full control over water they require.
The question of equity was addressed within the design of land treatment, unlike big dam and canal based irrigation. Demonstrations were made with varied degree of success. In some villages, where soil was not so sandy or clay loam, there was no need for irrigation even during a dry spell of 24 days (in September 1992) as local moisture of treated area with the 5 percent model got enhanced.
More systematic approach required
However, during the past three decades, demand for irrigation has gone up. Farmers are producing two to three crops. Therefore, a more systematic and scientific approach to rainwater harvesting is required to work out an appropriate design.
Recently, on a visit to rural West Bengal and Chhattisgarh, I found farmers have been encouraged to exploit groundwater to meet increased irrigation demand. The practice of using submersible pumps to draw water from 100 ft to 300 ft is now common.
In some places (for example, Kulik river basin in North Dinajpur of West Bengal), farmers said that the shallow water table (up to 50 ft) that was supplying water for the Rabi (winter) crop now gets so depleted in winter that it affects dry season flow in the local river. Similar experiences must be common in other river basin as well.
Farmers are now installing deep tube wells and selling water, earning Rs 2000 to Rs 3000 per bigha (about 0.3 to 0.5 acre, depending upon the local unit of bigha) per season. Thus, one tube well owner supplying water to 25 bighas is earning Rs 50,000 to Rs 75,000 in a cropping season, against her investment of Rs 100,000 to Rs 150,000. Thus, a common property is being exploited for individual profit without any accountability for the depletion of an aquifer.
A rough calculation shows that a winter crop of one acre would require about 0.3 acre meter to 0.5 acre meter (or 3,000 to 5,000 cubic meter) of water, depending upon type of crop. If the depth of each irrigation were 2 inches or 5 cm, a crop that needs six irrigations would require 30 cm, and if a crop demands 10 irrigations, it would require 50 cm. By multiplying this depth with area of land, one can get a volume of water in cubic meters. It could be possible that a tube well owner is drawing 100,000 cubic meter of water per season to earn Rs 50,000. These are rough calculations.
We may thus assume that to get 1 cubic meter of water, one needs to deplete about 4 to 5 cubic meter of aquifer volume. Thus, for 100,000 cubic meter of water, one needs to deplete 400,000 to 500,000 cubic meter of an aquifer. Deeper the aquifer, lower is the possibility of natural annual replenishment through monsoon rain. This would badly affect the future water availability in an area.
Regulate groundwater exploitation
Thus, there is a need to come up with policies to regulate groundwater exploitation. At the same time, we cannot stop growth of intensive farming. Where would the additional water come from? To my understanding, rainwater harvesting is only sustainable solution. Keeping the future scenario in mind, all state governments should come up with policies to encourage rainwater harvesting based on a scientific assessment of irrigation demand.
At least 70 percent of demand should be met from rainwater harvesting.
The fear of declining land availability from agriculture could be addressed through intensification and diversification in farming. Again, there are deeper technical matters involved in this and this paper in not the appropriate place to get in to that.
There have been many such initiatives made by different state governments under the rural jobs guarantee scheme but they need to be strengthened with right policies to stop free riding.
Some development experts say why should the onus of rainwater harvesting be only on farmers when groundwater depletion is a national problem? We must realize that out of the total national water use across sectors, about 80percent or more water is used for farming.
More that 70% or more rainwater is also received in rural areas since farmland is 60 percent of India’s geographical area and forest is 23 percent. I would also assume that about 60 percent of the water must be received directly on farmlands.
It could be assumed that the volume of runoff water is proportionate to sector-wise distribution of area of lands. So, the potential for rainwater harvesting is proportionate to the volume of runoff available from respective areas. That tells us that farmlands are significant in terms of its potential of rainwater harvesting.
Why should farmers be made responsible for this important task? As a nation, all of us responsible, but as we accept private ownership over land, how can we start any movement if the farmers are not ready? If rainwater is available on my piece of land, who can or should harvest it other than me? There are enough examples that farmers can increase on farm water availability by converting cultivable land into water harvesting structures. And that has immediate positive economic impact on a farmer family.
Under the present context, it is the farmers who should be made responsible to harvest their water that they use to earn their livelihoods.
If one is using 2,000 cubic meter of water (pumping it out either from a local river, or groundwater or a tank) to grow one acre of wheat or vegetables, who should be responsible to add same volume of water back in to her ecosystem so that she has access to same volume of water next year?
We also have to keep in mind that there are politics of water division. And there is going to be more aggressive political tension at the local to International levels. But let us also understand that the problem of water scarcity cannot be addressed through politics and power games. First, there has to be technological breakthrough in water resource management. Secondly, there is need for more effective extension of technologies. Thirdly, this requires policy support to make every water user responsible and accountable for the volume of water one uses.
All stakeholders, particularly farmers and institutions closer to the government, particularly Panchayati Raj Institutions, should be helped and made responsible and accountable with required policies to create their own water resources. Those who are not contributing to replenishing water resource in their ecosystem should not be allowed to draw water from other sources for farming. Only then we can ensure that rainwater harvesting and not unsustainable groundwater exploitation powers India’s agriculture.
Disclaimer: This article was first published in VillageSquare.in. The views expressed by the author are his/her own and do not necessarily reflect that of YourStory.