Bengaluru: A study conducted by researchers at the Dehradun-based Indian Institute of Remote Sensing (IIRS) — a wing of the Indian Space Research Organisation (ISRO) — has found that the water conservation policy implemented in the food-bowl states of Punjab and Haryana has led to faster depletion of groundwater and higher levels of pollution.
This has happened due to the shrinking of the crop harvesting window, which has resulted in stubble burning fires that were earlier spread out to now coincide with change in wind patterns, which causes winds to slow down and reduce aerosol dispersion, drastically increasing pollution over North India.
The study, titled ‘Long term influence of groundwater preservation policy on stubble burning and air pollution over North-West India’, was published on 8 February in Scientific Reports, an open access, peer-reviewed scientific journal based in the US.
The researchers investigated long-term satellite data sets of seasonal pollution sources and ground measurements to understand the impact of the Preservation of Subsoil Water Act, 2009. The Act was brought in by the Punjab and Haryana governments to preserve groundwater — a vital resource that has been exploited to the hilt in both states — by forbidding the sowing of paddy before 10 May and transplantation before 10 June, allowing for the crop to be sown only during the monsoon months.
As a result, wheat is sown in both states in November-December and harvested in April-May, while paddy is sown in June-July (monsoon months) and harvested in October-November.
The study also states that due to implementation of the National Policy for Management on Crop Residue (NPMCR) and awareness programmes among farmers, stubble burning has gone down marginally over the last four years.
The authors recommend use of shorter duration rice varieties, direct seeding of rice (as opposed to the traditional method of transplanting) which reduces water consumption, diversification of kharif crops, and economic solutions to farmers for better stubble management.
ThePrint sought comments on the issue from the Commission for Air Quality Management via email and text, and the chief ministers’ offices of Punjab and Haryana via email. This report will be updated when their responses are received.
Shift in harvest window
Earlier, paddy used to be transplanted from early June. Since the crop is water-intensive, the Preservation of Subsoil Water Act — which was implemented in both states separately — aimed to reduce groundwater consumption during a high period of evapotranspiration naturally occurring during peak summer. So the whole cycle was shifted forward by 10-15 days, to the July monsoons.
As a result, the harvest window has also shifted from the second week of October to the first week of November. This subsequently leaves farmers with less time to clear land for the next crop. For ease of clearing, farmers resort to burning crop residue, which releases aerosols and harmful particulate matter into the atmosphere.
Stubble burning & pollution
Of the total global biomass burning, 80 per cent is contributed by Southeast Asia, Southern Africa, South America and Australia — the tropical regions. A quarter of that is stubble burning, of which 34 per cent comes from Asia. Of that, 44 per cent is contributed by China, and 33 per cent by India.
In India, 16 per cent of biomass burning occurs in farms and fields. Paddy straw makes up the major chunk of the residue burned, followed by wheat straw and sugarcane. According to a 2014 study, Punjab burns 21.32 million tons of stubble each year, while Haryana burns 9.18 million tonnes. Over the last 15 years, the total production of wheat and paddy in both states has increased, as has their residue.
In Punjab and Haryana, wheat stubble is burned in April and May before the monsoons, while paddy stubble is burned in October and November, after monsoon.
From 2002 to 2020, the average number of fires in these two states pre-monsoon was 3,585 per year and 15,972 post-monsoon. Satellite data indicates that post-monsoon fires are four to five times higher in number than pre-monsoon fires. Paddy stubble has increased by a steady 36 per cent over the last two decades, while wheat stubble fires have increased by 4 per cent, the study found.
The data also shows that from 2010, fires have reduced in April and October, and have increased in May and November, indicating a very short harvest window.
According to the study, since 2010, the amount of aerosols suspended in the atmosphere from stubble burning has gone up nearly 10 per cent, with a 17.5 per cent increase in PM2.5 particulate matter. These particles get transported downwind from the two states towards the National Capital Region (NCR) over 4-6 days, deteriorating air quality below permissible standards.
Long-term satellite data shows that stubble burning has increased at a rate of 250 fires per year in the two states in the last 15 years, despite policies to tackle the problem.
The smoke from these fires is also a major contributor to the pollution over North India throughout the year, that adversely affects countless Indians. It is estimated that over 66,000 deaths can be attributed to the stubble burning period in 2015.
The study shows a corresponding shift in the accumulation of atmospheric particulate matter over NCR and other northern states consistent with the change in stubble burning patterns.
According to the researchers, satellite data shows that after 2010, post-monsoon paddy fires increased by 21 per cent. Fires have also shifted from April to May, and have a more significant jump from October to November.
A small increase in fires was observed during the pre-monsoon season as well from wheat.
The increase as well as shift in the peak of farm fires coincide with the festive season in North India, which further contributes dust, smoke and aerosol particulates PM 2.5 and PM 10 to the atmosphere.
The situation has been aggravated since 2010 due to delayed stubble burning after monsoon, when majority fires also coincide with a change in wind patterns. In October, aerosols disperse better before the change of winds that occur in early November, as also seen in satellite data before 2010, explained Dr Prakash Chauhan, IISR-ISRO director and one of the authors of the paper.
“From our analysis of long-term data, we can conclusively say that the act implemented by the government has led to higher pollution levels in North India,” he told ThePrint.
Groundwater level changes
From their analysis of groundwater data, the researchers found that unlike variations in stubble burning data, the groundwater levels have continued to be on a steady decline. Compared to 2002-2009, there was a temporary improvement in groundwater storage in 2010, but after 2014, the levels declined more drastically.
Punjab lost 1.29 cubic kilometres of groundwater every year between 2002-2009, while Haryana lost 1.46 cubic kilometres. Between 2014 and 2017, Haryana continued to experience the same level of groundwater loss, but Punjab’s increased to 1.32 cubic kilometres per year, the study says.
“The policy has failed. Not only has it been unable to save groundwater, it is also increasing pollution. This needs to be addressed immediately,” said Dr Chauhan.
He further said that the findings have been shared with the Commission for Air Quality Management, and the authors urge for policy changes to tackle the pollution and groundwater problem.
“In recent years, people are working on using biomass for other purposes. The government is also working on providing financial incentives or buyback of biomass. In the last 3-4 years, the number of fires seems to be going down,” said Dr Chauhan. The paper shows that there has been a marginal decline of 5 per cent in fires over the last four years.
Governments of the two states also have to start working aggressively with farmers on directing seeding of rice (DSR), he explained. The technique is shown to reduce water consumption by 30 per cent.
The authors also stressed on a need for policies on rainwater harvesting and adoption of other water conservation technology, as well as renovation and use of village ponds, improved irrigation with canals, shifting from monoculture to diversified crop patterns, and replacing rice varieties with shorter duration paddy varieties for faster harvest.
(Edited by Gitanjali Das)