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Insights into Editorial: Groundwater depletion may reduce winter cropping intensity by 20% in India

 

Introduction:

Water is indispensable for life, but its availability at a sustainable quality and quantity is threatened by many factors, of which climate plays a leading role.

The Intergovernmental Panel on Climate Change (IPCC) defines climate as “the average weather in terms of the mean and its variability over a certain time-span and a certain area” and a statistically significant variation of the mean state of the climate or of its variability lasting for decades or longer, is referred to as climate change.

 

India’s Irrigation system:

  1. India is the second-largest producer of wheat in the world, with over 30 million hectares in the country dedicated to producing this crop.
  2. But with severe groundwater depletion, the cropping intensity or the amount of land planted in the winter season may decrease by up to 20% by 2025, notes a new paper.
  3. Some of the important winter crops are wheat, barley, mustard and peas.
  4. The international team studied India’s three main irrigation types on winter cropped areas: dug wells, tube wells, canals, and also analysed the groundwater data from the Central Ground Water Board.
  5. They found that 13% of the villages in which farmers plant a winter crop are located in critically water-depleted regions.
  6. The team writes that these villages may lose 68% of their cropped area in future if access to all groundwater irrigation is lost.
  7. The results suggest that these losses will largely occur in northwest and central India.

 

Occurrence of Flash droughts:

  1. Flash droughts are those that occur very quickly, with soil moisture depleting rapidly. Normally, developing drought conditions take months, but these happen within a week or in two weeks’ time.
  2. Several factors including atmospheric anomalies, anthropogenic greenhouse gas emissions play an important role.
  3. In 1979, India faced a severe flash drought, affecting about 40% of the country and taking a toll on agriculture.
  4. An article published that year in the journal India International Centre Quarterly noted that the big granaries of Uttar Pradesh and Andhra were affected, and the country suffered a loss of about ₹5,000 crores.
  5. A new study has now pointed out that India could experience more such flash droughts by the end of this century.

 

Alternative sources of Irrigation:

The team then looked at canals to understand if they can be promoted as an alternative irrigation source and as an adaptation strategy to falling groundwater tables.

But the results showed that “switching to canal irrigation has limited adaptation potential at the national scale. We find that even if all regions that are currently using depleted groundwater for irrigation will switch to using canal irrigation, cropping intensity may decline by 7% nationally,” notes the paper published in Science Advances.

When asked what new or additional adaptation strategies can be implemented, corresponding author Meha Jain explains: “We can conjecture based on other literature and say that adoption of water-saving technologies like a sprinkler, drip irrigation and maybe switching to less water-intensive crops may help use the limited groundwater resources more effectively”.

 

Climate Change Scenario for Groundwater in India:

About 85% of the rural water supply in India is dependent on groundwater.

  1. India on the whole has a potential of 631 bcm/year of replenishable groundwater, Unfortunately, due to rampant drawing of the subsurface water, the water table in many regions of the country has dropped significantly in the recent years resulting in threat to groundwater sustainability.
  2. The overexploited areas are mostly concentrated on three parts of the country.
    1. In north western part in Punjab, Haryana, Delhi, Western Uttar Pradesh where through replenishable resources is abundant but there have indiscriminate withdrawals of ground water leading to over-exploitation.
    2. In western part of the country particularly in Rajasthan where due to arid climate, ground water recharge itself is less leading to stress on the resource and in peninsular India like Karnataka and Tamil Nadu where due to poor aquifer properties, ground water availability is less.
  3. The most optimistic assumption suggests that an average drop in groundwater level by one metre would increase India’s total carbon emissions by over 1%, because the time of withdrawal of the same amount of water will increase fuel consumption.
  4. A more realistic assumption reflecting the area projected to be irrigated by groundwater, suggests that the increase in carbon emission could be 4.8% for each metre drop in groundwater levels.
  5. It is recommended to study the aquifer geometry, establish the saline fresh interfaces within few km of the coastal area, the effect of glaciers melting on recharge potential of aquifers in the Ganga basin and its effects on the transboundary aquifer systems, particularly in the arid and semi-arid regions.

 

Unsuited soils: about the problem’s wheat farmers face in our country:

  1. There are several first-generation (productivity) and second-generation (sustainability) problems.
  2. In the green revolution era, policy-supported environment led to a large increase in rice cultivation in north-western India mainly in Punjab and Haryana which are ecologically less suitable for rice cultivation due to predominantly light soils.
  3. This policy-supported intensive agriculture led to unsustainable groundwater use for irrigation and in turn groundwater scarcity.
  4. There was also post-harvest residue burning to make way for the timely sowing of wheat.

There are enough groundwater resources supported with higher monsoon rainfall in eastern Indian states like Bihar.

But due to lack of enough irrigation infrastructure, farmers are not able to make use of natural resources there.

 

Conclusion:

We need better policies in eastern India to expand the irrigation and thus increase agriculture productivity. This will also release some pressure from north-western Indian states.

Water resource management plans increasingly need to incorporate the affects of global climate change in order to accurately predict future supplies.

Numerous studies have documented the sensitivity of streamflow to climatic changes for watersheds all over the world.

Most of these studies involve watershed scale hydrologic models, of which validation remains a fundamental challenge.

Moreover, outputs from general circulation models (GCM) can be rather uncertain and downscaling their predictions for local hydrologic use can produce inconsistent results.

Therefore, the sensitivity of streamflow to climate changes is perhaps best understood by analyzing the historical records.