Groundwater Depletion

Important Facts

  • The total estimated groundwater depletion in India is in the range of 122–199 billion metre cube.
  • With 230 billion metre cube of groundwater drawn out each year for irrigating agriculture lands in India, many parts of the country are experiencing rapid depletion of groundwater.
  • The Indo-Gangetic Plain, northwestern, central and western parts of India account for most intensive groundwater-based irrigation.
  • And among these regions, western India and the Indo-Gangetic Plain have more than 90% of the area irrigated using groundwater.
  • While districts with significant decrease in groundwater are located in the Indo-Gangetic Plain, northwest, and central (Maharashtra) regions, a few districts in Punjab show substantial decline in groundwater table.
  • With depletion occurring at a rate of 91 cm per year, Punjab has been witnessing a steep decline in groundwater table since 1996.
  • In northwestern India, the amount of groundwater extracted exceeds the total recharge leading to groundwater depletion
  • In contrast, some districts in western India, east coast and peninsular India have witnessed an increase in groundwater levels.
  • Low-intensity rainfall during the monsoon is responsible for groundwater recharge in northwest and northcentral India.
  • The study also found that carbon dioxide emission from pumping groundwater and release of carbon dioxide into the atmosphere from the soil when groundwater is depleted is less than 2-7% of the total carbon dioxide emissions in India.

 

Consequences:

  • If groundwater is depleted and the region experiences drought for two–three years consecutively, there will be serious challenges. Availability of even drinking water will be a huge problem.
  • Natural recharge during monsoon may not help much if groundwater depletion becomes acute, as rainfall of past several years controls the current groundwater storage levels.

 

Groundwater management using Tensiometers

  • More than 500 tensiometers to visually monitor soil moisture conditions in rice fields and irrigate the crops only when required were used in five districts in Punjab.
  • Irrigation based on information provided by the tensiometers helped farmers in the five districts save 10–36% groundwater.
  • Using groundwater to irrigate the field only when necessary led to a reduction in electricity consumption and greenhouse emissions.
  • The tensiometer gives visual information about the availability of soil moisture conditions.
  • Irrigating the field based on this information will help conserve groundwater.

 

About Tensiometer

  • The tensiometer is 2–3 feet long and has a ceramic cup containing numerous tiny pores at the bottom.
  • It is inserted up to 8 inches into the soil, which is beyond the root zone of rice.
  • The water inside the tensiometer reaches equilibrium with soil moisture, and rises or falls depending on the amount of moisture in the soil.
  • Farmers are advised not to irrigate the field when the water level in the tensiometer is in the green zone.
  • When the soil gets dry the water level in the tensiometer drops and reaches the yellow zone in the device.
  • Farmers should start irrigating the field at this time and never allow the water in the device to reach the red zone.
  • The instrument is quite accurate in monitoring soil moisture.
  • One device per farm would be sufficient, especially when the terrain is nearly flat.
  • So far, over 22,000 tensiometers, manufactured by Punjab Agriculture University, have been given to rice farmers in Punjab.

 

 

 

Way ahead

  • Since stopping or reducing the subsidy in electricity prices may not be possible, farmers in the regions where groundwater depletion has already occurred should consider cultivating less water-intensive crops, use better irrigation technologies and irrigate crops only when necessary.

 

Section : Environment & Ecolog

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