Groundwater exploitation and Land Subsidence

Subject :Geography

Section: Physical geography

Concept :

Several independent studies have found out that the excessive groundwater extraction is causing land subsidence in north-west India, including Punjab, Haryana, Delhi, and Faridabad.
The Central Ground Water Board (CGWB), a subsidiary body of the Jal Shakti Ministry, is tasked with assessing the state of India’s groundwater resources.
It has a system of groundwater observation-wells and monitors water levels four times a year. It, however, does not analyse the consequences of ‘over exploitation.’

Over exploitation:

Agricultural practices in north-west India are heavily dependent on groundwater withdrawal. With limited monsoon rain, the groundwater table is precariously low.
The CGWB has reported that many groundwater blocks are over-exploited, leading to the depletion of underlying aquifers.
In Punjab, for instance, 76% of the groundwater blocks are ‘over exploited’. In Chandigarh, it is 64% and about 50% in Delhi. This means that more groundwater than can be recharged is extracted.
Land subsidence is caused when these aquifers run dry and the layers of soil and rock above them start to sink.
GRACE (Gravity Recovery and Climate Experiment) satellites based analysis has shown a correlation between building deformities and groundwater withdrawals, and unplanned growth and urbanisation have exacerbated the issue in some parts of Delhi-NCR.
Land subsidence can lead to increased flooding, as the land sinks and reduces the capacity of water bodies to hold water. In the Ganga basin, over-extraction of groundwater has caused the land to sink, leading to flooding in the area.

Gravity Recovery and Climate Experiment (GRACE)

The Gravity Recovery and Climate Experiment (GRACE) was a joint mission of NASA and the German Aerospace Center (DLR).
Twin satellites took detailed measurements of Earth’s gravity field anomalies from its launch in March 2002 to the end of its science mission in October 2017.
By measuring gravity anomalies, GRACE showed how mass is distributed around the planet and how it varies over time.
Data from the GRACE satellites is an important tool for studying Earth’s ocean, geology, and climate.

GRACE-FO Mission

The Gravity Recovery and Climate Experiment Follow-On (GRACE-FO) mission is a partnership between NASA and the German Research Centre for Geosciences (GFZ).
GRACE-FO is a successor to the original GRACE mission, which orbited Earth from 2002-2017.
It carries on the extremely successful work of its predecessor while testing a new technology designed to dramatically improve the already remarkable precision of its measurement system.

Why need such data on groundwater and soil moisture?

Groundwater and soil moisture — which depicts wetness in soil — are crucial for irrigation and crop growth.
The need to constantly monitor groundwater and soil moisture is important since both act as useful indicators for predicting drought conditions.
One of the goals of the new global maps is to make the same consistent product available in all parts of the world, especially in countries that do not have any groundwater-monitoring infrastructure.
The data would help in managing the selection of appropriate agricultural crops and predicting yields.