Description

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Context

A recent study has found that depletion of soil moisture (SM) between 1979 and 2016 has contributed to 10.78 mm rise in Global Mean Sea Level highlighting an often overlooked contributor to sea level rise.

This corresponds to a loss of 3,941 gigatonnes of terrestrial water storage much of which is irreversible post 2003.

Regions

Regions with high depletion	Central Asia, East Asia, Central Africa, North & South America
Regions with recovery	Parts of India, North America, Australia (limited impact globally)

Mechanism

Soil Moisture Loss → Reduced Land Water Storage → Runoff into Oceans → Sea-Level Rise

Evapotranspiration + Rainfall Deficits + Deforestation + Urbanisation intensify SM loss.

Post-2003 losses are considered largely irreversible due to compounding effects of climate change.

Wider Climate Linkages

Drier spells now 1.7x more frequent than in 1850-1990.

Groundwater Depletion influenced by low SM and other factors like precipitation and land use.

Soil Moisture–Temperature Coupling especially in regions like north-central India.

Surface Energy Flux & Crop Yields are strongly dependent on SM variability.

India-Specific Observations

Soil Moisture Region Type	Examples	Hydrological Behavior
Wet SM Areas	Western Ghats, NE India	Energy-controlled evaporation regimes
Dry SM Areas	Northwest India	Weak evaporation variability
Moderate SM Areas	North-central India	Strong impact on surface temperature & evaporation variability

Modelling Results for India

SM Change	Impact on Extreme Temperature Events in N-Central India
+20% Soil Moisture	60–70% reduction in frequency; 20–30% reduction in duration
–20% Soil Moisture	60–100% increase in frequency; 15–40% increase in duration

Terrain-Specific Mitigation Strategies

High-Rainfall Areas

Flood management infrastructure

Improved drainage systems

Waterlogging-resistant crop varieties

Arid & Semi-Arid Regions

Efficient irrigation (drip/sprinkler)

Rainwater harvesting

Soil moisture conservation:

Mulching

Agroforestry

Drought-resistant crops

Technological Interventions

Remote Sensing e.g., GRACE, GRACE-FO

IoT based observational networks for real time SM tracking

Climate Models incorporating high resolution SM data

GIS tools for mapping SM and groundwater interactions

Global Focus

UNCCD COP 16 (Riyadh, 2024) emphasized land restoration and drought resilience.

There is a need for integrated land water climate management to combat desertification and adapt to climate impacts.

Soil Moisture

Aspect	Details
Definition	Soil moisture is the amount of water contained in the soil available for plant roots and microbes.
Types	1. Gravitational water – drains through soil quickly 2. Capillary water – available to plants 3. Hygroscopic water – tightly bound, unavailable to plants
Measurement Techniques	Gravimetric method, Tensiometers, Time-Domain Reflectometry,Satellite remote sensing
Importance	Crucial for agriculture, ecosystem health, drought prediction, weather forecasting, and groundwater recharge
Influencing Factors	Soil texture, structure, temperature, vegetation, topography, rainfall and land use practices
Soil Moisture & Climate	Affects land-atmosphere energy exchanges, influences temperature, rainfall patterns and monsoon variability
Impact on Agriculture	Determines irrigation needs, crop selection, planting and harvesting schedules
Relation with Drought	Decline in soil moisture is a key indicator of agricultural and hydrological drought
Monitoring Agencies (India)	ISRO (using satellites like SCATSAT-1), IMD, ICAR and Ministry of Agriculture
Conservation Methods	Mulching, cover cropping, contour bunding, organic manure use, rainwater harvesting, no-till farming

Sources:

DOWNTOEARTH

PRACTICE QUESTION

Q. Which of the following statements about soil moisture is/are correct?

Soil moisture directly influences surface temperature and evaporation rates.
Capillary water is the only form of soil moisture that is available to plants.
Satellite-based remote sensing techniques can measure soil moisture.

Select the correct answer using the code below:

a) 1 and 2 only
b) 2 and 3 only
c) 1 and 3 only
d) 1, 2 and 3

Answer: c

Explanation:

Statement 1 is correct: Soil moisture plays a vital role in surface energy balance influencing temperature and evaporation.

Statement 2 is incorrect: Hygroscopic water is unavailable, gravitational water drains quickly but capillary water is mainly available – not the only one.

Statement 3 is correct: Satellites like SMAP and SCATSAT-1 measure soil moisture globally.