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Global warming is intensifying a new climate phenomenon called thirst waves, where rising atmospheric evaporative demand causes rapid moisture loss from land and vegetation. This hidden crisis poses a serious threat to agriculture, especially in regions like Northern India and the Himalayas.

Key Concepts & Terms

Term	Description
Thirst Wave	A stretch of three or more days with abnormally high atmospheric demand for moisture.
Evaporative Demand	The atmosphere’s need for water vapor, influenced by temperature, solar radiation, wind, and humidity.
Short-crop Evapotranspiration	Standard measure for thirst waves, based on water loss from a well-watered grass surface.
Evapotranspiration	Combined water loss from soil (evaporation) and plants (transpiration).

What Causes Thirst Waves

Factor	Role
High Temperatures	Increases the atmosphere’s capacity to hold moisture.
Low Humidity	Dry air pulls more moisture from soil and plants.
Solar Radiation	Direct sunlight boosts evaporation.
Wind Speed	Enhances water loss by carrying moisture away from surfaces.

How Are Thirst Waves Different from Heatwaves

Feature	Heatwaves	Thirst Waves
Primary Driver	Temperature and wind	Evaporative demand (temp + radiation + wind + humidity)
Impact	Health stress, temperature rise	Faster drying of soil and plants
Measurement	Air temperature	Short-crop evapotranspiration

Impact of Thirst Waves

Sector	Consequences
Agriculture	Increased irrigation needs, crop stress, lower yields
Soil	Accelerated moisture depletion
Water Resources	Higher pressure on water use and storage
Climate Resilience	Reduced ability to cope with rising temperatures

Thirstwaves & India

Region	Impact
Northern India	Increasing evapotranspiration due to growing crops and vegetation
Western & Eastern Himalayas	Higher evaporative demand despite cold temperatures
Trend	Future warming expected to worsen atmospheric thirst even in humid zones

In a Nutshell (Mnemonic: “THIRST”)

Temperature rise
Humidity decline
Irrigation pressure spikes
Radiation and wind accelerate drying
Soil dries faster
Threat to food and water security

Prelims Practice Questions

1. What is the primary measurement tool used to detect thirst waves?
   a) Heat Index
   b) Relative Humidity
   c) Short-crop Evapotranspiration
   d) Atmospheric Pressure
   
2. Which of the following best differentiates thirst waves from heatwaves?
   a) Caused by greenhouse gases
   b) Include low humidity and radiation factors
   c) Measured using temperature alone
   d) Do not affect agriculture
   
3. Which of the following Indian regions is witnessing increasing evaporative demand?
   a) Western Ghats
   b) Deccan Plateau
   c) Northern India and Himalayas
   d) Sunderbans
   

Mains Practice Questions

1. Explain the concept of ‘thirst waves’ and discuss their implications on India’s food and water security. (GS 3 – Environment & Agriculture)
2. Thirst waves represent a silent stress on agriculture. How can climate-resilient practices help mitigate their impact? (GS 3 – Disaster Management)

Prelims Answer Key with Explanation

Ques	Answer	Explanation
1	c	Thirst waves are detected using short-crop evapotranspiration.
2	b	Unlike heatwaves, thirst waves factor in humidity, radiation, and wind.
3	c	Studies show rising evapotranspiration in Northern India and the Himalayas.