Rising evaporative demand spotlights India’s data and research gap, Pg9

Context:

•  This article highlights the rising atmospheric evaporative demand (AED) due to climate change and the lack of sufficient data and research in India to assess its impact on agriculture, water use, and policy planning.

Key Highlights:

• Evaporative demand is rising globally due to climate change, increasing atmospheric thirst and causing more water loss from land and plants.
• Researchers have coined the term “thirstwave” to denote three or more days of extreme evaporative demand; these are growing in intensity, frequency, and duration.
• Thirstwaves are influenced by temperature, humidity, solar radiation, and wind speed.
• The standardised short-crop evapotranspiration is used to estimate water loss and inform irrigation planning.
• A 2022 study across 100 Indian river basins found rising actual evapotranspiration, especially in Northern India and the Himalayas.
• Despite these trends, India lacks data and studies on extreme thirstwaves, limiting climate response.
• New research is underway to study thirstwave patterns in South Asia, with implications for food and water security.

Detailed Insights:

• Definition and Drivers: Evaporative demand measures the potential evaporation if water were abundantly available; it is driven by temperature, humidity, solar radiation, and wind.
• Impact on Agriculture: As evaporative demand increases, crops like rice and wheat lose more water, even if irrigation is adequate, impacting water-use efficiency and crop stress.
• Climate Data Gap in India: Though studies exist, there is limited high-resolution data or regional assessments on extreme evaporative events in India, especially on thirstwaves.
• Effect of Humidity: Historical data from IMD suggested reduced evaporation due to high humidity, but future projections indicate that rising temperatures will outweigh humidity, increasing AED.
• Policy Implications: The worst thirstwaves do not always occur in areas of highest evaporative demand, indicating the need to rethink climate risk zoning and adaptation planning.
• Global South Vulnerability: Nations like India, with high climate vulnerability and agrarian dependence, require urgent monitoring systems and farmer outreach to handle rising AED.
• Future Research: Initiatives like collaborations with NIT Jalandhar aim to explore thirstwave behavior in South Asia, potentially informing climate-resilient agriculture and water resource management.

Key Concepts Involved:

• Evaporative Demand: The atmospheric demand for moisture; a climatic measure of the potential for evaporation and transpiration from surfaces and vegetation.
• Thirstwave: A newly coined term for three or more consecutive days of high evaporative demand, analogous to a heatwave.
• Potential Evapotranspiration (PET): The theoretical maximum amount of water that can be evaporated from land and transpired by vegetation under ideal conditions.