CLIMATE CHANGE DISRUPTS EARTH’S WATER CYCLE

GS3 ENVIRONMENT

Climate change is severely disrupting the planet’s water cycle, leading to a cascade of consequences for ecosystems, human populations, and global water resources. According to the 2024 Global Water Monitor Report, compiled by researchers from Australia, Saudi Arabia, China, and Germany using data from ground stations and satellites, the impact of climate change on the water cycle is becoming increasingly severe.

The erratic nature of the water cycle is now threatening billions of people worldwide, leading to shifts in precipitation patterns, altered evaporation rates, and increased frequency of extreme weather events such as floods and droughts.

Understanding the Water Cycle:

The water cycle, also known as the hydrological cycle, describes the continuous movement of water through its various phases—liquid, gas, and solid. The process includes several stages:

• Evaporation: Water from oceans, lakes, rivers, and soil is heated by the sun, turning into water vapour and rising into the atmosphere.
• Condensation: As the vapour rises, it cools, condensing into clouds.
• Precipitation: Clouds release water in the form of rain, snow, or other precipitation, returning water to Earth’s surface.
• Runoff and Infiltration: Water flows over the surface (runoff) or soaks into the ground (infiltration), replenishing groundwater supplies.

This cycle is essential for sustaining life and regulating global weather patterns. However, the intensification of climate change is causing significant disruptions across the globe.

Impact of Climate Change on the Water Cycle:

As global temperatures rise, the water cycle has intensified. Key impacts include:

1. Increased Evaporation: Warmer air can hold more moisture—approximately 7% more moisture for every 1°C increase in temperature. This has led to an increase in evaporation rates, particularly from oceans and landmasses, increasing the moisture in the atmosphere.
2. More Intense Precipitation: The increased moisture in the atmosphere results in more intense storms, with heavier rainfall and snow events. This exacerbates flooding in many regions, particularly in areas that are not prepared for such extreme weather conditions.
3. Severe Storms and Flooding: The intense storms driven by the higher moisture content in the atmosphere are leading to catastrophic flooding events. Coastal areas, river basins, and low-lying regions are becoming more vulnerable to floods, posing risks to human lives, agriculture, and infrastructure.
4. Increased Frequency of Droughts: Despite more precipitation in some areas, many regions are experiencing longer and more severe droughts. This paradox occurs because increased evaporation rates, particularly in already dry regions, are causing soil moisture depletion. When rains do occur, they often run off dry, hardened soil, failing to adequately replenish groundwater stores or agricultural lands.
5. Water Scarcity and Displacement: The imbalance between areas experiencing floods and droughts is creating unprecedented challenges. Water scarcity, exacerbated by longer dry periods and reduced water storage, is threatening agricultural productivity and drinking water supplies, leading to displacement of populations and economic losses.

Regional Variability in Weather Patterns:

The impact of climate change on the water cycle is not uniform. Certain regions experience disproportionate effects:

• Flood-Prone Areas: Coastal and low-lying regions such as South Asia, parts of the U.S. Gulf Coast, and European river basins are seeing more frequent and intense floods.
• Drought-Stricken Regions: Areas such as the Sahel in Africa, the Middle East, and parts of South America are witnessing prolonged droughts, making agricultural production and access to clean water increasingly difficult.

Future Projections:

If greenhouse gas emissions remain unchecked, it is projected that global temperatures could rise by 2.6 to 3.1°C by the end of the 21st century. This would further exacerbate the intensity of the water cycle:

• Increased evaporation rates could lead to more frequent and severe droughts in already water-scarce regions.
• Extreme rainfall events will become more common, particularly in temperate zones, leading to greater flood risks and challenges in water storage management.
• The intensification of water-related disasters, such as flash floods, will displace millions of people, increase economic losses, and hinder global efforts to reduce poverty and promote food security.

Key Findings of the 2024 Global Water Monitor Report:

The 2024 report presents several alarming statistics:

• Over 8,700 fatalities occurred due to water-related disasters, with a displacement of 40 million people.
• The economic losses due to water-related events have surpassed $550 billion.
• There has been a 38% increase in record-dry months compared to the 1995-2005 baseline period.
• Rainfall records have been broken more frequently, with monthly and daily precipitation records occurring at alarming rates, indicating greater erratic variability in precipitation.

Terrestrial Water Storage (TWS) and Evapotranspiration:

• Terrestrial Water Storage (TWS) refers to the total amount of water on Earth’s continents, including groundwater and surface water. Disruptions in the water cycle lead to a fluctuation in TWS, influencing the availability of water for agriculture, drinking, and sanitation.
• Evapotranspiration, the combined process of evaporation and plant transpiration, plays a key role in the water cycle. Changes in climate lead to higher evapotranspiration rates, contributing to reduced water availability in areas already vulnerable to drought.

Climate Change and its Impact on Ecosystems:

The disruption of the water cycle by climate change poses significant risks to ecosystems:

• Biodiversity Loss: Aquatic ecosystems, including wetlands, rivers, and lakes, are experiencing changes in water levels, affecting the habitats of numerous species.
• Agricultural Challenges: Increased frequency of droughts and floods hampers crop yields, threatening food security and livelihoods, particularly in developing countries.
• Impact on Forests and Wetlands: Changes in precipitation and water availability affect forest growth and wetland ecosystems, which are vital for carbon sequestration and climate regulation.

Implications for Future Water Management:

The disruption of the water cycle by climate change calls for urgent and coordinated action to ensure sustainable water management:

1. Integrated Water Resource Management (IWRM): A holistic approach to managing water resources at local, national, and regional levels is essential to adapt to changing precipitation patterns, mitigate droughts, and prevent flooding.
2. Investment in Infrastructure: Building resilient infrastructure for water storage, flood protection, and drought mitigation is crucial. This includes improving irrigation systems, building reservoirs, and strengthening flood defenses.
3. Climate Adaptation Strategies: Countries must adopt adaptive water management policies that focus on both reducing greenhouse gas emissions and implementing climate-resilient water practices. This includes promoting efficient water use, investing in water-efficient agricultural practices, and enhancing water recycling technologies.
4. International Cooperation: Climate change is a global challenge that requires international cooperation. Sharing data, technologies, and best practices is essential for managing the global water crisis, particularly in cross-border river basins and transboundary water resources.

The intensification of the water cycle due to climate change is a pressing global issue that demands immediate attention. As temperatures rise, the erratic behaviour of the water cycle will continue to disrupt ecosystems and threaten human livelihoods.

Governments, industries, and individuals must collaborate to implement sustainable water management strategies, mitigate climate change, and ensure equitable access to water for all. The future of the planet’s water resources depends on the actions taken today to adapt to these changes and reduce the causes of global warming.

Practice Question:

“Discuss the impact of climate change on the water cycle and its implications for water security. Suggest measures to adapt to these changes, focusing on India’s challenges.”