Environmental Management (0680) | Drought

Environmental Management 0680: Study Notes on Drought

Hello future Environmental Manager! This chapter is all about understanding Drought—one of the slowest but most devastating natural hazards. Don't worry if weather systems seem complicated; we will break down the causes and look at practical ways we can manage this serious global challenge. Understanding drought is key to achieving food and water security for millions of people worldwide!

1. Defining and Classifying Drought

A drought is essentially a period of abnormal dryness in a region caused by a lack of precipitation (rain or snow) over an extended period of time.

What is the difference between dryness and drought?

Drought is not just a dry spell; it involves a significant shortage that causes environmental and economic damage. It is a slow-onset hazard, meaning it develops over months or even years, making it tricky to manage compared to sudden hazards like earthquakes.

Key Takeaway

Drought means much less rain than expected for a prolonged time, severely impacting water resources and ecosystems.

2. Causes of Drought (Syllabus 6.4)

Droughts are often caused by natural climate patterns, but human activity (climate change) is making them more frequent and intense.

A. Prolonged High Pressure Systems

This is the most direct cause of a lack of rain.

• High Pressure: In areas of high atmospheric pressure, air is sinking (moving downwards).
• No Rain: Sinking air heats up and becomes drier. This process prevents the formation of clouds and, therefore, prevents rain.
• The Effect: If a region stays under a high-pressure system for weeks or months, the lack of precipitation leads to drought.

Analogy: Think of high pressure like a heavy, invisible lid placed over a region. It seals off the lower atmosphere, meaning moisture cannot rise, cool, and condense into rain clouds.

B. Ocean Temperature Changes: ENSO

The state of the Pacific Ocean surface temperature can affect weather patterns across the entire globe. This phenomenon is called the El Niño Southern Oscillation (ENSO).

i. El Niño Events

El Niño occurs when the surface water in the central and eastern Pacific Ocean becomes significantly warmer than usual.

• This shift changes atmospheric circulation.
• It often leads to severe drought conditions in regions like Australia, Indonesia, India, and parts of Africa.

ii. La Niña Events

La Niña is the opposite—the Pacific waters become cooler than usual.

• While El Niño often causes dryness, La Niña can also alter rainfall distribution, sometimes causing floods in some areas and contributing to drought in others (like the southern USA).

Quick Memory Tip: El Niño means Everything's (often) Not OK, leading to dryness in many regions.

C. Effect of Climate Change

Global warming, driven by human activities, directly influences drought frequency and severity.

• Increased Evaporation: Higher global temperatures lead to increased rates of evaporation from soil, reservoirs, and rivers, drying out landscapes faster.
• Altered Precipitation Patterns: Climate change changes global wind and rainfall patterns. Some regions that used to receive reliable rainfall now experience long dry periods.

3. Impacts of Drought (Syllabus 6.5)

The effects of drought can be categorized into environmental (on the natural world) and socio-economic (on people and livelihoods).

A. Environmental Impacts

• Death of Organisms: Plants die, leading to the starvation and death of herbivores and the entire food web structure.
• Water Sources Dry Up: Rivers, lakes, and vital underground water stores (aquifers) shrink or disappear completely.
• Soil Erosion and Desertification: Dry, unprotected soil is easily blown away by the wind (wind erosion). Prolonged drought leads to desertification—the process where fertile land turns into desert, often due to a combination of climate stress and human activity (like overgrazing).
• Wildfires: Extremely dry vegetation acts as excellent fuel, leading to an increased risk and severity of large-scale wildfires.
• Decrease in Air Quality: Dry conditions lead to massive dust storms, lowering air quality and impacting human health (respiratory issues).

B. Socio-Economic Impacts

• Decline in Crop Yields and Starvation: Agriculture fails dramatically due to lack of water for irrigation, leading to food shortages, higher prices, malnutrition, and widespread starvation.
• Financial Losses: Farmers lose income, and national economies suffer due to reduced agricultural exports.
• Displacement: When farming land becomes unusable (desertification) and water sources disappear, communities are forced to leave their homes in search of water and food.

Did you know? The Sahel region of Africa has struggled with persistent drought, causing major famines and human displacement throughout the late 20th and early 21st centuries, illustrating the severe social impact.

4. Managing the Impacts of Drought (Syllabus 6.6)

Managing drought involves both preparedness and response. Strategies focus on monitoring, conservation (reducing demand), and increasing supply.

A. Monitoring and Preparation

Early warning systems are critical to allow governments and farmers to prepare.

• Monitoring: Using satellite imagery and weather stations to track rainfall patterns, soil moisture, and high-pressure systems.
• International Aid: Establishing plans and reserves for international assistance (food, water, medicine) *before* a crisis hits.
• Emergency Water Supplies: Stockpiling bottled water or preparing water purification units for immediate deployment.

B. Water Conservation (Reducing Demand)

Conservation aims to make the existing water last longer.

• Public Education: Launching campaigns to encourage people to use less water (e.g., shorter showers, avoiding car washing).
• Water-Efficient Technology: Installing low-flow toilets and showers, and using trickle drip irrigation in agriculture (where water is delivered directly to the plant roots, minimising waste from evaporation).
• Restrictions: Implementing strict government restrictions on non-essential water use (e.g., banning filling swimming pools).

C. Increasing Water Supply

This strategy focuses on long-term infrastructure to secure water independent of local rainfall.

1. Surface Storage and Transfer:

• Dams and Reservoirs: Building large structures to store huge volumes of water during wet periods for use during drought. (Need to remember the environmental impacts of dams, like habitat flooding, when evaluating this strategy!)
• Water Transfer Schemes: Moving water from areas with surplus (water-rich regions) to drought-stricken areas via canals or pipelines.

2. Groundwater Management:

• Wells and Use of Aquifers: Digging wells deeper to access underground water stores (aquifers). However, over-extraction can deplete the aquifer faster than nature can recharge it.

3. Advanced Technologies:

• Desalination: The process of removing salt from seawater to make it potable (drinkable). It is highly effective in coastal areas but is expensive and energy-intensive.
• Rainwater Harvesting: Collecting and storing rainfall (e.g., on rooftops, in cisterns) for later use. This is particularly useful in rural or developing areas.