Detailed Notes - The Water Cycle and Water Insecurity - Edexcel Geography A-level

PMT Resources: Tuition courses for Edexcel Geography A-level focusing on The Water Cycle and Water Insecurity.

The global water cycle consists of various stores:
- Oceans: Contain 97% of global water.
- Freshwater: Only 2.5% of global stores:
  - 69% in glaciers, ice caps, and ice sheets.
  - 30% in groundwater.
  - Surface water accounts for ~1% (includes lakes, rivers, swamps).
Polar Regions Hydrology:
- 85% solar radiation reflection.
- Impermeable surfaces due to permafrost.
- Frozen lakes/rivers; rapid runoff in spring.
- Seasonal release of biogenic gases.
Tropical Rainforest Hydrology:
- Dense vegetation consumes 75% of precipitation.
- Limited infiltration and high temperatures.
- Deforestation reduces evapotranspiration.
Water Residence Times:
- Oceans: 3600 years.
- Icecaps: 15,000 years.
- Groundwater: 10,000 years.
- Rivers/Lakes: 2 weeks to 10 years.
- Soil moisture: 2-50 weeks.
- Atmospheric moisture: 10 days.

ITCZ (Inter-tropical Convergence Zone): Six air circulation cells control climate.
Hadley Cell: Air rises at The Doldrums, cools over the Ferrel Cell, causing precipitation.
Polar Cell: Cold air sinks, forms precipitation in northern latitudes, then moves south.
Ferrel Cell: Middle cell influenced by Hadley and Polar cells.
Drainage Basin: Area drained by a river and tributaries; defined by watershed boundaries.

Local water cycle is open (includes inputs/outputs); Global water cycle is closed (no external inputs/outputs).
Inputs to Drainage Basin - Precipitation:
- Caused by cooling and condensation of atmospheric moisture.
- Affected by:
  - Seasonality: Climate patterns influencing rainfall.
  - Variability: Changes due to climate trends and randomness.
  - Latitude: Higher latitudes generally have colder climates.
Types of Rainfall:
- Convectional: Common in tropical climates; daily occurrence.
- Frontal/Cyclonic: Occurs when warm air meets cold air.
- Relief/Orographic: Moist air rises over high land.

Key outputs of drainage basins include:
- Evaporation: Loss of moisture due to weather conditions and surface area.
- Transpiration: Biological process of water loss from plants.
Storage Types:
- Soil Water: Utilized by plants (mid-term storage).
- Groundwater: Long-term storage in rock pores.
- River Channel: Short-term water storage.
- Interception: Short-term plant storage.
- Surface Storage: Variable water storage in puddles/lakes.

Physical Factors: Climate, soil composition, geology, relief, vegetation.
Anthropogenic Factors:
- Cloud Seeding: Artificially inducing rain.
- Deforestation: Increases overland flow and flooding.
- Afforestation: Enhances interception.
- Dam Construction: Alters downstream flow; causes evaporation losses.
- Groundwater Abstraction: Reduces water levels when over-extracted.
- Urbanisation: Increases runoff, reduces infiltration and water storage.

Water Budget: Reflects short and long-term water availability.
- Equation: Precipitation = Discharge + Evaporation ± Change in stores.
Soil Moisture Dynamics:
- Surplus, utilisation, maximum evaporation point, and deficit scenarios.
River Regimes: Variations in river discharge affected by groundwater and climatic conditions.
- Factors affecting river discharge include channel capacity, drainage basin relief, precipitation patterns, and anthropogenic impacts.

Storm Hydrograph Features:
- Rising Limb: Increase in discharge.
- Peak Flow: Maximum discharge after rainfall.
- Lag Time: Delay between rainfall and peak discharge.
- Falling Limb: Decrease in discharge.
- Base Flow: Normal discharge level.
Flashy vs. Subdued Hydrographs: Characteristics differ based on weather, rock type, soil, relief, basin size, vegetation, and antecedent conditions.

Sustainable management strategies to mitigate flood risks include:
- Growing rooftop vegetation for interception.
- Creating permeable pavements to enhance infiltration.
- Rainwater harvesting for greywater use.
- Establishing wetlands for natural water storage.
Human development impacts can exacerbate flooding risks, through deforestation and urbanisation.

Droughts: Result from insufficient water input leading to serious ecological impacts:
- Types of deficits: Rainfall, stream flow, soil moisture, and food deficits.
Impacts include agricultural failure, food shortages, rural migration, and increased wildfires.

El Nino: Disruption in water patterns affecting global weather;
- Warm waters migrate along the Peruvian coast, impacting fisheries.
- Triggers dry conditions in various regions.
Wetlands Role: Act as temporary water stores and natural filters, enhancing water quality.

Wetland functions include:
- Carbon storage.
- Nutrient recycling and fishery resource.
- Cultural and aesthetic values.
Meteorological Drought Effects: Reduced precipitation leads to ecosystem degradation.

Flood Risk Factors: Low-lying regions, urban environments, small basins.
Mitigation Strategies:
- Afforestation in uplands.
- Restrict construction on floodplains.
- Designating temporary flood plains.

Climate Change Effects: Increases in evaporation, drought frequency, and altered rainfall patterns.
Future uncertainties complicate the management of water cycles and drainage basins due to unpredictability.

Increased Water Prices: Scarcity leads to economic impacts on agriculture and industry.
Possible Solutions: Storing rainwater, increasing renewable energy use, and reducing demand with conservation techniques.

WPI Components: Assess localized water stress based on resources, access, management, use, and environmental indicators.
Scoring ranges from 0 (high stress) to 100 (no stress).

Integrated Water Resource Management (IWRM): Holistic approach emphasizing fair distribution.
Criteria for Water Sharing Treaties include natural factors, social needs, and economic efficiency.
Key organizations: UNECE Water Convention, UN Water Courses Convention.

UN Initiatives: UNECE promotes sustainable water management across Europe.
EU Water Framework Directive: Targets restoration of water bodies to improve quality.