AQA Geography: Water and Carbon Cycles & Coastal Systems/Landscapes Study Guide

Human Factors Affecting the Water Cycle

Deforestation: * Causes reduced evapotranspiration. * Results in decreased interception, leading to increased surface runoff and flooding. * Leads to soil compaction, which reduces infiltration and percolation.
Global Warming: * Increased precipitation contributes to flooding. * Increased evaporation rates lead to drought and desertification.
Dam Building: * Disrupts river discharge. * Causes flooding in upland areas to create reservoirs.
Urbanisation: * Increases the presence of impermeable surfaces, leading to less infiltration.

Data Analysis Methodology (Q1.2 & Q1.3)

Analysing Data (HLTA Framework): * H (Highs): Identify the highest values in the dataset. * L (Lows): Identify the lowest values in the dataset. * T (Trends): Look for overall or general patterns over time or space. * A (Anomaly): Identify outliers or data points that do not fit the general trend.
Application Requirements: * Always use specific data from the provided figures. * Manipulate the data: For example, compare the number of recording stations in the Northern Hemisphere versus the Southern Hemisphere. * Critique the data: Note if figures are overlapping, difficult to read, or limited in scope. * Apply own knowledge: Combine figure data with outside geographical principles.

Factors Affecting River Discharge

River Discharge Definition: The total amount of water in a river at a given point.
Determinants of Discharge: 1. Intensity and duration of rainfall. 2. Antecedent Rainfall (previous rainfall saturating the ground). 3. Snowmelt. 4. Porous Soil / Permeable Rocks. 5. Impermeable rock types. 6. Size of the drainage basin (larger basins collect more water). 7. Shape of the drainage basin. 8. Slope angle (steeper slopes increase runoff velocity). 9. Temperature (e.g., frozen ground preventing infiltration). 10. Vegetation type and coverage. 11. Land Use. 12. Urbanisation.
Lag Time: The duration between peak rainfall and peak river discharge.

Systems and Equilibrium

Dynamic Equilibrium: A state of balance where inputs and outputs are equal, causing stores to remain constant. * $Inputs = Outputs$ : Stores remain the same. * Inputs > Outputs: Stores increase (leads to flooding). * Outputs > Inputs: Stores decrease (leads to drought).
Feedback Loops: Occur when an element of the system changes, upsetting the equilibrium. * Positive Feedback: Effects of an action are amplified or multiplied by secondary effects. * Example in Carbon Cycle: Increased oceanic temperatures $\rightarrow$ Dissolved $CO_2$ released by warmer oceans $\rightarrow$ More atmospheric $CO_2$ $\rightarrow$ Atmospheric temperature rise (greenhouse effect) $\rightarrow$ Warmer oceans (loop repeats). * Negative Feedback: Effects of an action are nullified or dampened by subsequent effects. * Example in Carbon Cycle: Increased use of fossil fuels $\rightarrow$ Atmospheric $CO_2$ increase $\rightarrow$ Stimulated plant growth (increased photosynthesis) $\rightarrow$ Reduced atmospheric $CO_2$ level.
Open Systems: Systems that transfer both energy and matter across their boundaries (e.g., a woodland ecosystem).

The Carbon Cycle and Carbon Budgets

System Components: * Stores (Sinks vs. Sources): * The main stores are the lithosphere (rocks and soil), hydrosphere (oceans), cryosphere (snow and ice), atmosphere, and biosphere (plants). * Carbon Sink: Absorbs more carbon than it releases. * Carbon Source: Releases more carbon than it absorbs. * Transfers (Flows): Processes that move carbon between stores (e.g., photosynthesis converting $CO_2$ into carbohydrates like glucose).
Carbon Budget: The total amount of carbon stored and transferred within the carbon cycle ( $Carbon In$ vs. $Carbon Out$ ).

Climate Change Mitigation and Adaptation

Definitions: * Mitigation: Actions taken to reduce the severity of climate change by addressing its causes. * Adaptation: Adjustments made to address the impacts/consequences of climate change.
Afforestation: * Trees act as carbon sinks via photosynthesis. * Plantation forests absorb $CO_2$ faster than natural forests for up to $50\,\text{years}$ . * USA Investment: $\$40\,\text{billion}$ between 2010 and 2050 to increase storage by $28\%$ . * UK Project: $\pounds 24.9\,\text{million}$ in Brazil to recover $41,560\,\text{hectares}$ of degraded forest to reduce $10.71\,\text{million\,tonnes}$ of $CO_2$ over $20\,\text{years}$ .
Carbon Capture & Storage (CCS): * Technology captures up to $90\%$ of $CO_2$ from fossil fuel burning. * Process: Captured gas is compressed, transported by pipeline, and injected as a liquid into sedimentary rock layers. * UK Potential: Could provide >20\% of UK electricity and save $\pounds 30\,\text{billion }\text{per year}$ in climate targets. * Critique: Expensive, long-term storage security is uncertain, and does not promote renewables.
Carbon Sequestration: * Geologic: Source-captured $CO_2$ injected underground. Oceans can store carbon for weeks (surface) or millions of years (deep). * Biologic: Storage in plants (leaves, roots, soil). Usually lasts for the lifetime of the plant (decades).
Alternative Energy: * Sources: Hydro-electricity, nuclear (e.g., Hinkley Point), solar, wind, and tidal. * Impact: Solar panels save >1\text{ tone of } CO_2\text{ per year} per home. * Limitations: Solar is weather-dependent (ineffective at night).
International Agreements: * Kyoto Protocol (1997): Over 170 countries; aimed to reduce emissions by $5.2\%$ below 1990 levels by 2012. USA and Australia initially refused. Industrialised countries targeted $5\%-8\%$ . * Copenhagen Accord (2009): Financial support for developing nations; no legally binding targets. * Paris Agreement (2015): 195 countries; legally binding. Aim to keep temperature increase below $2^\circ C$ (limit to $1.5^\circ C$ ). Review every $5\,\text{years}$ . $\$100\,\text{billion}$ per year for developing nations by 2020.

Modifying Human Practices

Industrial Combustion: Equipping coal-fired plants with CCS to inject $CO_2$ into deep saline aquifers or depleted oil/gas reservoirs.
Aviation: Improving engine efficiency and capacity (target: $3\,\text{litres of fuel per passenger per km}$ ).
Agriculture: * Low Latitudes: Maize crops in Southern Africa could fall by $30\%$ by 2030; rice in South Asia could fall by $10\%$ . * High Latitudes: Increase in wheat production in Europe/North America. Mediterranean crops (vines/olives) may thrive in the UK. * Adaptation Strategies: Moving production locations, increasing irrigation, changing crop types (e.g., Potato Park in Peru growing crops at higher altitudes).
Cap and Trade Schemes: Setting limits (caps) on emissions and allowing companies to trade unused allowances.

Global Impact Case Studies

Sea Level Rise: * Risen $20\,\text{cm}$ since 1900; expected additional $26-82\,\text{cm}$ by 2100. * The Maldives: Highest point is $2.4\,\text{m}$ . Expected to be uninhabitable by 2030. * Maldives Management: $3\,\text{m}$ sea wall at Malé, houses on stilts, artificial islands, potential relocation to Sri Lanka/India.
Water Shortages: * Himalayas: 16,000 glaciers receding; threat to Asia's water supply. * Ladakh, India: Construction of artificial glaciers using diversion canals. * London: Households consume $167\,\text{litres/day}$ ( $\text{avg is } 146$ ). Boris Johnson's Water Strategy provided water-efficient devices. * Thames Water: Desalination plant in Beckton (2010) serves 400,000 homes; takes water at low tide.

Coastal Systems and Landscapes

Geology: * Discordant Coastline: Rock layers are perpendicular ( $90^\circ$ ) to the coast. * Differential Erosion: Soft rocks (clay/sand) erode faster than resistant rocks (chalk/sandstone/limestone).
Wave Types: * Constructive: Calm conditions, long/low, swash > backwash, frequency $6-9\text{ per minute}$ . Builds beaches. * Destructive: Storm conditions, high waves, backwash > swash, frequency $11-15\text{ per minute}$ . Erodes beaches.
Marine Erosion Processes: * Hydraulic Action: Force of water trapping/compressing air in cracks. * Cavitation: Imploding bubbles generating tiny high-pressure water jets. * Wave Quarrying: Scooping out unconsolidated material (sands/gravels). * Corrasion: Hurlng sediment at cliff bases. * Abrasion: Sandpapering effect dragging sediment across rocky surfaces. * Solution (Corrosion): Seawater acids dissolving alkaline rocks (chalk/limestone). * Attrition: Particles colliding and becoming rounder/smoother; not direct cliff erosion.
Weathering: * Mechanical: Frost shattering (freeze-thaw); water expands by $10\%$ when frozen. * Chemical: Carbonation (rainwater + $CO_2$ forms carbonic acid), Oxidation (rusting), and Solution. * Biological: Action of plants and animals.

Coastal Landforms

Erosional Landforms: * Headlands and Bays: Formed by differential erosion on discordant coasts. * Wave-cut Platforms: Cliffs undercut by wave-cut notches migrate inland, leaving a rocky platform. Limits own growth via negative feedback as wave energy dissipates over the platform. * The Cave-Arch-Stack-Stump Sequence: 1. Cracks exploited by hydraulic action. 2. Cavitation and abrasion deepen cracks into caves. 3. Wave refraction concentrates energy on sides of headlands; two caves meet to form an arch. 4. Arch roof collapses to form a stack (e.g., Old Harry, Dorset). 5. Stack base eroded and sub-aerial weathering leads to collapse into a stump.
Depositional Landforms: * Beaches: Temporary stores between high and low tide. * Spits: Long features of sand/shingle extending into estuaries (e.g., Spurn Head). Feature recurved tips and salt marshes. * Tombolo: Beach connecting an island to the mainland (e.g., Chesil Beach/Isle of Portland). * Barrier Beaches/Bars: Beaches extending between two headlands, often trapping lagoons. * Offshore Bars: Submerged ridges of sand; absorb wave energy. * Sand Dunes: Formed by onshore winds. Requires large sand supply, large tidal range, and dominant onshore winds. * Dune Succession (Psammosere): Pioneer species (xerophytic/halophytic) $\rightarrow$ Embryo dunes $\rightarrow$ Yellow/Fore dunes (Marram grass) $\rightarrow$ Grey dunes (humus) $\rightarrow$ Dune slacks $\rightarrow$ Climatic climax community.

Coastal Management Strategies

Integrated Coastal Zone Management (ICZM): Holistic management of entire coastal sections (sediment cells) rather than individual towns to resolve social, economic, and environmental conflicts.
Soft Engineering: * Beach Nourishment: Adding sand to beaches ( $\pounds 300,000$ for equipment). Requires constant maintenance due to longshore drift. * Mangroves: Natural buffer; dissipates wave energy; carbon sink; provides fish habitats.
Case Study: Odisha, India: * $480\,\text{km}$ coastline, dominated by deposition and major deltas. Acts as a significant sediment store.
Case Study: Holderness Coast, UK: * Fastest eroding coastline in Europe ( $1\text{m}-10\text{m}\text{ per year}$ ). * Geology: Chalk (Flamborough Head) and weak Boulder Clay. * Inputs: Erosion of till cliffs; Transfer: Longshore drift moving material south to Spurn Head. * Factors: Long fetch from North-East, powerful destructive waves, narrow beaches, and lack of initial defenses.

Longshore Drift

Waves approach the beach at an angle (prevailing wind).
Swash: Carries material up the beach at an angle.
Backwash: Pulls material straight down the beach due to gravity.
Result: Net zigzag movement of sediment along the coast. Groynes are used to interrupt this and widen beaches.