AQA A-level Geography: Water + Carbon

Inputs

Where matter or energy is added to the system.

Outputs

Where matter or energy leaves the system.

Stores

Where matter or energy builds up in the system.

Flows

Where matter or energy moves in the system.

Boundaries

Limits to the system (e.g. watershed).

Open systems

Systems that receive inputs and transfer outputs of energy or matter with other systems.

Closed systems

System that has inputs and outputs of energy but not matter e.g. global water and carbon cycle

Isolated systems

System with no inputs or outputs of energy and matter

Dynamic equilibrium

When inputs equal outputs despite changing conditions.

Positive feedback

When a chain of events amplifies the impacts of the original event.

Positive feedback loop involving sea ice

Increased sea temp. -> increased sea ice melt -> more dark surface is exposed -> fall in the albedo effect -> increased solar radiation absorbed (by sea) -> even greater sea temp. -> even more sea ice melt

Positive feedback loop involving thawing permafrost

Higher global temps. increase permafrost melt. This releases methane into the atmosphere, increasing the atmospheric methane concentration. As a greenhouse gas this further enhances the greenhouse effect leading to even higher global temps. and even more permafrost melt.

Negative feedback

A chain of events that nullifies the impacts of the original event, leading to dynamic equilibrium.

Negative feedback loop involving sea ice melt

Increased sea temps. leads to increased evaporation which leads to increased cloud cover which leads to increased albedo effect. This means that more radiation is reflected and less is absorbed. This leads to the earth cooling and sea temps. falling. This reduces evaporation

Negative feedback loop involving phytoplankton and cloud formation

Higher temps. causes phytoplankton to grow and photosynthesise quicker. Phytoplankton release substances that lead to the formation of clouds, meaning cloud cover increases. Albedo effect increases, this means less radiation is absorbed and more is reflected. This causes a fall in global temps. This therefore causes phytoplankton to grow less quickly and photosynthesise slower, reducing cloud cover.

Local scale

The carbon and water cycles are both open systems.

Global scale

On a global scale, the carbon and water cycles are closed systems.

Water Cycle

In a local drainage basin system, water may be lost as an output through evapotranspiration and runoff, but more water may be gained as an input through precipitation.

Precipitation

Any water that falls to the surface of the earth from the atmosphere including rain, snow and hail.

Convectional rainfall

Due to heating by the sun, warm air rises, condenses at higher altitudes and falls as rain.

Relief rainfall

Warm air is forced upward by a barrier such as mountains, causing it to condense at higher altitudes and fall as rain.

Frontal rainfall

Warm air rises over cool air when two bodies of air at different temperatures meet, condensing at higher altitudes and falling as rain.

Evapotranspiration

Compromised of evaporation and transpiration.

Evaporation

Occurs when water is heated by the sun, causing it to become a gas and rise into the atmosphere.

Transpiration

Occurs in plants when they respire through their leaves, releasing water they absorb through their roots.

Streamflow

All water that enters a drainage basin will either leave through the atmosphere, or through streams which drain the basin.

Infiltration

The process of water moving from above ground into the soil.

Infiltration capacity

Refers to how quickly infiltration occurs.

Grass crops and tree roots

Create passages for water to flow through from the surface into the soil, increasing the infiltration capacity.

Overland flow

Occurs when precipitation falls at a greater rate than the infiltration capacity - Moderate/Fast.

Percolation

Water moves from the ground or soil into porous rock or rock fractures; the percolation rate is dependent on the fractures present in the rock and the permeability of the rock - Slow.

Throughflow

Water moves through the soil and into streams or rivers; speed of flow is dependent on the type of soil. Clay soils with a high field capacity and smaller pore spaces have a slower flow rate, while sandy soils drain quickly due to lower field capacity and larger pore spaces - Moderate/Fast.

Surface Runoff (Overland flow)

Water flows above the ground, as sheetflow (lots of water flowing over a large area) or in rills (small channels similar to streams, that are unlikely to carry water during dry periods) - Fast.

Groundwater Flow

Water moves through the rocks, ensuring that there is water in rivers even after long periods of dry weather; jointed rocks such as limestone in Karst environments may transfer water very rapidly - Usually slow but variable.

Streamflow

Water that moves through established channels - Fast.

Stemflow

Flow of water that has been intercepted by plants or trees, down a stem, leaf, branch or other part of a plant - Fast.

Soil Water

Water stored in the soil which is utilised by plants - Mid-term.

Groundwater

Water that is stored in the pore spaces of rock - Long-term.

River Channel

Water that is stored in a river - Short-term.

Interception

Water intercepted by plants on their branches and leaves before reaching the ground - Short-term.

Surface Storage

Water stored in puddles, ponds, lakes etc. - Variable.

Water table

The upper level at which the pore spaces and fractures in the ground become saturated; used by researchers to assess drought conditions, health of wetland systems, success of forest restoration programmes, etc.

Water balance

Expresses the process of water storage and transfer in a drainage basin system and uses the formula: Precipitation = Total Runoff + Evapotranspiration +/- (change in) Storage.

Droughts

Conditions that can be explained by the water balance, affected by physical factors, especially during seasonal variations of temperature and precipitation.

Floods

Conditions that can be explained by the water balance, affected by physical factors, especially during seasonal variations of temperature and precipitation.

Deforestation

Leads to less interception by trees, increasing surface runoff; soil water storage decreases as the soil is no longer held together by roots, and transpiration decreases due to fewer plants.

Storm Events

Large amounts of rainfall quickly saturate the ground to its field capacity.

Field capacity

The maximum amount of water that soil can hold after excess water has drained away.

Pore spaces

The voids between soil particles or within rock that can hold water.

Permeability

The ability of a material (such as rock or soil) to transmit water.

Evapotranspiration

The sum of evaporation from the land surface plus transpiration from plants.

Change in storage

The difference in water storage over time, influenced by precipitation, runoff, and evapotranspiration.

Surface Runoff

Water that flows over the ground surface when the soil is saturated.

Prolonged Rainfall

Rainfall that occurs over an extended period, more effective at recharging water stores.

Infiltration

The process by which water enters the soil.

Percolation

The movement of water through the soil layers into groundwater stores.

Groundwater Stores

Underground reservoirs of water that are replenished by infiltration and percolation.

Seasonal Changes

Variations in vegetation growth and rainfall patterns throughout the year.

Spring

Season characterized by more vegetation growth and increased interception by vegetation.

Summer

Season likely to have less rain and harder ground, leading to more impermeable surfaces.

Autumn

Season with less vegetation growth, more rainfall, and increased soil moisture.

Winter

Season where frozen ground may be impermeable, encouraging runoff.

Pastoral Farming

Farming that relates to livestock, which can reduce soil infiltration.

Arable Farming

Farming that relates to crops, where ploughing increases infiltration.

Hillside Terracing

Agricultural practice that increases surface water storage and decreases runoff.

Irrigation

The movement of water by human intervention, which can lead to groundwater depletion.

Urbanisation

The development of impermeable surfaces that reduce infiltration and increase runoff.

Green Roofs

Sustainable urban design that uses vegetation to reduce impermeable surfaces.

Soil Water Budget

The annual balance between inputs and outputs in the water cycle affecting soil water storage.

Field Capacity

The maximum possible level of water storage in the soil.

Water Surplus

Condition where soil moisture levels increase due to greater precipitation than evapotranspiration.

Potential evapotranspiration

The maximum amount of water that can be evaporated and transpired from a given area during a specific time period.

Water surplus

A condition where the amount of water available exceeds the amount of water used or lost.

Evapotranspiration

The process of water evaporation from soil and transpiration from plants.

Water deficit

A condition where the amount of water available is less than the amount needed.

Global water cycle

The continuous movement of water on, above, and below the surface of the Earth.

Oceans

The largest water store, containing 97% of global water.

Freshwater

Water that has low concentrations of dissolved salts, comprising only 2.5% of global water stores.

Glaciers, ice caps, and ice sheets

These contain 69% of the world's freshwater.

Groundwater

Water that is stored underground, accounting for 30% of freshwater.

Surface freshwater

Accounts for around 1% of global water stores, including lakes, rivers, and swamps.

Hydrosphere

Any liquid water on Earth.

Lithosphere

Water stored in the Earth's crust and upper mantle.

Cryosphere

Any water that is frozen.

Atmosphere

Water vapor present in the air.

Aquifers

Underground water stores that can be unevenly distributed globally.

Shallow groundwater aquifers

Can store water for up to 200 years.

Fossil aquifers

Deeper aquifers formed during wetter climatic periods that may last for 10,000 years.

Glaciers

May store water for 20-100 years.

Lakes

Can store water for 50-100 years.

Seasonal snow cover

Stores water for 2-6 months.

Soil water

Acts as a temporary store, holding water for 1-2 months.

Inter-Tropical Convergence Zone (ITCZ)

A low pressure zone on the equator responsible for heavy rainfall and monsoons.

Jet-stream

A fast flowing air current that influences weather patterns.

Seasonal changes in the water cycle

Include less precipitation and more evapotranspiration in summer due to higher temperatures.

Storm events

Cause sudden increases in rainfall, leading to flooding and replenishment of water stores.

Droughts

Lead to depletion of major water stores and decreased activity of flows in the water cycle.

El Niño effect

Occurs every 2-7 years and causes warm temperatures in a predictable way.

La Niña effect

Occurs every 2-7 years and causes cooler temperatures in a predictable way.

Climate change impact on El Niño

It is likely that climate change will increase the probability of more El Niños in future.