Basics of carbon and water systems

What is mass balance in the global water system?

It’s the fixed amount of water globally – water can neither be gained nor lost

What is a store in the water cycle?

A place where water is held

What is a flow in the water cycle?

The movement of water between stores

Is the global water cycle open or closed?

Closed – no water is lost to or gained from outside the system

Name the Earth’s subsystems related to the water cycle

Hydrosphere

What is the cryosphere?

Parts of the Earth where water is solid

What are Milankovitch cycles?

Orbital changes influencing Earth’s climate over long timescales

Eccentricity

The change in the shape of Earth’s orbit from circular to elliptical over 100

Tilt

The variation of Earth’s axial tilt between 22° and 24.5° over 41

Precession

A wobble in Earth’s rotational axis over a 22

Is a drainage basin an open or closed system?

Open – water can enter and leave

What is throughfall?

Rain dripping from vegetation onto the ground

What is stemflow?

Rain running down stems and trunks to the ground

What is infiltration?

The process of water entering the soil

What is percolation?

Water moving from soil to bedrock

What is groundwater flow?

Water movement through rocks beneath the soil

What is overland flow?

Water moving across the ground surface

What is infiltration-excess overland flow?

Rainfall exceeds infiltration capacity of soil

What is saturation-excess overland flow?

Soil becomes saturated

What is channel flow?

Water moving in rivers and streams

What is interception?

Rainwater held on leaves and plant surfaces

What is soil moisture storage?

Water held in the pores of soil

What is channel discharge?

The amount of water leaving via a river over time

What is evaporation?

The change of water from liquid to gas

What is transpiration?

Water vapor released from plant stomata

What is a river regime?

The annual pattern of discharge in a river

What is a simple regime?

A river with one seasonal discharge peak

What is a complex regime?

A river with many tributaries and multiple peaks

What is discharge?

The volume of water (m³/s) passing a given point in a river

What is a storm hydrograph?

A graph showing a river's response to a rainfall event

What is peak discharge?

The maximum rate of river flow during a storm

What is peak rainfall?

The maximum rainfall recorded during a storm

What is the rising limb?

The section of a hydrograph where discharge increases

What is lag time?

The time between peak rainfall and peak discharge

What is the falling limb?

The section of a hydrograph where discharge decreases

What is preceding discharge?

The rate of river flow prior to the storm event

What is bankfull discharge?

The maximum discharge before flooding occurs

What is base flow?

The normal day-to-day flow of a river

How do antecedent conditions affect hydrographs?

Saturated soils cause faster runoff and flashier hydrographs

How does vegetation affect hydrographs?

More vegetation increases interception and evapotranspiration

How does rock type affect hydrographs?

Permeable rocks allow more infiltration and reduce runoff

How does soil depth and type affect hydrographs?

Deeper clay soils increase runoff

How does land use affect hydrographs?

Urban and agricultural land use can increase or decrease runoff and infiltration

How does basin shape affect hydrographs?

Circular basins cause faster drainage and flashier hydrographs

How does drainage density affect hydrographs?

Higher drainage density = faster flow and shorter lag times

How does slope angle affect hydrographs?

Steeper slopes = less infiltration and more surface runoff

What is convectional rainfall?

Rain caused by surface heating leading to rising and cooling air

What is frontal rainfall?

Rain caused when warm and cold air masses meet

What is orographic rainfall?

Rain caused when moist air is forced over mountains

What is the feeder-seeder mechanism?

Raindrops fall from high clouds and grow by collecting droplets from lower clouds

What is the Bergeron-Findeisen process?

Ice crystals in high clouds grow

What is the collision process?

Larger raindrops collide and merge with smaller droplets to grow in size

What is runoff?

Rainwater movement via overland flow

What is the effect of snowmelt and ice ablation?

Increases runoff into rivers

What is the effect of storm activity on runoff?

Intense or prolonged rainfall leads to excess runoff and possible flooding

How does urbanisation affect runoff?

Increases impermeable surfaces

What is the water balance equation?

P = Q + ET + ΔS

What causes a water deficit?

When precipitation is less than the sum of evapotranspiration and runoff

What causes soil moisture surplus?

High winter precipitation and low evaporation rates

What causes soil moisture deficit?

High summer temperatures and plant use of soil water

What is a meteorological drought?

A prolonged period of below-average rainfall

What is an agricultural drought?

Insufficient soil moisture for crop production

What is a hydrological drought?

Low water reserves in lakes

What is an aquifer?

A permeable rock layer that stores extractable groundwater

What is an artesian aquifer?

An aquifer confined between impermeable layers under pressure

What is the Aral Sea disaster?

A shrinking inland sea due to overuse for irrigation

What is the carbon cycle?

The movement of carbon through the Earth’s atmosphere

What percentage of Earth’s carbon is atmospheric?

Only 0.001%

What percentage of carbon is in living organisms?

0.004%

Where is most carbon stored?

In sedimentary rock and fossil fuels (99.9%)

What is a carbon sink?

A store that absorbs more carbon than it releases

What is a carbon source?

A store that releases more carbon than it absorbs

What is carbon sequestration?

The natural capture and storage of CO₂ from the atmosphere

What is photosynthesis?

Plants and phytoplankton fix atmospheric CO₂ into carbohydrates

What is respiration?

Organisms release CO₂ through breaking down glucose

What is decomposition?

The breakdown of organic matter releasing carbon through physical

What is combustion?

Burning organic material or fossil fuels

What is the physical (inorganic) carbon pump?

CO₂ dissolves in ocean surface and is transported to deeper layers

What is the biological carbon pump?

Phytoplankton absorb CO₂ and pass it through marine food chains

What is the carbonate pump?

Plankton use CO₂ to create shells

What is carbonation?

Chemical weathering where CO₂ dissolves in rainwater and reacts with rock

How is carbon released from rock?

Through volcanic activity

Where is carbon stored in biomes?

In biomass

What is a biome?

A major ecosystem type like a rainforest or tundra

How much carbon is in tropical rainforests?

550 GtC in biomass and soil

How much carbon is in temperate grasslands?

185 GtC in biomass and soil

How does deforestation affect carbon?

Reduces storage and increases atmospheric CO₂

What is afforestation?

Planting trees to increase carbon sequestration

How does agriculture affect carbon?

Soil erosion and vegetation loss reduce carbon storage

What is peat?

Partially decomposed vegetation in waterlogged anaerobic soil

Why is peat a carbon sink?

It accumulates plant material faster than it decomposes

Where are peatlands found?

In high rainfall upland areas like Scotland

How much land is peatland?

3% of Earth’s land surface stores 60 billion tonnes of carbon

What degrades peatlands?

Drainage

What is the effect of degraded peatlands?

They become carbon sources rather than sinks

What is peat restoration?

Rewetting and revegetation to restore carbon storage

What is desertification?

The degradation of land due to climate change or poor land use

How does desertification affect water and carbon cycles?

Reduces infiltration

What is NPP?

Net Primary Productivity – the rate of plant growth storing carbon

How does humus help?

It stores carbon and retains up to 90% of its weight in water