Dynamic equilibrium

~ water cycle

~ carbon cycle

*LAND USE CHANGES*

URBANISATION

Water cycle:

Impermeable artificial surfaces e.g. tarmac, concrete, brick replacing farmland and woodland

Drainage systems e.g. pitched roofs, guttering, sewerage systems

Encroaching on floodplains

Carbon cycle:

Increased anthropogenic emissions

Removal of vegetation

FARMING

Water cycle:

Crop irrigation

Less ... than forest/ grassland

Ploughing

Artificial underdrainage

Heavy machinery compacts soils

Carbon cycle:

Clearance of forest for agriculture

Ploughing and exposure of soil organic matter to oxidation

Harvesting of crops

Lack of biodiversity and short growth cycle

(Changes less apparent when replacing grassland)

FORESTRY

Water cycle:

Higher rates of rainfall interception in plantations in natural forests

Increased evaporation

Reduced run-off and stream discharge

Transpiration rates increased compared to farmland/ moorland

Clear felling to harvest timber

Carbon cycle:

Changing land use from farmland/ moorland to forestry

Forest trees extract CO2 from atmosphere and sequester it for hundreds of years

~ forest trees only a carbon sink for 100 years after planting

*WATER EXTRACTION*

RIVER KENNET CATCHMENT

Location

Main rock type

The rock type encourages ...

Urban areas relying on water supply from the area

Thames Water

Why water good for diverse habitat and use by humans

~ native fauna

Impact on regional water cycle:

- rates of groundwater extraction exceeded rates of recharge

- drop in river flow due to dry conditions

- lower discharge

- lower groundwater levels

Aquifers

~ groundwater

~ water table

~~ southern England

Artesian basin

~ artesian pressure

~ artesian aquifer

~ potentiometric surface

~ London

~~ London groundwater

~~ overexploitation

*FOSSIL FUELS AND THE CARBON CYCLE*

Fossil fuels

Increases CO2 concentration