PHYSICAL GEOGRAPHY EDEXCEL A-LEVEL WHSB

PHYSICAL GEOGRAPHY EDEXCEL A-LEVEL WHSB

Is the global hydrological cycle an open or closed system?

It is a closed system as it has no external inputs or outputs. Water can be stored in many forms and can change form, but it cannot leave the hydrosphere, and more water cannot be added.

What % of water is locked up in oceans?

96.5%

What % of water is held as fresh water?

2.5%

What % of fresh water is held in glaciers?

circa 70%

What percent of fresh water is groundwater?

circa 30%

What % of fresh water is surface freshwater?

1% of all freshwater

What is a flux?

A movement of water between stores.

What is residence time?

The average amount of time a water molecule remains in a store.

How long is residence time for the soil and atmosphere stores?

Short

Stores with a longer turnover (residence time) are more suseptible to what?

Pollution

What is blue water?

water stored in rivers, streams, lakes and groundwater in liquid form: it is the visible part of the water cycle.

What is green water?

water stored in the soil and vegetation: it is the 'invisible' part of the cycle.

What is the cryosphere?

Part of the water cycle that contains frozen water - ICE

Why is the Amazon rainforest so relevant to the hydrological cycle?

A fifth of the Earth's freshwater is found in the Amazon rainforest. It releases 20 billion tonnes of moisture to the atmosphere everyday. It can take 10mins for a raindrop to hit the forest floor due to the dense canopy.

Explain convectional rainfall

Sun heats land, which heats air above it. Warm air then rises, cools and condenses, forming clouds. This in turn causes rainfall.

What does the global water budget take into account?

It takes into account all the water that is held in stores and flows of the global hydrological system.

What does ITCZ stand for?

Inter-tropical Convergence Zone

Explain how and why the ITCZ works

https://www.youtube.com/watch?v=SGkvEk0-hoU

Explain the hadley, ferrel and polar cells.

How does thermohaline circulation affect oceans?

Thermohaline circulation (THC) is part of the large scale ocean circulation that is driven by global density gradients created by surface heat and salinity.

What is a drainage basin?

It is defined as 'the area of land drained by a river and its tributaries'. It is a subsystem within the global hydrological cycle, aka the 'local hydrological cycle'. It has inputs, outputs and fluxes.

What is the watershed?

It is the edge of a drainage basin.

Define precipitation

Moisture in any form

Define interception

Temporary storage, as water is captured by plants, buildings and hard surfaces before reaching the soil

Define vegetation storage

Any moisture taken up by vegetation and held within plants

Define surface storage

water held on the ground surface e.g. puddles

Define soil moisture

Water held within the soil

Define groundwater storage

water held within permeable rock (aka aquifer)

Define channel storage

Water held in a river or stream

Define infiltration

Water entering the topsoil. Most common through slow or steady rainfall.

Define throughflow

water seeping laterally through soil below the surface, but above the water table, aka inter-flow

Define percolation

The downward seepage of water through rocks under gravity, especially on permeable rocks e.g. sandstone and chalk

Define stemflow

Water flowing down plant stems or drainpipes

Define base-flow aka groundwater flow

Slow moving water that seeps into a river channel

Define channel flow (aka discharge/runoff)

The volume of water flowing within a river channel

Define surface runoff

flow over the surfac during an intense storm, or when the ground is frozen, saturated or on impermeable clay

Define evaporation

The conversion of water to vapour

Define transpiration

water taken up by plants and transpired onto leaf surface

Define evapotranspiration

The combined effect of evaporation and transpiration

Define river discharge

The volume of water passing a certain point in the channel over a certain amount of time.

Name 9 factors that can affect drainage basins

Climate, Soil, Geology, Relief, Vegetation, Deforestation, Urbanisation, Agriculture, Mega-dams

Name 4 factors that will affect evapotranspiration

Temperature, Wind, Vegetation cover, Soil moisture content

How will TEMPERATURE affect evapotranspiration?

rate of evaporation will increase with temperature.

How will WIND affect evapotranspiration?

Increase rate of evaporation by reducing relative humidity and preventing saturation of air

How will VEGETATION COVER affect evapotranspiration?

tranpsiration will increase with increased vegetation cover, which will depend on type of vegetation and season. Darker vegetation will absorb more solar energy, which will increasse evaporation.

How will SOIL MOISTURE CONTENT affect evapotranspiration?

this will determine the avaliability of water for transpiration, and is dependent on soil and rock permeablity.

Define the water budget.

The annual balance between inputs (precipitation) and outputs (evaporation and channel flows). It will either be positive or negative (surplus or deficit)

What is effective rainfall?

The amount of rainwater remaining after evaporation has occured.

What are river regimes?

The annual variation in the discharge of a river at a particular point.

What can affect a river's discharge?

Groundwater, runoff, antecedent rainfall, size of catchment, level of vegetation, human use (e.g. industry, agriculture etc), the relief, geology, soil type, climate

What is the difference between complex and simple river regimes?

A complex regime may cover multiple climate zones, whereas a simple regime only covers a particular climate zone.

What does a storm hydrograph show?

It shows the variation in river discharge (or channel flow) within a short period of time. It only focuses on discharge during storm events, and the main purpose is to see how a river responds to precitation.

Compare flashy and flat rivers in terms of storms.

flashy: short lag time, likely to fglood, higher peak discharge

flat: longer lag time, unlikely to flood, lower peak discharge

What factors affect whether a river is flashy or flat?

weather, geology, soil, relief, basin shape and size, vegetation, land use.

What is a drought?

A periods of abnormally dry weather that causes serious hydrological imbalance to a specific region.

How much of the world's land is severley affected by drought?

30%. It has doubled over the last 30 years.

What are the 4 different types of drought?

Agricultural, meteorological, hydrological, socio-economic (famine)

What are the causes of Agricultural drought?

Often initiated by low levels of precipitation, this drought is classified by a deficit in soil moisture which affects plant biomass.

What are the causes of meterological drought?

This is defined by shortfalls in precipitation driven by both short and long term variability which increases the lenth of dry seasons. It is usually driven by high temperatures, low humidity and high winds.

What are the causes of hydrological drought?

This type of drough is associated with reduced streamflow and groundwater levels.

What are the causes of socio-economic drought?

This occurs when the other 3 types have severe social, economic, environmental and political issues, leading to humanitarian crisies.

What are the impacts of Agricultural drought?

poor crop yields, a decline in pasture quality and rural economies, with many famers requring govt aid.

What are the impacts of meteorlogical drought?

Often the first type of drough to occur, with resultant impacts on soil moisture loss and the supply of irrigation water.

What are the impacts of hydrological drought?

loss of storage in wetlands and ecosystems. Often linke with a decreased supply of water for urban areas; water quality also declines, leading to health issues.

What are the impacts of socio-economic drought?

collapse of rural economies, increased malnutritions, and widespread failure of agricultural systems.

Explain what happens in the pacific in a non-El Nino year.

warm water is pushed towards Australia, and cold water is pushed towards S. america. Rainy in Australia due to convectional rainfall, very dry in Peru.

What happens in an El Nino year?

The trade winds just stop. This means warm surface water is not pushed towards Australia, and thus there is cold water in Australia and warm in Peru. Sea levels rise by 30cm in peru. Peru becomes V wet (4000mm in a month!!!), lots of flooding and fish economy collapses, AU has a drought.

Name 2 causes of human water insecurity

-Pollution: making water resources unsuitable for use

-Overabstraction: taking too much water from water sources

Name a drought you can use in a question

Murray-Darling basin

Discuss the Murray-Darling basin drought

2001-9, there was widespread drought in Australia. The MD basin covers around 1.6 million km2, and is essential for producing fruit, veg, diary, wheat and livestock. The 10 year drought negatively affected Australia's ability to feed its population, and had to import more food as a result - in 2006, the wheat yield was less than half expected. In 2006 also, reservoir volume fell to 40% of their capacity.

Name 4 physical causes of drought in Australia

-Most droughts associated with el nino

-low, highly variable rainfall associated with sub tropic, high pressure system

-long term climate changed is blamed for 2006 'big dry'

-major shift in rainfall patterns meaning the densely populated east coast has become drier.

What is a Wetland?

Areas where water covers the soil (or near the surface) for most of the year. They are rich in hydrophytes and thus the soil is nutrient rich. They are on every continent except antarctica.

Name the two types of wetlands

-Coastal/tidal

-Inland/non-tidal

How many people in the world live near and depend on wetlands?

300-400 million

Why are wetlands so important?

-act as a sponge to trap flood water and distribute it across the floodplain

-protect against coastal erosion and storm surges

-they are a vital habitat

-they support the livelhoods of many

-carbon sink (organisms don't decompose)

Why is the Okovango Delta being destroyed? How much has been destroyed purposely?

It is destroyed by slash and burn for houses. It is also significantly affected by the damming up the river in Angola. 2500million km2 have been purposely destroyed so far.

How much of the cattle died in the Sahel 1968-73?

50-70%

How many people died in the Sahel drought 1968-73?

100,000

In what year in the Sahel did it not rain at all?

1972

By 1973, by how much had had the Sahara advanced into the Sahel?

100km (62miles)

Mesopotamian marshlands - discuss

Between the 1950s-90s, Iraq marshlands were drained to force the Marsh Arabs who had rebelled in the 1991 uprising against Suddam Hussein. It was a classic religion conflict. At the turn of the century, only 1600 Marsh Arabs remained to preserve the culture.

Name 7 types of surpluses in the hydrological cycle

-Surface water (pluvial)

-reservoir flooding

-fluvial flooding

-groundwater flooding

-coastal flooding

-flash flooding

-sewer flooding

What is surface water (pluvial) flooding?

An occurence that is hard to predict, this occurs when rainwater fails to drain away sufficiently

What is reservoir flooding?

When a dam bursts and the contents of a reservoir causes damage to the surrounding area