Water Stores and Components

3.1.1.2 The Water Cycle

How much water does the atmosphere contain at any one time?

12,900km3

Describe the water in the Cryosphere.

It contains 68.7% of earth’s freshwater.

90% of this is in the Antarctic, 10% in Greenland.

Describe the water in the Biosphere.

It contains 0.001% of earth’s water.

Describe the water in the Lithosphere.

It contains 1.7% of earth’s water.

What percent of earth’s freshwater are wee actually able to access?

0.5%

Why is the demand for water becoming increasingly problematic?

Increasing population - over 10bn by 2050

Agriculture is a huge consumer of global freshwater

AI relies on freshwater to cool engines

What is condensation?

Gas to liquid

What is evaporation?

Liquid to gas

What is sublimation?

Solid to gas.

What is deposition?

Gas to solid.

Describe the factors affecting evaporation.

Amount of evaporation depends on amount of solar energy.

Availability of water.

Humidity of air (closer to saturation point the slower the rate of evaporation).

The temperature of the air(warmer air holds more water vapour).

Describe the factors affecting condensation.

Warm air comes into contact with a cold surface.

When the ground cools and warm air contacts it.

When air is forced to rise over hills and cools.

When a mass of warm air meets a mass of cool air.

When warm surfaces heat the air which makes it rise and cools it down.

Describe the water stored in the lithosphere.

In oceanic crust it is stored within the rock structure which it is composed of and in continental crust it is also found in rocks, minerals, and also in clay and as groundwater.

Main water stores in the lithosphere are groundwater held in aquifers and soil moisture within porous rocks and soils.

What is the Lithosphere?

The solid outer crust and upper mantle.

Describe the cryosphere.

All frozen water parts of the Earth, including glaciers, ice caps, and sea ice.

Describe the biosphere.

Water stored all living things on Earth: plants, animals, microorganisms, and the ecosystems they form.

Describe water stored in the atmosphere.

The layer of gases surrounding the Earth where water exists as vapour and cloud droplets.

Short residence time of about 10 days, due to rapid cycling via evaporation, condensation, and precipitation.

0.001% of earth’s surface water.

Describe the hydrosphere.

All the liquid water on or near Earth’s surface, including oceans, seas, lakes, rivers, and groundwater.

What is evapotranspiration?

The process by which water is transferred from the land to the atmosphere by evaporation from the soil and other surfaces and by transpiration from plants.

What is transpiration?

The process by which water is lost from a plant through stomata in its leaves.

What is groundwater flow?

The movement of water that is found beneath the Earth's surface.

This water is stored in soil and rocks and slowly moves through spaces and cracks underground.

It’s the slowest transfer of water within the drainage basin.

What is infiltration?

The passage of water into the soil.

Occurs relatively quickly at the beginning of a storm but falls quickly as the soil becomes saturated.

What is interception?

the process by which raindrops are prevented from directly reaching the soil surface.

Leaves, stems and branches on trees intercept water.

Evaporation removes some of this moisture from the system and it doesn’t reach the river as runoff.

What is percolation?

The downward movement of water within the rock under soil surfaces.

The rate of percolation depends on the nature of rock, some are impermeable so there’s no percolation or groundwater flow.

What is precipitation?

Water in any form that falls from the atmosphere to the surface of earth.

What is stemflow?

The water that runs down the stems and branches of plants and trees during and after rain to reach the ground.

What is throughfall?

The water that drips off leaves during a rainstorm. When more water falls onto the interception layer of the tree canopy than can remain on the leaves.

What is throughflow?

The water that moves down-slope through subsoil, pulled by gravity. It’s particularly effective when underlying impermeable rock prevents percolation.

What is interflow?

The lateral movement of water through the unsaturated zone towards a river channel.

What is groundwater flow?

The slow movement of water horizontally through the bedrock below the water table within the saturated zone, driven by gravity and hydraulic pressure.

What is surface runoff?

The movement of water across the land surface towards a channel.

What is baseflow?

The portion of a river’s discharge that is sustained over time by the continuous, slow release of groundwater from bedrock into the river bed and banks.

What is soil moisture storage?

Water stored in the soil.

What is channel fall?

The incline of a drainage basin.

What is a drainage basin also known as?

Catchment area.

The area which supplies the river with water.

What are the stats for how density of vegetation cover is important in the rate of interception?

A forest of needle-leaf trees capture 22% of rainfall whereas broad-leafed deciduous forest captured for 19%. Some tropical rainforests can capture as much as 58%.

Describe the factors responsible for the rate of infiltration.

1. The filling of small pores on the soil surface with water reduces the capillary action moving water into the soil.

2. If the soil is clay based, it will absorb moisture, causing the clay particles to expand, thus reducing the size of the soil pores for water to infiltrate.

3. Raindrops can impact heavily on the soil surface, breaking soil particles up and thus ‘blocking’ pores and preventing movement of water into the soil.

When does the soil become saturated?

If rainfall intensity is greater than the infiltration rate, then the soil has reached infiltration capacity.

How does vegetation influence throughflow?

The more vegetated an area, the faster the rate of throughflow, because it is aided by root channels in the soil.

What are aquifers?

An underground layer of permeable rock, sediment, or fractured material that stores and transmits groundwater, supplying wells and springs as a major freshwater source.

How does atmosphere influence precipitation?

Atmosphere influences input. Warm atmospheres (such as equatorial regions) can hold more moisture than cold atmospheres, so they receive higher precipitation unput.

How does latitude influence precipitation?

It affects how much solar radiation occurs.

High‑latitude areas get weak sunlight, which keeps the air cold. Cold air cannot hold much water vapor, so these regions tend to be dry with low precipitation.

Areas near the Inter-Tropical Convergence Zone have warm atmospheres and create heavy storms

How does relief influence precipitation?

In mountainous (high relief) areas, air is forced to rise, cool and condense over the mountains, and will eventually fall as precipitation. In low relief areas, air is less elevated, and so does not rise to cool and condense into clouds.

How does prevailing wind influence precipitation?

Prevailing winds move air masses.

When they blow over oceans, they pick up moisture. As this moist air reaches land and rises, it cools and condenses, producing more precipitation—often in coastal regions.

How does the time of year influence precipitation?

In winter months, air is cooler and therefore condenses more quickly.

How does the type of precipitation influence precipitation?

If the precipitation is not liquid (sleet, compact snow) it may take a while for it to melt, thus acting as a temporary store. When it melts, it may lead to flooding.

What effect does seasonality have on interception and infiltration?

During the winter months, in deciduous forests, the leaves on trees fall, which greatly reduces interception. However, in coniferous forests, for example, interception rate will remain similar as leaves do not fall. 

What factors effect evapotranspiration?

Temperature: The greatest source of energy for evaporation. Lower temperature means lower energy and thus lower evapotranspiration rates. Temperature varies by day, season and geographical location.

Relative Humidity: Warm air holds more moisture than cold air. If the humidity level is above 70%, evaporation will not occur.

Solar Radiation: More solar radiation will lead to more radiation being contained in earth's surface, increasing temperatures and evapotranspiration rates. Darker and denser vegetation increases how much energy is retained so increases evapotranspiration. The ground's ability to reflect sunlight off of it is called the albedo effect and lighter surfaces reflect more sunlight and are therefore cooler than darker surfaces, which absorb more sunlight.

Soil texture and depth: Evaporation rates are the highest in soils with coarse textures and large spaces between them

What conditions would likely cause a river channel to flood and why?

1. Narrower and shallower channels as they are less able to hold large amounts of water.

2. A burst of prolonged (antecedent) rainfall as this occurs over a short period of time, and there is likely to be more rainfall which will exceed the capacity of the river causing flooding.

3. Drainage basin relief: Having a steep drainage basin will mean more water travels quickly downhill due to gravity in all forms (groundwater, throughflow etc.)

4. Vegetation: if the surrounding area has more vegetation, more interception will occur, slowing the movement of water.

5. Season: rainfall more common in autumn and winter, so flooding is also more likely to occur.

How could humans influence whether a river will flood or not?

1. Urbanisation means there are more impermeable surfaces. This reduces infiltration and increases surface runoff / overland flow, which increases the likelihood of flooding.

2. Hard engineering such as the construction of dams or relief channels can reduce the likelihood of flooding by providing alternative routes for water to travel, increasing the river’s water capacity.

3. Deforestation reduces interception, leading to infiltration at a quicker rate. This increases the likelihood of overland flow.