Part 1: Water Flashcards
Water
Explain the interactions that are involved in environmental science?
Environmental science is the study of the interactions between the Hydrosphere (water) Atmosphere (air) Lithosphere (earth) Biosphere (life)
What disciplines in science does environmental science cover?
All disciplines including physics, chemistry, biology, ecology, geography, Earth sciences, social sciences and technology
What vegetation is found in terrestrial environments where liquid water is abundant?
Forests specifically, tropical rainforests in wetter equatorial regions and deciduous forests at higher, more temperate latitudes.
What impact does reduced water availability have on the type of vegetation that can grow in an environment?
t changes it. Grasslands and tundra (a vegetation type composed of low-growing plants such as dwarf shrubs, grasses, mosses and lichens) replace forests as water availability is reduced.
Where does water exist predominantly as a solid?
Water exists predominantly as ice and snow in the polar regions (high latitudes) and at high altitudes such as mountain peaks.
What is a catchment?
A catchment is the area from which rainfall flows into a river. Any rain falling in this area that makes its way into rivers or streams is ultimately destined to flow out of the catchment at a single point – in the Teign catchment this is through the estuary into the sea. Rivers and streams do not cross the catchment boundary. It is the area of interest.
what is gradient?
Gradient is a numerical expression of steepness.
Gradient is a defined as:
gradient = height change ÷ horizontal distance.
What is the hydrosphere?
The hydrosphere includes the parts of the Earth that are mainly water, such as the oceans, ice caps, lakes and rivers
What is the water/hydrological cycle?
Water moves over, on and through the Earth in a continuous cycle driven by the Sun and gravity. This process known as the water cycle or the hydrological cycle involves water as liquid, solid (ice and snow) and gas (water vapour).
What is hydrology?
The study of water movement on and beneath the ground and the physics and chemistry of the water is called hydrology.
what are the two main types of water in the hydrological cycle?
meteoric and saline
What is meteoric water?
meteoric, which is fresh water derived by condensation from the atmosphere that accumulates as surface water (rivers and freshwater lakes) and underground water
What is saline water?
saline, which is the seawater of the oceans and many lakes.
What other type of water can be included in the hydrological cycle apart from the two main types?
Small amounts of magmatic water from the interior of the Earth are also added to the cycle by volcanic eruptions.
What is a reservoir?
All parts of the hydrosphere that store water temporarily.
what percentage of total water on earth does the ocean
as a reservoir make up?
96.5
what percentage of total water on earth do ice caps as a reservoir make up?
1.9
what percentage of total water on earth does underground water as a reservoir make up?
1.6
what percentage of total water on earth do lakes as a reservoir make up?
0.012
what percentage of total water on earth does soil moisture as a reservoir make up?
0.001
what percentage of total water on earth does the atmosphere as a reservoir make up?
0.001
what percentage of total water on earth does the rivers as a reservoir make up?
0.0001
What is the resident time of water in the ocean in the water cycle?
about 4000 years
What is the resident time of water in the ice caps in the water cycle?
about 8000 years
What is the resident time of water in the underground water in the water cycle?
from a few weeks to more than 10000 years
What is the resident time of water in the lakes in the water cycle?
a few years
What is the resident time of water in the soil moisture in the water cycle?
a few weeks to one year
What is the resident time of water in the atmosphere in the water cycle?
about 11 days
What is the resident time of water in the rivers in the water cycle?
a few weeks
What is the hydrological cycle driven by?
The suns energy and the earths gravity
What does the water cycle involve?
The water cycle involves the movement of water, in all its forms, over, on and through the soil and rocks near the surface of the Earth and in the atmosphere.
How do you calculate the residence time for water in a reservoir?
It is calculated by dividing the mass in a particular reservoir by the rate of transfer to or from the reservoir.
In what reservoir is residence time the fastest?
it is fastest in the atmosphere (about 11 days) and rivers (a few weeks).
what do you call the transfer of water from the atmosphere to the earths surface?
Water that transfers from the atmosphere to the Earth’s surface is called precipitation,
How is precipitation commonly experienced?
It is commonly experienced in the form of rain, snow or hail. Water vapour may also precipitate by condensing as dew on the ground or hoar frost on vegetation or objects.
In what forms do precipitation exist?
It exists as vapour, liquid (clouds and raindrops) or in solid form (snow and ice).
At what rate does air cool when increasing in altitude?
it cools at a rate of around 1 °C per 100 m of altitude.
Why does air expand when it increases in altitude?
because of the decrease in pressure with altitude
What is needed in the air for water droplets to form? Give some examples.
Water droplets form around small particles in the air. This happens when water vapour condenses around them. Particles such as pollen grains, fungal spores, dust and salt from sea spray.
How do the formation of clouds occur?
Water vapour condenses around small particles in the air. This condensation over a large amount results in the formation of clouds.
How big are the droplets that form clouds in diameter?
The formation of clouds composed of 0.001–0.1 mm diameter droplets.
How big are the droplets of water when they precipitate to the ground? How do they become bigger?
Precipitation of this water occurs when these droplets coalesce to form larger drops about 1 mm in diameter, or when ice crystals form and they fall to the Earth’s surface.
what unit is precipitation commonly measured in?
mm
What is interception?
It is when most precipitation reaches the ground, but not all of it, as some is stopped by vegetation. This process is known as interception. It is part of a subcycle of the water cycle involving precipitation, interception and evaporation back to the atmosphere, but it bypasses that part of the main cycle where water reaches the ground.
What does the loss of precipitation caused by interception of vegetation depend on?
The proportion of the precipitation that does not reach the ground, the interception loss, depends on the type of vegetation, as well as its age and density and the season.
Values of interception loss averaged over the year are higher for coniferous forest than for deciduous forest (15–35% versus 9–25%).
Why is the average value of interception loss higher for coniferous forest?
Because coniferous forest retains its leaves throughout the year and the dense canopy of fine leaves (needles) is more effective at stopping precipitation reaching the ground.
In what part of the world has the most uneven global distribution of precipitation?
Near to the equator
What type of geological landscape is precipitation greatest over?
Mountainous areas
What is evaporation?
It is the process by which water is transferred as vapour from the land or ocean to the atmosphere.
In what conditions does evaporation occur?
Evaporation from liquid water can take place at any temperature under normal atmospheric pressure. It occurs only at the surface of the liquid. THIS SHOULD NOT BE CONFUSED WITH BOILING
What happens when water boils? and what conditions does it happen in?
It should not be confused with the process of boiling, whereby the conversion of liquid water to gaseous water (steam) takes place throughout the bulk of the liquid and occurs at a fixed temperature for a given pressure.
What is the boiling point for water?
The boiling temperature of water under normal atmospheric pressure is 100°C,
What happens to the boiling temperature of water with increasing altitude and why?
It reduces with increasing altitude as the air pressure reduces. For example, the boiling point of water at the top of Mount Everest is 71 °C.
Does the rate of evaporation increase or decrease with increasing temperature?
It increases
Does the rate of evaporation increase or decrease with increasing humidity?
It decreases
What is humidity?
It is a measure of how close the air is to saturation with water vapour.
How does wind speed affect evaporation of water?
Wind speed is also important, as wind carries moist air away from the ground surface, thus reducing the local humidity and allowing more water to evaporate.
What is the rate of evaporation aided by?
One explanation for this observation is that the rate of evaporation is not limited by the availability of water and is aided by the large surface area available. The temperature of the water is also a relevant factor. Water depth can also have an influence on evaporation rates.
Explain what will happen to the eavopration rate when dry air moving over land reaches the edge of a lake?
Initially the evaporation rate will be high but as the humidity of the air rises the rate of evaporation will decrease until, with a large lake, the net evaporation rate will reach zero. This is because evaporation rates decrease with humidity.
What can we assume with the levels of humidity over oceans?
Air travelling over oceans therefore has essentially constant humidity, due to its large surface area.
What can we assume with the levels of humidity over small lakes?
for small lakes a continuous high rate of evaporation is achieved as the humid air close to the water surface quickly diffuses away as the surface area is much less.
What are the evaporation rates like in a shallow lake in summer and why?
The water temperature of shallow lakes closely parallels that of the air, so evaporation rates are much higher when the air is warm in the summer than in the winter.
What are the evaporation rates like for deep lakes throughout the seasons and why?
For large, deep lakes, water temperature lags behind air temperature (in temperate climates, the ocean is always more agreeable for bathing at the end of the summer than at the beginning). So for deep lakes, evaporation rates may fall to a minimum in the early spring and actually be higher in the winter.
Are the evaporation rates higher in fresh water or salt water?
rates of evaporation are higher for freshwater than salt (saline) water.
How much salt per kg of water does seawater contain?
Seawater contains about 35 grams of dissolved salts per kilogram of water
What percentage is the evaporation rate of sea water lower than fresh water?
evaporation rate that is about 3% less than that of pure water.
Why does seawater have a decreased evaporation rate to that compared with fresh water?
A simplistic way of rationalising this is to view the dissolved material as occupying a proportion of the surface of the seawater and thereby reducing the effective area from which water molecules can evaporate
Does water evaporate quicker from open water or land?
Evaporation from bare soil (in contrast to open water) can be limited by the supply of water and, by extension, as a result of the type of soil the water is sitting on. For example, evaporation from a saturated sandy soil can take place nearly as quickly as it can from open water, whereas the rate for a saturated clay soil is slower: between 75% and 90% of that of open water.
What can aid evaporation from land soils?
Water is evaporated from any surface covered by a film of water and from water filling the spaces between grains of soil near the surface. Evaporation rates are initially high after rainfall, but decrease with time and may reach zero if there are no mechanisms available (such as plant roots) to bring deeper-lying water to the surface. Capillary processes can bring water to the surface, and it is more effective with fine-grained soils, where the spaces between the grains are small, than it is with coarse-grained soils. However, most soil is not bare, being covered with agricultural or natural vegetation.
Rainfall
plant roots
capillary processes
Where does over two-thirds of total global evaporation occur? and why?
within 30° of the Equator, because of the higher temperatures in equatorial and tropical areas.
Globally where does evaporation reach its greatest values?
Evaporation reaches its greatest values not at the Equator itself, but between latitudes of 10° and 20° in both hemispheres
How does the evaporation rate near the equator affect the precipitation rate?
The strong trade winds at these latitudes carry water vapour towards the Equator, giving very high precipitation in the equatorial zone where the trade-wind systems converge.
A graph shows that evaporation from the Earth’s surface is greater in the Southern Hemisphere than in the Northern Hemisphere. Suggest an explanation for this.
The Southern Hemisphere has more ocean than the Northern Hemisphere, and evaporation is greatest from open water.
Which two environmental factors are important in determining the dependence of evaporation rates on season?
Temperature and humidity. So although precipitation averaged over England is not very seasonal (it is more so in Scotland and Wales; see Figure 1.1.6), the availability of water is due in large part to the seasonality of evaporation.
How much energy is required to convert 1 kg of liquid to the gas phase?
What does this represent?
To convert one kilogram of liquid water at 100 °C to the gas phase at the same temperature requires an energy input of about 2.4 × 106
This represents the latent heat of vaporisation of water.
What is the albedo?
The proportion of that radiation that is reflected back into space, the albedo
What is the radiant energy from the sun used for?
some is used to heat the soil, vegetation or surface water (G)
some is used for heating the air above the land surface (H)
a tiny proportion goes towards the growth of plants (and so is ignored in the context of this discussion).
What does the amount of radiantion reaching the surface of the earth depend on?
The amount of radiation reaching the surface of the Earth at a particular point also varies with latitude, season, cloud cover and time of day.
Please look at the following flash card to compare the albedo values of different surfaces.
Albedo value ranges for different surfaces. Surface Albedo Forest (deciduous) 0.16–0.22 Forest (coniferous) 0.05–0.14 Grass and grain crops 0.12–0.28 Water 0.08–0.14 Snow 0.35–0.85 Soil and rock 0.05–0.45
