Water EQ1 (5.1) Flashcards
Transpiration definition:
The diffusion of water from vegetation into the atmosphere, involving a change from a liquid to a gas
Groundwater flow definition:
Water that flows deep underground into aquifers
Infiltration definition:
Water moves from the surface into the soil and the rock below
Systems approach:
Studies hydrological phenomena by looking at the balance of inputs and outputs and how water is moved between stores and flows
Fluxes definition:
The rate of flow between the stores
Cryosphere definition:
Areas of the Earth where water is frozen into snow or ice
Residence time definition:
The average time a water molecule will spend in a reservoir or store
Fossil water definition:
Ancient, deep groundwater from former pluvial (wetter) periods
What drives thy hydrological cycle?
Solar energy and gravitation potential energy. There can be changes in solar energy but gravitational potential energy stays constant
How does gravitational potential energy influence the hydrological cycle?
Accelerates water, transporting it to rivers and eventually the sea
What are the biggest stores of water?
- Oceans (97%)
- Ice on land (1.9%)
- Groundwater (1.1%)
How much water in the world is freshwater?
2.5%, only 1% is easily accessible
Blue water definition:
Freshwater stored in the visible parts of the hydrological cycle, such as rivers, streams and lakes
Green water definition:
Freshwater stored in the invisible parts of the hydrological cycle such as soil and vegetation
What is the residence time of groundwater?
Up to 10,000 years
Where is fossil water?
Polar regions and beneath many deserts
What is the problem with fossil water?
Some countries rely on it but it will eventually run out because the stores are not being replenished
Do oceans and landmasses lose the same amount of water they gain?
- Oceans lose more water through evaporation than they gain from precipitation
- Landmasses gain more water from precipitation than they lose through evapotranspiration
- The difference is made up by surface run off
Catchment definition:
The area of land drained by a river and its tributaries
Watershed definition:
The highland which divides and separates waters flowing to different rivers
Dew point definition:
The temperature at which dew forms; it is a measure of atmospheric moisture
Saturated overland flow definition:
The upward movement of the water table into the evaporation zone
Albedo definition:
A measure of the proportion of the incoming solar radiation that is reflected by the surface into the atmosphere and space
Potential evapotranspiration definition:
The water loss that would occur if there was an unlimited supply of water in the soil for use by vegetation
Afforestation definition:
The planting of trees in an area that has not been forested in recent times
Drainage basin definition:
An area of land drained by a river and its tributaries. It includes water found in the water table and surface run off. The line separating drainage basins is called a water shed. Usually this is an area of high land
Confluence definition:
The point where two rivers meet
Where is convectional rainfall common?
Tropical areas and the UK during summer
How does convectional rainfall work?
- When the land becomes hot, the air above it becomes warmer, expands and rises
- As it rises it cools and condenses, forming clouds
- If the air continues to rise, rain will fall
How does cyclonic rainfall work?
- Warmer air which is lighter and less dense is forced to rise over cooler, denser air
- As it rises it cools, condensation occurs and clouds and rain form
How does orographic rainfall work?
- When air is forced to rise over a barrier, such as a mountain, it cools and condensation occurs, causing rain to fall
- The downward slope receives relatively little rain, which is known as the rain shadow effect
What is convectional rainfall associated with?
Intense thunderstorms which occur in the tropics
What is cyclonic rainfall associated with?
A period of substantial, moderately intensive rain; associated with the passage of depressions
Where is orographic rainfall concentrated?
The windward slopes and summits of mountains
Interception loss definition:
The water that is retained by plant surfaces and later evaporated or absorbed by the vegetation and transpired. When the rainfall is light or of short duration, much of the water will never reach the ground and will be recycled through this process
Throughfall definition:
When the rainfall persists or is relatively intense and the water drops from the leaves, twigs, needles etc
Stem flow definition:
When water trickles along the twigs and branches then down the trunk
Factors that influence the impacts on the drainage basin:
- The amount of precipitation
- The type of precipitation
- Season
- Intensity of precipitation
- Variability
- Distribution of precipitation within a basin
How does interception affect the drainage basin?
Raindrops are prevented from falling directly to the ground because of a layer of vegetation. There may be secondary interception, where some of the undergrowth intercepts water falling from the canopy
What are the types of fluxes (flows) in the drainage basin?
- Interception
- Infiltration and through flow
- Direct run off (overland flow)
- Percolation and groundwater flow
What are the outputs in the drainage basin system?
- Evaporation and Transpiration
- Channel flow
Human factors that affect drainage basins:
- Deforestation
- Urbanisation
- Reservoirs
- Over abstraction
- Cloud seeding
How do reservoirs affect drainage basins?
- Delay flows
- Increase the amount of water lost through evaporation
- Floating plants on the surface increase evapotranspiration
How does cloud seeding work?
- It’s an attempt to change the amount or type of precipitation by dispersing substances into the air that serve as cloud condensation nuclei
- New technology claims it is a dependable and affordable water supply
- Its effectiveness is still debated
What climate regulation problems has deforestation in Amazonia caused?
- Reduced interception leading to rising river levels and flooding
- During the dry season, areas downstream of deforestation can have month long droughts
- Reduced rainfall because of a lack of evapotranspiration
- Losses of fresh water can lead to water insecurity
- Warmer, dryer, less predictable climate
- Habitat loss for many animals
River regime definition:
The annual variation in discharge or flow of a river form a particular point or gauging station, usually measured in cumecs
Rising limb definition:
The part of a storm hydrograph in which discharge starts to rise
Peak discharge definition:
The time when the river reaches its highest flow
Lag time definition:
The time interval between peak rainfall and peak discharge
Falling/ recessional limb definition:
The part of a storm hydrograph in which the discharge starts to decrease
Base flow definition:
The normal day-to-day discharge of a river
Hydrograph definition:
A graph showing changes in the discharge of a river over a short period of time
Factors that affect the shape of a storm hydrograph:
- Drainage basin size
- Drainage basin shape
- Drainage basin relief
- Soil type
- Rock type
- Drainage density
- Natural vegetation
- Land use
- Precipitation intensity
- Precipitation duration
- Snow fall/melt
- Evapotranspiration
How does drainage basin shape affect the shape of a storm hydrograph?
- If it is circular, it will take less time for the water to reach the channel as all the distances are equidistant
- If it is an elongated basin, it will take a long time for the water to reach the extremities
How does drainage basin relief affect the shape of a storm hydrograph?
- In steep sloped basins, water will reach the channel quickly
- With gentle slopes, the water can infiltrate the ground and travel slowly
How does snow fall/melt influence the shape of a storm hydrograph?
- With fast snow melt, water cannot infiltrate the froze ground, so it flows rapidly into the channel
- With slow snow melt, the ground thaws with the snow, so the melt water can infiltrate into the soils and rocks
How does evapotranspiration affect the shape of a storm hydrograph?
- Low rates mean fewer losses from the drainage basin
- High rates will reduce the discharge from the river channel
