Unit 1: The Water Cycle Flashcards
What is the water cycle?
Also known as the hydrological, describes the continuous movement of water between the atmosphere, oceans and land.
The amount of water in each store is determined by the concept of what?
Mass balance
What is the cryosphere?
Areas of the earth where water is frozen ( glaciers, sea ice and permafrost)
What are some main stores of water in a drainage basin?
•Atmosphere
•Soil
•Ocean
•Groundwater
What are the outputs in a drainage basin?
• Evaporation
• Transpiration
What are the inputs in a drainage basin??
• Precipitation
What are the flows in a drainage basin??
• percolation
• surface runoff
• fluxes
Why is a drainage basin an open system?
Because the quantity of water in that area can change.
Why is a drainage basin an open system?
Because the quantity of water in that area can change.
Why is the global water cycle a closed system?
Because the earth cannot gain or lose any water -> can’t create anymore
Out of all the water globally what percentage is freshwater?
2.5%
What are the main inputs and outputs into the oceans?
Main inputs = river flow, precipitation, glacier calving
Main outputs = evaporation
What are the main inputs and outputs into the Cryosphere?
Main inputs= snow, ice, wind-blown snow, avalanches
Main outputs= ablation (melting), wind blown snow, calving, sublimation,
What are the main inputs and outputs into the groundwater?
Main inputs = percolation
Main outputs = ground-water flow
What are the main inputs and outputs into rivers + lakes??
Main inputs = precipitation, river flow, surface run-off, ground-water flow
Main outputs = evaporation, river flow
What are the main inputs and outputs into the soil moisture?
Main inputs = infiltration
Main outputs = plant uptake, evaporation
What are the main inputs and outputs into the atmosphere?
Main inputs = evaporation, transpiration
Main outputs = precipitation
What are the main inputs and outputs into the biosphere?
Main inputs = plant-uptake
Main outputs = transpiration
Define soil water surplus
There is excess water available to the system and the soil is saturated. Precipitation exceeded evapotranspiration for a prolonged period and the excess is not being used by plants.
Define Soil water utilisation
There is a reduction of water available within the system as evapotranspiration exceeds precipitation. Plant growth increases transpiration rates and increasing temperatures increase evaporation.
Define soil water recharge
After a period of soil water deficiency, precipitation exceeds evapotranspiration. There will be an increase in water in the soli.
Define field capacity
Precipitation exceeds evapotranspiration. The maximum amount of water that soil can hold before it becomes saturated
What is the water balance/ budget?
It affects how much water is stored in a terrestrial(land) drainage basin system over a typical year. It is a function of the inputs (precipitation) and the outputs (river flow in to oceans and evapotranspiration)
What is the water balance formula?
Precipitation (P) = Stream/river flow (Q) + Evapotranspiration (E)
If P>Q+E what is the balance?
Positive
If P<Q+E what’s the balance?
Negative
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 a drainage basin?
Is the catchment area drained by a single river and its tributaries. The line which separates one drainage basin from another is called the watershed.
Why is a drainage basin an open system?
•not fixed inputs and outputs -> constantly occurring
•may get inputs from neighbouring drainage basins
•volume in the system is fluctuating
Define throughflow
Horizontal movement of water downslope through the soil
Define surface runoff (overland flow)
The flow of water over ground surface
Define interception
Water temporarily stored on the surface of vegetation
Define percolation
The vertical downward movement of water through the soil to the groundwater
Define infiltration
Movement of water from the ground surface into the soil.
Define precipitation
An input such as rain, snow, sleet, hail, dew.
It is any liquid or frozen water that forms in the atmosphere and falls back to the earth.
Define throughfall
Water dripping off vegetation to the ground surface
Define baseflow
Water flowing into a river from the ground - water store
Define surface storage
Water held in puddles, lakes and reservoirs
Define transpiration
Water lost from vegetation through the stomata cells
Define water table
The upper level of the groundwater
Define channel flow
Water flowing within a river
Define groundwater store
Water stored in soil and/or rock below the water table
Define channel store
Water held within a river
Define stem flow
Water flowing over leaves, stems and branches
Apart from the type of precipitation what are two other characteristics of precipitation that will impact on the drainage basin?
Intensity and duration of precipitation
What is interception loss?
This is the proportion of the precipitation that does not reach the ground due to interception.
What does interception loss depend on?
Type of vegetation and the season of the year
What is the % interception loss for forests?
15% - 35% for coniferous forests whilst for broad-leaved forests it is 9-25% depending on season and density of vegetation (highest in tropical rainforest, lowest in temperate forest in winter).
What is the % interception loss for natural grassland, arid and semi-arid areas?
For natural grasslands interception loss is 14-19% whilst crops have highly variable values from 7% to 40%. In arid and semi-arid areas, where there is little vegetation, the interception loss is negligible.
When is precipitation stored on the surface?
> water is frozen as snow or ice
water accumulates in depressions where any infiltration is slower than the input of water. on a small, temporary scale this would be a puddle whilst on a large, permanent scale a lake would occur.
What are the two main types of surface runoff/overland flow?
Saturation-excess and Infiltration-excess
What is saturation-excess overland flow?
If the soil is already saturated and there are no empty pore spaces between soil particles, then any further precipitation will runoff the surface.
What is infiltration-excess overland flow, also known as Hortonian flow?
This process operates on dry soil when the rate of precipitation is greater than the rate of infiltration(infiltration capacity). Consequently excess water accumulates on the surface and will begin to flow overland.
What can intense rainfall cause?
High levels on infiltration-excess overland flow, resulting in flash floods, such as Boscastle in 2004.
What will infiltration capacity and rate of throughflow be affected by?
The permeability of the soil
Why is the texture of the soil a key factor that will control the permeability of the soil?
Soil texture refers to the size of weathered rock particles that make up the soil, which in turn controls the size of pore spaces within the soil.
How does the size of pore spaces affect infiltration?
Coarse, bigger macropore spaces increases infiltration.
Smaller particles slow down infiltration rates.
What are other factors that control rates of infiltration and throughflow?
soil moisture, precipitation, landcover/vegetation, slope angle, surface roughness, slope length, slope direction, intensity, soil compaction, amount of dead organic matter and leaf litter.
Define gravitational water
Is the amount of water held in larger pore spaces
Define Retained or Capillary water
water which is held in pores that are small enough to hold water against gravity, but not tightly that roots cannot absorb it- field capacity, important for vegetation.
Define hygroscopic water
Means the tendency of absorbing moisture from the air. Not available for plants. Once capillary water has been drained hygroscopic water is left.
For groundwater to be stored and to flow the bedrock must be what?
Permeable and have certain characteristics. The bedrock must contain pore spaces (porous spaces) and/or contain joints/cracks (pervious rocks)
If a rock is capable of storing and transmitting water it is called a what and if it is not it is called a what?
Aquifer
Aquiclude
What are examples of impermeable rocks?
Granite, Slate, Clay
What is a pervious rock?
Water is stored or passes through cracks within the rock, eg. limestone
What is a porous rock?
Water is stored or passes through the spaces(pores) between the rock particles, eg. sandstone, chalk.
Why do rivers keep flowing even after prolonged periods of dry weather?
Groundwater flow, which maintains a normal minimal flow of the river.
What is evaporation?
Is the process by which liquid water is converted into water vapour. It transfers water from the surface to the atmosphere.
What three factors result in high rates of evaporation?
- High temperatures
- High humidity
- High wind speeds
What is river regime?
The amount of water flowing(discharge) through a river over a year will tend to have a predictable pattern which can be represented graphically as a river regime.
What are the two categories which a river regime can be broken into?
Simple and complex
What is a simple regime?
Is one in which there is a clear seasonal difference between a period of high water levels and a period a low water levels.
What is a complex regime?
Is one in which the pattern of discharge has multiples peaks and more variable flow?
Whats a location example of a complex river regime?
The river Po in Italy has two peaks during a year (one in may and one in November) and two troughs (one in January and one in august)
Whats a place example of human influences on river regimes?
Colorado River, Arizona, USA
- it flows through an arid region
- peak rainfall occurs in august dur to intense storms from convectional rainfall - highest temps so lots of evaporation so high water vapour in air.
When was the hoover dam built and what was it designed for?
It was built in 1936
- to be a source of power generation (supports 1.3 million people with 4 billion killwatts)
- as flood control
- for water storage of 2.8 million acres of water
What are some effects after the construction of the Hoover Dam?
- lower river level as water is taken out and used for power generation
- humans can regulate the release of stored water from lake mead
- flood control (population growth)
- the building of it provided jobs after the great depression - boosts economy
How does the Hoover dam work?
It takes water from Colorado river and stores it in lake mead (largest reservoir in America)
What does a storm hydrograph show?
Shows river discharge response before and after a storm or rainfall event
What is lag time?
The period between maximum precipitation and peak discharge
What is the rising limb?
The rising portion of the hydrograph showing increased levels of discharge
What is the falling limb?
The period where discharge is decreasing and the level of the river is falling
What is bankfull discharge?
When the level of discharge is at the channel capacity and any further increase in discharge will result in flooding
What is baseflow/ground water flow?
The proportion of discharge fed from groundwater flow
What is peak flow/discharge?
The point in time where the river reaches its highest level
What is a flashy hydrograph?
Flashy profiles with short lag times, steep rising and falling limbs and high peak discharge
What is a non-flashy hydrograph?
Non-flashy profile with long lag times, shallow rising and falling limbs and low peak discharge.
What is the catchment shape of a non-flashy hydrograph?
Elongated drainage basins have lower peak discharge as the water at the head of the basin takes longer to reach the river mouth than water closer to it.
What is the catchment shape of a flashy hydrograph?
In a circular drainage basin, water takes less time to reach the river as all points in the drainage basin are roughly equidistant from the river so all precipitation reaches the river at the same time resulting in a high peak discharge.
How does drainage density affect hydrographs?
Drainage density refers to the total length of streams/river per unit area of land. Basins with lots of streams and rivers(a high drainage density) will have a short lag time and fairly steep falling limb because water will drain out of them quickly.
How does slope gradient affect hydrographs?
Basins with steep slopes will have a high peak discharge and a short lag time because the water can travel faster downhill.
