2. The water cycle Flashcards
define interception
rainwater which hits the surface of something
define stemflow
water flowing out of the plant
define infiltration
water enters the pores of the soil
water table
the depth at which the rock becomes saturated
define percolation
the movement of water through soil, soil -> ground water
why does water flow horisontally
in order for water to flow horizontally the vertical flow must be impeded, this is done by:
1. impermeable surface - no spaces for water to infiltrate so surface runoff occurs
2. saturated ground - all spaces are full of water and it cannot take in anymore - saturation excess overland flow
3. porosity/infiltration rate - if the rate of precipitation is greater than the rate of infiltration - infiltration excess overland flow
what factors affect the rate of evaporation
- insulation/solar radiation - radiation and the resulting heat causes evaporation of water
- availability of water - is the water liquid or solid, is the water exposed or absorbed (i.e. soil)
- temperature of air - warmer air can hold more moisture
- humidity - the closer the air is to saturation point the slower the rate of evaporation
what causes condensation (and thus precipitation)
for condensation to take place water vapour must have something to condense onto e.g.dust or pollution (condensation nuclei)
warm, moist air passes over a cool surface causing it to condense
condensation is the direct cause of precipitation
what causes orographic/relief rainfall
formed when air is forced to cool when it rises over relief features in the landscape such as hills or mountains. As it rises it cools, condenses and forms rain
what is continentality
A location’s proximity to the sea affects its temperature and how often it rains
during summer, the sea heats up less quickly than the land. During winter, the opposite happens, and the sea retains heat from the sun longer than the land.
define sublimation
strong sunlight and dry winds (low relative humidity) hits a snowpack and frozen water goes directly from solid to gas
define deposition
moist air touches a cold surface and instantly freezes (hoar frost)
why might the magnitude of water cycle stores change over time
hourly/daily -
during the day rain clouds can build up, forecasting rain
seasonally -
snows more in winter - colder avg temps, rainy seasons/monsoons
over longer periods - ice ages
how has the hydrosphere changed with climate change
95.6% of the earth’s water is stored in the oceans
the burning of fossil fuels has caused bodies of water to become more acidic - Carbon dioxide reacts with sea water to produce carbonic acid. The resulting increase in acidity (measured by lower pH values) changes the balance of minerals in the water
as ice sheets decline water is released into the oceans
how has the cryosphere changed with climate change
almost all freshwater is locked up in glaciers (68.7%)
the amount of water held in ice caps fluctuates due to the varying temps
climate change decreases the volume of water in the cryosphere
rate of melting in the andean glaciers is threatening many cities in peru
how has the lithosphere changed with climate change
30% of earths freshwater is stored in the ground
climate change has changed the distribution of water in the lithosphere - desertification in reducing soil moisture
the changing weather patterns like high winds can increase erosion
drought, dry soils as well as flooded soils all affect food production
how has the atmosphere changed with climate change
increased temps lead to warmer air, more evaporation
rising warm air holds water vapour which condenses to form clouds - changed weather patterns, more storms
water vapour is a greenhouse gas and furthers climate change
describe the factors and flows that affect the drainage basin
vegetation and land use -high vegetation leads to high rates of interception, root uptake and evapotranspiration (reduces river discharge)
in low temps there is less growth so there is less root uptake and less interception
rainfall - long duration leads to saturation excess overland flow
shape of land - steep land means gravity will pull water down faster
climate - weeks of rainfall rises the water table meaning the basin can become saturated faster
high temps increase evapotranspiration which reduces drainage
low temps freeze water so there will be no runoff
soil type and depth - sandy soils have a faster rate, clay soils allow very little throughflow which results in less surface runoff
bedrock - permeable rock (chalk and sandstone) allows water to percolate through
impermeable rock (granite) stops percolation resulting in high surface runoff, soils become saturated
conditions in drainage basin - if soil is frozen it is impermeable, baked ground (so hot and dry) is also impermeable
size and shape of river basin - in a large basin water takes a long time to travel to the channel
in a circular basin all points are equivalent so there will be a shorter lag time
elongated basins have longer lag times and lower peak discharge
define recharge
A time when water is added to soil moisture storage the recharge create a cousin facilitation exceeds potential evapotranspiration but the soil has yet to reach its field capacity
define surplus
Occurs when precipitation exceeds potential about the transpiration and the soil has reached its field capacity
any additional water applied to the soil runs off if this water runs off into nearby streams and rivers it could cause flooding
the intensity and duration of surface can be used to predict potential flooding
define utilisation
The utilisation season is a time and water is withdrawn from soil moisture storage
the utilisation period occurs and potentially backward transpiration exceed the precipitation but soil storage has yet to reach 0 (dry soil)
define deficit
The deficit season occurs when potential evapotranspiration exceeds precipitation and soil storage has reached zero
what is a river regime
The variability in a river discharge throughout the course of a year in response to precipitation temperature in evapotranspiration and drainage basin characteristics
what are ephemeral streams
Ephemeral streams are temporary streams
found in arid or semi arid environments like Arizona
high evapotranspiration, soil deficit and low precipitation
streams appear following intense precipitation - precipitation exceeds infiltration rate but disappear very quickly
