Water Cycle π§ Flashcards
what is the systems approach?
group of interacting parts connected by flows of energy or matter
open - energy and matter can enter and leave
closed - only energy can enter and leave, matter cant
cascading systems - where output of one subsystem is an input to another
dynamic equilibrium in water cycle
tendency towards a natural state of balance between inputs and outputs
- change triggers + or - feedback
closed system - no water enters or leaves, recycled
drainage basin = open system, inputs and outputs can change
equilibrium upset by natural (storm events) and human changes
Positive feedback in the water cycle
- temperature rise
- evaporation increases
- amount of water vapour in atmosphere increases
- greenhouse effect increases
Negative feedback in water cycle
- temperatures rise
- evaporation increases
- increase water vapour, causes more clouds to form
- increased cloud coverage, reflect more sunlight back to space
- temperatures fall
how are systems affected by feedbacks?
if input and outputs are balanced = dynamic equilibrium
- positive - moves system further from equilibrium
- negative - moves system closer to equilibrium
What is an open system?
Both energy and matter can enter and leave
- drainage basin, water (energy from sun and water)
- rainforest, carbon
What is a closed system?
Matter canβt enter or leave but energy can
- carbon cycle (energy from sun enters and leaves, but carbon remains same)
Flows in the water cycle
Evaporation - liquid to gas, uses solar energy, can be affected by seasons or glacial periods
Condensation - gas to liquid, water vapour cools to dew point, loses energy
Cloud formation - warm air cools and condenses onto condensation nuclei, varies seasonally and location
Precipitation - main flow from atmosphere to ground
Cryospheric processes - accumulation and ablation
Natural changes that impact the water cycle
Seasonal changes
Storm events
Human changes that impact water cycle
Deforestation
Urbanisation
Farming
water abstraction
climate change
what are βprocesses driving changeβ?
factors affecting the size of stores in the water cycle
dictated by:
- flows (eg evaporation)
- global factors
- local factors
local processes driving change
flows and transfers
(in a drainage basin)
affecting by physical and natural factors
global processes driving change
cryospheric processes
clouds and precipitation
evaporation
condensation
climate change
effects of evaporation on the water cycle
increases the amount of water stored in atmosphere
from hydrosphere, biosphere etc
magnitude (rate) varies due to location and season:
- amount of solar energy
- availability of water (pond vs field)
- humidity (higher = less)
- temperature (warmer air holds more water)
effects of condensation on the water cycle
happens when air containing water vapour cools to dew point
(cool air holds less water)
decreases amount of water stored in atmosphere
condense on surfaces or particles below dew point temperature
magnitude depends on
- amount of water vapour in atmosphere
- temperature (large drop = more condensation)
- condensation nuclei
effects of cloud formation and precipitation on the water cycle
precipitation returns atmospheric water to terrestrial
- causes, water vapour cooled (see next)
magnitude depends on
- seasons (eg UK, more rain in winter than summer)
- location (higher at tropics than poles)
distribution affected by global atmospheric circulation model
- hot at equator = evaporation, low pressure
low pressure = clouds
causes of rainfall (3)
frontal - warm air is less dense, so when meets cool air, forced above
cools as it rises and condenses
orographic - warm air meets mountains, forced to rise
causes it to cool and condense
convectional - sun heats up ground, moisture evaporates and rises
cools as it gets higher, condenses
effects of cryospheric processes on the water cycle
changes to the amount of water stored in cryosphere
Major store of water
magnitude depends on
- season (more ice in winter)
- temperature
glacial periods - inputs in cryosphere greater than outputs, no melting
interglacial - outputs larger than inputs, melting
- causing sea level rise, more volume in hydrosphere
varies on different scales, annual or thousands of years (glacial periods)
effects of climate change on water cycle (global factors)
last ice age = increased size of store in cyrosphere
less storage in the hydrosphere
outline drainage basins
- area of land drained by a river and its tributaries
- boundary is called the watershed
- open systems with inputs and outputs