Hydrological Cycle Flashcards
Fluxes definition
The rate of flow between stores
Precipitation definition
The movement of water in any form from the atmosphere to the ground
What is a closed system?
No inputs or outputs
Evaporation
The change in state of water from a liquid to a gas
Residence time
The average time a water molecule will spend in a reservoir or store
Fossil water
Ancient deep groundwater from former pluvial periods
Transpiration
The diffusion of water from vegetation into the atmosphere, involving change from a gas to a liquid
Groundwater flow
The slow transfer of percolated water underground through pervious or porous rocks
What is a drainage basin?
A catchment. An open system with external inputs and outputs which cause the amount of water in the basin to vary over time
What’s an example of a large drainage basin?
The river Nile basin
What is a confluence?
Where 2 rivers meet
How does the amount of water affect the drainage basin?
With more water there is less variability in its pattern
How does the type of precipitation affect drainage basin?
Snow can store large fluxes of water released after rapid melting
How does seasonality affect drainage basin?
In some climates, strong seasonal patterns of rainfall/snowfall will have a major impact on physical processes
How does the intensity of precipitation affect drainage basin?
If rainfall is intense it can’t infiltrate as soil capacity exceeds
How does distribution affect drainage basin?
In the river Nile, tributaries start in different climatic zones
Convectional rainfall
When the ground warms up, evaporation takes place and the air above is heated and rises. Rainfall is often intense with electrical storms and thunder
Cyclonic rainfall
A period of sustained, moderately intensive rain. Associated with passage of depressions.
Orographic rainfall
Warm moist air is forced to rise over upland areas causing the moisture to condense and make rain
Interception loss
Water retained by plant surfaces and water evaporated or absorbed by vegetation and transpired
Throughfall
When the rainfall persists or is relatively intense and the water drops from the leaves
Stem flow
Water flooding through plants/branches/twigs
Infiltration
The movement of water from the ground surface into the soil
What are the drainage basin system outputs?
-Evapotranspiration
-Potential evapotranspiration
-Evaporation
-Transpiration
What is potential evapotranspiration? What is evapotranspiration?
Potential- the water loss that would occur if there was an unlimited supply of water in the soil.
Evapotranspiration- the combined effect of evaporation and transpiration
What influences evaporation?
Increases in warm windy and dry conditions.
Affected by temperature, hrs of sunshine, wind speed/size, water depth/quality, vegetation cover, surface colour
What do rates of transpiration depend on?
Loss of water from plant stomata to atmosphere. Affected by season, vegetation cover, moisture availability, growing season
Human factors affect drainage system
Farming and irrigation
Building dams/river defences
Cloud seeding
Global warming
Urbanisation
Pollution from industry
Overpopulation
Deforestation
How does urbanisation affect drainage basin?
More runoff due to concrete/tarmac
How does deforestation affect drainage basin?
Less trees = more runoff
Less interception
Resulting in flooding
What are water budgets?
The water budget is the annual balance between inputs( precipitation) and outputs (evapotranspiration and channel flow)
River regime
The annual variation in discharge/ flow of a river at a particular point or gauging station. Usually measured in cumecs
What factors affect a river regime?
Climate: high rainfall increases flow
Geology: Permeable rocks allow infiltration reducing flow
Soil type: permeability
Vegetation: Dense vegetation promotes infiltration reducing runoff
Human: Dams/ reservoirs etc
Relief: Steeper= more runoff
Size of catchment area: large catchment = more rain
Flashy vs subdued river
Flashy:
Shorter lag time
Steeper rising limb
High peak
Subdued:
Longer lag time
Shallower rising limb
Define drought
An extended period of deficient rainfall relative to the statistical multi-year average
Define drought
An extended period of deficient rainfall relative to the statistical multi-year average
Define meteorological drought
Shortfalls in precipitation due to short term variability or longer trends which increase the duration of the dry period. This is combined with high temperatures increasing evaporation
Agricultural drought
Can be accelerated by farming practices like overgrazing. Deficiency in soil moisture caused by less rainfall. This produced poor yields
Hydrological drought
Reduced stream flow and groundwater levels due to less precipitation. Threats to wildlife and wetlands
Famine drought
Failure of agriculture=food shortages
What is the Palmer drought severity index?
Way of measuring drought.
Applies to long term drought, uses current data, monitors duration and intensity on a large scale and drought induced atmospheric circulation
What are the physical causes of drought?
ENSO cycle (El Niño southern oscillation)
Blocking anticyclones
Failure of seasonal and monsoon rains
What is the ENSO cycle.
Movement of warm water mass in equatorial Pacific Ocean.
Normally trade winds move EAST to WEST.
During ENSO cycle they move WEST TO EAST.
This results in air rising over EASTERN PACIFIc and descending air over western pacific
Occurs every 2-7 years
What are blocking anticyclones?
-Associated with high pressure systems.
-High pressure=High amount of air in surface
-Thus deflects other incoming weather conditions due to greater pressure
-Lasts 2 weeks
Human causes of drought
Climate change
Deforestation
How does deforestation cause drought?
And give example
Less evapotranspiration occurs
So less water given back to atmosphere
So less precipitation
The Amazon produced its own rain. Deforestation for agriculture is stopping this
400Bn trees transport humidity inland
Impacts of drought
-Reduced biodiversity
-Tree mortality increased
-Threat of wildfires
Causes of flooding
-Monsoon rainfall
-Tropical cyclones
-Glacial outburst flood
-Snowmelt
How do human factors exacerbate flood risk?
-Ploughing compacts soil
-Grazing animals trample soil
-Deforestation
-Sewers add water to channel
-Channelisation
-Urbanisation=impermeable areas
How has climate change impacted California
-Reduced surface runoff
-50% change of 30yr mega droughts
Define water stress
When the annual supply of water per person falls below 1700m^3
Define virtual water
The hidden flow of water when food or other commodities are traded
Define water insecurity
Where present and future supplies cannot be grunted leading to a need for physical or political and economic solutions
What are physical causes of water insecurity?
-Tropical convection
-Convergence of warm humid air and cooler fronts
-West African monsoon
-ENSO
What are human causes of water insecurity?
Example
-Arsenic in Ganges, India
-600m no access in India so use Ganges
-The river is 1000x the permittible level for bathing
What are the 5 factors of the water poverty index?
What do they mean?
-Resources(Quantity of surface and groundwater per person and quality)
-Access(Time and distance involved in obtaining sufficient safe water)
-Capacity(how well community manages its water)
-Use(how economically water is used at home and in industry)
-Environment(ecological sustainability)
Reasons for water insecurity in Israel
-Israel consumes more water
-Demand greater than supply
-Uses 2200Bn L pp. only has 1700
-Conflict with Palestinians over water sources
Egypt vs Ethiopia water conflict
-Egypt is downstream
-Ethiopia has a fast growing population and has a HEP dam
-Egypt can now veto
-Egypt relies on Nile
Human and physical causes of Kent/Sussex hosepipe ban 2022
Human:
-Higher population so more usage
-High usage for recreation/leisure in summer
-Infrastructure issues
Physical:
-Low rainfall in 2022 + heatwaves
-More rain in North
Disadvantages of 3 Gorges dam
-1.3m ppl displaced
-Landslides due to erosion
-Loss of farm land
- $22.5 Bn
-Flooding downstream
-Build up of toxic material in reservoir
Benefits of 3 Gorges dam
-Source of renewable energy
-Decreased fossil fuel usage
-Worlds biggest HEP plant
-More water for irrigation
-Facilitated better transportation along Yangtze rivers
-Prevents flooding in key areas
Water conservation strategies
-Magic stones
-GM crops
-Hydroponics
-Recycling toilet water
-Donestic conversion methods
-Water metre
How does the UN influence management of water resources?
Water courses convention - Guidelines on protection and use of trans boundary rivers
Equitable water sharing is applied to whole drainage basins
Helsinki rules - Criteria for water sharing should be based upon natural factors like rainfall amounts and social/economic needs
Amazon rainforest deforestation
-Around 17% lost
-A 20-25% loss would cause a drier ecosystem
-Forest supports 10% of worlds species
-Deforestation disrupts making its own rainfall
-Moistture from Amazon has global influence
MOISTURE RECYXLING
River Severn flooding cause study
-2007 floods
-Rainfall along river = record levels 129mm
-12 killed
-Waterfront developments in Tewkesbury flooded
Tanzanian water problem
-Privatisation due to IMF and World Bank conditions for loans
-Water now too expensive and scarce
-Exacerbated by lack of infrastructure
-Biwater contracted to manage but only want profit
-Unsafe sources used
Costs and benefits of desalination
Costs:
-Expensive
-Dumping leftover water that is 2x salt concentration of normal harms coral reefs
-Fossil fuels used eg Kuwait
Benefits
-New tech= cheaper and less energy intensive
-Carbon nanotube membranes
Water transfer schemes costs and benefits
Costs
-Expensive as energy intensive
-Co operation between water companies is difficult
-Spread of diseases harms fish stocks
Benefits
-Water to areas in need
