Studied by 6 people
What is the global hydrological cycle?
The closed system of all of earths water. It consists of many different stores, by which water is moved in and out of by solar and gravitational potential energy.
What is a store in the global hydrological cycle?
A place where water is held. Eg a reservoir or the atmosphere
What is a flow in the global hydrological cycle?
The movement of water between stores. Eg a river or rain
What is a process in relation to a flow?
A process is a physical mechanism that drives a flow. Eg gravitational pull drives a river
Name the flows in the global hydrological cycle
Surface runoff, infiltration and percolation, through flow and groundwater flow.
What is the difference between infiltration and percolation?
Infiltration is rainwater soaking into the soil, whereas percolation is the movement of water within the soil itself.
What is the difference between throughflow and groundwater flow?
Through flow is the downslope movement of water through the soil, roughly parallel to the ground surface whereas
Groundwater flow is the very slow horizontal movement of water through rock
What are the two different categories of water store?
Blue water- visible water such as rivers and lakes
Green water- non visible water in stored such as trees and soil
What is residence time?
Average amount of time a water molecule stays in its store
What is a drainage basin?
The area of land drained by a a river and it tributaries.
What is a watershed?
The boundary of a drainage basin
What are the tree types of rainfall?
Orographic, frontal and conventional
What is orographic rainfall?
orographic rain is 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 which falls on one side of the mountain, whereas the other side remains dry
What is frontal rainfall?
Frontal rainfall occurs when a warm front meets a cold front. The heavier cold air sinks to the ground and the warm air rises above it. When the warm air rises, it cools. The cooler air condenses and form clouds. The clouds bring heavy rain.
What is conventional rainfall?
When the sun heats the earths surface, the air above it warms and rises. As it rises it cools and condenses to rainfall. This type of rainfall is common in tropical areas
What are the two outputs in the hydrological cycle?
Evaporation and transpiration. (Evapotranspiration EVT)
What is potential EVT?
The water loss that would occur if there was an unlimited supply of water in soil available for plants.
Name the physical factors the effect drainage basins
The climate (eg the amount of precipitation and seasonal patters)
vegetation (type and amount) -the soil
the geology of the area (permeable or impermeable)
the relief
Name the human factors that effect drainage basins
Reservoir creation
deforestation (reduces interception so surface runoff increases)
land use change (use of tarmac, which is impermeable, can cause flooding)
What is a water budget?
It is the annual balance between precipitation, evapotranspiration and runoff
What is the water budget equation and what does each character stand for?
P= Q + E +/- S
P= Precipitation Q= Channel discharge E= Evaporation S= Change in store
How can this equation show positive or negative water balance?
P>Q+E = +ive
P<Q+E = -ive
What is a river regime?
The annual variation in discharge or flow of a river at a particular point or gauging station. Usually measured in cubic meters per second (cumecs)
Simple river regime
Where the river experiences seasonally high discharge followed by seasonally low discharge. Inputs typically depend on meltwater or storms.
Tends to be rivers in temperate and mountainous regions
Complex river regimes
Where larger rivers cross several different relief/climatic zones and so also experience different seasons + effects. Eg the river Ganges or the amazon
Human factory’s can also make river regimes more complex. Eg dams
Other factors that impact river regimes
Catchment size
geology
land use
evaporation rate
vegetation type
What does a storm hydrograph show?
The variation in discharge of a river within a short period of time in response to input of precipitation
What are the two types of hydrograph?
Flat and flashy
What physical factors can effect the shape of a hydrograph?
vol and duration of precipitation
river size
catchment area
relief +geology
vegetation cover
What human factors can effect the shape of a hydrograph?
deforestation (Vegetation cover)
urbanisation (surface runoff)
What are the four types of drought?
meteorological
hydrological
agricultural
famine drought
What is meteorological drought?
Drought caused by lack of precipitation
What is hydrological drought
Drought caused by changes in the input and output of bodies of water
What is agricultural drought?
When water content of soil is low, causing plant biomass to decrease
What is famine drought?
A humanitarian crisis in which agricultural failure has lead fo wide spread food shortages
What are the natural causes of drought?
Short term-
blocking anicyclones
Med term-
ENSO (MAKE MORE NOTES ON THIS)
Long term- -global atmospheric circulation (worldwide system of winds)
What are human causes of drought?
over abstraction of surface water
deforestation
climate change
over extraction of ground water
CASE STUDY
SAHAL AFRICA
CASE STUDY
AUSTRALIA
ENSO (El nino southern oscillation)
a variation in air circulation around the world that results in
warmer whether to the Americas
wet weather and flooding in Africa
happens ever 3-7 years
la nina is the opposite pattern
is being worsened by climate change
more frequent
more severe
What are the ecological impacts of drought on wetlands?
very vulnerable when dry as organisms are adapted to wet environment
soil dries up- can lead to easier erosion and oxidation of soil (which can real ease pollutants and nutrients in dangerously conc levels)
some species such as birds may leave the area
What are the ecological impacts of drought on forests?
tree growth is slowed + leaves drop which can take up to 4 years to recover from
tree death changes food chains as well as carbon cycle
pests spread easier in dry conditions
What are the types of flooding?
ground water, surface water flooding, flash flooding
What is ground water flooding?
occurs after ground is fully saturated and can no longer take in anymore water after prolonged heavy rain fall
What is surface water flooding?
when intense rainfall doesn’t have enough time to infiltrate and so flows over land
What is a flash flood?
A flood with a very short lag time (most dangerous)
Natural causes of flooding
wet seasons/ too much rainfall
impermeable rock type
low-lying area
area at the bottom of high relief
Human causes of flooding
land use change (urbanisation- impermeable materials, deforestation- less interception)
building over flood plains
hard engineering such as straightening channels and dredging (increasing depth or river channels) while these may benefit some areas, down stream it can cause issues such as moor flooding .
How is spearman’s rank calculated?
Rs = spearman’s rank coefficient
DÂ = difference in rank
n = number of samples
CASE STUDY
UK FLOODING 1953
CASE STUDY
Pakistan floods LIC (geofile)
What is eutrophication?
The process of farming chemicals such as fertilisers being carried into rivers by rain water.
Why is eutrophication bad?
the nutrients carried into the river causes a huge dense growth of plants
higher plants (eg algae) block light from reaching deeper parts of the river- causing plant death of underwater plants
animal death occurs due to lack of photosynthesis by underwater plants leading to low O2 concentrations in water
overall- decreasing the biodiversity of the river
water insecurity
when people do mot have enough quality water to sustain a quality life, as well as to support socio-economic development.
physical scarcity
the lack of available water sources such as surface and ground water
CASE STUDY- physical water scarcity
salt water encroachment- Kiribati?
economic scarcity
lack of ACCESS water due to lack of money or management
CASE STUDY- economic water scarcity
Kathmandu Nepal
Mexico city (also case study for water conflicts)
cape town ?? (also case study for water conflicts)
CASE STUDY- human water scarcity
aral sea
water poverty index
factors in Resources Access Capacity Use and Environment
and is a measure of TIME needed to collect a certain volume of water
factors that increase water demand
population
agriculture
hot climate (climate change)
standard of living (better life styles= need more water)
factors that determine water supply
climate (precipitation levels)
topography (shape of land/ relief)
rock type (permeable or not)
river systems
pollution makes more water unusable)
urbanisation (causes more surface runoff)
CASE STUDY- water insecurity UK
the south of england is more water insecure to the the warmer climate. and as it is a small country there are fewer water sources.
most of Englands water comes form scotland which is a very water secure country
CASE STUDY - conflicts over water
the Nile
mexico city
cape town
colorado river
CASE STUDY- who is on control of the water (gov vs TNC)
Bolivia and the private water company Bechtel Corporation
CASE STUDY- solutions to water insecurity
UNICEF
IWRM
integrated water resources management
a process which promotes co-ordinated development of water management between countries
things that determine the price of water
how hard water is to access
demand
level of infrastructure
who is on control of the water (gov vs TNC)
players in water distribution
consumers
company / gov in control / economy
environment
CASE STUDY- managing water supply
three gorges dam china
water transfer schemes china
singapore holistic management
desalination isreal
IWRM
UNs Helsinki rules
→ Colorado river
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