Lesson 3: Drainage basin:
- Human impacts:
1. Ground Water Abstraction
In some places water is taken from aquifers at a rate higher than the replacement level. This causes reduced groundwater flow and a lower
water tale. Increased industry or deforestation also increases groundwater storage, increasing the risk of flooding if the water table reaches the
surface.
Where?
In China, groundwater irrigates 40% of farmland and provides 70% of drinking water in the north-west and north. Groundwater dropped by a
metre per year between 1974-2000.
2. Deforestation
3. Urbanisation
Building creates impermeable surfaces that reduce infiltration and increase surface runoff and throughflow through artificial drains. Often
increases river discharge as a result.
Where?
- increased flooding in Maidenhead (2014), York (2015) and Manchester (2015).
4. Dam Construction
Building dams increases surface water stores and evaporation. They reduce downstream river flow and discharge.
Where?
Lake Nasser behind the Aswan Dam in Egypt is estimated to have evaporation losses of 10-16 billion cubic metres every year. This represents a
loss of 20-30% of the Egyptian water volume from the River Nile.
5. Cloud Seeding
- attempt to change the amount or type of precipitation by dispersing substances into the air that serve as cloud condensation nuclei
(hygroscopic nuclei). New technology and research claims to have produced reliable results that make cloud seeing a dependable and affordable
water-supply practice for many regions, but its effectiveness is still debated.
Where?
,China used cloud seeding in Beijing just before the 2008 Olympic Games to create rain to clear the air of pollution.
It is used in the Alpine Meadows ski area in California to improve snow cover, and was used in 2015 in Texas to reduce the impact of drought.
Lesson 4: River regime - Complex
River Location River regime
Amazon South America - 6,308km long, drains a 6 million km2 basin.
River (Peru, Venezuela,
Factors:
Brazil, Ecuador and
Bolivia) - Climate: Humid tropical climate
- Annual precipitation: seasonal – every month but divided into high and low season.
- Evapotranspiration levels high.
Human influence: increasing – large dam used by Brazil’s major cities for irrigation and HEP.
Yukon River North America - 3,540km long with a drainage basin of 850,000 km2.
(Canada and
- Climate: Tundra, Taiga and mountainous climate.
Alaska, US)
- In winter the temperature drops so water freezes. In summer, meltwater is an input into the system.
- High summer temperatures, rainfall and snowmelt
Human: relatively low – most landscape is wilderness. Some HEP use for mining industries.
River Nile Northern Africa - Warm, arid climate.
- Huge drainage basin.
- In 1970, the construction of the Aswan Dam significantly altered the regime. Flow reduced by around 65%
and the seasonal flow was changed
Murray- Australia - Climate: seasonal sub—tropical, with monsoon in northern tributaries of Queensland, temperate climate in
Darling the south
- Most of the basin lies in a rain shadow and undergoes long period of drought.
, - Water drawn by major cities and farms for irrigation.
Lesson 5 + 7: Drought + Climate change
Name Causes Impacts
Tropical - Usually: moist air moves in a westerly Social:
drought – direction from the South Atlantic across
- water rationing for 4m pp
Brazil the Amazon Basin -> encounter Andes
(2014-15) Mountain, forced to turn southwards, - water supplies were cut off for 3 days/week in some town
maintaining the flow of moisture around - power cut due to halting of HEP production -> threaten dependency (create 70% electricity)
the Basin.
- protest in Sao Paulo
- However, a series of high-pressure
systems diverted rain-bearing winds - drill illegal wells (70% of new wells were illegal) due to high fees for license ($3500) and more
further north, away from the Amazon expensive to drill (30-35k)
and prevented them from diverting - not monitored for water safety, might contain industrial pollutants and higher bacteria levels.
southwards from the Andes
Economic:
- Heavy rains occurred in Bolivia+
Paraguay - dry air remains in Brazil - a reduced crop of Arabica coffee beans -> push up the global coffee prices by 50%
Environmental:
- depletion of 17 largest reservoirs to dangerously low levels (some to 1% of capacity)
- increased groundwater abstraction -> aquifers dangerously low.
Name Background Factors Impacts
California - Population of 40 million Physical: Social:
people
- El Nino = typical - water rationing
in California, meaning
conditions
there are human pressures California has mountains which affect rainfall. Towards the eastern border is the
reversed, making
on water supplies Arizona desert
drought worse.
- forecast intense mega- Hydrological cycle:
Human
droughts + decade-long dry - Surface runoff and soil moisture levels have declined.
periods.
- Human impacts:
1. Ground Water Abstraction
In some places water is taken from aquifers at a rate higher than the replacement level. This causes reduced groundwater flow and a lower
water tale. Increased industry or deforestation also increases groundwater storage, increasing the risk of flooding if the water table reaches the
surface.
Where?
In China, groundwater irrigates 40% of farmland and provides 70% of drinking water in the north-west and north. Groundwater dropped by a
metre per year between 1974-2000.
2. Deforestation
3. Urbanisation
Building creates impermeable surfaces that reduce infiltration and increase surface runoff and throughflow through artificial drains. Often
increases river discharge as a result.
Where?
- increased flooding in Maidenhead (2014), York (2015) and Manchester (2015).
4. Dam Construction
Building dams increases surface water stores and evaporation. They reduce downstream river flow and discharge.
Where?
Lake Nasser behind the Aswan Dam in Egypt is estimated to have evaporation losses of 10-16 billion cubic metres every year. This represents a
loss of 20-30% of the Egyptian water volume from the River Nile.
5. Cloud Seeding
- attempt to change the amount or type of precipitation by dispersing substances into the air that serve as cloud condensation nuclei
(hygroscopic nuclei). New technology and research claims to have produced reliable results that make cloud seeing a dependable and affordable
water-supply practice for many regions, but its effectiveness is still debated.
Where?
,China used cloud seeding in Beijing just before the 2008 Olympic Games to create rain to clear the air of pollution.
It is used in the Alpine Meadows ski area in California to improve snow cover, and was used in 2015 in Texas to reduce the impact of drought.
Lesson 4: River regime - Complex
River Location River regime
Amazon South America - 6,308km long, drains a 6 million km2 basin.
River (Peru, Venezuela,
Factors:
Brazil, Ecuador and
Bolivia) - Climate: Humid tropical climate
- Annual precipitation: seasonal – every month but divided into high and low season.
- Evapotranspiration levels high.
Human influence: increasing – large dam used by Brazil’s major cities for irrigation and HEP.
Yukon River North America - 3,540km long with a drainage basin of 850,000 km2.
(Canada and
- Climate: Tundra, Taiga and mountainous climate.
Alaska, US)
- In winter the temperature drops so water freezes. In summer, meltwater is an input into the system.
- High summer temperatures, rainfall and snowmelt
Human: relatively low – most landscape is wilderness. Some HEP use for mining industries.
River Nile Northern Africa - Warm, arid climate.
- Huge drainage basin.
- In 1970, the construction of the Aswan Dam significantly altered the regime. Flow reduced by around 65%
and the seasonal flow was changed
Murray- Australia - Climate: seasonal sub—tropical, with monsoon in northern tributaries of Queensland, temperate climate in
Darling the south
- Most of the basin lies in a rain shadow and undergoes long period of drought.
, - Water drawn by major cities and farms for irrigation.
Lesson 5 + 7: Drought + Climate change
Name Causes Impacts
Tropical - Usually: moist air moves in a westerly Social:
drought – direction from the South Atlantic across
- water rationing for 4m pp
Brazil the Amazon Basin -> encounter Andes
(2014-15) Mountain, forced to turn southwards, - water supplies were cut off for 3 days/week in some town
maintaining the flow of moisture around - power cut due to halting of HEP production -> threaten dependency (create 70% electricity)
the Basin.
- protest in Sao Paulo
- However, a series of high-pressure
systems diverted rain-bearing winds - drill illegal wells (70% of new wells were illegal) due to high fees for license ($3500) and more
further north, away from the Amazon expensive to drill (30-35k)
and prevented them from diverting - not monitored for water safety, might contain industrial pollutants and higher bacteria levels.
southwards from the Andes
Economic:
- Heavy rains occurred in Bolivia+
Paraguay - dry air remains in Brazil - a reduced crop of Arabica coffee beans -> push up the global coffee prices by 50%
Environmental:
- depletion of 17 largest reservoirs to dangerously low levels (some to 1% of capacity)
- increased groundwater abstraction -> aquifers dangerously low.
Name Background Factors Impacts
California - Population of 40 million Physical: Social:
people
- El Nino = typical - water rationing
in California, meaning
conditions
there are human pressures California has mountains which affect rainfall. Towards the eastern border is the
reversed, making
on water supplies Arizona desert
drought worse.
- forecast intense mega- Hydrological cycle:
Human
droughts + decade-long dry - Surface runoff and soil moisture levels have declined.
periods.
