Water Case Studies Flashcards
Greenland ice sheet
It links the cryosphere and ocean stores. Ablation is greater than accumulation so glacier ice melts and as a result ocean levels have rose by 7pm due to ablation of the Greenland ice sheet.
The River Po, Italy
It’s an example of a complex river regime, and it has two peaks and 2 troughs in a yearly cycle. The two peaks occur during may + November and the 2 troughs occur in January and August.
Colorado River, USA
It’s an example of human influence. The Colorado river runs through an arid region of the USA. Peak rainfall occurs in August due to the intense rainfall from storms from conventional rain. The storms can lead to flash flooding due to infiltration excess overland flow.
Human management of the Colorado river
The Hoover dam - Was built in 1936 and was designed for:
- To be a source of power generation
- As a floor control
- For water storage - as its an arid region.
February flood 2020 UK
It’s an example of prolonged rainfall. The Uk experiences the 5th wettest winter on record and rainfall increased by 158% compared to the winter before when it was 43%.
Why did we receive prolonged rainfall in 2020?
The meeting point between 2 air masses of warm tropical air and cooler polar air is known as the polar front. This front is controlled by the jet stream, it stayed over the UK for much of winter 2020, hence the long periods of conventional rainfall.
Bostcastle floods
It’s an example of intense rainfall. Warm moist air from an ex-category 2 hurricane moved eastwards over the Atlantic and towards Cornwall. Air rose over 600m to form orographic rainfall.
- 75mm of rainfall fell in 2 hours
- 5 buildings were demolished and 60 more were badly damaged
- over 100 people were rescued.
Human factors affecting surface run off - Haiti
Infiltration rates into the soil was 67x higher under trees than under sheep pasture. 60% of Haiti was covered by forests in 1932 and overtime this has decreased to just 4%. The catalyst for deforestation is an increase in population (of around 80%. Increased surface run off has exacerbated 4 tropical storms affecting over 800,000 people and killing around 200 people.
Urbanisation
When there is natural ground coverage, 40% of the water is prevented from reaching the surface through evapotranspiration. When the surface is changed to 75% or more coverage impermeable materials,this makes run-off over 5x in volume and 10% less evapotranspiration.
Egyptian desert - Growing potatoes
Egypt produced over 400,000 tons of potatoes per year, exporting them to wealthy countries such as the UK. They are irrigated using spray irrigation and a lot of this spray is intercepted and evaporated which means it’s 90% inefficient and much of the water is lost. For every 1kg of potato produced it used 5kg of water. This shows that the rate of extraction of the aquifer water is greater than the rate of recharge, as Egypt is an arid region, so the water table will drop and ultimately the groundwater source will disappear.
California’s central valley aquifer
1/3 of the USA’s fresh food is produced in California. 80% of California’s water use is in central valley and due to recent droughts, there has been increasing pressure on central valley aquifer to meet the water needs. California’s water supply from aquifers make up 60% of all water supply in California.
California’s central valley aquifer - Management (artificial recharge)
Due to frequent droughts, wells are being drilled. In a 2 year period (from 2011 and 2013) the number of wells has doubled just to get groundwater stores. As as result, groundwater stores have dropped by 20m. It would take 50 years for the aquifer to fill naturally so artificial recharge is being used and employed. Recharge basins are being trialed and have been successful throughout California. Another strategy used by farmers is smart irrigation. Soil moisture monitors ope and close valves, which are connected to drip pipes in the soil at the roots of crops. These are 90% efficient - 90% is directly used up by the plant and are much more uniform as all plants in the fields are receiving the same amounts of water.
