Human Impact

Question 1

What human impacts are there on evaporation and evapotranspiration?

Answer 1

-Dams: increase in evaporation, Aswan Dam loses 1/3 of water. water loss reduced by using chemical sprays, building sand-fill dams and covering d,as with plastic
-Urbanisation: reduction in evapotranspiration as lack of vegetation and may be increase in evaporation due to higher temperatures and increased surface storage

Question 2

What human impacts are there on interception?

Answer 2

-Deforestation: reduces evapotranspiration, increases surface runoff, decline in surface storage, decline in lag time
- farmland areas intercept less than broad leaves and leave a lot of soil bare

Question 3

What does the construction of larger dams lead to?

Answer 3

• increased storage of water
  -decreased flood peaks
  -low flows in rivers
  -decreased sediment yields
  -increased losses due to evaporation and seepage, leading to changes in temperature and salinity of water
  -decreased flooding of land
  triggered earthquakes
  -salinisation, eg Indus Valley in Pakistan 1.9 million hectares are severely saline and 0.4 million hectares are lost to salinity
  -large dams can cause local changes to climate

Question 4

Case study: changing hydrology of the Aral Sea

Answer 4

-began shrinking in 1960s when soviet irrigation schemes took water from the Syr Darya and the Amu Darya rivers
-reduced water reaching the Aral sea
1994 shorelines fallen by 16m and surface area reduced by 50% and volume reduced by 75%
-salinity levels increased by 300%
salinity killed off fishing industry and salt from the dry seabed reduced soil fertility and frequent dust storm as are ruining cotton production
- drinking water polluted by pesticides and fertilisers
-rise in respiratory and stomach disorders and one of the highest infant mortality rates

Question 5

What are the advantages of the Aswan High Dam on the River Nile?

Answer 5

-flood and drought control
-irrigation: 60% water from Aswan Dam used for irrigation
-hydro-electric power: 7000 millionkW hours each year
-improved navigation
-recreation and tourism

Question 6

What are the disadvantages of the Aswan High Dam on the River Nile?

Answer 6

-water losses: dam provides less than half the water expected
-salinisation: crop yields reduced by 1/3 of the area irrigated by the water from the dam because of salinisation
-groundwater changes. seepage leads to increased groundwater levels
-displacement f population: 100000 Nubian people removed from ancestral homes
-seismic stress: November 1981 earthquake caused by Aswan Dam as water levels increased so does seismic activity
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