Hydrosphere

• What has increased the global demand for water?

  > Increase in population

  > Increase in per-capita use with increased affluence

  > Increased irrigation of farmland

  > Industrialisation
• What are the biggest human uses of water?

  > Agriculture (70%)

  > Industry (22%)

  > Domestic uses (8%)
• Stores and the percentage of total water

  > Oceans (97%)

  > Land ice (2%)

  > Groundwater (0.7%)

  > Lakes and rivers (0.01%)

  > Soil moisture (0.005%)

  > Atmosphere (0.001%)

  > Living organisms (0.00004%)
• Residence time of stores


  > Oceans (Up to 4000 years)

  > Land ice (20-100 years)

  > Groundwater (100-10,000 years)

  > Lakes and rivers (2 months - 100 years)

  > Soil moisture (2 months)

  > Atmosphere (10 days)

  > Living organisms (1 week)
• What are the human impacts on the hydrological cycle?

  Deforestation, agriculture, urban development, global climate change and water abstraction.
• How does deforestation impact the hydrological cycle?

  The loss of trees can cause a significant reduction in precipitation in downwind areas as more of the water infiltrates the ground, or runs off into rivers.
• How does agriculture impact the hydrological cycle?

  > Soil can be compacted by the use of heavy machinery, water does not infiltrate as easily into compacted soil so soil moisture levels drop and runoff increases.

  > Crop irrigation increases evaporation rates

  > The loss of soil biota such as worms reduces infiltration, increases surface runoff and reduces water retention by the soil.
• How does urban development impact the hydrological cycle?

  Urban areas often have impermeable surfaces such as concrete and tarmac. This reduces infiltration while increasing the rate of runoff. Rapid runoff from large urban areas can increase river flooding downstream.
• How does global climate change impact the hydrological cycle?

  > Higher global temperatures affect rates of melting, evaporation and condensation as well as wind patterns. These combine to alter the type, amount, timing and location of precipitation.

  > More rapid melting of snow and ice is caused by the warming associated with global climate change.

  > Changes in evaporation temperature and wind velocity/ direction will change the timing, type and amount of precipitation.
• How does water abstraction from rivers and reservoirs impact the hydrological cycle?

  Some abstraction of river water has little impact on the river as the used water is cleaned and returned to the river. However, rivers have often been used to carry water away wastes. Some abstractive uses do not return the water to the river which reduces downstream flow, for example, agricultural irrigation.
• What are the environmental effects of reservoirs?

  Habitat change, wildlife barriers, river regime downstream of dams, sedimentation, microclimates.
• Examples of over-exploited rivers

  Rivers flowing into the Aral Sea, the River Nile and the River of Tibet.
• Features of aquifers

  > Porosity

  > Permeability

  > Associated geological structures
• Examples of new sources of water to be exploited

  > Rainwater collection

  > Rivers

  > Reservoirs

  > Estuary barrages

  > Seawater
• What are some ways to manage water sustainably?

  > Artificial recharge of aquifers

  > River-regulation reservoirs

  > Inter-basin transfers

  > Unexploited aquifers

  > Afforestation

  > Water conservation

  > Water treatment