5. Hydrosphere

• Distribution of the worlds water resources

  • Oceans - 97%
  • Ice caps & glaciers - 2%
  • Groundwater - 0.7%
  • Rivers and lakes - 0.01%
  • Soil moisture - 0.005%
  • Atmosphere - 0.001%
  • Living organisms - 0.00004%
• The natural hydrological cycle is in a state of dynamic equilibrium
• Human activities are altering the rates of the processes in the hydrological cycle
• There are developments in sustainable exploitation of water from various sources
• Abstractive uses of water - Water is removed from the environment prior to use

  • Domestic
  • Industrial
  • Agricultural
• Non-abstractive uses - water is not removed from the environment prior to use

  • Recreational
  • Transport
  • Wildlife conservation
  • Energy production
• Conflicts of water use

  Some uses of water are not compatible e.g. wildlife conservation may conflict with recreation, Energy production may conflict with transport
• Spatial zoning 


  only allowing certain activities in certain places e.g. not allowing water sports in an area set aside as a nature reserve
• Temporal zoning 


  allowing different activities at the same place but at different times e.g. recreation and energy production
• Human impacts on the hydrological cycle

  • Deforestation (vegetation changes where precipitation hits the ground and gets soil water to the atmosphere via transpiration)
  • Agriculture (Soil compaction increases runoff, crop irrigation increases evaporation, loss of soil biota reducing infiltration and water retention)
  • Urban development (increasing impermeable surfaces, can lead to flooding)
  • Global climate change
• Water quality is a measure of the purity of a supply of water
• Physical criteria 


  Turbidity is a measure of how turbid or cloudy water is. Water with a high level of suspended sediment is known as turbid
• Chemical criteria

  Various chemical techniques can be used to test for different chemicals e.g. pH, pesticide and heavy metal concentrations
• Biological criteria 


  The detection of pathogens in the water e.g. the presence of E. Coli
• Different water quality is needed for different uses e.g.

  • Cooling a power station
  • Drinking
  • Flushing a toilet
  • Fish farming
  • Irrigation of crops
  • Chemical production
• Reasons for global demand for water increasing:

  • Increase in population
  • Increase in per-capita use with increased affluence
  • Increased irrigation of farmland
  • Industrialisation
• Sources of freshwater

  • Surface stores (rivers & lakes)
  • Sea water stores via desalinisation
  • Groundwater stores (aquifers)
  • Artificial reservoirs
  • Rainwater
• The quantity and quality of water from each source if affected by various factors :

  • Turbidity
  • Level of contamination
  • Annual discharge amount
  • Fluctuations in discharge
• A reservoir is a larger natural or artificial lake used as a source of water supply
• Factors affecting locations of reservoirs


  • Topography (needs a valley with a large volume and a small surface area)
  • Geology (impermeable, no unstable faults, fissures or seismic activity)
  • Catchment area (large catchment area to allow max water volume reaching the reservoir)
  • Water supply (reliable, regular rainfall and low evapo-transpiration)
  • Existing land use (needs low value land)
  • Pollution risk (no urban, industrial or agricultural activity within the catchment)
  • Sedimentation (needs low levels of sediment load to stop clogging)
  • Infrastructure (should be near areas of high water demand)
• Environmental impacts of reservoirs

  • Sedimentation
  • Habitat changes
  • reduced river flow
  • Microclimate changes
• Sedimentation 


  lack of sediment downstream will cause deltas to shrink, and the valuable wetland habitat they form will be lost
• Microclimate changes

  • Local temperatures will change, they will be cooler in the day and warmer at night
  • Wind speed will be increased as friction over the water is low
  • Relative humidity will be increased due to the evaporation of the water from the reservoir
• Reduced river flow

  • when dam gates are shut, less water passes through them downstream
  • Water quality is often poorer in rivers downstream of the dam
  • Rivers downstream can start to dry up
  • Rivers downstream will flood less affecting the nutrient levels of floodplains
• Habitat changes

  • Habitats are lost at the rivers mouth as deltas and mudflats disappear due to a reduced amount of sediment arriving
  • Habitats are lost as land is flooded to create the reservoir
  • Habitats are lost downstream as the river dries up and fluvial ecosystems disappear
• Aquifer 


  an aquifer is a rock that can store water. They are permeable and may be porous and have holes within which water can be stored
• effects of over use of aquifers

  • Salinisation
  • Subsidence
  • Water table changes
  • Ecosystem changes
  • Reduced river flow
• Water table changes

  Rivers, lakes and marshes are fed by ground water flowing from aquifers. Over-exploiting aquifers may lead to lower water tables (highest point of water saturation)
• Salinisation

  In coastal areas, if the water table is lower than sea level, the sea water will enter the aquifer. The salt will make the aquifer unsuitable for irrigation, as it will kills the crops by osmotic dehydration 
• Subsidence

  Water in the interstitial spaces of the rocks helps provide structural support. Without this water, the rock particles are compacted by the weight of the material above. Any thing above this will collapse with it
• Water management

  • Increase supply (abstraction)
  • Reduce demand (water conservation)
  • Increase availability by reducing pollution of potential water resources
• increasing water supply

  • Catchment management
  • Inter-basin transfer
  • Estuarine barrages
  • Desalinisation plants
  • Aquifer storage and recharge
  • Surface storage reservoirs
• Surface storage reservoirs 


  A river is dammed and a reservoir created behind it
• Surface storage reservoirs - advantages

  • Can be used to produce renewable energy via hydroelectric plant
  • Can store large amounts of water
• Surface storage reservoirs - disadvantages

  • Not suitable for areas where precipitation rates are low and evapo-transpiration rates are high
  • Causes erosion downstream
  • Changes the microclimate of the area
  • Causes a lot of land to be lost
• Aquifer storage & recharge 


  Use of groundwater stores contained in permeable rocks such as chalk, sandstone & limestone. When water supply > demand water can be pumped back into the aquifer to recharge it
• Aquifer storage and recharge - advantages

  • Is relatively cheap
  • Water is purified by percolating through the aquifer
• Aquifer storage and recharge - disadvantages

  • Taking too much water out causes wetlands and rivers to dry up and subsidence to occur
  • Some aquifers are confined, so don’t have a recharge zone
• Desalinisation plants 


  Sea water has salt removed from it via the process of multi-flash distillation or reverse osmosis
• Desalinisation plants - advantages

  • sea water is in almost endless supply