The hydrosphere
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What do human activities do to the hydrosphere?
They can alter the rate of processes in the hydrological cycle which can lead to changes in the residence time and quantities in reservoirs of water.
How do you calculate residence time?
vol of water in reservoir/ mean transfer rate
Why is the global demand for water increasing?
Increased population Increase in per-capita with increased affluence so more piped water, water appliances Increased irrigation of farmland for growing populations Industrialisation e.g. chemical and steel
What are the inputs for the hydrological cycle?
Precipitation
What are the outputs of the hydrological cycle?
Evaporation Transpiration
What are the ways water moves to different reservoirs/ transfer processes?
Percolation Ground water flow to the ocean
What drives the hydrological cycle?
Solar energy-evaporation etc Gravitational potential energy- water moves through rocks to the ocean
How do you convert m3 to km3?
Divide by 1000
What is the residence time?
The average time a water molecule will spend in a reservoir
How does deforestation affect the hydrological cycle?
Vegetation intercepts rainfall which may evaporate before reaching the ground. Trees return alot of water from the soil to atmosphere by transpiration.
How does agriculture affect the hydrological cycle?
Soil being compacted will reduce infiltration and increases runoff Crop irrigation may increase evaporation Loss of soil biota will reduce infiltration, increases run off and reduces water retention.
How does urban development affect the hydrological cycle?
Replacing impermeable surfaces like concrete with gravel/sand will increase infiltration and reduce runoff.
What water sources have been exploited unsustainably?
Aquifers and reservoirs
What was the main reason for the aral sea drying up?
Irrigation of cotton and rice crops using water from rivers that fed into the aral sea. Pollution from pesticides and fertilisers
What is an aquifer?
An underground layer of water bearing rock
What are the features of rock suitable as an aquifer?
Good porosity so alot of space to hold water, limestone/chalk Rock above should be permeable but rock underneath should not be, granite or clay.
How are aquifers recharged?
By rain, they are usually in dynamic equlibrium.
When does an aquifer become over exploited?
When human abstraction is greater than recharge.
What water is usually in ancient aquifers?
Saline water, so it causes soil salination, osmotic dehydration and then crop death if used for irrigation
What are the ecological impacts of over exploiting aquifers?
Plants die Wetland habitats will decrease killing aquatic plants and animals Affects inter-species relationships and food webs
What is salt water incursion?
When aquifers are exploited their water table lowers, it could become lower than the sea level causing seawater to flow in to replace what has been lost. This makes the aquifer saline, water cannot be used in irrigation
What is subsidence?
Over exploitation of aquifers means less water is held in porous rock, the rocks therefore have less support and will become compacted by the weight of material above.
How can you measure aquifer depletion?
Checking the water table Grace satellite/ gravity recovery and climate experiment: the orbit of this satellite is affected by gravity which is influenced by the mass of water in aquifers
Describe the ogollala aquifer and what the problems are
A high plains aquifer Agriculture relies on this aquifer however it is being over exploited/ abstraction is greater than recharge. The water in this aquifer is paleowater, so it was last recharged years ago