EQ1: What are the processes in the hydrological cycle, from global to local? GapFill

We get our energy from the  MooncoreatmosphereSun, but most of that energy is reflected and re-emitted back to space.   In this way, the Sun’s energy is both an input to and an output from the system.  So if you ignore the small gains and losses of material, we’re a closed system.  Overall, the water system is a closed system, but on a smaller, ‘local’ scale – for example, a drainage basin or a woodland – the cycles are  closedseparatedopenbroken. 

The water on Earth has been here for a long time before the earliest life, billions of years ago, and possibly the water formed with the Earth itself.  Water is  a finitea non-renewablean infinitean artificial resource which has been cycling around the hydrological cycle for millennia.

The proportion of water in each of the stores has changed.  During  watericerainsleet ages, sea levels fell, and the hydrological cycle slowed down, while water fell as snow on the land surface but there was little melting, so not much water was returned to the sea, but water continued to evaporate from the oceans.  The remaining ice is still melting away, and humans are probably speeding up that process because of climate change.   Liquid oxygenPermafrostDewRime ice is also melting, so the underground cryosphere is shrinking too.  Climate change is also changing the hydrological cycle. For example, we’re beginning to see a rise in extreme weather events, such as floods and droughts. Over short time periods, natural weather phenomena can affect the local cycle, and events such as El Niño Southern Oscillation (ENSO) cycles. 

Water can be stored for days, or millennia.  The average time that a molecule of water is stored for is called its  clockresidencehalldormitory time.

Water cycles through the system via different processes, including:

•  Cloud formationDew formationCombustionEvaporation, where energy from the Sun allows liquid water to turn into gaseous water vapour. 
•  NaturalisationCombustionSnowfallCondensation, where cooling air reaches its ‘dew point’, the point where water vapour condenses into droplets. 
•  SnowfallCloud formationCombustionDew formation leads to condensation when it rises; for example, resulting from orographic uplift (over hills), at the rising areas of pressure cells, where the ground is heated more than the surrounding area, and at weather fronts.

A  waterfallhillslopeleveedrainage basin is simply an area drained by a river and its tributaries.  Rainfall usually starts on higher ground before dropping towards the sea.  Such areas are separated by high ground called a  mountaintopleveewatershedbasin.

Drainage basins are open systems.  We can calculate the balance between the inputs and outputs, which is the change in storage.

The basic equation is:

Change in storage =  inputscombustionsublimationequality – outputs

If the balance is  positiveexponentialequalnegative, there is more precipitation entering the system than run-off and evapotranspiration removing water from the system, and more water is stored.

If the balance is  negativeequalexponentialpositive, then more water leaves the system than is added through precipitation, and stores are diminished.