Change in water cycle

• The curvature of the earth leads to heat being spread over a larger surface at the poles making them colder.
• The global atmospheric circulation is essentially the distribution of heat. The albedo effect is the reflection of the suns energy off the earth (stronger on white -poles making them colder)
• Air at equator rises and spreads out towards the poles, where air cools and sinks.
• Descending air is dry and cool is high pressure has little rain.
• Rising air is wet and warm has low pressure and lots of rain.
• The inter tropical convergence zone (ITCZ), is a low pressure zone found at the equator. seasonally it moves north and south.
• Storms impact water cycle: intence rainfall increases magnitude of local stores.
• Seasonal change impacts water cycle: can impact magnitude of stores and speed of transfers via temperature.
• Urbanisation can impact water cycle through a increase in impermeable surfaces. Water flows fast through pipes to nearby river channels causing flooding.
• Farming impacts water cycle as it increases that amount of water running on the ground.
• Things impacting small scale water systems: deforestation; storms; seasonal change; urbanisation; farming
• In a small scale water system farmers control levels of water carefully. Eg they will extract groundwater, and will ensure the soil only has enough water for the plants (not much will infiltrate)
• antecedent conditions: things that happened before. Eg Rain - full drains. 3 days later rain again - flood. Antecedent condition was rain before.
• Impact of vegetation: different vegetation can have different impacts on the amount of water reaching soil. EG temperate pine forest intercepts 94% of water whereas grassland intercepts 30 - 60%.
• Irrigation in the middle east impacts aquifers and they are in danger of becoming depleted.
• When an area is deforested often the new vegetation has fewer leaves and shallower roots, it uses less water than the forest it replaces meaning there is more overland flow
• The california drought lasted from 2012 - 2016, agriculture declined and wildfires occured, there was a reduction in water stores. Heat and dry air causes initial high rates of evapotranspiration which declines as water on the ground dries up and trees transpire less.
• Summer and winter variations in the uk impact the water cycle.