Precipitation and Excess Runoff in the Water Cycle Flashcards
What is orographic rainfall?
Air is forced to rise over higher land, causing a loss of mass and therefore precipitation.
What is frontal rainfall?
When air masses of different temperatures meet, the warmer, less dense air rises over the cooler air mass, causing a loss of mass and therefore precipitation.
What is convection rainfall?
Daytime heating off the ground warms air in contact with it, forcing it to rise and therefore precipitation.
What is a condensation nuclei?
When rising air expands, resulting in cooling. When it cools to its dew point, water molecules condense around small particles called condensation nuclei, forming clouds.
What is the collision coalescence process?
In warm tropic areas, water condenses around large condensation nuclei. Larger droplets fall to earth, colliding with smaller droplets and absorbing them.
What is the Bergeron-Findeison Process?
High-altitude clouds with a temperature below 0C contain ice crystals and super-cooled water droplets.
The ice crystals grow as water evaporates off of the droplets and deposits on the ice.
The ice crystals gain weight and fall as snowflakes.
Snowflakes melt in warmer air layers, forming rain.
How is prolonged precipitation a cause of excess runoff generation?
Prolonged precipitation results in saturation excess overland flow.
How are intense storms a cause of excess runoff generation?
Intense storms result in saturation excess and infiltration excess overland flows.
How is monsoon rainfall a cause of excess runoff generation?
Monsoon rainfall has a similar impact to prolonged and storm precipitation in areas of monsoon climate.
How is snowmelt a cause of excess runoff generation?
Melting of accumulations of snow and ice results in saturation excess overland flow, especially if the ground is frozen.
How is increased urbanisation a cause of excess runoff generation?
Urbanisation makes the surface impermeable, reducing infiltration and the soil moisture soil. Drainage transports water quickly to rivers, reducing lag time. Less vegetation reduces evapotranspiration, increasing runoff.
How is river basin mismanagement a cause of excess runoff generation?
Large-scale deforestation increases runoff because removing roots also decreases the saturation threshold. It also removes any interception, so all the precipitation hits it at once and causes infiltration excess overland flow.
Straightening and canalisation of rivers speeds up the flow, increasing runoff downstream.
How is the loss of floodplain storage a cause of excess runoff generation?
Loss of floodplain storage due to channelling and the construction of dykes for flood management results in increased runoff, creating bigger floods downstream. This was a contributing factor in the 2006 Danube floods where 80% of floodplain storage was lost.
