R - Hydrological Cycle Flashcards
What is the hydrological cycle?
The process whereby water in it various forms is continually cycled between the land, sea and atmosphere
What type of system is the global hydrological cycle? Why?
A closed system - there are no inputs or outputs
What type of system is a drainage basin system?
An open system
What are the four main processes in the hydrological cycle?
Interception, evapotranspiration, infiltration and precipitation
What are the inputs of a drainage basin?
Precipitation
What is precipitation?
All forms of moisture that reaches the Earth’s surface, including rain, snow and dew
What are the storage things in a drainage basin?
Interception, vegetation storage, surface storage, groundwater storage and channel storage
What is interception?
The prevention of precipitation from reaching the Earth’s surface by trees and vegetation
What is vegetation storage?
Water being taken up by plants - it’s all the water contained in plants at any one time
What is surface storage?
The total volume of water held on the Earth’s surface in lakes ponds and puddles
What is groundwater storage?
The storage of water underground in permeable rock strata
What is channel storage?
Water held in a river or stream channel
What are the flows and processes in a drainage basin?
Surface runoff Throughfall Stemflow Throughflow Infiltration Percolation Groundwater flow Baseflow Interflow Channel flow
What is surface runoff?
Water flowing over the land surface as channel flow and overland flow. (aka surface flow and overland flow)
What is throughfall?
Water dripping from one leaf (or plant) to another
What is Stemflow?
Flow down plant trunks and stems following interception
What is throughflow?
The movement of water downslope within the soil layer
What if Inifltration?
The downward movement of water into soil surface
What is percolation?
The gravity flow of water within soil
What is goundwater flow?
The deeper movement of water through the underlying rock strata
What is baseflow?
Water that reaches the channel largely through slow throughflow and from permeable rock below the water table
What is interflow?
Water flowing downhill through permeable rock about the water table
What is channel flow?
The movement of water within the river channel
What are the outputs of a drainage basin?
Evaporation
Transpiration
Evapotranspiration
River discharge/River flow
What is evaporation?
The transformation of water droplets into water vapour by heating
What is transpiration?
Evaporation from plant leaves
What is evapotranspiration?
The loss of water from a drainage basin into the atmosphere from the leaves of plants
What is the water balance?
The balance between the inputs and outputs
What happens to the water balance in wet seasons? What are the results?
Precipitation exceeds evapotranspiration - this creates a water surplus
The ground stores fill with water so there more surface runoff and higher discharge - so river levels rise
What is a surplus?
More than is needed
What happens to the water balance in drier seasons?
Precipitation is lower than evapotranspiration
Ground stores are depleted as some water is used (eg by plants & humans) and some flows into the river channel - but isn’t replaced by precipitation
What happens at the end of a dry season?
There is a deficit of water in the ground - the ground stores are recharged in the next wet season
What is a deficit?
A shortage
