Hydrological Cycle and Rivers Flashcards
Why is the global hydrological system a closed system?
The main output (evaporation) is balanced with the main input (precipitation). Water is continually circulating through the system.
What is the global water budget?
The annual balance of water fluxes (the flows between stores)
What is groundwater otherwise known as?
Fossil water
What percentage of the worlds water is accessible immediately in rivers and lakes?
0.01%
What are the inputs of the drainage basin system (1)?
Precipitation
What are the outputs of the drainage basin system (2)?
- channel flow
* evapotranspiration
What are the stores of the drainage basin system (4)?
- soil moisture storage
- groundwater storage
- surface storage
- interception storage
What are the transfers of the drainage basin system (6)?
- through flow
- surface runoff
- groundwater flow
- channel storage
- infiltration
- percolation
What is the rate of infiltration influenced by? (2)
- amount of precipitation and vegetation
* degree of soil saturation
What is groundwater affected by (2)?
- the angle of the rock strata. Steeper = gravity
* rock porosity. More porous = more flow
What human action can stop infiltration?
Urbanisation
What can lessen interception?
•deforestation/ removal of forest canopy
Equation for a balanced water budget
P=Q+E(+/-)S •P=precipitation •Q=river discharge •E=evapotranspiration •S=change in storage
What do water budgets show?
If areas experience a soul moisture surplus and deficit at certain times of the year
What is a river regime?
The seasonal variability in a rivers discharge throughout the course of a year in response to precipitation, temperature and evapotranspiration
What is a simple regime?
When the river experiences a period of seasonally high discharge followed by low discharge
What type rivers typically have a simple regime? Give an example
Rivers where inputs depend on glacial meltwater or seasonal storms
•Rhône France
What is a complex regime ?
Where larger rivers cross several different relief and climatic zones and experience the effects of different seasonal climatic effects
Give an example of a river with a complex regime
The Mississippi
Factors that cause changes to the regime of the River Rhône (5)
- differing local climates
- glacial melt
- Atlantic air masses
- confluence
- summer evaporation
What does a storm hydrograph show?
Variations in a rivers discharge at a specific point over a short period of time (before,during and after a storm)
What are the two types of storm hydrographs?
- Flashy- rapid increase in discharge and high risk of flooding
- subdued- the opposite
Three types of rainfall
- frontal
- orographical
- conventional
How does drainage basin size affect a storm hydrograph?
the smaller the basin the more rapidly the water will reach the channel as it has shorter distance to travel
How does drainage basin shape affect a storm hydrograph?
for circular basins it takes less timefor water to reach the channel as all the extremeties are equidistant from the channel while elongated basins, water will take longer
How does drainage basin relief affect a storm hydrograph?
Steeper slopes mean water flows downhill and reachs channel more quickly
What drainage basin characteristics affect a storm hydrograph (3)?
- size
- shape
- relief
How does soil type affect a storm hydrograph?
thin soils become saturated quickly while thick soils allow more inflitration
How does rock type affect a storm hydrograph?
with impermeable rock, water cannot percolate, increasing surface runoff
How does drainage density affect a storm hydrograph?
High drainage density means a large number of surface streams per km^2 meaning the storm water will reach main channel quickly
How does natural vegetation affect a storm hydrograph?
Forest and woodland mean high rates of evapotranspiration and more infiltration so less water reaches the channel and more slowly
How does land use affect a storm hydrograph?
Urban areas will have more hard surfaces and drains which carry water quickly and directly to river
How does precipitation intensity affect a storm hydrograph?
high intensity precipitation means surface runoff occurs and transports water rapidly to the channel
How does precipitation duration affect a storm hydrograph?
Prolonged rainfall means the water table rises and soil becomes saturated, causing runoff, which travels quickly to channel
How does snowfall affect a storm hydrograph?
Fast snowmelt means meltwater cannot infiltrate into frozen ground so flows to channel rapidly
How does evapotranspiration affect a strom hydrograph?
Low rates results in fewer losses from the drainage basin which increases discharge into the river channel
