Lesson 2 - Drainage Basins Flashcards
What is a drainage basin?
An area of land that is drained by a river and its tributaries, and separated from neighbouring drainage basins by an area of highland called a watershed.
How is a drainage basin an open system?
It has eternal inputs and outputs that cause the amount of water in the basin to vary over time.
What is drainage basin referred to as?
catchment (the area of land drained by a river and its tributaries).
Was it the boundary of the drainable basin referred to as?
Watershed (the highland which divides and separates water flowing to different rivers).
Drainage Basin inputs?
Precipitation
Drainage basin stores?
Interception
Drainage basin flows (fluxes)? (7)
Infiltration direct run off Saturated overland flow Through flow Percolation Groundwater flow Channel flow
Drainage basin outputs? (3)
Evaporation
Transpiration
River Runoff
How does the climate influence the drainage basin?
Has a role in influencing the type and amount of precipitation overall and the amount of evaporation, i.e. the major inputs and outputs. It also has an impact of the vegetation type.
How does soil influence the drainage basin?
Determines the amount of infiltration and throughflow and, indirectly, the type of vegetation.
How does geology influence the drainage basin?
Can impact on the subsurface processes such as percolation and groundwater flow (and, therefore, on aquifers). Indirectly, it can alter soil formation
How does relief influence the drainage basin?
Can impact on the amount of precipitation. Slopes can affect the amount of runoff.
How does vegetation influence the drainage basin?
The presence or absence of this can have a major impact on the amount of interception, infiltration and occurrence of overland flow, as well as transpiration rates.
How does Precipitation influence the drainage basin? (4)
Can act as temporary store.
The amount (higher less variability in its pattern).
Seasonality affects physical processes.
Intensity, impact flows and amount absorbed.
How is precipitation variable?
Secular variability, LT, climate change trends.
Periodic variability, Annual, seasonal, daily, ect
Stochastic variability, Random factors
How does storage influence the drainage basin? (4)
Interception loss, amount intercepted varies with each tree, needless ones have a greater capacity.
Meteorological conditions, increase interception losses and evaporation.
Intensity and duration of rainfall, rainfall increases more interception losses decrease, excess rain reaches ground.
Interception increase with crop density
How does flows influence the drainage basin?
infiltration
Factors that effect infiltration? (5)
water already in soil, excess water saturated.
slope angle, steep more overland run off, shallow more infiltration.
Soil surface and structure, compact infiltrate less.
vegetation, infiltrate more in areas that are vegetated.
Soil texture, sandy soils infiltrate more.
How do flows and transfers influence the drainage basin? (5)
surface run off is the main way water is transferred to rivers, precipitation must exceed infiltration rates. Percolation Saturated over land flow through flow channel flow
What is saturated overland flow?
the upward movement of the water table
What is channel flow?
Water reached from all transfers in a river.
What outputs influence the drainage basin? (3)
Evaporation
transpiration
evaportranspiartion
How does basin size influence the drainage basin?
Larger basins collect more precipitation giving them a longer lag time as it takes longer for all the water to travel through.
How does drainage density influence the drainage basin?
A low drainage density means a slower movement of water across a basins area, permeable rocks have a low drainage basins.
How does elevation and slope influence the drainage basin?
Forested slopes intercept more precipitation more evaporation and less surface run off where as steep slopes promote faster movement and shorter storage times.
How does rock and soil type influence the drainage basin?
Impermeable rocks prevent infiltration and cause surface saturation.
How does land use influence the drainage basin?
Urban surfaces are impermeable and increase rapid surface runoff.
