EQ1 5.2 DRAINAGE BASIN Flashcards
what system is the drainage basin
an open system
what is the drainage basin
a drainage basin is an area drained by a river and its tributaries
what in an open system
it has external inputs and outputs the cause the amount of water in a basin to vary over time. these variations can happen at different temporal scales
what can drainage basins also be referred to as
catchment areas because they catch precipitation falling within the watershed
what is a watershed
an imaginary line around the edge of the basin, separating one basin from another
what’s a drainage basin in relation to the hydrological system
a subsystem
how do drainage basins lose water
evaporation and evapotranspiration into the atmosphere
surface run off (or overland flow) to the sea
percolation into groundwater stores
precipitation (input)
moisture in any form
interception (storage)
temporary storage, as water is captured by plants, buildings and hard surfaces before reaching the soil
vegetation storage (storage)
any moisture taken up by vegetation and held within plants
surface storage (storage)
any surface water in lakes, ponds, puddles
soil moisture (storage)
water held within the soil
groundwater storage (storage)
water held within permeable rocks (also known as an aquifer)
channel storage (storage)
water held in rivers and streams
infiltration (flows and processes)
water entering the topsoil. most common during slow or steady rainfall
throughflow (flows and processes)
also known as inter-flow; water seeping laterally through soil below the surface, but above the water table
percolation (flows and processes)
the downward seepage of water through rock under gravity, especially on permeable rocks e.g. sandstone and chalk
stem flow (flows and processes)
water flowing down plant stems or drainpipes
base flow (flows and processes)
also known as groundwater flow. slow moving water that seeps into a river channel
channel flow (flows and processes)
the volume of water flowing within a river channel (also called discharge and run off)
surface runoff (flows and processes)
also called overland flow. flow over the surface during an intense storm, or when the ground is frozen, saturated or on impermeable clay.
evaporation (outputs)
the conversion of water to vapour
transpiration (outputs)
water taken up by plants and transpired onto the leaf surface
evapotranspiration (outputs)
the combined effect of evaporation and transpiration
river discharge (outputs)
the volume of water passing a certain point in the channel over a certain amount of time.
how will snow capped peaks affect flow of water within a drainage basin
increased flow due to summer melt
in winter the flows will decrease as water is stored as snow and ice on mountains
how will steep slopes affect flow of water within a drainage basin
increased surface run off at a faster rate as water doesn’t have time to infiltrate so reaches the river faster through tributaries and streams
how will permeable land affect flow of water within a drainage basin
increased infiltration and therefore percolation taking place so water moves at a slower pace through groundwater flow
how will having a high drainage density affect flow of water within a drainage basin
fast movement of water across the basin as high drainage density means lots of rivers and streams in one drainage basin
how will rural land affect flow of water within a drainage basin
more likely to be permeable soil so infiltration takes place and throughflow so therefore reaches the river at a slower rate. rural land could be farmed leaving tracks and creating channels potentially
how will reservoirs affect flow of water within a drainage basin
surface storage so therefore more evaporation eg. in the tropics, decreasing the flow of water as less output as the water is being controlled