EQ1 5.2 DRAINAGE BASIN Flashcards
1
Q
what system is the drainage basin
A
an open system
2
Q
what is the drainage basin
A
a drainage basin is an area drained by a river and its tributaries
3
Q
what in an open system
A
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
4
Q
what can drainage basins also be referred to as
A
catchment areas because they catch precipitation falling within the watershed
5
Q
what is a watershed
A
an imaginary line around the edge of the basin, separating one basin from another
6
Q
what’s a drainage basin in relation to the hydrological system
A
a subsystem
7
Q
how do drainage basins lose water
A
evaporation and evapotranspiration into the atmosphere
surface run off (or overland flow) to the sea
percolation into groundwater stores
8
Q
precipitation (input)
A
moisture in any form
9
Q
interception (storage)
A
temporary storage, as water is captured by plants, buildings and hard surfaces before reaching the soil
10
Q
vegetation storage (storage)
A
any moisture taken up by vegetation and held within plants
11
Q
surface storage (storage)
A
any surface water in lakes, ponds, puddles
12
Q
soil moisture (storage)
A
water held within the soil
13
Q
groundwater storage (storage)
A
water held within permeable rocks (also known as an aquifer)
14
Q
channel storage (storage)
A
water held in rivers and streams
15
Q
infiltration (flows and processes)
A
water entering the topsoil. most common during slow or steady rainfall
16
Q
throughflow (flows and processes)
A
also known as inter-flow; water seeping laterally through soil below the surface, but above the water table
17
Q
percolation (flows and processes)
A
the downward seepage of water through rock under gravity, especially on permeable rocks e.g. sandstone and chalk
18
Q
stem flow (flows and processes)
A
water flowing down plant stems or drainpipes
19
Q
base flow (flows and processes)
A
also known as groundwater flow. slow moving water that seeps into a river channel
20
Q
channel flow (flows and processes)
A
the volume of water flowing within a river channel (also called discharge and run off)
21
Q
surface runoff (flows and processes)
A
also called overland flow. flow over the surface during an intense storm, or when the ground is frozen, saturated or on impermeable clay.
22
Q
evaporation (outputs)
A
the conversion of water to vapour
23
Q
transpiration (outputs)
A
water taken up by plants and transpired onto the leaf surface
24
Q
evapotranspiration (outputs)
A
the combined effect of evaporation and transpiration
25
river discharge (outputs)
the volume of water passing a certain point in the channel over a certain amount of time.
26
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
27
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
28
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
29
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
30
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
31
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
32
how will urban surfaces affect flow of water within a drainage basin
impermeable rock which increases overland flow which will speed up the rate at which the water reaches the river
prevents infiltration
however more drainage systems eg gutters speed up water flow
33
how will impermeable soils and rocks affect flow of water within a drainage basin
increased surface run off as no percolation therefore increased flooding
34
how will forested areas affect flow of water within a drainage basin
deforestation- soil moisture-soil erosion
interception of precipitation so temporary storage and increased evapotranspiration.
the more trees, the more interception, the slower the water takes eg. trickles down the trees= more controlled
35
how will a low drainage density affect flow of water within a drainage basin
slow movement of water across the basin area
36
how will large drainage basins affect flow of water within a drainage basin
collect more precipitation and are affected by more basin-wide factors than small basins
37
what's responsible for the natural movements within a drainage basin
solar energy and gravity
38
what factors determine what happens to the precipitation that falls in the basin
physical and human factors
39
what is the climates impact on the drainage basin
main influence on inputs (precipitation)
affects the rate of evaporation
indirectly climate impacts on vegetation in the drainage basin which then impacts on infiltration, interception rates
40
what is the soils impact on the drainage basin
soils directly affect the rate of infiltration and through flow. impervious (water cannot pass through) surfaces (such as rock) can lead to more surface water flow than in basins with more absorptive soils
indirectly impacts on the type of vegetation that can grow
41
what is the geology impact on the drainage basin
impacts on subsurface processes eg. percolation, groundwater flows and therefore on aquifers
indirectly, geology alters soil formation
42
what is the reliefs impact on the drainage basin
altitude affects on precipitation in total
slopes increase surface run off
slopes decrease infiltration rates
43
what is the vegetations impact on the drainage basin
more vegetation means more water is intercepted
more vegetation can reduce infiltration
less vegetation can lead to more overland flow
it also increases the rate of transpiration
44
8 human factors that influence the drainage basin
```
altering the course of the river
cloud seeding
aforestation
urbanisation
building dams and resevoirs
industrialisation
agriculture and farming
```
45
how does cloud seeding impact the drainage basin
varying impact on precipitation
46
how does deforestation eg.nepal impact the drainage basin
removal of trees causes a decrease in interception therefore increased infiltration. reduction in evapotranspiration rates
increase in surface run off= flooding=decline in surface storage=water reaches rivers quicker= speeds cycle
47
how does afforestation impact the drainage basin
planting of trees causing increased interception through vegetation storage so therefore increased infiltration due to trickling water instead of heavy flow.
opposite affect to deforestation- in theory afforestation should trap sediement and slow the hydrological system however immediately after planting young trees , there is an increase in run off and sediement loss as a result of compaction of soil by tractors - stops after 30 years when fully grown
48
how does landuse impact the drainage basin
forest- vegetation storage
grassland- infiltration is 5x greater underforests compared with grasslands
farmland- creates channels from farming = reduced interception, increased soils compaction= more overland flow
49
how does irrigation impact the drainage basin
increased saturated land therefore increased surface run off
| increased irrigation for cereal farming/historic cotton growing has decreased water table levels
50
how does manufacturing impact the drainage basin
water using manufacturing has increased amount of groundwater becoming extracted = groundwater levels rising = surface flooding
51
how does channelisation of rivers in urban areas impact the drainage basin
reduction in surface storage which then leads to less evaporation
52
There are three types of precipitation that input into a drainage basin:
orographic, frontal and convectional
53
what is orographic precipitation
when air masses rise over mountains causing it to condense and rain.
54
what is frontal precipitation
when two air masses meet at an area of low pressure creating rain.
55
what is convectional precipitation
rainfall caused by water turning to water vapour due to solar radiation.
56
The water processes we identify as outputs in a drainage basin are:
evaporation, transpiration, channel flow
57
evaporation
when water turns to water vapour and leaves the drainage basin.
58
transpiration
when water leaves plants through holes in their leaves.
59
channel flow
the volume of water that is flowing in a river channel.
60
The drainage basin hydrological cycle includes the following water flows:
interception, infiltration, direct runoff
61
interception
when plants capture precipitation in their leaves.
62
infiltration
when precipitation enters into the soil.
63
direct runoff
when water from precipitation or snowmelt flows across the ground’s surface because the surface is impermeable i.e. tarmac.
64
other flows that happen in a drainage basin:
saturated overland flow, throughflow, percolation, groundwater flow
65
Saturated overland flow
when the ground is full of water, resulting in runoff.
66
through flow
the horizontal flow of water through soil/rock layers
67
percolation
the vertical flow of water between soil and rock layers.
68
Groundwater flow
the flow of water horizontality once it has reached the water table.
69
how can climate affect the drainage basin
Where cold climates allow for precipitation to fall as snow, the water can be stored and held back until it is thawed (melted).
This may reduce the channel flow during the winter but lead to an increase during the spring and summer months due to glacial melt water.
70
how can soil type affect the drainage basin
Impermeable soils can stop infiltration and lead to surface saturation resulting in increased surface runoff.
Where there are permeable soils, infiltration and percolation can happen. This can cause groundwater to recharge.
71
how can relief of the land affect the drainage basin
Steeper slopes mean faster surface runoff and shorter times for water storage.
72
how can vegetation cover affect the drainage basin
When an area has a high coverage of vegetation, the interception and evapotranspiration increases but the surface runoff decreases.
73
how can rock type affect the drainage basin
Some rocks are impermeable and can stop the infiltration of water into the ground. Similarly to impermeable soils, these types of rocks can cause the ground to saturate and lead to surface runoff and increase flows in rivers.
In contrast, permeable rocks allow for infiltration and percolation to happen.
74
how can over-abstraction affect the drainage basin
Abstraction is the process by which humans remove water from underground water stores (e.g. aquifers).
Over-abstraction is when the volume of water being removed is greater than the volume of groundwater being replenished.
Over-abstraction can lead to rivers drying up during periods of low rainfall.
75
how can urbanisation affect the drainage basin
Urbanisation is a change of land use that results in moving away from the natural environment to towns and cities.
Urbanisation leads to a large number of impermeable surfaces i.e. tarmac, slate, concrete. These impermeable surfaces reduce infiltration, whilst increasing surface runoff.
76
how can deforestation affect the drainage basin
Deforestation is the term used to describe the removal of trees. The impact of deforestation reduces interception and consequently, rainfall strikes soil directly, leading to soil compaction.
Soil compaction and the removal of tree roots can reduce infiltration.
Ultimately deforestation causes an increase in surface runoff, resulting in more soil erosion and flooding.
77
how can reservoirs affect the drainage basin
Reservoirs are man-made stores that disrupt the natural water flow, by delaying the flow and increasing water lost from evaporation.
Dams reduce the water flow further downstream resulting in loss of vegetation.
When vegetation grows on the reservoir’s surface, an increase in evapotranspiration happens and in turn increase in salinity of the water.
78
how can deforestation affect the drainage basin
Deforestation is the term used to describe the removal of trees. The impact of deforestation reduces interception and consequently, rainfall strikes soil directly, leading to soil compaction.
Soil compaction and the removal of tree roots can reduce infiltration.
Ultimately deforestation causes an increase in surface runoff, resulting in more soil erosion and flooding.
