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A-Level AQA Geography > Water and Carbon Cycles: Drainage Basins > Flashcards

Water and Carbon Cycles: Drainage Basins Flashcards

1
Q

What are the inputs in a drainage basin?

A

Precipitation

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2
Q

What are the outputs in a drainage basin?

A

River Discharge and Evapotranspiration

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3
Q

What are the flows in a drainage basin?

A

Interception, stemflow, throughfall. overland flow, infiltration, throughflow, percolation, groundwater flow and channel flow

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4
Q

What are the stores in a drainage basin?

A

Interception storage, surface storage, soil storage, groundwater storage, channel storage

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5
Q

What type of system are drainage basins?

A

Open, local hydrological cycles with the boundary being the watershed

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6
Q

What is evapotranspiration?

A

The total output of water from the drainage basin directly back into the atmosphere

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7
Q

What is run-off?

A

All the water that enters a river channel and eventually flows out of the drainage basin

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8
Q

What factors influence evapotranspiration?

A
  • Most important factor is high temperatures, causes water to evaporate at a faster rate as there’s more KE, increased rate of transpiration, invigorates plant growth (increases flow)
  • Plant growth increases flow, as it increases the total respiration of plants which releases water as a product
  • High humidity decreases rate of flow as the air is saturated, less capacity to hold water
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9
Q

What factors influence interception?

A
  • High density of vegetation increases store as there is more vegetation thats intercepting and more water held in store
  • Plants with broader leaves increase store as there is a larger SA to intercept rainfall
  • Intense wind and rains decrease stores as they shake leaves and trees, instead increasing throughfall and stemflow
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10
Q

What factors influence overland flow?

A
  • Perception, if there is little precipitation the overland flow won’t be large
  • Topography, if its flat water will sit directly on the surface, if it’s stepp water can’t infiltrate soil so flows downhill
  • Impermeable surfaces reduce infiltration and therefore enhance overland flow, permeable surfaces have the opposite impact
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11
Q

What factors influence infiltration?

A
  • Small pores (soil porosity) lead to soil becoming easily saturated, reducing capacity t hold water and reduce rate of infiltration
  • Land use, urban areas decrease rate of infiltration as there is a large areas of impermeable surfaces (increasing overland flow)
  • Intense and long periods of rainfall (intensity + duration) declines rate as soil becomes saturated
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12
Q

What factors influence groundwater storage?

A
  • Rock porosity, large air spaces in rock allows store to increase, larger capacity to hold water
  • Abstraction rate, if rate is high enough the store will decrease (over-abstraction)
  • Intense precipitation causes water to run-off straight into rivers, not being absorbed into groundwater storage
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13
Q

What factors influence river discharge?

A
  • Characteristics of the drainage basin (large + steep relief + impermeable rocks and soils = high discharge)
  • High precipitation leads to a high increase in river discharge
  • More impermeable surfaces, water runs into drains and makes its way quickly into rivers
  • Deforestation, more water reaches the ground faster, ground becomes saturated, makes it way quicker to river
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14
Q

What is the concept of the water balance?

A

Within the drainage basin the balance between the inputs (precipitation) and outputs (evapotranspiration and channel discharge) is known as the water balance

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15
Q

What is the equation of the water balance?

A

Precipitation (P) = Discharge (Q) + Evapotranspiration (E) +/- Changes in stores (S)

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16
Q

Describe water balance in the wet seasons?

A
  • precipitation will be higher than evapotranspiration
  • this creates water surplus
  • ground stores fill very quickly so there’s more surface run-off
  • higher river discharge and water levels rise
  • input is greater than output
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17
Q

Describe the water balance in the drier seasons?

A
  • precipitation is lower than evapotranspiration
  • ground stores are being depleted as water is being used, not being replaced by precipitation
  • deficit of water
  • output greater than input
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18
Q

What factors lead to a steady river regime?

A
  • Arable land use (encourages interception and infiltration)
  • Permeable soils, e.g. loamy (encourages infiltration)
  • Gentle slopes (encourages water to stay in surface store and infiltration)
  • Porous geology and rock types, e.g. chalk (encourages percolation to groundwater store, slow movement to channel via groundwater flow)
  • Circular River Basin
19
Q

Why do all factors influencing a steady river regime have in common?

A

All encourage water to flow gradually into rivers

20
Q

What factors lead to a flashy river regime?

A
  • Impermeable rock types (discourages percolation, increases overland flow)
  • Land use that removes vegetation, eg urban or grazing land (increases overland flow)
  • Higher annual precipitation (soil likely to be saturated more often)
  • Narrow drainage basin (precipitation has less distance to travel to reach the river channel)
21
Q

What is the rising limb?

A

discharge (cumecs) going up to peak discharge

22
Q

What is peak discharge?

A

Point of a flood hydrograph when river discharge is at its greatest

23
Q

What is the lag time?

A

Time taken from the peak rainfall to peak discharge

24
Q

What is the base flow?

A

Normal day-to-day discharge of the river (throughflow and groundwater)

25
Q

How does the size of the drainage basin control shape of the storm hydrograph?

A
  • large basin = catches more precipitation = higher peak discharge
  • small basin = shorter lag time, water reaches river rapidl
26
Q

How does the shape of the drainage basin control the shape of the storm hydrograph?

A
  • circular basin = flashy, less time for water to reach river
  • elongated basin = water will take a long time for water to reach the river
27
Q

What are the physical factors that change the shape of storm hydrographs?

A

topography, drainage density, infiltration capacity, soil/rock type, vegetation cover and land use

28
Q

What are the climatic factors that change the shape of storm hydrographs?

A

Precipitation intensity, duration, snowfall (snowmelt), evapotranspiration

29
Q

What is river regime?

A

The variability in its discharge throughout the course of a year in response to precipitation, temperature, evapotranspiration and drainage basin characters

30
Q

What is river discharge?

A

The volume of water passing a measuring point in a given time

31
Q

What is a storm hydrograph?

A

A graph of discharge of a river over the time period when the normal flow of the river is affected by a storm event

32
Q

What factors change storm hydrograph shape?

A

shape of the river, drainage basin shape, drainage density, infiltration, soils and rocks, vegetation thickness, amount of precipitation, deforestation, agriculture and growth of urban areas

33
Q

What are natural causes of change in the water cycle?

A

Storms and precipitation

Seasonal changes and vegetation

34
Q

What are human causes of change in the water cycle?

A

Deforestation
Farming Practices
Abstraction

35
Q

How does storms and precipitation cause change in the water cycle?

A
  • intense storms generate more precipitation

- staurates in the ground much faster, in

36
Q

How does storms and precipitation cause change in the water cycle?

A
  • intense storms generate more precipitation
  • staurates in the ground much faster, increasing overland flow and decreasing infiltration and other soil flows
  • results in a greater peak discharge
  • wind intensity in storms shakes trees and decreasing interception
37
Q

What are the human causes to the Winchester 2014 floods?

A
  • Large expanse of urban areas with impermeable tarmac surfaces -> no infiltration, high run-off, sudden increase in river discharge
  • Low-lying and homes built on a flood plain
  • Climate change, sea levels rise, winter rainfall increases and flash floods become more frequent

Human causes just exaggerate effects of natural causes

38
Q

What are the natural causes to the Winchester 2014 floods?

A
  • Winchester is underlain by a permeable chalk aquifer at a shallow depth -> chalk is very porous so lots of water is absorbed during periods of rainfall and aquifer being shallow amplifies the risk
  • During January and February there was heavy and prolonged rain (severe depressions caused by intense storms) 6 months of rain within the first 2 months of 2014
39
Q

What are the economic impacts of the 2014 Winchester floods?

A

Cost the county council £68.5 million
Money had to be pulled from elsewhere in Hampshire to pay
Disruption to travel (hub for links to London), local people lost money as they were unable to work

40
Q

What were the social impacts of the 2014 Winchester floods?

A

Homes flooded, possessions destroyed, evacuation and temporary relocations = emotional impacts
Disruption to education = may affect grades

41
Q

What were the environmental impacts of the 2014 Winchester floods?

A

Sewage contamination in homes and parks

Public health response

42
Q

What was the short term management of the Winchester 2014 floods?

A
  • Hampshire Fire Service brought 2 high volume pumps, pumping 84000 litres to prevent the city flooding
  • Multiple agencies (firefighters, navy, council, police etc) joined to build a 70ft wide barrier across creating an artificial pond taking pressure off of the city with 80, 1 tonne sandbags
43
Q

What are the future plans after the Winchester 2014 floods?

A

Environment Agency planning erecting permanent barriers: watertight walls, 1 m tall that are concrete

44
Q

What was the long-term management of the Winchester 2014 floods?

A

Planning controls, lower value land-use in some high risk flood plain locations (e.g. playing fields and nature reserve)

A-Level AQA Geography (13 decks)

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