River Regime and River Discharge Variations Flashcards Preview

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Flashcards in River Regime and River Discharge Variations Deck (11)
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1
Q

Physical factors influencing river regime

A
  • annual precipitation patterns
  • snowmelt
  • temperatures and evaporation
  • relief
  • underlying soil and geology
2
Q

Human factors influencing river regime

A
  • construction of damns and reservoirs

- levels of irrigation (water supply to plants artificially)

3
Q

What Is a simple river regime?

A

periods of high and low channel flow

4
Q

what is a complex river regime?

A

river with lots of tributaries flowing through variety of climates and environments

5
Q

EXAMPLE : Colorado River

A

damn construction - hover (1935) and glen can (1966)
before dams, high flow between April and September
summer snowmelt - water 13x higher than in winter
peak discharge in autumn, lowest peaks evened out by damn construction

6
Q

Factors affecting the delay between high rainfall and peak channel flow (lag time)

A
  • difference in geology, vegetation and land use
  • material of drainage basin
  • levels of interception
  • permeable geology = slow water transfer via infiltration, percolation and groundwater flow
7
Q

Storm Hydrographs

A

peak discharge = max rate of flow during storm event
peak rainfall = max rainfall recorded in one time interval
rising limb = discharge rises
lag time = time between peak rainfall and peak discharge
baseflow = normal minimum flow of river
preceding discharge = rate of flow prior to storm event

8
Q

Climatic influences on storm hydrographs

A
  • rainfall intensity and duration
  • antecedent conditions (weather and soil conditions prior to storm event)
  • e.g flashy hydrograph = soil already saturated
  • low intensity rain on dry ground unlikely to produce flashy hydrograph
  • type of precipitation, snow can be stored on ground before melting (longer lag time)
9
Q

Non-climatic influences on storm hydrographs

A
  • steep relief and impermeable geology = flashy
  • free draining sandy soils/ high permeability lowers overland flow and flood risk
  • flashy hydrographs in poor drained upland regions of UK, low interception and grassy or peaty ground
10
Q

Effects of soil and land use on river discharge

A
  • soil type = clay - decreases infiltration capacity
  • agriculture and well-established pasture = decreases infiltration rate
  • soil aeration and graces and leaves store water on the surface
  • paved areas increase hydrographic peaks for urbanised drainage basins
11
Q

Variations of basin size, shape and drainage density

A

long and narrow = low discharge over period of time
round = much steeper increase and greater peak discharge
dense = discharge greater at a sooner time
less dense = discharge very low, peak later after rainfall event