River Regime and River Discharge Variations

Question 1

Physical factors influencing river regime

Answer 1

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

Question 2

Human factors influencing river regime

Answer 2

• construction of damns and reservoirs

- levels of irrigation (water supply to plants artificially)

Question 3

What Is a simple river regime?

Answer 3

periods of high and low channel flow

Question 4

what is a complex river regime?

Answer 4

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

Question 5

EXAMPLE : Colorado River

Answer 5

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

Question 6

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

Answer 6

• 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

Question 7

Storm Hydrographs

Answer 7

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

Question 8

Climatic influences on storm hydrographs

Answer 8

• 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)

Question 9

Non-climatic influences on storm hydrographs

Answer 9

• 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

Question 10

Effects of soil and land use on river discharge

Answer 10

• 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

Question 11

Variations of basin size, shape and drainage density

Answer 11

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