Factors affecting discharge

• What does the storm hydrograph record?

  The storm hydrograph records the discharge of a river in response to rainfall.
• How does a river's discharge respond to rainfall?

  The discharge increases with the amount of rainfall in the catchment area.
• What processes influence a river's discharge?

  Groundwater flow and snowmelt play key roles in a river's discharge.
• What happens to river flow during a small amount of precipitation?

  The river flow responds very slowly to a small amount of precipitation.
• What is the rising limb of a hydrograph?

  The rising limb results from a rapid increase in rainwater reaching the river.
• What factors affect the shape of the rising limb?

  The shape of the rising limb depends on soil characteristics before and during rainfall.
• What are the characteristics of Hydrograph A and Hydrograph B?

  • Hydrograph A: Prolonged light rain, saturated soil
  • Hydrograph B: Dry soil, short heavy rainfall
• What is peak discharge?

  Peak discharge occurs when the river reaches its highest discharge level.
• What is lag time in relation to hydrographs?

  Lag time is the time between peak rainfall and peak discharge.
• How do impermeable surfaces affect lag time?

  Impermeable surfaces decrease lag time by resulting in surface runoff.
• How do forested areas affect lag time?

  Forested areas increase lag time due to interception and infiltration.
• Why does a short lag time often lead to flooding?

  A short lag time means the river responds quickly, leading to floods.
• What does a falling discharge line indicate?

  A falling discharge line indicates that river levels are decreasing after rainfall.
• Why is the falling line not as steep as the rising level?

  It takes longer for water to reach the river channel due to groundwater flow.
• What happens to river discharge after a storm passes?

  The river discharge returns to normal levels after the storm has passed.
• When do the lowest discharges typically occur in Britain?

  The lowest discharges usually occur in summer.
• What causes higher river discharges in spring?

  Higher river discharges in spring are caused by snowmelt.
• What is the river regime?

  The river regime describes the annual variation in river discharge.
• What factors determine a river's regime?

  The size of the area, rainfall amount, and infiltration rates determine a river's regime.
• How do extreme events affect river discharge?

  Extreme events cause discharge to increase quickly, often leading to flooding.
• What are the characteristics of flat and flash hydrographs?

  • Flat hydrographs:
  • Gentle rising limb
  • Long lag time
  • Low peak discharge
  • Gentle falling limb
  • Flash hydrographs:
  • Steep rising limb
  • Short lag time
  • High peak discharge
  • Steep falling limb
• How does relief affect discharge and hydrograph shape?

  Steeply sloping land leads to rapid water flow and a steep hydrograph.
• How does basin size affect lag time?

  Smaller basins have shorter lag times due to shorter distances to the river.
• How does basin shape influence hydrograph response?

  Circular basins have shorter lag times and higher peak discharges than elongated basins.
• How do clay soils affect infiltration rates?

  Clay soils reduce infiltration due to small pore spaces, leading to fast flow processes.
• How do sandy soils affect hydrograph characteristics?

  Sandy soils increase infiltration and lead to a gentle hydrograph response.
• What is the effect of permeable land on hydrographs?

  Permeable land leads to slower water transfer and a lower peak discharge in hydrographs.
• How do seasons affect discharge in afforested areas?

  Summer has more interception and transpiration, while winter has less interception and uptake.
• How does drainage density influence flooding?

  High drainage density leads to rapid runoff and increased flooding potential.
• What is the impact of previous weather conditions on hydrographs?

  Antecedent rainfall can saturate soil, reducing infiltration and increasing surface runoff.
• How does temperature affect infiltration and runoff?

  Extreme temperatures can restrict infiltration and increase surface runoff.
• What is the difference between annual and storm hydrographs?

  Annual hydrographs show variation over a year, while storm hydrographs show impact from intense rainfall.
• What factors control the annual hydrograph?

  Precipitation, temperature, and snowmelt control the annual hydrograph.
• How does snowmelt affect river discharge?

  Snowmelt causes spring peaks in river discharge.
• What can actual hydrographs be used for?

  Actual hydrographs can be used to examine land use changes and ensure adequate water supply.