Hydrographs

• What is a hydrograph?

  Record of river discharge over time
• How does a river's discharge respond to a storm event?

  It shows changes in discharge levels
• What is an annual hydrograph?

  Hydrograph over a whole year
• What does river regime refer to?

  Changes to river discharge over a year
• What is a storm hydrograph?

  Hydrograph for a short period after a storm
• What is lag time in hydrology?

  Distance between peak rainfall and peak flow
• Why might flooding occur a second time after a storm?

  Ground is saturated and stores are full
• What causes discharge in rivers?

  Overland runoff, groundwater springs, meltwater
• What factors influence a river regime?

  Precipitation, rock type, drainage basin shape
• What is one key difference in European river regimes?

  River Shannon has a winter maximum
• What is the peak flow pattern for Gloma in Norway?

  Peak in spring associated with snowmelt
• What are the two main maxima for the Po river near Venice?

  Autumn and winter rains, spring snowmelt
• How does precipitation type and intensity affect a hydrograph?

  Steep rising limb and high peak flow
• What effect does temperature have on a hydrograph?

  Reduces peak of hydrograph in warmer nations
• What is the effect of antecedent moisture on a hydrograph?

  High peak flow and short time lag
• What features of a drainage basin influence a hydrograph?

  Rock type, permeability, shape, slope
• How does permeability affect a hydrograph?

  Less movement leads to a subdued hydrograph
• How does vegetation cover influence a hydrograph?

  More vegetation leads to more interception
• What is the effect of a steep slope on a hydrograph?

  Increased surface runoff leads to a flashy hydrograph
• How does land use change from arable to pastoral affect hydrographs?

  Pastoral leads to less infiltration and runoff
• What is the impact of deforestation on hydrographs?

  Less trees increase peak flow and decrease time lag
• What is the impact of afforestation on hydrographs?

  More trees reduce peak flow and increase time lag
• How do changes in agricultural practices affect hydrographs?

  Arable increases interception, pastoral decreases infiltration
• What is the purpose of dam or reservoir building in relation to rivers?

  To artificially manage river flow