5.3a

• what is a water budget?

  the annual balance between inputs and outputs in a hydrological system
• what are water budgets used for?


  they can help farmers plan the frequency and amount of irrigation needed by their crops (based on the level of groundwater recharge possible and the availability of soil water)
• what is the formula for water budget?

  P = Q + E +- S
• in the water budget equation?

  P = precipitation

  Q = channel discharge

  E = evapotranspiration

  S = change in storage
• describe the water budget in wet seasons?

  precipitation (inputs) exceed evapotranspiration (outputs), creating a water surplus. the ground stores fill with water so there's more direct runoff and higher discharge so river levels rise
• describe the water budget in dry seasons?

  evapotranspiration exceeds precipitation. ground stores are depleted as some water is used by plants and humans and some flows into the river channel but isn't replaced by precipitation
• describe the water budget from January to April in a temperate climate?

  water surplus:

  • precipitation exceeds evapotranspiration - soil water stores are full and can be used by crops
• describe the water budget from April to September in a temperate climate?

  water deficit:

  • soil water store starts to deplete as precipitation levels are low due to increased atmospheric temperatures and evapotranspiration levels are high
  • farmers may need to irrigate their land
  • any precipitation is likely to be absorbed by the soil rather than produce runoff
• describe the water budget from September to December in a temperate climate?

  • atmospheric temperatures start to decrease, along with levels of evapotranspiration. the amount of precipitation increases, which leads to the recharge of soil water stores
  • any precipitation will percolate into the ground and groundwater stores will be recharged