Water Budgets

Influence on Flow of a River

Water Budgets, figure 1

Water budgets and river systems

Water budgets show the annual balance between:

  • inputs (precipitation)
  • outputs (evapotranspiration and channel flow)
  • their impact on soil water availability

Water budgets are influenced by climate type (tropical or temperate or polar examples).

River regimes indicate the annual variation of discharge of a river and result from the impact of climate, geology and soils as shown in regimes from contrasting river basins. (Yukon, Amazon, Indus).

We can look at water budgets on any__ scale__ from the global hydrological cycle to a local drainage basin.

The water budget can either have a

positive water balance (where there is a surplus of water)

negative water balance (where there is a deficit of water)

You can calculate the annual water budget using the following equation…

P = Q + E ± S

P= precipitation

Q= Discharge

E= evapotranspiration (EVT)

S= storage

Water budgets are usually presented as a graph showing change throughout the year.

Explain what a water budget is.
Your answer should include: Inputs / outputs.

Climate Types and Their Impact

Water budgets are especially useful for looking at the soil moisture.

We can use a water budget graph to predict and monitor soil moisture.

Usually, areas in similar climate zones will have a similar water budget.

The UK is an example of a temperate climate:

Water Budgets, figure 1

The water budget shows the annual variation in discharge of a river at a particular point.

A river’s discharge is supplied by:

  • Groundwater
  • Run-off
  • precipitation.

The water budget graph masks anomalies caused by precipitation.

River Regimes Around the World

Water Budgets, figure 1

Describe differences between river regimes around the world.
Your answer should include: Snowmelt / freezing / Amazon / Yukon / Nile.

Factors Influencing Regimes

Water Budgets, figure 1

  • Intense rainfall can make the ground saturated quickly leading to surface run-off
  • The geology can be impermeable increasing surface run-off
  • A small catchment means there a shorter lag time from precipitation occurring and it reaching the river basin as it is a shorter distance
  • Vegetation can intercept precipitation and store it
  • Urbanisation can mean there are more impermeable land surfaces
  • Climate affects the amount of inputs to the system
  • Previous precipitation can make the ground saturated
Explain the factors that influence river regimes around the world.
Your answer should include: size / land use / climate / precipitation / vegetation