Influence on Flow of a River
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
E= evapotranspiration (EVT)
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:
The water budget shows the annual variation in discharge of a river at a particular point.
A river’s discharge is supplied by:
The water budget graph masks anomalies caused by precipitation.
River Regimes Around the World
- Describe differences between river regimes around the world.
- Your answer should include: Snowmelt / freezing / Amazon / Yukon / Nile.
Factors Influencing Regimes
- 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