Drainage density: The density of rivers and streams in each area.
Discharge: The rate of water flow in a river.
Impermeable: Rock or soil which will not transmit water.
River regime: The variation in annual river discharge.
Aquifer: underground porous rock which will hold groundwater and let it through.
CLIMATE:
- The distribution of water globally is related to the Earth’s climatic zones.
- Regions near to the equator receive high levels of annual precipitation, while some tropical areas suffer recurring drought (HADLEY CELL/ITCZ).
- Rainfall may also vary with the seasons.
- Equatorial areas such as Amazon lowlands have two distinct periods of wet weather per year.
- High mountainous with snowpack hold vast reserves of water, some of which is released in late spring and during the summer.
GEOLOGY:
- Where the rocks underlying a river basin are impermeable, water will remain on the surface as runoff, creating a high drainage density.
- Permeable soils and rocks such as limestone may allow water to pass into underground drainage systems.
- Aquifers such as chalk and porous sandstones can store vast quantities of water underground.
SURFACE PROCESSES:
- World’s major rivers store large quantities of water and transfer it across the continents.
- River flows generally increases downstream as tributaries feed into the main river, though high temperatures can lead to considerable water loss by evaporation.
- Seasonal changes in climate can also create significant variations in discharge and produce distinctive river regimes.