OPTIONS - freshwater

Mouth

Lowest point from sea level (Lower course), connection to the largest body of water.

Tributary

Small rivers connecting to the main channel.

Confluence

Where different rivers meet.

Throughfall

Water that falls through gaps in vegetation or drops from leaves and twigs.

Throughflow

Water flowing through the soil, occurring quickly in porous soils such as sand.

Stemflow

Water that trickles along twigs and branches and finally down the trunk of the tree.

Overland flow

Water that flows over the land’s surface when precipitation exceeds infiltration.

Channel flow

The movement of water in channels such as streams and rivers.

Infiltration

When water soaks into the soil.

Percolation

When water moves slowly down from the soil into the bedrock.

Groundwater

Subsurface water flow through aquifers, below throughflow.

Baseflow

Part of a river’s discharge provided by groundwater seeping into the river bed.

Interception

The water that is caught and stored by vegetation.

Soil water

The subsurface water held in soil above the water table.

Field capacity

Amount of water held in the soil after excess water is drained away.

Wilting point

Range of moisture content in which permanent wilting of plants occurs.

Soil moisture deficit

How far below field capacity soil moisture falls.

Soil moisture recharge

When dried up pores are refilled with water.

Evaporation

Process by which a liquid is changed into a gas (water vapor).

Transpiration

Process by which water vapor escapes from living plants into the atmosphere.

Evapotranspiration

The combined effects of evaporation and transpiration.

Potential evapotranspiration

Water loss that would occur if there was an unlimited supply of water in the soil.

Aquifers

Rocks containing significant quantities of water, permeable rocks like sandstone and limestone.

Groundwater recharge

Occurs due to infiltration and percolation from above.

Laminar flow

Water flows in sheets (laminae) parallel to the channel bed.

Turbulent flow

Water flows in irregular patterns due to high velocity.

Helicoidal flow

Water flows in a corkscrew motion due to alternating pools and riffles.

Abrasion

The wearing away of riverbed and banks by sediment carried in the flow.

Attrition

Erosion caused when rocks and boulders bump into each other.

Hydraulic power

Process by which water compresses air pockets in bed or banks, causing erosion.

Traction

Heavy rocks and boulders rolled along the river bed during floods.

Saltation

Small stones and pebbles are bounced along the river bed.

Suspension

Very small particles of sand or clay that are suspended in water.

Alluvium

Sand and gravel deposited by running water on flood plains.

Thalweg

Line of maximum velocity in a river.

Discharge

The amount of water flowing in a river channel, measured in cubic metres per second.

Peak rainfall

The height of the storm.

Lag time

The time between the peak rainfall and maximum flow in the river.

Rising limb

The rising river discharge during a flood event.

Recessional/falling limb

The falling river discharge showing how quickly the water level declines.