River

Transpiration

The process where plants release water vapor from their leaves into the atmosphere through small pores called stomata.

Infiltration

The process of water entering the soil from the surface.

Evapotranspiration

The combined loss of water to the atmosphere through evaporation and transpiration.

Evaporation

The process of water changing from a liquid into water vapor and rising into the atmosphere from surfaces such as rivers, lakes, and soil.

Condensation

The process where water vapor cools and changes into liquid water, forming clouds or dew.

Surface Runoff

Water flowing over the land's surface into rivers, lakes, or oceans, often after heavy rain when the ground cannot absorb more water.

Streamflow

The flow of water within natural channels such as rivers and streams.

Throughflow

The sideways movement of water through soil toward rivers or streams.

Interception

The capture of precipitation by leaves, branches, and vegetation before it reaches the ground.

Groundwater Flow

The movement of water through rocks and underground aquifers toward rivers, lakes, or the ocean.

Precipitation

Water released from clouds to the Earth's surface as rain, snow, sleet, or hail.

Erosion

The removal of weathered sediment by the force of river water.

Attrition

The process where sediment carried by a river collides with other sediment, causing it to become smaller and rounder.

Hydraulic Action

The force of water hitting the bed and banks of a river, causing erosion.

Abrasion

The process where a river's load repeatedly hits the bed and banks, creating a sandpapering effect that deepens and widens the channel.

Solution

The process where soluble rocks are dissolved by river water and become part of the water.

Traction

The process where the largest material is rolled along the river bed, usually during times of high discharge.

Saltation

The leapfrogging movement of small stones and grains of sand as they bounce along the river bed.

Suspension

The process where fine, light material is carried within the river water.

Vertical Erosion

Downward erosion by a river, which is dominant in the upper course and helps form waterfalls and V-shaped valleys.

Deposition

The process where a river drops material when discharge or velocity decreases, or when its carrying capacity is exceeded.

Transportation

The movement of sediment by a river.

Drainage Basin

An area of land drained by a river and its tributaries.

Source

The place where a river begins.

Spring

A flow of groundwater that naturally emerges at the Earth's surface.

Oxbow Lake

A crescent-shaped lake formed when a meander is cut off from the main river channel.

Upper Course of a River

The mountain stage of a river, characterized by steep gradients, narrow valleys, and mainly vertical erosion.

Middle Course of a River

The section of a river with a medium gradient, gently sloping valley sides, and a wider and deeper channel.

Lower Course of a River

The section near the river's mouth where the river is wider, the land is flatter, and deposition becomes more common.

Alluvium

Rock particles such as clay, silt, sand, and gravel deposited by a river.

Bedload

Material carried by a river that is bounced or rolled along the river bed.

Delta

A river mouth where deposited sediment causes the main channel to split into smaller branching channels called distributaries.

Depth

The depth of a river channel, which generally increases downstream as tributaries join the river.

Discharge

The amount of water passing a specific point in a river per unit of time. It is calculated as cross-sectional area × velocity and is measured in cubic metres per second (m³/s).

Estuary

The tidal mouth of a river, often with large, flat expanses of mud exposed at low tide.

Eutrophication

The process where excess nitrates and phosphates cause excessive plant and algae growth, reducing oxygen levels and potentially leading to the death of aquatic organisms.

Flood Plain

The wide, flat floor of a river valley, made up of sediments such as alluvium deposited by the river.

Freeze-Thaw Weathering

A type of physical weathering where water enters cracks in rocks, freezes and expands, putting pressure on the rock and causing pieces to break off.

Glaciated Valley

A river valley widened and deepened by glaciers, creating a U-shaped valley instead of the V-shaped valley formed by river erosion.

Gorge

A steep-sided, narrow rocky valley formed as a waterfall retreats upstream.

Gradient

The slope of a river profile, which is generally steep near the source and becomes gentler toward the mouth.

Interlocking Spurs

Alternating ridges of high land that a river winds around as it descends through its upper course.

Lateral Erosion

Erosion by a river on the outside of a meander, which causes the valley to widen and contributes to flood-plain formation.

Levées

Raised river banks formed naturally by deposition during floods.

Load

The material transported by a river as bedload, suspended load, or dissolved load.

Mouth

The place where a river ends, usually at a lake, sea, or ocean.

Particle Size

The size of sediment particles, ranging from tiny clay particles (about 0.001 mm) to large boulders (500+ mm).

Physical Weathering

The breakdown of rock into smaller pieces without changing its chemical composition, caused by processes such as freeze-thaw and exfoliation.

Plunge Pool

The deep pool of water found at the base of a waterfall.

Pot Holes

Holes eroded into the solid rock of a river channel, often formed when pebbles become trapped in swirling water and grind into the bed.

Profile

The cross-section of a river from its source to its mouth, generally showing a concave shape.

Rapids

Fast-flowing sections of a river where it passes over resistant rock, often occurring before a waterfall.

River Cliff

A steep bank on the outside of a meander bend, formed by the erosive effect of fast-flowing water.

Sedimentation

The settling of suspended particles from a body of water.

Slip-Off Slope

A gently sloping area on the inside of a meander bend formed by deposition in slower-flowing water.

Suspended Load

Very small and light material, usually fine clay and silt, carried within the river water.

V-Shaped Valley

A deep, narrow valley with steep sides, usually found in the upper course of a river where vertical erosion is strong.

Velocity

The speed at which water flows through a river channel.

Waterfalls

Features formed where a river flows over a band of resistant rock followed by softer rock, causing erosion and the eventual retreat of the waterfall and formation of a gorge.

Watershed

The highland area that separates one drainage basin from another.

Weathering

The breakdown or decomposition of rock by biological, physical, or chemical processes.