Essential Hydrology Terms and Water Cycle Definitions

Key Hydrological Terms

Aquifer

An aquifer is an underground layer where infiltrated water accumulates in significant quantities, typically contained by impervious rocks.

Groundwater

Groundwater percolates through permeable rocks and lies below the upper limit of the zone of saturation. It is easily contaminated.

Head of a River

The head of a river is where a river originates, often coinciding with the highest sector of the basin.

Channel

A channel is the bed or land where rivers, creeks, and streams run, usually corresponding to the line joining the lowest points of a river valley.

Flow

Flow is the amount of water in a river at a particular place and time. It varies depending on the season and rainfall.

Watershed

A watershed defines the borders of a river and its tributaries, draining the land that feeds the water system.

Delta

A delta is a zone of accumulated river sediment that forms at the mouth of some rivers when tides are weak and alluvium accumulation exceeds erosion. It typically has a triangular layout.

Water Divide

A water divide (divisoria) is the line joining points from which waters flow into different watersheds. This line can vary as a result of erosion.

Endorheic Basin

An endorheic basin is a closed basin where waters do not flow into the sea but into lakes, shallow ponds, or rivers. This is characteristic of plains and offshore areas, caused by natural or cultural factors.

Runoff

Runoff consists of water from rain and snowmelt that flows freely across the earth's surface toward the main channel. Its speed is higher on slopes, lower in forested areas, and increases with heavy rainfall.

Drought

A drought refers to the low or minimum flow of a river during a certain time of year, which can lead to the river drying up completely.

Exorheic Basin

An exorheic basin is one with water drainage systems organized in an interconnected network of channels.

Trowel (Marshland)

The term trowel relates to marshes and wetlands that are subjected to intense evaporation during the summer and can become dry.

Flow Regime

The flow regime refers to the evolution and variation of a current's flow throughout the year, influenced by climatic, geological, or biotic factors.

Torrent

A torrent is a watercourse defined by a steep gradient, high speed, and a small, irregular flow regime. It acts as an active agent of erosion.