Glossary

Baseflow

Water in a stream that comes from groundwater discharging into the surface water system.

Basin

An area of land that channels rainfall and snowmelt into a common outlet, such as a body of water or stream.

Synonyms: drainage basin, watershed, and drainage area. 

Confluence

The point where two or more rivers or streams meet and merge into a single channel. 

Discharge

The volume of water flowing through a river or stream per unit of time, typically expressed in cubic meters per second (m³/s). 

Synonyms: flows, outflows.

Flooding

The overflow of water onto land that is normally dry, often caused by rising water in nearby rivers, streams, or drainage. 

Freshet

A large increase in water discharged into a river during the spring months due to snow melt and sometimes rainfall. 

Geodetic Reference

A standardized coordinate system or datum used to measure and represent positions and elevations on the Earth’s surface. 

Headwater

The source or upper tributaries of a river or stream, typically located in highland or mountainous areas. 

Hydraulic model

A mathematical representation of water movement within a system (such as rivers, channels, or reservoirs) used to simulate and predict water behavior (for example, flows, water levels, and flow velocities) under various conditions. 

Hydroelectric

The generation of electricity using the energy of moving water, typically by directing water through turbines in dams or other facilities. 

Hydrographic

Pertaining to the mapping and charting of water bodies, including rivers, lakes, and oceans, often for navigation or resource management. 

Hydrological

Relating to the study or science of water movement, distribution, and properties within the Earth’s atmosphere and surface. 

Hydrometeorological

Relating to the combined study of atmospheric and hydrological processes, including precipitation, evaporation, and their impact on water resources and weather patterns. 

Inflow

The quantity or amount of water flowing into a stream, river or water body that comes from spring snowmelt and rainfall.

Percentile

A type of statistical representation of a value in terms of percentages.  For example, the 10th percentile is the value below which 10% of historical flows or levels are found, and above which 90% are found.

Probability of Occurrence

The chance or likelihood that an event will happen over a period of time.

Reservoirs

An area upstream of a dam where water is or can be stored for a long period of time (several weeks and sometimes months). A large reservoir can regulate (or alter) the flows in the downstream river section.

Run-of-river Dam

A type of hydroelectric facility where no or little water is stored. A dam is built to cause water to pond upstream, ensuring the river water is high enough to enter the pipes leading to turbines. A run-of-river facility has little ability to regulate (or alter) the flows in the downstream river section.

Synonym: run-of-river facilities. 

Runoff

The excess water, from rainfall or snow melt, that isn’t retained in the ground and flows into the surrounding streams.

Tributaries

A stream or river that flows into a larger lake or river, for example, the Petawawa and Gatineau rivers.

Water flow

The movement of water within a river, stream, or other channel, often described by its speed and volume. 

Synonym: discharge 

Water level

The height of the water surface in a river, lake, reservoir, or other water body. It is usually measured relative to a specific reference point, such as the mean sea level.