Glossary

Baseflow

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

Drainage Basin

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

Synonyms: basin, watershed, and drainage area. 

Freshet

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

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.

Reservoir

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.

Tributary

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