Ottawa RiverRegulationPlanning BoardCommission de planificationde la régularisationde la rivière des Outaouais



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 body of water or stream.


Large increase of water discharged in a river during spring months due to snow melt and sometimes rainfall.


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


A type of statistical representation of a value in terms of percentages.  For example, the 25th percentile is the value below which 25% of historical flows or levels are found, and above which 75% are found.

probability of occurence

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


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

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.


The excess water, from precipitation or spring melt, which isn’t retained in the ground and flows into the surrounding streams.


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