Rideau WatershedOn average 926mm of precipitation falls in the Rideau River Watershed each year. 60% of this precipitation is used by plants and trees or goes back to the atmosphere. The remaining 40% of the precipitation either flows into the rivers and streams or infiltrates into the ground and may eventually reach the groundwater table and recharge the aquifers or moves underground downstream to eventually discharge back to streams and rivers.

The average monthly runoff varies from 7mm to 95mm as recorded by the conservation authority's most northern station along the Rideau River at Ottawa. The highest average monthly stream flows occur in April due to snow melt, rain and runoff. The lowest flow is in August when most of the volume is from baseflow which is groundwater discharging back to surface water.

RVCA collects rain data in tipping buckets at two locations in the Rideau Watershed. There are 11 snow pack collection sites in the Rideau Watershed. RVCA operates five sites below/downstream of Smiths Falls (starting around 1977) and Parks Canada operates six sites above/upstream of Smiths Falls (starting around 1989). Snow depth cores are taken at each site. The snow cores are weighed and the snow water equivalent (SWE) is recorded based on the weight of the snow.

Adapted from RVCA: Annual Rideau Valley Watershed Checkup 2006