Average annual precipitation in the upper stretches of the Ottawa River totals 819 millimetres and is comprised of 625 millimetres of rain and 195 centimetres of snow. There are on average each year 170 frost-free days, 156 days of precipitation, and 144 days with snow cover.

In the southern stretches of the river, the climate is generally milder and more humid. Average annual precipitation totals 965 millimetres, and is comprised of 187 centimetres of snow and 779 millimetres of rain.

The Ottawa River has over 50 major dams and 13 reservoirs. It is a highly regulated river. The dams were constructed either as a means of flood control, energy production, or to improve navigation.

A total of 43 hydroelectric generating stations and dams are located in the Ottawa River basin, and these are important for the two provinces’ economies. The generating stations are owned by Ontario Power Generation (a for profit company, formerly Ontario Hydro), or by Hydro Quebec, or by Public Works and Government Services Canada, and one is jointly owned and operated by Ontario Power Generation and Hydro Quebec (Chats Falls, 56 km northwest of Ottawa).

Link to real-time water flow data

Link to real-time water level data

Water shortages can have a large impact on economics and quality of life aspects of a community. Low water levels can also be disastrous for natural ecosystems such as wetlands. Over consumption and decreased rainfall can lead to water shortages even in a country like Canada with an abundance of freshwater. Summer droughts can be a source of stress on the local ecosystem, agricultural producers and industry, as well as public recreation and drinking water safety. The Ottawa River came within 11 cm of its lowest level in 50 years on August 14, 2001.

Stormwater is water from rain or melted snow that flows over roofs, yards, parking lots, ditches and streets, and eventually enters a city's storm sewer system. The storm sewer system is a network of ditches, culverts and sewers that transports stormwater to nearby creeks, lakes or rivers. Catch basins are the openings you see along curbs in streets and parking lots where rainwater can enter the storm sewer system.

City of Ottawa

Healthy productive soil is the foundation of a stable, productive economy and the many environmental amenities all Canadians enjoy - clean air and water, enhanced fish and wildlife habitat, and diverse plant and animal communities. Soil erosion is a naturally occurring process on all land, however, human activity tends to accelerate this process substantially.

The Ottawa River Basin is in a medium to heavily-populated area. Primary water uses are as a source for hydroelectric power generation, domestic water supply, effluent dilution (wastewater), recreational boating and a limited amount of log driving.