Flow

Project main page || Data || Relationships || Further resources

Introduction:

In broad terms, flow is an overview of how much water is present in an area of the river and how fast it’s moving. Although it can be neatly summarized as the quantity/volume and movement of water, flow is actually a very complex indicator of watershed health making it very interesting and important to monitor. Any changes to flow almost certainly affects other ecological aspects of the watershed. 

Flow can both influence and mediate the impact that other indicators have in a given area. Potential threats to water quality from contaminants such as sewage, mercury, and excess nutrients like phosphorus have less impact on deeper, faster-moving areas, because they can be dispersed and diluted more rapidly than in shallow or slow-moving areas. Depth and flow rate also strongly influence water temperature and dissolved oxygen. In deep, still water, less sunlight reaches the bottom than the surface, meaning surface water is warmer than deeper waters. Waters with less flow can also become stratified, resulting in dissolved oxygen availability varying with depth. However, stratification is uncommon in river systems such as the Ottawa River watershed, where flow rates and turbulence cause mixing and a more even distribution of oxygen and temperature. 

How quickly surface water moves can also influence what occurs on the water’s surface. For example, swift moving water is unlikely to have ice form, therefore limiting ice on conditions in parts of the watershed with fast moving rapids. Similarly, algal blooms tend to form in bays or in areas where the conditions for a bloom are present but also where the water’s surface is stable enough to allow algae to accumulate, once again restricting this phenomenon to specific parts of the watershed.

Human activity can also influence flow, most notably through the installation of dams and hydroelectric facilities. This type of infrastructure can result in large reservoirs that can hold back a significant volume of water, or, for run of river facilities, fluctuations in local flow rates. The presence of a dam on a river system disrupts flow connectivity, alters habitat, and can fragment species, all of which have significant impacts on biodiversity. This includes native species of fish and benthic invertebrates, but also aquatic plants and animals that are specifically adapted to certain habitat conditions. Migratory aquatic species, like the American eel which used to be abundant throughout the watershed, are not able to access or move freely on the Ottawa River, while other historically prevalent species, like Lake Sturgeon, are now restricted to specific reaches.

Another influence on flow is changes in land use due to human activity. The removal of vegetation and changes to land cover impacts the capacity for retaining precipitation, increasing the volume of overland runoff, which can result in more intense peak flows.  Similarly, retaining healthy, vegetated riparian zones stabilize shorelines, slow the flow of water when water levels rise and help to maintain flow-controlling natural bends in the river.

Flow data has been collected in the Ottawa River watershed by hydrometric gauging stations for many years, however data availability has been greatly reduced over the last couple of decades. Data is also available from dams and hydro-electric power generating stations on the Ottawa River mainstem. While that might only tell part of the story of flow in the whole watershed, it does allow for a better understanding of any trends in flow that might be occurring due to changes in the watershed or to factors associated with climate change.

What does flow data look like in the watershed?

This map shows the locations of all Water Survey of Canada hydrometric stations along the length of the Ottawa River. Green stations are currently active, collecting real-time flow data. Red stations collected flow data in previous years, but currently no longer do. To see what years each station collected flow data, see the chart below the map which illustrates when each station was active. Stations are listed with the most upstream station at the top and the station furthest downstream at the bottom.

Hydrometric stations are also present on many of the tributaries that feed into the Ottawa River, however Ottawa Riverkeeper’s flow monitoring efforts will focus initially on the mainstem. Therefore, for simplicity, tributary stations have not been included.

This map does not include any dams or power-generating sites. Although many dams do collect flow data, long term or historical data is typically not readily available to the public and therefore much more difficult to access. It is for this reason that these data sources have not been included.

An important takeaway from this figure is that while there may appear to be plenty of historical data and potential for widespread understanding of flow all along the length of the Ottawa River, a large number of hydrometric stations were shut down before the year 2000. We therefore only have limited data for current flow conditions along the mainstem of the Ottawa River.

Relationships to other indicators:

Flow

How much water or volume of water present at a given time and how quickly it moves along the length of the river determines flow. Flow can provide context to a number of other indicators and as an important measure to factor when examining water chemistry or understanding impact of pollutants (for example, the same concentration of pollution will impact a river with low flow differently than one with high flow). Comparing flow within the same reach can help identify different trends and, when affected by barriers, can impact aquatic biota.

Flow
Algal Blooms Water Temperature Dissolved Oxygen Chlorophyll-a Total Phosphorus Riparian Connectivity Combined Sewer Overflows Change in Land Use Benthic Invertebrates Invasive Species Fish Richness Water Mercury Ice On/Off

Algal Blooms

Algae are a group of single-celled and multicellular plant-like organisms. Algal growth contributes and supports the ecosystem in much the same way that plants do, through the production of oxygen and as a potential food source for smaller animals. However, when environmental conditions shift from their normal ranges, this can promote algal blooms, a rapid increase in population size of algae.

Find out more!

Water Temperature

With global temperatures on the rise, water temperature (particularly annual maximum temperatures) will be a crucially important indicator of watershed health moving forward. Water temperature is strongly correlated with a number of other important indicators of ecological status, and can often help to explain, give context to, or even predict changes in habitat quality.

Find out more!

Dissolved Oxygen

Dissolved oxygen (DO) is the concentration of free oxygen in the water column and comes from aquatic plants and algae through photosynthesis, and can also be transferred from the air at the surface of the water. DO is essential for all aquatic life and for the decomposition of organic waste. The amount of available oxygen in the water column is also affected by several abiotic factors including temperature, salinity, pressure and depth, wind, flow, and wave action.

Find out more!

Chlorophyll-a

Chlorophyll-a is used in oxygenic photosynthesis and is the predominant form of chlorophyll in green plants and algae. Measuring the presence of chlorophyll-a in an aquatic environment allows for a better understanding of the density and prevalence of algae which can have an impact on the concentration of dissolved oxygen or likeliness of algal blooms.

Find out more!

Total Phosphorus

Phosphorus is a fundamental building block of life. It has key structural roles in genetic material (eg. DNA) and cellular membranes, and is an active component of cellular energy production, storage, and transfer, meaning many necessary biochemical processes that all living organisms rely on (such as respiration, and nutrient absorption) can only happen if phosphorus is available.

Find out more!

Riparian Connectivity

Natural, vegetated riparian areas, the unique, transitional space between aquatic and terrestrial ecosystems, provide numerous benefits including nearshore habitat, filtering runoff, moderating local temperatures, and stabilizing shorelines. Measuring riparian connectivity can provide important information on the health of a watershed and a better understanding of the resilience to threats these areas have compared to shorelines that have been developed.

Find out more!

Combined Sewer Overflows

Everytime there is a Combined Sewer Overflow, sewage, along with stormwater is released into a waterbody introducing pollutants, pathogens and excess organic waste. Untreated or inadequately treated sewage poses health risks for people who use the water for recreational activities, such as swimming, paddling, etc. It also impacts aquatic ecosystems as the presence of organic matter, and its decomposition, decreases the amount of dissolved oxygen available.

Find out more!

Change in Land Use

Land use is a classification for all the various ways an area of land be used and includes agriculture, urban, roads, natural and harvested forests, wetlands and protected areas. Changes in land use have implications for both the quantity and quality of water introduced to the river through runoff and can help analyse changes in other indicators in proximity to where land use changes have occurred.

Find out more!

Benthic Invertebrates

Benthic invertebrates are the organisms found in soils, rocks and organic materials that make up stream, river, and lake beds. Pollution tolerance varies greatly between different species, so the relative abundances of pollution-sensitive and pollution-tolerant benthic invertebrate species is a good indicator of water quality and ecosystem health.

Find out more!

Invasive Species

Invasive species are non-native species that have been introduced to a habitat and are able to outcompete native species. Invasive species disrupt the established ecosystem which can result in a decrease in habitat quality and health.

Find out more!

Fish Richness

Fish richness is a measure of how many different species of fish are present in an ecosystem or habitat. Generally speaking, higher species richness is better, but some confounding factors include habitat type and the presence of invasive species (which can increase richness while threatening ecosystem health).

Find out more!

Water Mercury

Mercury is highly toxic, but naturally occurring concentrations of it are bound by plants and sediment and removed from the water column. However, human activity introduces excess mercury, resulting in free mercury in the water column. Water mercury is therefore a useful indication of human impact on the watershed.

Find out more!

Ice On/Off

Ice on is the date when a body of water is fully covered by ice, and ice off is the date when the ice disappears from the water surface. These measurements provide information about several environmental conditions, such as air temperature, water temperature, and flow.

Find out more!

Further resources:

Blogs:

6 things you should know about the 2019 Flooding (June 2019) There has been a lot of talk about how much water was in our watershed this year. But where did it all come from? How has this contributed to the flooding?