Stressed: Tree loss harms water
Deforestation is having an impact on drinking water in the area, where quality ranges from “excellent” to “very poor,” and shrinking forest cover has contributed to “stressed” conditions in the South Nation River watershed.
Areas where surface water quality is poor typically have low forest cover along the banks of rivers, leading to a loss of filtration, erosion control and habitat, the South Nation Conservation Authority notes in its State of the Nation Watershed Report Card.
Groundwater, which is found in underground aquifers, is an important and vital natural resource, since it provides drinking water to more than 95 per cent of the rural population within the SNC’s jurisdiction.
“We rely on nature for multiple benefits for both a healthy, productive environment and healthy people,” says Katherine Watson, SNC’s Water Resources Specialist.
The elimination of trees along water courses has led to increased sedimentation.
Environment and Climate Change Canada recommends that 75 per cent of stream length be naturally vegetated on both sides (i.e. the riparian area). In the watershed, the riparian cover is poor. “At only 22 per cent, our programs and projects need to take a renewed focus on increasing riparian cover,” cautioned Ms. Watson.
Total forest cover in the SNC jurisdiction is “good,” estimated at 28 per cent in 2014, with forest cover being the lowest in the central region of the basin.
Environment and Climate Change Canada recommends a minimum 30 per cent forest cover to help reduce flooding and erosion, filter air and water, provide wildlife habitat, and support aquatic systems at a watershed scale.
While the federal agency recommends ten per cent, forest cover is 8 per cent in the forest interior, the wooded area that is more than 100 metres from a forest’s edge, the habitat that is required by many species for survival.
However, the watershed enjoys a strong wetland cover rating at 17 per cent, providing natural flood management during peak flows and water retention reservoirs during dry weather. “Wetlands also filter pollutants and provide important wildlife habitat,” Ms. Watson noted.
Environment and Climate Change Canada recommends 10 per cent wetland cover.
Wetlands provide natural flood control during peak flows and act as water reservoirs during dry weather. They filter pollutants before they enter streams, provide important habitat for plants and animals, and provide numerous economic, recreation, and aesthetic benefits.
Wetlands include swamps, marshes, fens, and bog habitat.
Encompassing 4,384 square kilometres, the SNC jurisdiction comprises parts of StormontDundas-Glengarry, PrescottRussell, Ottawa, Leeds and Grenville. From headwaters north of Brockville, the South Nation River flows northeast for 175 kilometres, and empties into the Ottawa River near Plantagenet.
Visit nation.on.ca/water/reports/watershed-report-cards to see the full report card.
All over the map
Water quality in the South Nation jurisdiction covers the gamut for a number of reasons.
Phosphorus levels routinely exceed the Provincial Water Quality Objective (0.03 mg/L), while benthic invertebrate communities range from unimpaired to poor (impaired) condition, depending on the location.
Benthic macroinvertebrates are small creatures, such as insects, mollusks and worms, that live in the river. They are very sensitive to pollution and are excellent indicators for water quality and stream health.
Phosphorus is naturally occurring in rivers, but can be elevated due to detergents, fertilizers, and sewage. Too much can result in algae blooms, affecting oxygen levels, and the fish and biota that live there.
Chloride and nitrate concentrations are better than drinking water standards in most wells. Several wells have higher chloride concentrations, which are naturally occurring due to the influence of the Champlain Sea.
Chloride is a naturally occurring element, however, concentrations can be increased in shallow groundwater systems due to human activity, such as road salt, landfills, and septic systems, and in deeper wells it occurs naturally from deposits of the previous Champlain Sea from post-glacial melting and flooding.
Nitrate can naturally occur in rocks and groundwater, however, concentrations can be increased by human activities such as leaky septic systems and application of excessive amounts of fertilizer.
Although wetland cover in the jurisdiction is meeting minimum guidelines, wetlands have been greatly reduced over the last 200 years. Pre-settlement (c.1800) wetland cover estimates for the jurisdiction are at 40 to 50 per cent, largely the result of the last Ice Age.
The Champlain Sea was a temporary inlet of the Atlantic Ocean created by retreating glaciers during the close of the last Ice Age. The best evidence of this former sea is the vast clay plain deposited along the Ottawa and St. Lawrence Rivers. This resulted in distinctive forest types, large wetlands, and associated ecosystems.
The quality of forest cover conditions were measured using Geographic Information Systems (GIS) and aerial imagery from 2014.