Influence of Natural Cover and Land Use on Water Quality and Quantity

A glass of water on a table outdoors.

Five-part Series Highlighting the Top Stories of the Watershed Plan

The first phase of the Watershed Plan characterizes the health of the Credit River Watershed and how it has changed from the 1950s to today.

This newsletter dives into our third story: the influence of natural cover and land use on water quality and quantity in stream and groundwater ecosystems.

Our data show:

  • We are not meeting the targets for natural cover
  • Urban cover has increased
  • Land use practices continue to impact the quality and quantity of water across the watershed

The Role of Natural Cover

The amount of natural cover influences water resource systems. When it rains, plants and soil in forests and wetlands absorb and store water. This helps to reduce the risk of flooding in surrounding areas. Forests and wetlands also act as filters by cleaning water as it seeps into the ground.

Natural cover in the watershed has declined over the last two centuries. In the 1800s, the Credit River Watershed was mostly covered by forests and wetlands. Today, the percentage of urban, agricultural and natural cover in the watershed is almost equally split.

The Impacts of Land Use on Water Quality and Quantity

The way water moves across the watershed and into receiving streams, forests, wetlands and lakes is related to three factors:

  • How much natural cover remains
  • How much of the landscape is covered by paved surfaces
  • Other types of land uses

Areas that have a lot of paved surfaces such as roads and parking lots, especially in rapidly urbanizing areas of the watershed, are more likely to have degraded ecological health. Some land use practices are also more likely to introduce pollutants to the environment.

Our data show that changes to natural cover and land use leads to:

Increasing Chloride Concentrations in Streams and Groundwater

A salt truck applying salt on a snow covered road.
Salt is applied to roads in winter.

Paved surfaces result in stormwater runoff after a rainfall. Runoff washes chlorides from road salt into our streams and groundwater. Although road salts are the biggest source of chlorides in the watershed, water softeners can also be a source of chlorides.

We’re seeing an increase in chloride concentrations in streams and groundwater since the early 2000s. Chloride is toxic to aquatic life, but elevated concentrations are also a concern for human health and infrastructure. High chloride concentrations can damage pipes, buildings and roads.

High Total Phosphorus Concentrations

A stream with thick mats of algae.
An algae bloom in a stream.

Phosphorous concentrations have decreased by 15 per cent since 2000. This is a result of banning phosphates in detergents in the 1970s, as well as improving technologies at wastewater treatment plants. However, the amount of total phosphorus in streams exceeds the Provincial Water Quality Objective for aquatic health.

Runoff containing fertilizers and sediment from soil erosion are sources of phosphorus. Phosphorus is important for plant growth, but too much can cause excessive algae growth in streams. Algal blooms can deplete oxygen levels, making them less suitable for fish and other aquatic wildlife.

Increasing Streamflows and Erosion

A river flowing through a forested area.
Credit River at Forks of the Credit.

Our data show that average and low streamflows are increasing across the watershed. Streamflow trends are influenced by factors such as increasing stormwater runoff in urban areas and water discharging into streams from wastewater treatment plants.

Streamflow increases can cause erosion of stream channels, making them unstable. While erosion is a natural process, it can be hazardous to people and property when it occurs quickly. These changes can also negatively impact the health of aquatic habitats by increasing the amount of sediment in the water.

Declining Groundwater Levels

A person checking a groundwater level logger next to a field.
Staff checking a groundwater logger to determine how well it is measuring groundwater levels.

We have observed declines in groundwater levels at wells across the watershed. Paved surfaces prevent rain and snowmelt from soaking into the ground. This reduces the ability of aquifers, which store water underground, to recharge and continue to provide water over the long term.

Declines in groundwater can also be the result of weather events such as drought, increased water taking for drinking and crop irrigation, and dewatering from new or expanded aggregate pits and quarries.

Ways to Improve Water Quality and Quantity

Learn more ways to protect water quality and quantity on your property and in your community. To learn more about the Watershed Plan, visit

By Shanice Badior, Coordinator, Watershed Plans and Analytics

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