Managing Stormwater Quality in Urban Lakes

Stormwater runoff can have serious impacts on the water quality of urban lakes and other receiving water bodies. An innovative technique called Contaminant/Sediment Control (CSC) Filter Systems has been shown to greatly improve water quality by removing stormwater pollutants before they drain into the natural system. These filters have been placed at stormwater outfalls around First Lake in Lower Sackville, Nova Scotia, which has led to significant improvements in the lake's water quality. Check out our latest video, featuring Larry Bell of W.A.T.E.R Research Associates, to see the filters in action!

Bioretention and Rainwater Harvesting

Improving stormwater in urban and rural areas helps to protect the health of rivers, streams and lakes.  Improvements made to an existing building or parking lot are known as a retrofit.  The Ecology Action Centre is currently considering sites within the city of Halifax for a potential stormwater retrofit project.  Learning from retrofit projects in other cities is helpful for developping options for a site in Halifax.


The short video below demonstrates two types of retrofits: a bioretention pond that captures and treats runoff from a large parking lot and rainwater harvested off a roof that is used for irrigating a sportsfield.

Grey water and black water recylcing

Check out our first interview with Shawn Wilkie of Grun-Sol Technologies explaining the basics of grey water and black water recycling. Recycling water is an efficient way to conserve water, save costs and alleviate some of the strain on wastewater systems.

Low Impact Development

Low Impact Development (LID) is an innovative stormwater management approach that aims to replicate a site's predevelopment hydrology by using simple design techniques that impacts of runoff while having a low impact on the environment. LID are cost-effective, site-level BMPs that address runoff close to the source and improve human health, enhance habitat and save municipalities, contractors, developers and homeowners money. Some common examples include downspout disconnection, vegetation plantings and preservation, raingardens, cisterns and sidewalk storage (if you are not familiar with all of these tools, don’t worry, we’ll cover them in upcoming posts!). The LID concept came out of Prince George County, Maryland in the mid 1980’s as a way to address growing environmental and economic costs of urban stormwater runoff. The following objectives and principles come from Maryland’s Department of Environmental Resources Programs and Planning Division document Low-Impact Development Design Strategies: An Integrated Design Approach.

Green Roof at Dalhousie University

LID Runoff Control Objectives:

• minimize disturbance
• preserve and recreate natural landscape features
• reduce effective impervious cover
• increase hydrologic disconnects
• increase drainage flow paths
• enhance off-line storage
• facilitate detention and infiltration opportunities

The Principles of LID are to:

• integrate stormwater management early in site planning activities
• use natural hydrologic functions as the integrating framework
• focus on prevention rather than mitigation
• emphasize simple, nonstructural, low-tech, and low cost methods
• manage as close to the source as possible
• distribute small-scale practices throughout the landscape
• rely on natural features and processes
• create a multifunctional landscape

Stormwater BMPs

The increase in stormwater runoff velocity and volume caused by a high impervious surface cover in urban areas can lead to decreased water quality, increased erosion and damage to homes and infrastructure. Climate change is expected to bring about more frequent and intense precipitation events which will only escalate the problems. So what can be done?

Around the world cities and towns are implementing a range of stormwater best management practices (BMPs) which are control measures to mitigate quality and quantity of runoff. BMPs can be source control measures which are installed on-site, conveyance control measures which manage runoff between the source and output (ie, in sewers and ditches), end of pipe measures which provide mitigation at the end of the conveyance system and general BMPs such as public education and policy development. Specific examples include:

Source controls - rain barrel, porous pavement, green roof, rain garden, lot grading.

Conveyance controls – vegetated swales, pervious pipe systems

End of pipe controls- constructed wetlands, detention/retention facilities, buffer strips

Many of these methods are already being used in Halifax. We will explore each of these tools in more detail to understand how they work and when they should be used. If you can’t wait and need more information now, check out HRM Stormwater Management Guidelines for a detailed description of stormwater BMPs.

Permeable pavers are a great alternative to concrete driveways and parking lots