Where does stormwater go when it runs off my roof or driveway?

In urban areas, stormwater runoff from impervious surfaces flows along the side of the road until it reaches a storm drain, which is an opening or grate in the curb.  From there, the water flows through a series of underground pipes, open channels, or ditches until it reaches the nearest creek or stream.  This water is not treated along the way so any pollutants (oil, trash, fertilizer, pesticides) it may be carrying are deposited directly into our local creeks and streams and eventually reach Lake Thunderbird. 

Why should I be concerned about stormwater runoff?

Stormwater runoff can carry pollution from impervious surfaces to nearby creeks and streams through the storm sewer system.  Any pollutant exposed to stormwater is at risk of being washed into storm drains and carried to local waters that we use for drinking water and/or recreation, like Lake Thunderbird.

In addition to the potential to pollute our creeks and streams, increased volumes of stormwater runoff from impervious surfaces can lead to flooding.  As we add houses, driveways, roadways, and parking lots, the areas where water can soak into the ground decreases.  As a result, the volume of water that runs off these areas increases.  During heavy rainfall events, storm sewer systems can be overwhelmed by this volume and result in flooding of low-lying areas.  

What is a TMDL?

A Total Maximum Daily Load or TMDL is a calculation of the maximum amount of a pollutant a waterbody can receive and still meet water quality standards.  A TMDL is developed after a waterbody is found to be impaired through water sampling and analysis.  It sets limits on various sources of pollution such as industrial facilities, municipal wastewater treatment plants, or municipal storm sewer systems in an effort to clean up the water and make sure water quality standards are met.  

A TMDL has been developed for the Lake Thunderbird watershed.  The pollutants of concern in this watershed are nitrogen, phosphorus, and sediment.  Nitrogen and phosphorus comes from fertilizers and pet waste.  Sediment comes from construction sites, agricultural practices, and streambank erosion.  We will all have to work together to reduce the amount of these pollutants being discharged to Lake Thunderbird by reducing the amount of fertilizer we use, picking up after our pets, and ensuring that our septic systems are properly maintained.

What is a watershed?

A watershed is an area of land that catches and drains water into a creek, stream, or lake. Everyone lives, works, and plays in a watershed.  That means that everything you do has the potential to affect our water quality.   

Facts about Lake Thunderbird and its watershed:

• Construction began on the lake in 1962 and was completed in the 1965. 

• It was built by the Bureau of Reclamation to provide drinking water to Del City, Midwest City, and Norman.

• Norman is the only member of the LTWP that both contributes stormwater to and consumes water from Lake Thunderbird.  In other words, Norman residents drink our stormwater.

• Designated as a Sensitive Water Supply lake by the State of Oklahoma in 2002.

• Listed on the Oklahoma Department of Environmental Quality (ODEQ) 2008 303(d) list, which lists the waterbodies in the state that don’t meet water quality standards. 

• Sediment and nutrients, like nitrogen and phosphorus, are the pollutants causing the impairment.

• In 2013, ODEQ established a Total Maximum Daily Load (TMDL) for the lake in an effort to improve water quality.

What is LID?

Low Impact Development, or LID, is an approach to land development (or re-development) that works with nature, mimicking its processes, to manage stormwater as close to where it falls as possible. This approach seeks to maintain natural site hydrology within the developed arena. It reduces stormwater runoff volumes and improves stormwater quality through infiltration, evaporation, transpiration and storage. LID employs principles such as reducing impervious surfaces to allow water to soak into the ground where it lands, preserving and re-creating natural landscapes, and treating stormwater as a resource instead of a waste product. When holistically applied throughout a watershed, LID can even greatly reduce the damage caused by flooding.

Examples include:

• Rain water harvesting with rain barrels or cisterns to allow reuse of stormwater;

• Commercial and residential rain gardens or bioretention which capture, soak in and treat stormwater;

• Green roofs which can provide habitat and reduce the heat island effect;

• Pervious pavers, concrete and asphalt which allows stormwater to infiltrate into the subsoil; and,

• Green parking which can include pervious pavement, bioswales, rain gardens, and narrower spaces.

What is the issue?

The natural hydrologic cycle is dramatically changed when land is developed in the usual way. That is because vegetation is removed, soils are compacted, and impervious surfaces like roads, parking lots and roofs are installed. Unlike in natural, undeveloped areas where stormwater is primarily captured by plants and soil, in developed areas, impervious surfaces stop infiltration and lead to increased runoff which, in turn, leads to flooding and pollution. Conventional stormwater infrastructure is designed to get that water out of the way and to the streams as quickly as possible to try to lessen the local impact of flooding. Of course, these measures do not stop flooding completely and add to downstream fish and wildlife habitat loss, as well as increase the amount of pollutants discharged into waterways. Low Impact Development (LID) reduces runoff volumes and improves stormwater quality. 

What can I do to help?

• Install a rain barrel which promotes conservation and saves money on water bills by storing stormwater for later use for irrigation, car washing, and other activities;

• Install a rain garden in a low area that will capture stormwater runoff from your property to be stored and treated by native plants;

• Direct water from your downspouts away from hard surfaces and onto landscaped areas or into areas that will disperse its energy; 

• Use pervious pavers, concrete or asphalt when installing a driveway, patio or sidewalk, so that the stormwater will infiltrate instead of runoff; and,

• Talk to your neighbors or neighborhood association to discuss installing neighborhood-sized features.