What is stormwater NZ?

Stormwater NZ is the collective term for water that flows into NZ rivers, lakes, and coastal waters from stormwater infrastructure including pipes, drains, parking lots, and road surfaces. Stormwater NZ is also called runoff or surface runoff. Stormwater NZ is short-term, unplanned, or ‘burst’ flows of water that occur after big rainstorms, but also from smaller, less frequent rainfall and snowmelt.

Stormwater runoff is the runoff from rain, melted snow, and other precipitation that drains off of your property into a stormwater drainage system.

Stormwater NZ is a recently created term to describe the volume of runoff from rainwater, melted snow, and other sources that drains off of your property into a stormwater drainage system (SWDS). The SWDS is typically a pipe (or pipes) that is connected to a larger drainage system, such as a river, lake, or ocean. Stormwater NZ does not include groundwater that is naturally flowing or groundwater that drains off of your property. Stormwater NZ is the total discharge of all stormwater runoff from all sources on a property, including runoff from impervious surfaces.

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It’s called stormwater because it comes from storms, which are short but intense rainstorms.

Stormwater NZ is any runoff that drains off your property or building. Stormwater runoff may come from puddles, gutters, trees, and your lawn, for example. Stormwater NZ is collected in ditches, ponds, lakes, and rivers. It includes rainwater and snow melt as well as pollutants like soil, plant matter, oil, and grease. Stormwater NZ may contain contaminants like pesticides, fertilizers, and bacteria, which can harm plants and animals and affect water quality.

Stormwater runoff is often called “graywater” because it doesn’t look like the water in your water faucet.

Stormwater runoff is water that drains from your home or business after precipitation. Stormwater runoff consists of surface runoff and groundwater. Surface runoff is water that flows over the earth’s surface, like a rainstorm. Groundwater is water that seeps into the ground, such as a puddle after a rainstorm. Stormwater NZ is the portion of stormwater runoff that drains into the nearest natural water body, or into a sewer system.

It’s sometimes called “urban runoff” to include rainwater runoff from other surfaces, such as streets, roofs, and parking lots.

Stormwater runoff is the volume of water that flows over the surface of the earth during a rainstorm. It is the water that drains from pavement, driveways, roofs, yards, and other structures. Stormwater NZ is the portion of stormwater runoff that originates from developed areas, including roads, parking lots, and neighborhoods. Stormwater NZ contains pollutants such as chemicals, oil, and trash that are washed into storm drains and eventually reach the water bodies.

Stormwater runoff is different from sewage water.

Stormwater is the water that flows down drains and gutters after precipitation. Stormwater NZ is the portion of stormwater that is not from sewage (or toilet water).

Sewage water comes from your home and is treated in a sewage treatment system.

Stormwater is water from precipitation that runs off your property during a storm. It may also contain pollutants such as grass clippings, dirt, sand, pesticides, oil, and other contaminants picked up by your lawn. Stormwater is collected in a storm sewer system and sent to a treatment plant. Stormwater NZ is the water that flows into the system after a rain event and before sewage water enters a sewage treatment plant.

Stormwater and sewage water are not the same.

Stormwater is the runoff from rainstorms that flows into a sewer system. It does not include sewage water, which is collected in a separate pipe from toilets and drains. Stormwater runoff is collected by a network of major pipes called combined sewer systems (CSS), which carry stormwater and sewage water to a single treatment plant.


Stormwater is water that flows down a surface, such as a road, pavement, or a pipe. Stormwater includes runoff from precipitation, sewer overflows, and grease, oil, and soap that is washed off of your house or yard. Stormwater NZ is the combined flow of all stormwater from your property and any other properties that drain into the same stormwater system. Stormwater NZ is collected by stormwater drains and then eventually flows into watercourses.