Urban runoff
Water running off impervious surfaces in urban areas tends to pick up gasoline, motor oil, heavy metals, trash, and other pollutants from roadways and parking lots, as well as fertilizers and pesticides from lawns.
Roads and parking lots are major sources of polycyclic aromatic hydrocarbons (PAHs), which are created as the byproducts of the combustion of gasoline and other fossil fuels, as well as of the heavy metals nickel, copper, zinc, cadmium, and lead.
This reduction of reservoir capacities can lead to increased expenses for public land agencies while also impacting the quality of water recreational areas.
[9][clarification needed] Overwatering through irrigation by sprinkler may produce runoff reaching receiving waters during low flow conditions.
[15] One of the most pronounced effects of urban runoff is on watercourses that historically contained little or no water during dry weather periods (often called ephemeral streams).
As an example, on many Southern California beaches at the mouth of a waterway, urban runoff carries trash, pollutants, excessive silt, and other wastes, and can pose moderate to severe health hazards.
After heavy rains, organic matter in the waterway is relatively high compared with natural levels, spurring growth of algae blooms that soon consume most of the oxygen.
[16] Such a project may stabilize the immediate area where flood damage occurred, but often it simply shifts the problem to an upstream or downstream segment of the stream.
There are many different ways that polluted urban runoff could harm humans, such as by contaminating drinking water, disrupting food sources and even causing parts of beaches to be closed off due to a risk of illness.
[18] Pollution prevention practices include low impact development (LID) or green infrastructure techniques - known as Sustainable Drainage Systems (SuDS) in the UK, and Water-Sensitive Urban Design (WSUD) in Australia and the Middle East - such as the installation of green roofs and improved chemical handling (e.g. management of motor fuels & oil, fertilizers, pesticides and roadway deicers).
[20][21] Providing effective urban runoff solutions often requires proper city programs that take into account the needs and differences of the community.
Human factors such as urbanization rates, land use trends, and chosen building materials for impervious surfaces often exacerbate these issues.
Street sweeping vacuums collect particles of dust and suspended solids often found in public parking lots and roads that often end up in runoff.
Creating a productive discussion on urban runoff and the importance of effective disposal of household items can help to encourage environmentally friendly practices at a reduced cost to the city and local economy.
Stormwater harvesting projects often have multiple objectives, such as reducing contaminated runoff to sensitive waters, promoting groundwater recharge, and non-potable applications such as toilet flushing and irrigation.
