What impact does impervious cover have on water quality?

What impact does impervious cover have on water quality?

• A. It reduces runoff and filters pollutants.
• B. It has no impact on water quality.
• C. It decreases pollutant concentrations by absorbing pollutants.
• D. It increases runoff volume and velocity, causing higher sediment and phosphorus levels.

Answer: (D)

Impervious cover, like pavement and rooftops, prevents rainfall from soaking into the soil. That forces more water to run off quickly, increasing both the amount of water entering streams and the speed at which it moves. The higher volume and faster flow scours streams and transports more sediment and associated pollutants, including phosphorus, into waterways. This leads to higher sediment loads and nutrient levels, degrading water quality. So the description that matches this effect is: increasing runoff volume and velocity, causing higher sediment and phosphorus levels. The other statements don’t fit because impervious surfaces do not reduce runoff or filter pollutants, they don’t absorb pollutants to lower concentrations, and there is a real impact on water quality from impervious cover.

Impervious cover, like pavement and rooftops, prevents rainfall from soaking into the soil. That forces more water to run off quickly, increasing both the amount of water entering streams and the speed at which it moves. The higher volume and faster flow scours streams and transports more sediment and associated pollutants, including phosphorus, into waterways. This leads to higher sediment loads and nutrient levels, degrading water quality. So the description that matches this effect is: increasing runoff volume and velocity, causing higher sediment and phosphorus levels. The other statements don’t fit because impervious surfaces do not reduce runoff or filter pollutants, they don’t absorb pollutants to lower concentrations, and there is a real impact on water quality from impervious cover.