Surface water, or rainwater is essential to all life. Contaminated by man, pollutants can cause health problems. Surface water* affects ground water through infiltration. Many cities and towns draw their drinking water from surface and ground water. Once the ground water strata (aquifer) becomes contaminated with pollutants (chemicals) it becomes useless for years.
*Surface water includes springs, creeks, streams, rivers, ponds and lakes.
If you see a sheen or a rainbow on surface water you should suspect a hazardous liquid or chemical has impacted or polluted that body of water. This applies to a bucket, a drum, a tank or larger body of water. Both flowing or non-flowing.