The study looked at pollution in stormwater runoff in Las Vegas. They found that the first part of the runoff carries a lot of pollutants like dirt and nutrients. This can affect the quality of water in rivers and lakes. The researchers collected samples during big storms and saw that the first bit of runoff had the most pollutants. They found that the amount of rain and the type of pollutants affected how dirty the water was. This information can help make changes to keep our water clean.