Question

You notice that the water level flowing in a stream near your house increases when it rains, and the water turns brown. Which of these are the best hypothesis to explain why the water turns brown?

a) Increased sediment runoff during rainstorms
b) Chemical reaction with rainwater
c) Algae growth due to rainwater nutrients
d) Higher water temperature during rain

Answer 1

The water in the stream turns brown when it rains due to increased sediment runoff during rainstorms and the growth of algae.

Step-by-step explanation:

The best hypothesis to explain why the water in the stream turns brown when it rains is increased sediment runoff during rainstorms (a). Sediment runoff occurs when rainwater washes over the land and carries loose particles, such as soil and dirt, into the stream. These particles can cause the water to appear brown or muddy. This is supported by the information that faster-moving water in headwater streams is clear, while the water becomes brown as it flows away from the source and slows down.

Additionally, the given information mentions that when trees and plants border the water, the leaves and other organic material that fall into the stream decompose, releasing organic material and nutrients into the water. This organic material can support the growth of algae, which may also contribute to the brown color of the water (c).