Which of the following best describes "downstream"?

"Downstream" refers to the direction in which a stream or river is flowing, indicating the movement of water from higher elevations towards lower ones. This concept is crucial in contexts such as irrigation and water management because it describes how water moves through an ecosystem, impacting areas such as agriculture and natural habitats downstream of its source.

The other options, while relevant to various fields, do not accurately capture the specific meaning of "downstream." The path of goods to consumers pertains more to logistics and supply chain processes, and is not directly related to the flow of water. The process of economic development is a broad concept that encompasses various elements of growth and progress in an economy, which does not relate to the physical flow of water. Lastly, while the environmental impact of water usage is an important consideration, it does not define "downstream" in a geographical sense. Thus, the clear definition pertaining to the flow of water solidifies the choice as the best descriptor for "downstream."