What does 'river regime' refer to?

River regime describes the annual variation in the flow of a river, which is influenced by factors such as rainfall patterns, snowmelt, and seasonal changes. Understanding river regime is crucial for managing water resources, predicting floods or droughts, and studying the ecological impact of changes in flow. The flow can vary significantly throughout the year, with periods of high and low discharge, allowing for better predictions of how a river will behave over time.

Factors such as climate, geography, and land use contribute to the specifics of a river's regime, which can differ from one river to another. For example, a river in a temperate region may exhibit a distinct flow increase during spring due to snowmelt, while a tropical river might experience changes in flow linked to the rainy season.

The other options, while related to rivers, do not accurately define river regime. Sediment transport pertains to the movement of particles within the river, geological features focus on the physical structure of riverbanks, and types of fish species concern the biological aspects of the river ecosystem. All these aspects are important in their own right but do not encapsulate the concept of river regime.