Final answer:
Variable factors that affect a river's regime include reservoir and dam operations, abiotic features that change along the river's length, and habitat destruction through land development and damming.
Step-by-step explanation:
The variable factors that affect a river's regime include:
- Reservoir and dam operations: Changes in water temperatures, chemistry, flow characteristics, and silt loads can significantly impact the ecology and physical characteristics of the river upstream and downstream.
- Abiotic features: Along the length of a river, abiotic features such as temperature, nutrient availability, water flow speed, and channel width can vary. The source water is usually cold, low in nutrients, and clear, while the downstream regions have wider channels, slower currents, higher temperatures, and increased silt deposition.
- Habitat destruction: Land development, damming, and water removal can modify rivers and streams, affecting flow regimes and access to habitat. These changes can lead to population declines and extinction of species adapted to specific flow patterns and habitats.