Which of the following is a consequence of excessive sediment accumulation in a reservoir?

• A. It increases storage capacity.
• B. It reduces storage capacity, degrades water quality, increases treatment costs, and harms aquatic habitats.
• C. It improves water clarity.
• D. It reduces sediment transport downstream.

Answer: (B)

Excessive sediment accumulation in a reservoir primarily reduces the usable storage space, since sediment fills the volume that previously held water. That loss of storage means less capacity to meet demand during dry periods or to regulate flows, and it also concentrates contaminants and nutrients in the remaining water, leading to degraded water quality and higher turbidity. The combination of reduced storage, tougher and more costly water treatment, and harmed aquatic habitats from sediment smothering and altered flow conditions are the main, direct consequences. This situation does not increase storage capacity or improve water clarity. While a reservoir can trap sediment and thus lessen downstream sediment transport, that effect is separate from the reservoir’s own negative impacts and does not outweigh the broad set of consequences described.