Correct Answer - Option 1 : Regulated reservoir
A spillway is located at the top of the reservoir pool. Dams may also have bottom outlets with valves or gates which may be operated to release flood flow, and a few dams lack overflow spillways and rely entirely on bottom outlets.
The two main types of spillways are controlled and uncontrolled.
A controlled spillway has mechanical structures or gates to regulate the rate of flow. This design allows nearly the full height of the dam to be used for water storage year-round, and flood waters can be released as required by opening one or more gates.
An uncontrolled spillway, in contrast, does not have gates; when the water rises above the lip or crest of the spillway, it begins to be released from the reservoir. The rate of discharge is controlled only by the depth of water above the reservoir's spillway. The fraction of storage volume in the reservoir above the spillway crest can only be used for the temporary storage of floodwater; it cannot be used as water supply storage because it sits higher than the dam can retain it.