Understanding the Question
The question is asking about the behavior of the outflow hydrograph in reservoirs with an uncontrolled spillway in relation to the inflow hydrograph. The options provided are related to the position and magnitude of the peak of the outflow hydrograph.

Uncontrolled Spillway
- An uncontrolled spillway is a type of overflow structure in a reservoir that allows excess water to flow out when the water level exceeds the maximum capacity of the reservoir.
- Unlike controlled spillways, which can be regulated, uncontrolled spillways do not have gates or valves to control the outflow.

Peak of the Outflow Hydrograph
- The outflow hydrograph represents the discharge of water leaving the reservoir through the uncontrolled spillway.
- The peak of the outflow hydrograph is the point of maximum discharge during a given period.
- This peak represents the maximum amount of water that can be released from the reservoir through the spillway.

Peak Position in Relation to Inflow Hydrograph
- The inflow hydrograph represents the inflow of water into the reservoir during a given period.
- The peak of the inflow hydrograph is the point of maximum inflow into the reservoir.
- In reservoirs with an uncontrolled spillway, the peak of the outflow hydrograph is expected to occur at a later time than the peak of the inflow hydrograph.
- This is because it takes time for the water to fill up the reservoir and reach the spillway level before it can start flowing out through the spillway.
- Therefore, the peak of the outflow hydrograph lies on the recession limb of the plotted inflow hydrograph.

Explanation of the Correct Answer
The correct answer is option B, which states that the peak of the plotted outflow hydrograph lies on the recession limb of the plotted inflow hydrograph. This means that the outflow hydrograph peak occurs after the peak of the inflow hydrograph, as explained above.

Other Options
- Option A states that the peak of the outflow hydrograph lies outside the plotted inflow hydrograph. This is incorrect because the outflow hydrograph is directly related to the inflow hydrograph and is expected to occur after the inflow peak.
- Option C states that the peak of the outflow hydrograph lies on the peak of the inflow hydrograph. This is incorrect because the outflow peak occurs after the inflow peak, as explained above.
- Option D states that the peak of the outflow hydrograph is higher than the peak of the plotted inflow hydrograph. This is incorrect because the magnitude of the outflow peak is dependent on the inflow peak and other factors, and it can be lower or higher than the inflow peak.