In rainfall-runoff modeling, what is the unit hydrograph used for?

In rainfall-runoff modeling, what is the unit hydrograph used for?

• A. It is convolved with actual rainfall to simulate runoff.
• B. It predicts rainfall depth.
• C. It estimates evaporation.
• D. It measures soil moisture.

Answer: (B)

A unit hydrograph acts as a discharge response function for a watershed. It represents how outlet flow responds to a unit amount of effective (rainfall excess) rainfall over a chosen duration. In rainfall-runoff modeling, you use this function by convolving the unit hydrograph with the rainfall excess over time to produce the runoff hydrograph—the predicted discharge at the outlet. This is about transforming rainfall into runoff, not predicting rainfall depth, estimating evaporation, or measuring soil moisture. Rainfall depth is the input input need, while evaporation and soil moisture are related to losses and storage, not the runoff response function itself.

A unit hydrograph acts as a discharge response function for a watershed. It represents how outlet flow responds to a unit amount of effective (rainfall excess) rainfall over a chosen duration. In rainfall-runoff modeling, you use this function by convolving the unit hydrograph with the rainfall excess over time to produce the runoff hydrograph—the predicted discharge at the outlet. This is about transforming rainfall into runoff, not predicting rainfall depth, estimating evaporation, or measuring soil moisture. Rainfall depth is the input input need, while evaporation and soil moisture are related to losses and storage, not the runoff response function itself.