Rainfall Representation – Definition of a Hyetograph In hydrology, a hyetograph is a plot representing which rainfall variable as a function of time?

Introduction / Context:
Effective storm characterization requires understanding not only the total rainfall depth but how it varies with time. The hyetograph is the standard tool for displaying the temporal distribution of rainfall intensity, which strongly influences runoff generation, peak discharge, and infiltration dynamics in catchments.

Given Data / Assumptions:

• Time axis spans the storm duration.
• Vertical axis represents rainfall rate (e.g., mm/h).
• Discrete time steps (e.g., 5-min, 10-min) or continuous curve may be used.

Concept / Approach:

A hyetograph plots intensity versus time, making it straightforward to derive cumulative depth (by integrating intensity over time) and to synchronize with streamflow hydrographs. Distinguish this from related graphs: mass curves (cumulative depth vs time) and IDF curves (intensity vs duration for specified exceedance probabilities).

Step-by-Step Solution:

Verification / Alternative check:

Converting a hyetograph to a mass curve by time-integration should reproduce the measured storm depth; conversely, differentiating a mass curve in time reconstructs the hyetograph.

Why Other Options Are Wrong:

• Volume with time: That is a cumulative or mass curve.
• Intensity with duration: Describes IDF relationships, not a single-storm time plot.
• Intensity over an area: Refers to isohyetal maps, not time series.

Common Pitfalls:

Confusing cumulative depth with instantaneous intensity; mixing time steps, which can distort peak intensities.

Final Answer:

Rainfall intensity with time