Chapter 16.1, Problem 1BYL

To determine

The variables that are plotted on a hydrograph and the indication of such graph.

Answer to Problem 1BYL

A hydrograph is a graph that shows the volume of discharge over time. It provides information about a river and the area it drains. The variables plotted in a hydrograph are discharge and time. Discharge (Q) is the volume of water that flows in a given amount of time. It can be calculated by multiplying the cross-sectional area of a stream with the flow velocity of the stream. The variables following a storm are plotted on a hydrograph as shown below:

Explanation of Solution

A hydrograph is a graph that shows the volume of discharge over time. The above hydrograph displays the increased discharge that has decreased over time in response to a storm. The shape of the hydrograph indicates the response of a river to precipitation and thereby provides valuable information regarding a river and the region it drains.

The variables that are plotted in a hydrograph are discharge and time. Discharge is the volume of water that flows in a given amount of time. It has units of cubic meters per second or m³/s. Discharge is calculated by the multiplication of the cross-sectional area of the stream by the velocity of the flow. It is denoted by the letter ‘Q’. The formula for calculating discharge is expressed below:

$\text{Q = Stream depth }\times \text{ Stream width }\times \text{ Stream velocity}$