WMS:Storage Capacity Curves

There are three different methods for defining storage capacity: volume vs. elevation, area vs. elevation, and known geometry.

In all three cases a relationship between elevation and volume will be computed. For the volume vs. elevation option this is explicitly defined. If area vs. elevation is specified, then a corresponding volume for each elevation is computed using the conic method. The conic method is illustrated below.

The volume between incremental areas $A_{1}$ and $A_{2}$ is computed using the following equation:

$\Delta V12={\frac {h}{3}}(A_{1}+A_{2}+{\sqrt {A_{1}A_{2}}})$

where:

$\Delta V12$ – The volume between areas $A_{1}$ and $A_{2}$.

$A_{i}$ – surface area $i$.

$h$ – vertical distance $(E_{2}-E_{1})$ between surface areas $A_{1}$ and $A_{2}$.

$E_{i}$ – elevation of surface area $i$.

The same equation is used to compute the volume between each adjacent set of surface areas, with the bottom area assumed to be 0. A TIN can be used to automatically create and store for use in the detention basin calculator the elevation-volume relationship.

If the basin geometry option is chosen then an elevation vs. volume relationship is computed directly from the geometry defined for the basin.

Related Topics

• Detention Basin Calculator
• Elevation Discharge Relationship