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 A₁ and A₂ is computed using the following equation:

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

where:

Δ V 12 – The volume between areas A₁ and A₂.

A_i – Surface area i.

h – Vertical distance (E₂-E₁) between surface areas A₁ and A₂.

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