WMS:Overview of Basin Data Equations

Dodson (Dodson & Associates, 1992) compiled several equations from hydrologic publications. WMS has implemented many of these equations and allows you to choose from the ones listed below to automatically compute lag times/times of concentration. Because most of the equations were developed for specific watersheds (e.g. size, land cover etc.) you should consider the assumptions made about a given equation, and try to identify one that used watershed conditions similar to the one you are studying. The following is a list of the equations available in WMS. The SCS also found that for many cases the lag time could be related to the concentration time by the following equation:

$T_{LAG}=0.6\ast T_{c}$

This relationship is always used by WMS to determine lag time when a method for computing time of concentration is chosen, or to compute time of concentration when a method for lag time is chosen. Methods used for lag time begin with “$T_{LAG}=$“ whereas methods used to compute time of concentration begin with “$t_{c}=$“.

Lag Time Based Equations:

Colorado State

Customized

Denver

Eagleson

Espey

Putnam

Riverside County

SCS

Taylor Schwartz

Tulsa District

Time of Concentration Based Equations:

Fort Bend

Kerby

Kirpich

Ramser

Related Topics

• Travel Times from Basin Data
• Travel Times from Map Data
• Assigning an Equation