A general expression for basin lag time

Basin lag time is an important variable in the calculation of peak discharge resulting from a specified precipitation input. For the case of ungauged basins, the lag time must be estimated, normally from one or more expressions relating lag time to basin physical characteristics. A number of such expressions exist but each was developed for a particular range of basin size and geographic region. To overcome the problem of using an expression that may not be appropriate, a tentative general expression for basin lag time has been developed using data from basins representative of many regions in North America and ranging in area from 0.5 ha to 5840 km2. The tentative expression has only one basin characteristic, basin length divided by the square root of basin slope, , and applies to natural basins with minimal effective lake and swamp storage. When more data become available, the expression will be modified to include the effects of urban development and significant storage. Key words: lag time, peak disch...