Why does the USGS use the spelling "gage" instead of "gauge"?

The spelling of “gage” is part of our very rich USGS history. We have used that spelling for over a hundred years.

In 1888, USGS Director John Wesley Powell met a very forward-thinking graduate student named Frederick Haynes Newell. Powell was so impressed that he made Newell the first full-time appointee to the new Irrigation Survey, which was created to investigate the potential for dams and canals in the western United States.

At that time, there were no practical and systematic techniques for obtaining daily streamflow (or discharge) records, so Newell set up a training camp on the Rio Grande River at Embudo, New Mexico. Newell’s Camp of Instruction developed water measurement methods that are widely used by the USGS today. During the next ten years, Newell continued to play an important role in the development of streamflow gaging techniques and methods, and he eventually became the first Chief Hydrographer of the USGS.

Newell is purported to be the person responsible for the adoption of the USGS spelling of “gage” instead of “gauge”. Around 1892, Newell reasoned that “gage” was the proper Saxon spelling before the Norman influence added a 'u'. USGS historian Robert Follansbee speculated that Newell might have also been influenced by the adoption of “gage” in the Standard Dictionary (the first dictionary produced by Funk and Wagnalls).

See pages 28 and 50 of A History of the Water Resources Branch, U.S. Geological Survey: Volume I, From Predecessor Surveys to June 30, 1919.