A Photo Says It Better

The first paragraph in “Challenges to Water Reuse” mentions a “fading, decades-old photo” of a man standing next to a telephone pole marked at different heights to illustrate the land subsidence that has occurred over the decades in the San Joaquin Valley (C&EN, April 25, page 38). That photograph is of U.S. Geological Survey scientist Joseph F. Poland, who literally wrote the book on land subsidence due to groundwater withdrawals (wwwrcamnl.wr.usgs.gov/rgws/Unesco).

USGS continues to study land subsi-dence in California’s Central Valley (usgs.gov/newsroom/article.asp?ID=2300) and elsewhere, using state-of-the art tools, such as Interferometric Synthetic Aperture Radar (InSAR), as described in USGS Fact Sheet 051-00 (pubs.usgs.gov/fs/fs-051-00). And although these tools produce amazing illustrations of the land-surface elevation changes that are the result of groundwater withdrawals, these images don’t have quite the same charm as that old photo of Poland and the telephone pole.

By Lisa D. Olsen
ElkGrove, Calif