Seepage investigations were conducted annually by the U.S. Geological Survey from 1988 to 1998 and from 2004 to 2013 along a 64-mile reach of the Rio Grande from below Leasburg Dam, Leasburg, New Mexico, to above American Dam, El Paso, Texas, as part of the Mesilla Basin monitoring program. Results of studies conducted from 2006 to 2013 are presented in this report. Seepage investigations were conducted over a period of 1-2 days in February of each year, during low-flow conditions in the non-irrigation season.