At least 135 rock falls have occurred from Glacier Point in Yosemite Valley since 1870. Rock falls in 1996 and 1998–1999 led to hypotheses that these events were triggered by water system discharges from visitor facilities (leachfield and storage tank overflows, respectively). Geological and hydrological data indicate that water system discharges are highly unlikely triggers. Evidence for hypothesized discontinuities that might connect water system discharge points to rock fall sources is equivocal; even if such features exist, they are intercepted by numerous cross-cutting discontinuities, including large regional fractures that direct surface and shallow groundwater away from rock fall sources. The seasonal timing of rock falls does not support water system triggering because summertime rock falls are common throughout Yosemite Valley. When all data are evaluated, rock fall timing does not correlate with water system discharges. Natural sources of infiltration at Glacier Point vastly exceed water system discharges; watershed analyses demonstrate that at the time of the 1996 and 1999 rock falls, volumes of natural water available for infiltration were 30 to 100 times greater than water system discharge volumes. Precipitation on upslope rock faces is likely the source of seepage observed at rock fall source areas, and exfoliation joints are present there to transmit this water. We conclude that the Glacier Point rock falls of 1996 and 1998–1999 were due to natural processes unrelated to water system discharges.