Summary of Precipitation at Saguaro National Park (2000-2010)

Rojas, Rafael; Swann, Don; Alvarez, Tiffany

This report reports on the amount of precipitation recorded at four locations in Saguaro National Park: the Tucson Mountain District (TMD) Visitor Center, Rincon Mountain District (RMD) Visitor Center, Rincon Creek (on the southern boundary of RMD) and Manning Cabin, at 8,000 feet elevation in RMD. The data have been analyzed for four categories of interest (annual, monsoon, winter, and average monthly) for each location so that readers can easily compare them. There is little past information on precipitation at Saguaro National Park. Although precipitation data have probably been gathered throughout the history of the park, to our knowledge they have not been collected or analyzed in any consistent or systematic way. The only known published dataset is in Ecology of the Saguaro II (1983) by Steenbergh and Lowe, saguaro researchers who summarized monsoon and annual data in desert areas of the two districts for the period 1968-1976. However, there may be valid data available that we do not yet know about. Average annual rainfall at the four stations during 2000-2010 was 11.70 inches for the RMD Visitor Center, 11.23 inches for the TMD Visitor Center, 9.93 inches for Rincon Creek, and 20.8 inches for Manning Camp. As expected, the annual rainfall at Manning Camp, at 8,000 feet elevation in the Rincon Mountains, is much greater than at the RMD Visitor Center. However, precipitation recorded at the two visitor centers over the 10-year period is almost identical. This is surprising because it is generally assumed that RMD receives more rain that than TMD due to the lower elevation of TMD. During 1968-1976, Steenbergh and Lowe recorded 12.30 inches at RMD and 10.27 inches at TMD, with much of that being higher monsoon precipitation in the RMD. That the two district averages are similar may simply reflect specific rainfall patterns during the past decade. It is noteworthy, however, that the published data from the TMD station (http://www.wrh.noaa.gov/twc/climate/seaz_rainfall_normals.php) for the period from 1985 (presumably) through 2000 is 12.53 inches! Our hope is that this report will provide baseline data for precipitation at the park that can be added to and improved in future years.