Rainfall Records for the Sonoran Desert

Abstract

The scientific investigation of a region from the viewpoint of any branch of modern geography with its numerous ramiifications should include accurate information concerning the climatic conditions. This is particularly true for biological studies in a typically arid region such as the Sonoran Desert of southwestern Arizona, southeastern California, and northwestern Sonora. Here the rainfall, because of its relative scarcity and uncertain distribution, is undoubtedly the most important climatic factor to be considered. It has a profound influence upon the survival and distribution of the various species which constitute the flora and fauna. A record of the rainfall at the Desert Laboratory, Tucson, Arizona, has been kept since its establishment by the Carnegie Institution of Washington in 1903. The following year a raingauge was placed in the foothills of the Santa Catalina Mountains some ten miles distant from the Laboratory. Nunmerous other rainfall stations were established from time to time and were maintained for longer or shorter periods in connection with experimental projects. In 1925, however, an extensive investigation of the rainfall on the Sonoran desert area was begun. The pronounced local nature of the majority of the storms in this region made it essential that as extensive an area as practical be included in the study. Two principal lines of raingauges were established along diverging routes from Tucson and a series of gauges has lbeen concentrated on the grounds of the Laboratory and in the immediate vicinity. The approximate location of most of these rainfall stations is shown by Sykes ('31) on a map of southern Arizona and northern Sonora. Since his publication appeared additional stations have been established. Figure 1 shows the location of the stations for which data are presented in this paper. The series of gauges known as the Libertad line extends in a southwesterly direction from Tucson to Cirio Point, formerly designated as Kino Point, nine miles south of Puerto Libertad, Sonora, on the Gulf of California. The outstanding features of the topography and of the vegetation along the Libertad line have been presented by Shreve ('24). Each gauge has been located at a point which possesses some particular botanic or topographic feature. The,Camino line of gauges follows a route which leaves the Libertad line 24 miles west of Tucson. This route continues on to Ajo, 135 miles west