WATER LOSSES FROM WET AREAS 35 



at iutervals. The station is protected from intrusion by a high wire 

 fence with a gate, which is kept locked. 



METEOROLOGICAL RECORDS 



The three experiment stations just described are spaced at nearly 

 equal intervals of about 25 miles along the Santa Ana River. While 

 the distances between the stations are not great, the topography of the 

 area is such as to cause material differences in climate. The Santa 

 Ana River Valley is divided into two distinct basins, known as the 

 upper and lower, connected by the lower Santa Ana canyon. The 

 Santa Ana station lies on the coastal plain of Orange County below 

 the canyon and has a distinctly coastal climate characterized by ocean 

 breezes and light summer fogs, both of which modify the summer tem- 

 peratures. The Prado station, in Prado basin, Riverside County, is 

 in the lower part of the upper basin at the upper end of the canyon. 

 It is slightly remote from the coast but not far enough away to be 

 removed entirely beyond the effect of the coastal breeze. The principal 

 difference is the absence of coastal fog, with some increase in tempera- 

 ture. The San Bernardino station, San Bernardino County, in the 

 upper basin, is removed farther from the effect of ocean modifying 

 influences. The climate is classed as interior and the temperature is 

 higher in summer than at either of the other two stations. 



The prevailing winds are from the southwest, off the ocean, and 

 pass through the Santa Ana canyon by the Prado station. The total 

 yearly wind movements here and at Santa Ana are about equal, but 

 during the summer months the greatest movement occurs at Prado. 

 This condition combined M'ith higher summer temperature results in 

 a higher rate of evaporation than at the other stations. 



Rainfall is deficient throughout the whole of the Santa Ana River 

 basin except in the higher mountain districts, and occurs almost entirely 

 between November and April, inclusive. Other months are almost 

 devoid of precipitation. 



Meteorological data for the three stations for the period of the 

 investigation, showing monthly mean maximum, mean minimum and 

 mean temperatures, rainfall, and wind movement in miles per month 

 are given in Tables 1 to 3, inclusive. Rainfall at Santa Ana and San 

 Bernardino is shown for storm periods in Tables 4 and 5. 



