IRRIGATION INVESTIGATIONS 



THE LOWER SANTA CRUZ VALLEY 



The investigations started previously in the Casa Grande 

 Valley have been continued during the past year. The surface 

 waters have been measured at Tucson and Sasco, and in part at 

 points farther west, but the measurements of seepage losses have 

 not confirmed those of the previous year as could have been ex- 

 pected. Water table fluctuations, including the special observations 

 in the vicinity of active pumping plants, have been confirmatory of 

 those previously reported. 



Fig. 12. — Section acr 



os.s Santa Cruz Valley at the point of the Tucson Mountains, 

 seventeen miles northwest of Tucson 



The drilling of an almost dry well at Rillito has led to special 

 study of that locality. The well, that of Dr. Mark R. Smith, is 

 just on the edge of the Recent valley fill and consequently it was 

 drilled wholly in Pleistocene deposits. These deposits, like those 

 of the Rillito Valley,* have been so altered by cementation and by 

 decomposition of feldspathic grains that they are quite impervious. 

 The important economic effect of this change is that the area of 

 good water-bearing strata from Rillito southward is confined to the 

 immediate river valley, and only rarely can it be expected that good 

 wells will be found outside of this area. The nearby wells of Pruild 

 Bros, and Henry Proctor are among the best in Arizona. A cross- 

 section of this part of the valley is shown in Fig. 12, and the logs 



»Ariz. Agr. Exp. St a. Bui. No. «). pp. ir,r,-lCO. 



