448 Thirtieth Annual Report 



The U. S. Indian Service, through the agency of an employee, 

 has been keeping flood data at Cockleburr for several years. During 

 1919 there were three summer floods and one winter flood. It is 

 estimated from the records that not over 6,000 acre-feet entered the 

 valley and from records taken at the railroad culverts it is thought 

 that about one-sixth of this amount passed the railroad. 



Water table fluctuations have been greatest along the north 

 margin of the valley, representing the extensive recharge due to 

 floods in the Gila River. Considerable variations of water level 

 have been found in the vicinity of areas irrgated by flood waters 

 from the Gila, and some effects noted have been due to seepage 

 froin the Florence Canal. Some erratic fluctuations of the water 

 table west of Casa Grande can be explained by the character of 

 the buried topography, which includes a long flat hill of volcanic 

 rock. 



The depression of the water table due to pumping operations 

 has been most marked between Casa Grande and the Casa Grande 

 Ruins, the greatest being near the Tweedy and W. S. Prouty 

 ranches. The average depression for the season was about one 

 foot. The recovery during the fall and winter has been complete 

 over about two-thirds of the area of depression. 



A group of water-table records is shown in Fig. 4. The Vas- 

 quez well is situated about three miles south of Casa Grande, the 

 Elliott well two miles west of Casa Grande, the Ward well just 

 below the Florence reservoir, the Bigelow well near the center 

 of the main pumping area, and the Munk well a mile south of the 

 Gila River. 



Some determinations of the quality of the well waters have 

 been made for comparison with former records. In some cases the 

 alkalinity has changed slightly, but in general the composition of 

 the soluble contents has remained practically constant. 



Progress has been made on the negotiations with the United 

 States Department of the Interior with a view to storing and 

 utilizing the floodwaters of the Gila River. It is hoped that the 

 project of the United States Indian Service for building a diversion 

 dam at Sacaton will be abandoned in favor of the pro])osed diver- 

 sion dam fourteen miles upstream from Florence. The Sacaton 

 dam would be very costly, would be difflcult to maintain, and 

 would serve a comparatively small acreage. The Florence dam 

 would be only one-fifth as long as the Sacaton dam, would be tied 

 to bedrock except for about 200 feet in mid-channel, and would 

 serve the lands of both Indian and American farmers equally well. 



