84 CONSERVATION OF GROUND WATER 



hundred ground-water reservoirs have been listed, and in only 

 three of those is the draft from wells considered to be close to 

 the average natural replenishment. In several others perhaps 

 half to two-thirds of the available water resources are now be- 

 ing utilized, but most of these ground-water reservoirs are still 

 practically undeveloped. Nevada has a number of undevel- 

 oped valleys of varying potentialities, and the state engineer 

 in cooperation with the Federal Geological Survey and Soil 

 Conservation Service has a comprehensive program under way 

 to delineate the areas where ample water resources and 

 suitable lands are available for development. 



Perennial streams drain several of the valleys in which there 

 is substantial draft on ground water by native vegetation. The 

 Safford Valley along the Gila River in Arizona is noteworthy 

 because of the heavy losses by evapotranspiration, but most 

 ground-water reservoirs along major streams furnish water for 

 substantial evapotranspiration, as well as for some of the 

 stream flow. Attempts to recover and utilize the water now 

 lost to native vegetation may cause a depletion in stream flow 

 and thus infringe upon the rights of downstream users, even 

 though there is an increase in the total water put to beneficial 

 use. Maximum utilization of water resources in these places 

 requires fairly complete knowledge of the relationship be- 

 tween ground water and surface water. These problems are 

 discussed further in the section on Watercourses. 



Safford Valley of Gila River Basin, Ariz. 2 * Water was 

 diverted from the Gila River for irrigation in Safford Val- 

 ley as early as 1872. Land irrigated from the river, based on 

 diversion rights of 1 second-foot for each 80 acres, increased 

 to 16,000 acres by 1890 and to 32,500 acres by 1920, after 

 which no further diversion rights were granted. Pumping 



28 References: Gatewood, J. S., et al., Use of Water by Bottom-land Vegeta- 

 tion in Lower Safford Valley, Arizona, U.S. Geol. Survey 

 Water Supply Paper 1103, 1950, 210 pp. 

 Turner, S. F., et al., "Ground-water Resources and Problems 

 of the Safford Basin, Arizona," U.S. Geol. Survey, Mimeo. 

 rept., December 1946, 28 pp. 



