PROBLEMS FROM DEVELOPMENT 151 



along watercourses in disregard of the intimate relation be- 

 tween the ground-water reservoir and the flow of the stream. 

 The Gila River Basin in Arizona and the Rio Grande Basin 

 in New Mexico are examples. 



Safford and Duncan-Virden Valleys, Ariz, and N. Mex. 7i 

 (see also page 84). Since Coolidge Dam was constructed in 

 1928, there never has been enough water to fill the reservoir, 

 and the lands irrigated from that reservoir have experienced 

 perennial shortages of surface water. Upstream from Coo- 

 lidge Reservoir the Gila flows through Safford Valley, and 

 closer to the headwaters, Duncan Valley in Arizona and 

 Virden Valley in New Mexico (the latter two being parts 

 of a single large valley). The ground-water reservoirs of 

 both Safford and Duncan-Virden Valleys are part of the 

 Gila watercourse and are recharged chiefly by irrigation, 

 using water from the stream. In Duncan-Virden Valley 

 ground-water pumpage increased from 1,000 acre-feet in 

 1941 to 27,000 in 1948, and in Safford Valley about 1 10,000 

 acre-feet was pumped in 1948. This pumpage must inevita- 

 bly cause some depletion in the flow of the Gila River be- 

 low Safford Valley. On the other hand, it has been estimated 

 that evapotranspiration loss in Duncan-Virden Valley ex- 

 ceeds 10,000 acre-feet and is of the order of 50,000 acre-feet 

 in Safford Valley. Wherever pumpage from wells has de- 

 pressed the water table sufficiently to reduce these natural 

 losses, some water has been salvaged for beneficial purposes. 



Middle Rio Grande Valley, N. Mex. 75 Albuquerque and 

 some other towns pump water from wells in the alluvium of 

 the Rio Grande Valley for municipal supplies, but for ir- 

 rigation the valley depends almost entirely upon water 



i* Reference: Turner, S. F., et al., "Water Resources of Safford and Duncan- 

 Virden Valleys, Arizona and New Mexico," U.S. Geol. Sur- 

 vey, Mhneo. rept., 1941. 



75 Reference: "Regional Planning. Part IV. The Rio Grande Joint In- 

 vestigation in the Upper Rio Grande," National Resources 

 Committee, vol. 1, 1938, 566 pp. 



