OCR Text |
Show - 17 - and for comparison the table below is presented. Basin Safe annual yield (acre-feet) Average annual overdraft 1946-50 (acre-feet) 1. Salt River Valley 500,000 - 1,000,000 59o,000-l,095,000 2. and 3. Lower Santa Cruz and Avra-Altar 135,000 750,000 Sub-total - Maricopa- Pinal area 1,340,000 - 1,840,000 4. Upper Santa Cruz 100,000 Question VI. Give in acre-feet for this basin an estimate of the average annual water loss due to transpiration from swampy areas overgrown with water-loving vegetation? The annual use of water by water-loving vegetation (phrea-tophvtes) in Arizona has been estimated by Turner (S. F. Turner and others, 1951). Data adapted frojn that estimate are reproduced below for the basins included in the present report. Between 274,000 and 354,000 acre-feet of water is lost annually through transpiration of phreatophvtes in the nine basins. Area occupied Annual use Basin by phreatophytes (acre-feet) 1. Salt River Valley 22,500 75,000 2. Lower Santa Cruz 25,000 100,000 -150,000 3. Avra-Altar Xo data Probably negligible Sub-total. Maricopa-Pinal area 47,500 175,000-225,000 4. Upper Santa Cruz Xo data Probably small 5. and (i. L'pper and Lower San Pedro 10,000 - 20,000 30,000 - (50,000 7. Upper San Simon Xo data Probably negligible |