OCR Text |
Show -11 - Lower San Pedro Basin (Basin 6) The Lower San Pedro Basin is about 70 miles long, and averages about 8 miles wide. The total area of the basin is about 370,000 acres (575 square miles). The southern upstream limit of the basin is at a natural ground-water barrier separating this basin from Basin 5. The northern or downstream limit is arbitrarily drawn at the Gila River. The deepest drilling in the basin bottomed in valley fill at 1,485 feet. This well encountered about 100 feet of younger fill, predominantly sands and gravels, and about 1,400 feet of older fill consisting of about 500 feet of clays and silts below which were about 900 feet of clays and sands containing some water under artesian pressure. Upper San Simon Basin (Basin 7) The Upper San Simon Basin extends from the vicinity of Rodeo, Xew Mexico; northwestward into Arizona to an arbitrary line between townships 9 and 10 south. For the purpose of this report the southeastern limit of the basin is drawn at the Arizona-New Mexico State Line. The Upper San Simon Basin is about 60 miles long and about 15 wide. The Upper San Simon Basin includes about 640,000 acres (1,000 square miles). That part of the basin within New Mexico probably contributes little water to Arizona. A generalized log near the central axis of the basin would show that the alluvial cover of younger fill consisted of sands and gravels to a depth of about 200 feet underlain by older fill consisting of 400 feet of clay, below which are silts, clay, sands and gravels to a depth of 2,800 feet. Artesian aquifers occur at depths between 400 and 2,300 feet. Lower San Simon-Gila River Basin (Basin 8) The Lower San Simon-Gila River Basin extends northwest from the northern boundary of the Upper San Simon Basin. The lower basin is about 70 miles long, and averages about 25 miles wide. The area contains about 735,000 acres (1,150 |