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<br />OG13JO <br /> <br />,., <br /> <br />" <br /> <br />The southern High Plams, or Llano Estacado, lies south of the <br />Canadian River in Texas an:! New Mexico. It has a total area of some <br />30,000 square miles. Conspicuous escarpments form the east and west <br />borders. The north border is the deep canyon of the Canadian River. <br />The Ogallala formation is the aquifer, and its boundaries are <br />essentially those of the High Plains. The Ogallala is thin or absent <br />in sane areas but is more than 600 feet thick in other areas. The <br />total water potential~ available frCl'll storage in the Texas portion in <br />1958 was about 200 million acre-feet (Cronin, 1959, p. 11), but the <br />annual average rate of recharge is o~ about 50,000 acre-feet. <br />Storage and recharge in the Ne.. ~x:ico part of the High Plains are <br />perhape a third as great. Thus, total storage in the southern High <br />Plams was perhaps 250 to 275 million acre-feet in 1958. About <br />40 million acre-feet had already been pumped, and the curren\; rate of <br />pumpmg is BIOre than 100 times the recharge. Obviousl3', limiting <br />,develoPJ11ent to the rate ot recharge would mean that the large volume <br />'of vater in storage wauJ.d not be utili7.~d.. ~ther, even if it ..ere <br />decided so to limit the developnent, it would be physicall,y almost <br />impossible to carry out the decision if the premise were that doing <br />so wwld result in a perennial water supply. The only means of develop- <br />ing water from an aquifer on a perennial basis is to locate wells so <br />that, over a long time, the natural discharge can be stopped, and <br />therefore diverted to the pumps, or the recharge can be increased, <br />or both, in an amount equivalent to the consumptive use. <br /> <br />.1 <br /> <br />Most of the discharge from the High Plains occurs along or near <br />the eastern escarpment. Originall3' some discharge occurred fran ground- <br />sater lakes such as at Portales, N. Mex., and 11uleshoe, Tex. Over <br />most of the Plains the water table is more than 50 teet below the <br />land surface, and lowering of water levels in these areas cannot induce <br />more recharge. Therefore, it is not physically possible, except in <br />small areas, to locate wells on the High Plains so that the water <br />pumped 11111 come other than from storage. <br /> <br />The lowering of vater levels caused by pumping from a water-table <br />aquifer such as the Ogallala fonnation is transmitted laterall,y at a <br />slow rate. The major lowering at water level occurs in the vicinity <br />of the well. The areal spread of the cone of depression is independent <br />of the pumping rate and is a fUnction at timB and the hydraulic <br />characteristics at the aquifer. An increase in pumping, or localized <br />heavy pumping, such as caused by l1lalV wells in ollS locality, deepens <br />aIXi steepens the cone at depression. The water can be pumped at such <br />a rate that it is virtu~ exhausted in the area of heavy pumping, <br />yet water levels are affected only slightly and slowly a few miles <br />away. For example, pwnping on the High Plains has been concentrated <br />in the areas where the laIXi is suitable tor irrigated faming aIXi <br />where adequate wells can be obtained. As a consequence, water levelS <br />have declined more than 100 feet in some of these areas and an average <br /> <br />" <br /> <br />5 <br /> <br />/ <br />