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<br />j <br />I <br /> <br />I.Htilt <br /> <br />From a pract1cal standpo1nt. the amount of ground water <br />that can be withdrawn from an artesian aquifer is not closely <br />related to the amount of ground water in storage nor the <br />amount of replenisbment available. Other factors, such as <br />the phyaicalbounduies of the aquifer, the permeability and <br />thickness of the aquifer, and the allowable Cira1llldown of water <br />levels in PW!lPinc; wells. senerally are much more iInportant. <br />The artesian aquifer. therefore, is substantially different <br />from the major aquifers in unconsolidated materials. where <br />amount of storage and replenishment rates are of considerable <br />importance. <br /> <br />From the foregoing discussion, it appears likely that <br />the ground-water resources of most artesian aquifers in <br />COlorado can be managed separately from the surface-water <br />resources. Regulations pertaining to the control of artesian <br />p"c_ures probably are the chief ones needed for planned <br />managemeJlt;. ~ prefisures could be controlled either by <br />regulating spacing of weUS and discharge rates or by regulating <br />pUmping levels. Other regulations perta1nill.g to the conservation <br />Of" the supply might include one preventing the uncontrolled <br />di"Dh&rg8 from flowing _Us, one preventing the intermingling <br />of water from other aquifers, and others coilllllonly considered <br />for all aquifers. <br /> <br />Conso11dated artesian aquifers have been extensively <br />developed in only two major areas in the State--the Denv~ <br />metropolitan area and the Grand Junction area. wells tapping <br />the Dakota in t:he Arkansas Valley are closely spaced in some <br />areas, Buch as those near Rocky Ford. The problems in these <br />areas, however. probably are not as ser ious as thoso in the <br />Denver and Grand. Junction areas. In other areas, the development <br />is scattered and artesian pressures have not declined substantially. <br /> <br />The most highly developed artesian aquifers in the <br />Denver &rea are the Denver anei Arapahoe formations, the Dawson <br />arkose, the upper divieion Laramie formation, and the Fox Bills <br />sandstone. The pressure in some of tbem was originally <br />S'.1fficient to make wells flow throughout a large area. The <br />withdrawals for industrial and domestic use are so great that, <br />near the center of Denver, the pressure has declinetl as IlD.Ich <br />as 700 feet in the Arapahoe formation, and t:he water level is <br />now about 450 feet below the land surface in one well. Declines <br />generally are lesa in ~Ie Fox Hills although locally declines <br />of more than 400 feet have been measured. <br /> <br />~ <br />