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<br />. <br /> <br />GU13j1 <br /> <br />... <br /> <br />the rocks therefore may be "worth their weight in water" to the <br />econoDW of the Plains. <br /> <br />Aquifers of the second category with respect to development am <br />management--that is, those associated with streame - correspond to <br />tt.ose having "watercourse" problems aM genera14 to those having <br />"pipeline" problell1B as discussed by Thomas (1951, p. 36). These are <br />aquifere in which the mount of water that can be developed 111 <br />sufficiently large to waITant management on a perennial basiB. The <br />ground water in these aquifers is related to surface stre8llls, either <br />directly along a stream reach or indirectly through spring flow or <br />other natural discharge. <br /> <br />" <br /> <br />The priJne requisites for development of water from an aquifer <br />on a perennial basis are as follows: (8) the location aDd character <br />of the discharge areas are such that pUl1lping from wells can effect- <br />ively reduce the natural discharge from the aquifer, and (or) (b) <br />recharge to the aquifer can be increased in the recharge area or <br />induced in the discharge area. Development can be perennial if the <br />net cons\D1lptive use of developed water does not exceed the SUlll of <br />(a) natural discharge stopped and (b) recharge induced or increased, by <br />virtue of the development or by other artificial means. <br /> <br />Ground-water reservoirs in alluvial valleys of essenti~ <br />perennial strelllllB, wherein the surface and ground vaters are intimately <br />related, fit this category. Examples of such are the Middle, the <br />Rincon, and the Mesilla Valleys of the Rio Grams in New Mexico ani <br />the Duncan-Virden and the Safford Valleys of the Gila River in <br />New fieldco aM Arizona. In Colorado the South Platte and ArkBDsaa <br />River Valleys and sane of their major tributaries also fit th:1a cate- <br />gory. <br />In such valleys, surface water is usually applied to irrigate the <br />lands. A part of the surface water infiltrates to the ground.water <br />b0d3 and returns to the streem through drains and by ground-water <br />seepage. The amount of water available for net consumptive use is <br />essentially equal to the difference betwesn the inflow, primarily that <br />brought in by the stream, and the outflow that must be allowed by <br />virtue of prior water needs and right!! downstream (and by the necessity <br />of maintaining salt balance). In many such valleys, the valley <br />consUlllptive use of water exceeds the beneficial consumptive use because <br />of the areas of native phreatopb;ytiC vegetation. For example, in 1936 <br />the consumption by irrigated lands in the Middle Valley of the upper <br />Rio Graoo.e was 157,000 acre-feet, whereas the total consumptive use <br />was 5B3,000 acre-feet (Natural Resources Committee 1938, p. 91). <br /> <br />I <br />~ .0> <br /> <br />, <br /> <br />~ <br />, <br />~ <br />I <br /> <br />I, <br /> <br />Streamflow in such valleys is occasionally inadequate for the <br />needs, in spite of regulation by surface reservoirs. Consequently, <br />wells have been installed. As these wells commonly are located at a <br />spot convenient to provide water, evapotranspiration by native vegeta- <br />tion is reduced little if an;yJ accordingly, net consumptive use of the <br /> <br />" <br /> <br />7 <br />