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<br />(j"ll.gf' <br />lJ 1 ' <br /> <br />8. <br /> <br />. <br /> <br />In the al:Dve 12-mile reach water in large amounts has been <br />drawn from storage for at least l3 years. If the present rate of with- <br />drawal is maintained, the resource will be exhausted for practical pur- <br />poses in another lO or l5 years. <br /> <br />., <br /> <br />Pawnee Creek <br /> <br />This creek has a small constant flow in it below the north Ster- <br />ling Inlet Canal. The small amount of ground-water use has not disturbed <br />the water table except for very short periods. <br /> <br />ARKANSAS VALLEY <br /> <br />Main Valley <br /> <br />Except for short distances above and below John Martin Reser- <br />voir, ground water is available and being used for irrigation from <br />Pueblo to the state line. That part of the valley containing water bear- <br />ing alluvial gravels is quite narrow seldom exceeding 4 miles in width. <br />Pumping plants are to be found on the discontinuous terraces on both <br />sides of the river as well as on the bottom lands. Because of the limited <br />saturated depth, terrace wells have a capacity seldom exceeding <br />600 g. p. m. In nearly all cases the irrigation wells are in areas cover- <br />ed by surface supplies and water tables have remained stable. During <br />drought periods there have been temporary declines but recovery has <br />occurred during periods of good water supply. Since long-time obser- <br />vations are available only between Pueblo and La Junta, these statements <br />are valid only in that portion of the valley. A system of observation <br />wells has been set up by C. S. U. and U. S. G. S. below La Junta but <br />these have been in existence but a short time. U.S.G.S. now has a <br />survey of ground-water conditions in progress upstream from the state <br />line and has completed Prowers County. This will be the first published <br />report on ground water in the valley. Work done by C. S. U. has been <br />limited to the establishment of observation wells and casual study of <br />conditions in areas of development. Some of the records date back to 1929. <br /> <br />I .1 <br /> <br />It is rather obvious to me that all the bottom land development <br />belongs in Classification 1. I am not so sure about terrace development. <br />For instance, the st. Charles terrace on the south side of the river from <br />Pueblo to Avondale cont ains a water table higher and independent of the <br />flood-plain water table. The water bearing gravels lie on top of a shale <br />terrace which itself is often higher than the flood plain. This gives rise <br />to springs along the contact especially in the side drainage s. The effect <br /> <br />, .. <br /> <br />- 8 - <br />