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<br />liflO ill!, <br /> <br />S..:-dgwick, and Washington Counties, and part of Larimer County. Of this are:!, <br />thl' alluvial aquifers cover about 2,600 mi2 (4.300 km2). The alluvial <br />aquift:'rs COl1sist of unconsolidated interbedded sand. gravel, clay, nod silt. <br />Depths to .....aler range from less than 2 ft (0.6 m) to more thilll 121 ft (36 m). <br />'me s.1lurated chickness ran~es from 0 to about 300 ft (0 to 90 m). Water from <br />thest.> aquifers is used as <1 supplemental supply for irrigation in the South <br />Platte River valley and some of the tributary valleys. The alluvial aquifers <br />Clrt' the primary water supply for irrigation in several of the tributary <br />valleys. The .,11uvial aquifers range from less than I mt (}.6 km) to as much <br />as 10 m! (16 km) Idde and are found in valley fill deposited 1n broad troughs <br />cut into the underlying sedimentary bedrock forrn..1.tions or in terrace gravel <br />deposited on thl' bedrock of l.ate Cretaceous to Tertiary age. <br /> <br />l..'<It!;;'r levels fluctuate in response to recharge from precipHatlon. <br />rt'chaqw from applied irrigation ......1ter. and discharge resulting from ground- <br />\.Iatl'r pumpage. seepage to surface water. and evapotranspiration. In areas <br />wht":'re pumpage is the predominant source of irrigation w1Iter. with little or no <br />surface-water application. water levels generally have declined; the magnitude <br />of thlo' decline depends on the volume of water .....ithdra...'n. Such is the Cilse in <br />Kio.....a Crlo'C'k ilnd Bijou Creek valleys where changes ranged from a decline of <br />12.8 ft ().9 m) to a rise of 4.6 ft (1.4 m) from ~Iarch 1976 to ~larch 1977. In <br />areas where surface ....ater and ground ....ater are used r.:onjunctively. such as <br />most of the main-stem South Pl.1ttl~ River val lev. ~ll1d major tributaries. such <br />as the Cache 1.1 Poudre River valley. water levels fluctuate durinl'!. the <br />irrigatIon season but ~enerally return to about the same It.vel from season to <br />season. In these :ueas. water-level changes fr0m :--ta.rch 1976 to r-l;'lrch 1977 <br />ranged from a decl1l1C of :1b()ut 1.5 ft (0.46 m) to a rise of ahout 1.0 ft <br />(0,]0 m). In the f......., isolated areas of predominantly surface-....ater <br />appliciltion. ~round-....ater levels tend to respond to th~' amount of surfan'- <br />wat~r application. <br /> <br />Groulld-....aler levels measured ill M.lrch 1977 .1 it' tht. result nf irril-\<1tioll <br />!'O',ithdr.l....als and applications during the 1976 irrir,ation sC'ason and residual <br />effects of withdrawal and .1pplicatiolls from preVious years. Lo.... 1976-77 <br />.....inter precipitation ....ill affect surface-...'.Jter supplies availaht~ for th~ 1977 <br />irrig:nioll season. :--1.Jrch 1978 .....ater levels will retlect this deficiency <br />h....cause most recharKc is from infiltration of irrigation watpr. <br /> <br />I..'ELI. LOG\T10~ <br /> <br />In thIs T('p,'rt, the 10catioll5 of ....10'115 are based on th~ t'.S. Burel1l1 of <br />Lam.! ~:'lna~emcnt system of land !':uhdivislon (fig. 2). <br /> <br />TII'> local ....ell number l(h.::ates 11 ....ell ....ithin a 10-cler", (....O-h<1.) tract <br />lISillg thp ll.S, Bureau of I.and ~dnaget:lent ~Y5tcm of land suhd1visiroll. The <br />l'OmpDnl'nts of the 11'cat well number proceed from thE" largest to the smallest <br />J.md subdivisir>i1s. This is in cOlltrast to the l~gal d~scriptioll. ....hich <br />pTl'cceds from the smallest to the Llrgest land subdivision, <br /> <br />3 <br />