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<br /> <br /> <br />........~--'1J--D <br /> <br />." <br /> <br />",. <br />rlI~~ <br /> <br />J <br /> <br />a <br /> <br />. ...... <br />',J, <br /> <br />I:l ~", ,.."" <br />'(. 'i\.::' <br />( ."'''.'''./:.. <br />. ~'.!': -~~,::,,~~. <br />r .y.' .. <br />~ ."., <br />~...~'v;':' <br />., . :0....:, <br />/,.~ <br />JS' <br /> <br />,. - <br />- . <br /> <br />\. <br /> <br /> <br />Ii <br /> <br />~ <br /> <br />. <br /> <br />Il'. <br /> <br />": <br /> <br />( <br />;:.. <br />- . .... <br />;;; -fO"" ~ <br /> <br />'" <br /> <br />'" <br /> <br />I~ ~ <br />-', <br /> <br />" <br /> <br />--_... <br />... - ....." <br />-" <br /> <br />" <br /> <br />/,", <br /> <br />JI <br />r <br /> <br />(If <br />1 <br />U~\l <br />~'I-'I <br />1l1l!~~ ... <br />, CfJ '; <br />iJ <br /> <br />,. <br />"...;, <br /> <br />~ <br /> <br />~., <br /> <br />~ <br /> <br />I <br /> <br />~~ <br /> <br />:;;: <br /> <br />.:iO , <br />f 1oP. ~r.. l\l ... <br />" J" . < !g. ~ rl.~ <br />~ ~,.rP )-'. .:" IOld".., <br />.& "".,~ <br /> <br />~ ~ :~~~ <br />. e",,,,,,: ~..' <br />~ . ~ -.fJ ~",,' <br />.P~~!J!'.... . <br />Irriqation west of Berthourl <br /> <br />~ <br />. <br /> <br />r.I <br /> <br />... .. <br /> <br />,.0;:- ~_ <br /> <br />a problem of comprehensive land use <br />planning more than one of water resources <br />planning. Once the best uses of the lands <br />have been determined, water supplies can <br />be developed, managed, and preserved to <br />meet those needs. <br /> <br />WATER QUALITY <br /> <br />The total dissolved solids (TDS) for 2 years <br />of record (October 1971 through <br /> <br />September 1973) range from 24 milligrams <br />per liter (mg/l) in North St. Vrain Creek near <br />Lyons to 1,535 mg/l in the Big Thompson <br />River at the mouth near LaSalle. Thus, flows <br />originating in the upper reaches of the <br />drainage basins are excellent in quality but <br />deteriorate rapidly downstream due to use <br />and reuse on the lands and by municipal and <br />industrial effluents. <br /> <br /> <br />At the same time surface water is being <br />diverted for agricultural use, ground water <br />is being pumped for that purpose. A part of <br />the water applied to the surface finds its way <br />back into the ground-water aquifer, a portion <br />runs off, and some is lost to <br />evapotranspiration. Each time this use <br />pattern occurs, dissolved salts are <br />concentrated in the water. This reduces <br />water quality and limits its usefulness. <br /> <br />, <br /> <br />Trends in TDS content of ground water from <br />alluvial aquifers were investigated to <br />determine if degradation is occurring. The <br />increasing TDS content of ground water <br />indicated that degradation has occurred <br />throughout most of the South Platte River <br />Basin. <br /> <br />The alluvial aquifers are recharged by <br />surface water during periods of high <br />surface-water flows. However, at times of <br />low surface-water flows, the reverse <br />situation often occurs and ground water <br />enters the streams from seeps and springs <br />along the stream channels. The relationship <br />between surface- and ground-water quality <br />was investigated by comparing the average <br />TDS for each supply. Exhibit 111-2 shows the <br />results of that comparison. The average TDS <br />of the ground water shows close agreement <br />with the average high TDS of the surface <br />water. The average high TDS of the surface <br />water corresponds to periOds of low flow <br />when seepage of ground water into the river <br />is significant. <br /> <br />Table 111-1 lists small communities in the <br />study area which obtain their water supply <br />from the ground-water aquifer. <br /> <br />111.3 <br />