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<br />1\: t' ..., '" '7'" <br />,') U :'.. ,.,j , '.-~ <br /> <br />. <br /> <br />Hydrology <br /> <br />The water quality deteriorates in the lower part of the basin <br />as a result of return flow from presently irrigated lands. <br /> <br />Chemical analyses of surface waters from St. Vrain Creek near <br />its mouth were performed by the U. S. Geological Survey between 1950 <br />and 1956. They indicate that the sodium content ranged within the <br />limi ts given above. However, the soluble salts are much higher at <br />this station than they are at the upper stations. The specific <br />conductance of samples taken during this period ranged from 1080 <br />to 1930micromhos (EC x 106), with the exception of one sample of <br />630 micromhos. <br /> <br />Boron concentrations were not determined for the samples taken <br />in the 1957-through-1960 period at the upper stations. However, <br />samples of the St. Vrain Creek water near its mouth collected between <br />1950 and 1956 indicated a boron content ranging from 0.19 to 0.42 P.P.Ill. <br />This boron concentration should be greater than that of the upper <br />stations; consequently, the boron content at the upper stations should <br />not be harmfUl to the crops generally grown in the basin. No recent <br />ahalyses for boron concentrations have been made. However, it is <br />assumed that the boron content has not changed significantly since 1956. <br /> <br />. <br /> <br />WATER UTILIZATION <br /> <br />Water Rights Administration <br /> <br />In administering water rights, the State of Colorado follows <br />what is known as the Colorado Doctrine, which is based upon the <br />principle of appropriation for beneficial use. Water rights are <br />established at general adjudication proceedings in the district <br />courts. In these proceedings, the first date of beneficial use is <br />determined for each claimant to water and priority numbers are assigned <br />to appropriators in chronological order. <br /> <br />Water rtghts are divided into two classes: direct flow and <br />storage. Direct-flow rights are decreed in terms of a given quantity <br />per unit of time, usually cubic feet per second. In most cases, these <br />rights do not specifically limit the period during which diversions ' <br />can be made; however, limitations are imposed in'that water must ,be <br />used beneHcially. Water obtained under such rights may not be stored <br />but must be used as it is being diverted. Storage rights are decreed <br />in terms of cubic feet or acre-feet, and the total decrees usually <br />equal the capacity of the reservoir. <br /> <br />. <br /> <br />15 <br /> <br />ch _,ii,. '"', _~ ';J' ,-_<:.J. <br /> <br />.,__~C,"_..._ J;._,,::';'~i~,__~~.-~~._ - <br /> <br />