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<br />. <br /> <br />. <br /> <br />. <br /> <br />,~ <br />r-- <br />~'? <br />CJ <br /> <br />-'CHAPTER III <br /> <br />RIVER BUDGET RESULTS <br /> <br />From 1965 to around 1976 the Grand Valley Canal made virtually no winter <br /> <br />runs, and from 1976 to present has usually made one winter run. Some very <br /> <br />rough calculations were done to quantify the effect of winter water on salt <br /> <br />pickup. The results indicated that because the durations of the winter water <br /> <br />runs were short, that the salt loading due to winter water was small, and <br /> <br />hence, the recent reduction in winter water could have only a small effect on <br /> <br />the total annual salt pickup. <br /> <br />Secondly, it is conceivable that the soil has less available salt due to <br /> <br />leaching over the 90 plus years of irrigation. The argument against this is <br /> <br />that for practical purposes, the Mancos derived soil can be thought of as <br /> <br />pure gypsum and by leaching, the ground water simply works il:s way down to <br /> <br />more pure gypsum. <br /> <br />A third downward influence may be the irrigation system improvements <br /> <br />done by the Soil Conservation Service in recent years. Another trend causing <br /> <br />factor could be urbanization, although it is not clear whethl!r its influence <br /> <br />would be upward or downward. For all this, due to the large variation in <br /> <br />annual salt pickup values and the brevity of record, no signi.ficant trend can <br /> <br />'be deduced at this time. <br /> <br />IlI-5 <br />