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n <br />U <br />The irrigation ditches operated (1970 - 1980) on the <br />average between 185 (Stewart Ditch) and 255 days (Fire Mountain <br />Canal) per year, and the average daily flow for the same period <br />of time was between 45.9 cfs (Stewart Ditch) and 137.7 cfs (Fire <br />Mountain Canal). <br />3.1.2 SURFACE WATER QUALITY <br />The water quality of the North Fork and of the irrigation <br />ditches near Somerset is very good. The water is a calcium- <br />bicarbonate type, which is typical for mountain areas, and <br />contains an average dissolved solids concentration of 100 to 150 <br />mg/1. These data were confirmed during our field investigation in <br />September, 1982, when the electric conductivity of the water in <br />• the North Fork and Farmers Ditch was equal to 212.0 umhos (Table <br />2) at the points of entry to the CWI permit area. <br />Downstream from the coal loadout facility, between Paonia <br />and Hotchkiss, the water quality of the river changes only <br />slightly during the spring runoff, but deteriorates rapidly <br />during the rest of the year due to agricultural activities. After <br />the spring runoff the water changes to a calcium, magnesium, <br />sodium, sulfate type, reflecting active leaching by the <br />irrigation return flow. The dissolved solids concentration <br />increases to more than 1,500 mg/1 during the middle and late <br />summer and averages about 500 mg/1 through the fall and winter <br />months (Hydrology Description in the Application for Permit to <br />Mine). <br /> <br />7 <br />ccw+wao coNSU~nr~, wc. <br />