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MINING AND RECLAMATION PLAN January, 1986 • <br />MT. GUNNISON NO. 1 MINE Revised October, 1989 <br />Extreme low flow conditions are unlikely to occur during or <br />following high precipitation runoff events. A joint frequency <br />analysis of low flow conditions and high precipitation events was <br />performed to assess the likelihood of runoff following high <br />precipitation events during low flow conditions. The cumulative <br />joint frequency is presented in Table 2.8.1.Y using data from the <br />Paonia precipitation gage for the period of record, 1957 to 1979 <br />and streamflows on the North Fork for the day following the <br />precipitation event. The extreme high precipitation/low flow cases <br />observed during the period of record, 1957 to 1979 are underlined <br />in Table 2.8.1.Y. <br />Water quantity data from this station will be included in the <br />Annual Hydrology Report. Should the U.S.G.S. discontinue <br />monitoring at this location, WECC will make other arrangements to <br />monitor quantity in the North Fork of the Gunnison River. <br />Baseline Characterization of Streamflow - Minnesota Creek Basin <br />Streamflow measurements started in 1977 at five stations in the _ <br />Minnesota Creek Basin and have continued, with an additional <br />station added in the basin on East Fork - Minnesota Creek above Dry <br />Fork and on Minnesota Creek below Dry Fork. Also, the gage on <br />Upper Dry Fork Minnesota Creek was relocated in November, 1981. • <br />The records are generally good except in the winter and early <br />spring. Because of the remote location of these gages and the <br />harsh winter conditions, frozen floats and equipment malfunctioning <br />have resulted in some loss of data. <br />Statistical analysis of stream flows has been performed to fill in <br />missing data and extend the record by using the long term records <br />from U.S.G.S. gages on the Smith Fork and the North Fork. <br />Multiple regression analysis was performed with monthly flows on <br />Smith Fork and North Fork as independent variables and monthly <br />flows at the gaging stations in the Minnesota Creek basin as the <br />dependent variables. The regressions were performed on the natural <br />logarithms of flow. The regressions were good with the exception <br />of Lower Dry Fork. Since Lower Dry Fork flows are controlled <br />almost entirely by release from Minnesota Reservoir, a poor <br />relationship would be expected. <br />2-358 <br />i <br />~~ <br />J <br />