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• A similar trend has been observed at the downstream station on <br />Middle Creek (Site 29) although conductivity levels are lower. The <br />spring runoff conductivity at Site 29 has increased from 600 <br />umhos/cm to 1500 umhos/cm. Also the irrigation season level has <br />increased from the range of 1000 to 2000 mmhos/cm prior to 1987 to <br />the range 2000 - 3000 umhos/cm since 1987. Other than increased <br />levels of TDS, sulfate, and specific conductance in the stream, the <br />only other significant water quality trend is a decline in the <br />levels of total recoverable iron and manganese during the period <br />1986 through 1991. Total iron and total manganese measurements <br />taken prior to 1986 indicate an increase in these constituents from <br />1979 through 1986. <br />Suspended solids concentrations at all three sites were low both in <br />absolute quantities and in comparison with the historic record. <br />The historic record provided in the 1990 Annual Hydrologic Report <br />generally shows low suspended concentrations (less than 100 mg/1) <br />at all stations except during high spring runoff events. The high <br />seasonal flows during the period 1984 through 1986 exhibit <br />substantial increases in suspended sediment concentrations. <br /> <br />Page 7 <br />• <br />