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Permit C-81-071 1994 Annual Hydrology Report <br />Flows <br />Due to the size of the streams, they must be rated instead of using a more accurate controlled <br />section, such as a flume. The USGS maintains continuous recorders at Station 700, 800 and <br />900. Plots of the historic flow measurements on Foidel Creek are presented on Figures 21 to <br />27 and Figure 47. Plots of the historic flow measurement on Middle Creek are presented on <br />Figures 29 and 30. Plots of historic flow measurements on Fish Creek are presented on <br />Figures 31 and 32. Plots of the historic flow measurements on Trout Creek are presented on <br />Figures 33 and 34. The flow rate data are summarized on Table 28. <br />The stream flow data shows the typical seasonal variation with a rapid rise and fall of flow rates <br />during Spring runoff. Flows from Stations 16, 69, 1001, 8, and 1002 are not measured during <br />the winter due to the streams being frozen. Station 14 on Foidel Creek often did not record flow <br />in the creek during the fall, winter and summer because it is located near the top of the <br />drainage. Foidel Creek flows tend to be maintained nearly year-round by discharges from the <br />spoil springs feeding the sediment ponds. !1994 was a low rainfall year (see Figure 55) and <br />most gaging stations that are not directly affected by mine related discharges had very low <br />flows. <br />The data indicates a fairly good correlation between upstream and downstream stations on <br />each stream. As expected the upstream stations generally had a lower flow than the <br />downstream stations on each stream. On Trout Creek the downstream station has a lower flow <br />than the upstream station, probably due to irrigation withdrawals, the effects of which are also <br />reflected in the site 301 data. <br />• <br />Water Quality <br />Water quality samples are collected at all the primary sites on a regular. The water quality <br />summaries are presented on Tables 29 through 46. Plots of historic water quality data for <br />Foidel Creek are presented on Figures 35 through 38, Figure 51 and Figure 54. A plot of <br />historic water quality data for Fish Creek is presented on Figure 39. A plot of water quality data <br />for Middle Creek is presented on Figure 40. Plots of historic water quality data for Trout Creek <br />area presented on Figures 41 and 42. <br />The base level of field conductivity measured during spring runoff, was higher in the <br />downstream sites on Foidel Creek. It is approximately 750 umhos/cm in the upstream site (14) <br />and from 1500 to 1900 umhos/cm in the downstream sites (800 and 8). Since 1981 the base <br />level for conductivity at both downstream sites has been increasing although there appears to <br />have been a leveling off since 1989. The upstream site also conductivity also increased in <br />1986, presumably as a result of lower runoff flows since that time. During the second half of <br />the 1994 irrigation season, the field conductivities at Station 14 could not be measured as there <br />was no measurable flow. The field conductivity at Station 8 was approximately 3300 <br />umhos/cm. <br />The difference between the conductivities at the upstream and downstream stations is <br />attributable primarily to spoil spring discharges related to surface mining. These discharges <br />cause increased concentrations of dissolved solids, calcium, magnesium, and sulfate and a <br />• reduction in SAR in Foidel Creek. However, the increase in TDS levels during irrigation season <br />is not sufficient to cause material damage. While the spoil springs area adding some <br />EP4TE%T.DOC 09/17/97 Page 5 <br />