REP23293

• Permit No: C1980001
• IBM Index Class Name: Report
• Doc Date: 2/5/1999
• Doc Name: 1998 AHR text and data
• Annual Report Year: 1998
• Permit Index Doc Type: HYDROLOGY REPORT
• Media Type: D
• Archive: No

•
III. SIIRFACE WATER
GAUGING STATIONS
Figure 1 shows the continuous streamflow records for Trout Creek at TR-a and
TR-b. The graphs showing the results of the gauging stations along Trout Creek
indicate that the monitoring program is being placed on-line early enough in the
year to record flow prior to the peak runoff period for each year. The individual
data points show the monthly average flows and give some indication of the
variability between mild winters (winters of less snow accumulation) and harsh
winters. The graph showing 1996-1998 data indicates a slight variation in the total
streamflow between 1997 and 1998. The 1989-1998 graph suggests that 1994 was the
driest winter over the past decade and 1993 was the wettest for the watershed.
The flow record for 1998 shows the peak flow to have occurred in June as it
did during 1988, 1969, 1990, 1991, 1993, 1995 and 1997. The later peak flows for
these years were probably due to more harsh winters or the on-set of warmer
temperatures occurring later in the spring. The 1997 and 1998 records suggest that
snowmelt from the mine area was fairly rapid when it occurred as evidenced by the
flow differential between TR-a and TR-b in the early part of the year. In previous
years, snowmelt appears to have been more uniform throughout the Trout Creek
watershed.
The stage/flow rating curve for TR-a was reviewed in June of 1994 to ensure
its continued accuracy. Sufficient differences in the channel cross-section at TA-a
were noted during the review to warrant development of a new stage/flow rating
curve. Over the 1994-1995 seasons, a total of five cross-sections were developed
and compared to ensure channel stability. An averaged cross-section was then
developed to compute a stage/rating curve. The stage rating curve data covered
flows ranging from approximately two cfs to 85 cfs. The equation and rZ for the
curve are as follows: z.ica6
y = 13.817x where y = flow in cfs and x = depth of flow;
r~ = 0.98. During 1996, cross-section measurements were taken to confirm that the
channel configuration had remained stable during the past annual monitoring period.
Flow data for TR-b consists of both instantaneous flow and continuous flow
measurements. The flow data presented in Figure 1 consists only of information
derived from continuous flow records. Instantaneous flow measurements obtained
between 1989 and June 1994 for this location are provided in Appendix A. Prior to
that time, instability of the stream channel caused by a 1984 flood precluded the
installation of any type of monitoring station in the vicinity.
Instantaneous flow measurements were recorded at TR-b during 1989 in
conjunction with water quality samples taken at TR-D, except for the October
. sampling period. Between the sampling periods of September and October in 1989,
2