PacifiCorp / Cowlitz PUD Hydroelectric Projects FERC Project Nos. 935, 2071, 2111, 2213

TABLE OF CONTENTS

2.2 STREAMFLOW STUDY (WTS 2) ...... WTS 2-1 2.2.1 Study Objectives...... WTS 2-1 2.2.2 Study Area ...... WTS 2-1 2.2.3 Methods ...... WTS 2-1 2.2.4 Key Questions...... WTS 2-4 2.2.5 Results...... WTS 2-4 2.2.6 Discussion...... WTS 2-31 2.2.7 Schedule...... WTS 2-36 2.2.8 References...... WTS 2-40 2.2.9 Comments and Responses on Draft Report ...... WTS 2-41

WTS 2 Appendix 1 Monthly Flow Duration Curves

LIST OF TABLES Table 2.2-1. Selected stream gages on the Lewis River...... WTS 2-7 Table 2.2-2. Peak flow frequencies...... WTS 2-28 Table 2.2-3. Summary of streamflow statistics for Lewis River stream gages. ..WTS 2-34

LIST OF FIGURES

Figure 2.2-1. Stream Gages Analyzed...... WTS 2-5 Figure 2.2-2. January flow duration curve for the Lewis River near Trout Lake gage...... WTS 2-8 Figure 2.2-3. Daily flow exceedence curves for Lewis River near Trout Lake.....WTS 2-9 Figure 2.2-4. Daily flow exceedence curves for Lewis River above Muddy River near Cougar...... WTS 2-10 Figure 2.2-5. Daily flow exceedence curves for Muddy River below Clear Creek near Cougar...... WTS 2-11 Figure 2.2-6. Daily flow exceedence curve for Lewis River near Cougar...... WTS 2-12 Figure 2.2-7. Daily flow exceedence curve for Lewis River above Merwin near Amboy...... WTS 2-13 Figure 2.2-8. Daily flow exceedence curve for Speelyai Creek upstream of diversion near Cougar...... WTS 2-14 Figure 2.2-9. Daily flow exceedence curve for Lewis River at Ariel...... WTS 2-15 Figure 2.2-10. Daily flow exceedence curves for Swift No. 2 canal...... WTS 2-16 Figure 2.2-11. Base flow for Lewis River near Trout Lake...... WTS 2-17 Figure 2.2-12. Base flow for Lewis River above Muddy River...... WTS 2-17 Figure 2.2-13. Base flow for Muddy River below Clear Creek...... WTS 2-18 Figure 2.2-14. Base flow for Lewis River near Cougar...... WTS 2-18 Figure 2.2-15. Base flow for Lewis River near Amboy...... WTS 2-19 Figure 2.2-16. Base flow for Speelyai Creek above diversion...... WTS 2-19 Figure 2.2-17. Base flow for Lewis River below at Ariel...... WTS 2-20 Figure 2.2-18. Base flow timing for Lewis River near Trout Lake...... WTS 2-21

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Figure 2.2-19. Base flow timing for Lewis River above Muddy River...... WTS 2-22 Figure 2.2-20. Base flow timing for Lewis River near Cougar...... WTS 2-23 Figure 2.2-21. Base flow timing for Lewis River near Amboy...... WTS 2-24 Figure 2.2-22. Base flow timing for Lewis River at Ariel...... WTS 2-25 Figure 2.2-23. Base flow timing for Muddy River below Clear Creek...... WTS 2-26 Figure 2.2-24. Base flow timing for Speelyai Creek near Cougar...... WTS 2-27 Figure 2.2-25. Peak flow hydrographs for USGS gages in the upper and middle Lewis River basin...... WTS 2-29 Figure 2.2-26. Peak flow hydrographs for USGS gages in the lower Lewis River basin...... WTS 2-30 Figure 2.2-27. Peak flow hydrographs for USGS gages on tributaries in the Lewis River basin: Muddy River below Clear Creek and Speelyai Creek near Cougar...... WTS 2-30 Figure 2.2-28. Peak flow timing in the upper and middle Lewis River basin. ....WTS 2-33 Figure 2.2-29. Peak flow timing in the lower Lewis River basin. Peak flows at Ariel prior to 1924 and 1925 were predicted from observed annual flood flow near Amboy...... WTS 2-34 Figure 2.2-30. Peak flow timing for selected tributaries in the Lewis River basin...... WTS 2-35 Figure 2.2-31. Spill events and magnitude (cfs) into the Swift bypass reach...... WTS 2-36 Figure 2.2-32. Spill events and magnitude (cfs) at Yale powerhouse tailrace. ...WTS 2-37 Figure 2.2-33. Spill events and magnitude (cfs) at Merwin powerhouse tailrace...... WTS 2-37 Figure 2.2-34. Annual runoff at the Lewis River near Ariel gage and annual precipitation at Vancouver 4NNE weather station...... WTS 2-38 Figure 2.2-35. Regression of annual runoff vs. precipitation...... WTS 2-38 Figure 2.2-36. Mean daily flows at the Lewis River at Ariel gage...... WTS 2-39

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2.2 STREAMFLOW STUDY (WTS 2)

2.2.1 Study Objectives

The objective of the Streamflow Study is to describe flow conditions at selected gages in the Lewis River watershed. The study analyzed daily flows and peak flows to characterize the hydrology in 6 reaches:

• Lewis River upstream of Swift Reservoir • Lewis River in the Swift bypass reach • Lewis River between Merwin Dam and Eagle Island • Speelyai Creek upstream of the diversion • Speelyai Creek downstream of the diversion • Swift No. 2 canal

The rate of flow change (ramping rate) in the Lewis River just downstream of Merwin Dam was also characterized.

2.2.2 Study Area

The study area for the Streamflow Study includes selected stream gages in the Lewis River watershed. These are listed below and shown on Figure 2.2-1.

• Lewis River near Trout Lake, (U.S. Geological Survey [USGS] 14213200) • Lewis River above Muddy River near Cougar, Washington (USGS 14216000) • Muddy River below Clear Creek near Cougar, Washington (USGS 14216500) • Lewis River near Cougar, Washington (USGS 14218000) • Lewis River near Amboy, Washington (USGS 14219500) • Speelyai Creek near Cougar, Washington (USGS 14219800) • Lewis River at Ariel, Washington (USGS 14220500) • Swift No. 2 canal (maintained by project operators) • Speelyai Creek at hatchery intake (maintained by Speelyai Hatchery operators)

2.2.3 Methods

The Streamflow Study will include 3 tasks, as described below.

Task 1. Collect Available Data

Mean daily and annual peak flow data will be collected from selected stream gages in the basin (see table below). These data are available from the USGS Internet site, Cowlitz PUD, or the Speelyai Hatchery. Both PacifiCorp and Cowlitz PUD project spill and outflow records will be used for the Swift bypass reach. In addition, 15-minute or 1-hour (as available) flood flow hydrograph data will be requested from the USGS for chosen floods to analyze rates of flow change during historic and current conditions.

Stream gage data are available for Speelyai Creek upstream of the point where it is diverted into Yale Lake. Speelyai hatchery records and observations of the stream

April 2004 Final Technical Reports - Page WTS 2-1 \\Neoserver\disk1\Projects\Lewis River\Final Tech Reports 04-04\02.0 WTS\WTS 02 Final 032304.doc PacifiCorp / Cowlitz PUD Lewis River Hydroelectric Projects FERC Project Nos. 935, 2071, 2111, 2213 channel will be used to determine current conditions in the reach downstream of the diversion.

Monthly precipitation records at the climatic station in the watershed with the longest record will also be collected for comparison with annual streamflow records. The weather station at Merwin Dam has precipatation data back to 1948; weather stations in Portland and Vancouver have records back to the late 1800s.

Period of Record USGS Gage Drainage Area Number Station Name (sq. mi.) Peak Flows Daily Flows 1421320 Lewis River near 127 1958-1972 1958-1971 Trout Lake, Washington 14216000 Lewis River above 227 1927-1934; 1927-1934; Muddy River near 1954-1977 1954-1970 Cougar, Washington 14216500 Muddy River 135 1927-34; 1927-34; below Clear Creek 1954-73; 1954-73; near Cougar, 1983-present 1983-present Washington 14218000 Lewis River near 481 1917-1977 1924-1958 Cougar, Washington 14219500 Lewis River near 665 1911-1930 1910-1930 Amboy, Washington 14219800 Speelyai Creek 12.6 1959-present 1959-present near Cougar, Washington 14220500 Lewis River at 731 1923-present 1923-present Ariel, Washington Other Flow Data: Cowlitz PUD Swift No. 2 Power 481 n/a 1958-present Canal Speelyai Hatchery Speelyai Creek at 15 n/a weekly flows Hatchery intake

Task 2. Analyze Data and Extend Record

Streamflow data from the selected stream gages will be analyzed using standard computer programs (HECEXE) and spreadsheets. The following steps will be undertaken:

• Develop monthly flow duration curves (one graph for each month of the year showing percent of time flow exceeded on x-axis and flow on y-axis);

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• Develop daily exceedance curves (graph with month of year on x-axis, flow on y-axis, and curves for 10%, 25%, 50%, 75%, and 90% exceedance values for each month based on an analysis of daily flows);

• Determine baseflows (annual 1-day, 3-day, and 10-day minimum flow magnitudes and timing);

• Develop flood frequency curves (graph of high flow magnitude versus recurrence interval based on U.S. Water Resources Council method);

• Analyze flood timing (graph annual peak flow magnitude and time of year for period of record);

• Document project spill events (prepare table of spill magnitude and date at each project);

• Display historic and current rates of flow change (during flood and ramping events) based on analysis of 15-minute flow record of selected floods. Selection of flood events for analysis will in some part depend upon availability of 15-minute data from USGS; and

• Compare total annual water year runoff (total discharge from October 1 to Septem- ber 30) for each year of record at Lewis River near Ariel/Lewis River near Amboy gages (to provide record from 1910 to present) with total annual precipitation for same period (October through September, 1910 to present). Examine and describe trends in runoff and precipitation, including wet/dry/normal years and any observed cyclic nature of runoff/precipitation patterns.

Some data sets may need to be extended to complete the analysis. For example, the peak flow record for the Lewis River at the Ariel gage (downstream of Merwin Dam) extends from 1923 to present. This means that the record contains only 8 peak flows prior to construction of . This is not long enough to provide an adequate record for flood flow analysis following the guidelines of Bulletin 17B (U.S. Water Resources Council 1981), so the data will be extended back to 1911 (the longest period of record available) using information from the Lewis River near the Amboy gage and correlation methods such as those described in Maidment (1993) and Linsley et al. (1982).

Task 3. Prepare Plots and Tables Comparing Historic and Current Conditions, and Evaluate Differences

Plots and/or tables will be prepared for all analyses displaying the differences between historic and with-project conditions. For daily flows, the past 10 years of streamflow data will also be analyzed to display the effect of current project operations.

These plots and data will be used to satisfy FERC and NEPA requirements and as part of the Aquatic Resources, Terrestrial Resources, Stream Channel Morphology and Aquatic Habitat, and Flood Management studies. In addition to the standard monthly flow duration curves and flood frequency graphs, plots will be used to help display the

April 2004 Final Technical Reports - Page WTS 2-3 \\Neoserver\disk1\Projects\Lewis River\Final Tech Reports 04-04\02.0 WTS\WTS 02 Final 032304.doc PacifiCorp / Cowlitz PUD Lewis River Hydroelectric Projects FERC Project Nos. 935, 2071, 2111, 2213 magnitude, frequency, and timing of flows in project-affected reaches. A summary of this study is presented in the table below.

Topic Description Study Type Descriptive Study Area Selected stream gages in the Lewis River Watershed Schedule October 1999 – August 2000 Budget $20,000 Requested by Lewis River Watershed Studies Aquatic Working Group Key Personnel Kathy Dubé, Yunbing Shi (HARZA)

2.2.4 Key Questions

This report helps address the following “key” watershed questions identified during the Lewis River Cooperative Watershed Studies meetings:

• What are the historical and current hydrological patterns?

• How do the hydroelectric projects affect baseflows in the Lewis River downstream of the ?

• How do the hydroelectric projects affect the timing, frequency, magnitude, and/or duration of high flows in the Lewis River downstream of the dams?

The following key question is partially addressed in this report based on existing gage information, and more fully addressed in the Speelyai Creek Connectivity and Hatchery Protection Study (AQU 9) and the Swift Bypass Synthesis Report (WTS 4):

• How are instream flows in Speelyai Creek and the Swift bypass reach affected by diversions?

2.2.5 Results

Flow information was analyzed for 7 USGS gages and 1 other streamflow measurement site in the basin (Table 2.2-1; Figure 2.2-1). At each site, streamflow data were separated into pre-project and with-project periods, if appropriate for that site. The Study Plan Document stated that flows in Speelyai Creek at the hatchery intake would be analyzed. However, based on recent discussions with Speelyai Hatchery personnel, they do not actually measure flows in the stream or at the intake, so no data were available to analyze.

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PacifiCorp / Cowlitz PUD Lewis River Hydroelectric Projects FERC Project Nos. 935, 2071, 2111, 2213

Table 2.2-1. Selected stream gages on the Lewis River. Drainage Period of Record Analysis Period USGS Gage Area Pre- With Number Station Name (sq. mi.) Peak Flows Daily Flows Project Project 14213200 Lewis River near 127 1958-1972 1958-1971 -- 1958- Trout Lake, WA 1972 14216000 Lewis River 227 1927-1934; 1927-1934; 1927- 1958- above Muddy River 1954-1977 1954-1970 1934; 1970 near Cougar, WA 1954- 1957 14216500 Muddy River 135 1927-34; 1927-34; 1927- 1958- below Clear Creek near 1954-73; 1954-73; 1934; 1973; Cougar, WA 1983-present 1983-present 1954- 1983- 1957 1998 14218000 Lewis River 481 1917-1977 1924-1958 1917- 1958- near Cougar, WA published; 1957 1975 1959-1975 unpublished 14219500 Lewis River 665 1911-1930 1910-1930 1910- -- near Amboy, WA 1930 14219800 Speelyai Creek 12.6 1959-present 1959-present -- 1959- near Cougar, WA 1998 14220500 Lewis River 731 1924-present 1924-present 1924- 1932- at Ariel, WA 1930 1998

Other Flow Data Cowlitz Swift Canal 481 n/a 1958-present n/a 1958- PUD 1999 Speelyai Speelyai Creek at 15 not available not available -- -- Hatchery Hatchery intake

2.2.5.1 Monthly Flow Duration Curves

Monthly flow duration curves were developed for each gage site. These graphs display flow versus percent of time that flow is exceeded during a particular month. An example for January at the Lewis River near Trout Lake gage is shown in Figure 2.2-2. Graphs for all gages and all months are included in WTS 2 Appendix 1.

2.2.5.2 Daily Exceedence Curves

Daily exceedence curves were prepared for all stream gage stations with available flow data (Figures 2.2-3 through 2.2-10). These graphs were prepared from mean daily flow values, grouped by month, and analyzed to produce 10 percent, 25 percent, 50 percent, 75 percent, and 90 percent exceedence values. This is the same analysis performed for the monthly flow duration curves discussed in the previous section, but data are displayed in a different manner. The 5 exceedence curves are all plotted on a single graph of flow vs. month. These plots show how flow varies through the year at each gage site for median as well as extreme values. Two plots are shown for each station, corresponding to the pre-project period (prior to 1958 for all gages upstream from Merwin Dam; prior to 1931 for the gage downstream from Merwin Dam) and the project period. This was done even for stream reaches not affected by project operations to provide consistent analysis periods.

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January Flow Duration Curves for Lewis River near Trout Lake (USGS Gage #14213200)

10,000

1958-1972

1,000

Average Flow(cfs) Daily

100 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% Percent Exceedence

Figure 2.2-2. January flow duration curve for the Lewis River near Trout Lake gage.

2.2.5.3 Baseflows

Baseflows were computed as the lowest 1-day (daily mean), 3-day running mean, and 10-day running mean from the mean daily flow data for each year. The daily mean values correspond to the lowest daily flow recorded at that gage in a given calendar year. The 3-day running mean values and 10-day running mean values correspond to the lowest 3-day and 10-day running mean values in a given year, so they are slightly higher than the daily mean values. Figures 2.2-11 through 2.2-17 show the baseflow values by year for the gage sites. No analysis was performed for the Swift canal since baseflows would be 0 each year when the project was shut down for maintenance or emergency situations or stopped generation for a few days.

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1

No Pre-project Data Flow (cfs)

0 Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec Month

2,500 Post-project

10% 2,000

1,500 25%

50%

Flow (cfs) Flow 1,000 75%

90% 500

0 Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec Month Figure 2.2-3. Daily flow exceedence curves for Lewis River near Trout Lake (USGS Gage 14213200, post-project data 10/1/58 to 12/7/71).

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4,000 Pre-project 3,500

3,000 10%

2,500 25%

2,000 50% Flow (cfs) Flow 1,500 75%

1,000 90%

500

0 Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec Month

4,000 Post-project 3,500 10%

3,000

2,500

25% 2,000 Flow (cfs) Flow 1,500 50% 1,000 75% 90% 500

0 Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec Month

Figure 2.2-4. Daily flow exceedence curves for Lewis River above Muddy River near Cougar (USGS Gage 14216000: pre-project data 9/1/27 to 9/30/34 and 10/1/54 to 9/31/57; post-project 10/1/58 to 9/30/70).

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3,000 Pre-project

2,500

2,000 10%

25% 1,500 50% Flow (cfs) 1,000 75%

90% 500

0 Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec Month

3,000 Post-project

2,500 10%

2,000

25% 1,500 Flow (cfs) 1,000 50%

75% 500 90%

0 Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec Month

Figure 2.2-5. Daily flow exceedence curves for Muddy River below Clear Creek near Cougar (USGS Gage 1426500: pre-project 10/1/27 to 9/30/34 and 10/1/54 to 9/31/57; post- project 10/1/58 to 12/31/73 and 10/1/83 to 9/30/98).

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9,000 Pre-project 8,000

7,000 10% 6,000

5,000

4,000 25% Flow (cfs) 3,000 50% 2,000 75% 90% 1,000

0 Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec Month

25 3,000 Post-Project 10% 20 2,000

15 1,000 25%

Flow (cfs) 10 0 50% 75% 90% -1,000

5 10% Exceedence Flow (cfs)

0 -2,000 Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec Month

Figure 2.2-6. Daily flow exceedence curve for Lewis River near Cougar (Swift No. 2 bypass reach, USGS Gage 14218000: pre-project 7/1/24 to 9/31/57; post-project 10/1/58 to 12/31/77). Note: On the post-project graph, the 10% exceedence flow curve is plotted on different scale.

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14,000 Pre-project 12,000

10,000 10%

8,000

6,000 25% Flow (cfs)

4,000 50% 75% 2,000 90%

0 Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec Month

1

No Post-project Data Flow (cfs)

0 Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec Month

Figure 2.2-7. Daily flow exceedence curve for Lewis River above Merwin Dam near Amboy (USGS Gage 14219500: pre-project from 10/1/10 to 4/30/31).

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1

No Pre-project Data Flow (cfs)

0 Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec Month

500 Post-project 450

400 10% 350

300

250

Flow (cfs) 200 25%

150 50% 100 75% 50 90% 0 Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec Month

Figure 2.2-8. Daily flow exceedence curve for Speelyai Creek upstream of diversion near Cougar (USGS Gage 14219800, from 6/1/59 to 9/30/98).

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16,000 Pre-project 14,000

12,000 10%

10,000

8,000 25%

Flow (cfs) 6,000 50% 4,000 75% 2,000 90%

0 Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec Month

14,000 Post-project 12,000 10% 10,000

25% 8,000

50% 6,000 Flow (cfs)

4,000 75% 90% 2,000

0 Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec Month

Figure 2.2-9. Daily flow exceedence curve for Lewis River at Ariel (below Merwin Dam, USGS Gage 14220500). Pre-project is from 1909 through 1930 and post-project is from 1932 through 1998. Daily flow from 1910 through 1923 was estimated based on Lewis River flow at USGS Gage 14219500 near Amboy.

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1

No Pre-project Data Flow (cfs)

0 Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec Month

9,000 Post-project 8,000 10% 7,000 25% 6,000

5,000 50%

4,000 Flow (cfs) 75% 3,000

2,000

1,000 90%

0 Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec Month

Figure 2.2-10. Daily flow exceedence curves for Swift No. 2 canal (discharge from Swift No. 1 turbines, from 1/1/89 to 12/19/00).

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200 Daily Mean 3-Day Running Mean 10-Day Running Mean

180

160

140

120 Annual Minimum Flow (cfs)

100

80 1958 1959 1960 1961 1962 1963 1964 1965 1966 1967 1968 1969 1970 1971 Year Figure 2.2-11. Base flow for Lewis River near Trout Lake (RM 73.3, USGS Gage 14213200).

500 Daily Mean 3-Day Running Mean 10-Day Running Mean

450

400

350

300

250

Annual Minimum Flow (cfs)

200

150

1926 1928 1930 1932 1934 1936 1938 1940 1942 1944 1946 1948 1950 1952 1954 1956 1958 1960 1962 1964 1966 1968 1970 Year

Figure 2.2-12. Base flow for Lewis River above Muddy River (RM 62, USGS Gage 14216000).

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450 Daily Mean 3-Day Running Mean 10-Day Running Mean

400

350

300

250

200

150

Annual Minimum Flow (cfs) 100

50

0

1927 1930 1933 1936 1939 1942 1945 1948 1951 1954 1957 1960 1963 1966 1969 1972 1975 1978 1981 1984 1987 1990 1993 1996 Year Figure 2.2-13. Base flow for Muddy River below Clear Creek (USGS Gage 14216500).

1200 Daily Mean 3-Day Running Mean 10-Day Running Mean

1000

800

600 Annual Minimum Flow (cfs)

400 1924 1926 1928 1930 1932 1934 1936 1938 1940 1942 1944 1946 1948 1950 1952 1954 1956 1958 Year

Figure 2.2-14. Base flow for Lewis River near Cougar (RM 46.8, USGS Gage 14218000). Note: only the pre-project flow record was used to compute baseflows due to the inconsistent recording of low flows after Swift was constructed.

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3000 Daily Mean 3-Day Running Mean 10-Day Running Mean

2500

2000

1500

1000 Annual Minimum Flow (cfs)

500

0

1909 1910 1911 1912 1913 1914 1915 1916 1917 1918 1919 1920 1921 1922 1923 1924 1925 1926 1927 1928 1929 1930 1931 Year Figure 2.2-15. Base flow for Lewis River near Amboy (RM 30.9, USGS Gage 14219500).

20 Daily Mean 3-Day Running Mean 10-Day Running Mean

15

10

5 Annual Minimum Flow (cfs)

0 1958 1960 1962 1964 1966 1968 1970 1972 1974 1976 1978 1980 1982 1984 1986 1988 1990 1992 1994 1996 1998 Year Figure 2.2-16. Base flow for Speelyai Creek above diversion (USGS Gage 14219800).

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3500 Daily Mean 3-Day Running Mean 10-Day Running Mean

3000

2500

2000

1500

1000

Flow (cfs) Minimum Annual 500

0

1909 1913 1917 1921 1925 1929 1933 1937 1941 1945 1949 1953 1957 1961 1965 1969 1973 1977 1981 1985 1989 1993 1997 Year

Figure 2.2-17. Base flow for Lewis River below Merwin Dam at Ariel (RM 19, USGS Gage 14220500).

The timing of base flows for each of the study gages was plotted as magnitude of flow vs. the day(s) of the year that flow occurred (Figures 2.2-18 through 2.2-24). Base flows occur during September and October at most gages, at the end of the drier summer months. There are some slight variations in timing at different gages; the Speelyai Creek gage has some base flows that spread into August, and some of the gages in the upper watershed have a few baseflows in November.

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200 One-Day 150

100

50 Flow (cfs) Flow

0 1-Jul 1-Jan 1-Jun 1-Jan 1-Feb 1-Sep 1-Oct 1-Apr 1-Mar 1-Aug 1-Nov 1-Dec 1-May Day of Year

200 Three-Day 150

100

50 Flow (cfs) Flow

0 1-Jul 1-Jan 1-Jan 1-Jun 1-Feb 1-Sep 1-Oct 1-Apr 1-Mar 1-Aug 1-Nov 1-Dec 1-May Day of Year

200 Ten-Day 150

100

50 Flow (cfs)

0 1-Jul 1-Jan 1-Jun 1-Jan 1-Feb 1-Sep 1-Oct 1-Apr 1-Mar 1-Aug 1-Nov 1-Dec 1-May Day of Year

Figure 2.2-18. Base flow timing for Lewis River near Trout Lake (USGS Gage 14213200). Base flows were estimated annual minimum of daily average flow, 3-day running average flow, and 10-day running average flow.

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500 One-Day 400

300

200 Pre-Swift Dam Construction Flow (cfs) Flow 100 Post-Swift Dam Construction 0 1-Jul 1-Jan 1-Jun 1-Jan 1-Feb 1-Sep 1-Oct 1-Apr 1-Mar 1-Aug 1-Nov 1-Dec 1-May Day of Year

500 Three-Day 400

300

200 Pre-Swift Dam Construction Flow (cfs) 100 Post-Swift Dam Construction 0 1-Jul 1-Jan 1-Jan 1-Jun 1-Feb 1-Sep 1-Oct 1-Apr 1-Mar 1-Aug 1-Nov 1-Dec 1-May Day of Year

500 Ten-Day 400

300

200 Pre-Swift Dam Construction Flow (cfs) Flow 100 Post-Swift Dam Construction 0 1-Jul 1-Jan 1-Jun 1-Jan 1-Feb 1-Sep 1-Oct 1-Apr 1-Mar 1-Aug 1-Nov 1-Dec 1-May Day of Year

Figure 2.2-19. Base flow timing for Lewis River above Muddy River (USGS Gage 14216000). Base flows were estimated annual minimum of daily average flow, 3-day running average flow, and 10-day running average flow.

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1,200 One-Day 1,000 800 600 400 Flow (cfs) Flow 200 0 1-Jul 1-Jan 1-Jun 1-Jan 1-Feb 1-Sep 1-Oct 1-Apr 1-Mar 1-Aug 1-Nov 1-Dec 1-May Day of Year

1,200 1,000 Three-Day 800 600 400 Flow (cfs) 200 0 1-Jul 1-Jan 1-Jun 1-Jan 1-Feb 1-Sep 1-Oct 1-Apr 1-Mar 1-Aug 1-Nov 1-Dec 1-May Day of Year

1,200 1,000 Ten-Day 800 600 400 Flow (cfs) Flow 200 0 1-Jul 1-Jan 1-Jun 1-Jan 1-Feb 1-Sep 1-Oct 1-Apr 1-Mar 1-Aug 1-Nov 1-Dec 1-May Day of Year

Figure 2.2-20. Base flow timing for Lewis River near Cougar (USGS Gage 14218000). Base flows were estimated annual minimum of daily average flow, 3-day running average flow, and 10-day running average flow.

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2,000 One-Day 1,500

1,000

500 Flow (cfs) Flow

0 1-Jul 1-Jan 1-Jun 1-Jan 1-Feb 1-Sep 1-Oct 1-Apr 1-Mar 1-Aug 1-Nov 1-Dec 1-May Day of Year

2,000 Three-Day 1,500

1,000

500 Flow (cfs)

0 1-Jul 1-Jan 1-Jan 1-Jun 1-Feb 1-Sep 1-Oct 1-Apr 1-Mar 1-Aug 1-Nov 1-Dec 1-May Day of Year

2,000 Ten-Day 1,500

1,000

500 Flow (cfs) Flow

0 1-Jul 1-Jan 1-Jun 1-Jan 1-Feb 1-Sep 1-Oct 1-Apr 1-Mar 1-Aug 1-Nov 1-Dec 1-May Day of Year

Figure 2.2-21. Base flow timing for Lewis River near Amboy (USGS Gage 14219500). Base flows were estimated annual minimum of daily average flow, 3-day running average flow, and 10-day running average flow.

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2,000 One-Day 1,500

1,000

500 Pre-Merwin Dam Construction Flow (cfs) Post-Merwin Dam Construction 0 1-Jul 1-Jun 1-Jan 1-Jan 1-Sep 1-Oct 1-Feb 1-Apr 1-Aug 1-Nov 1-Dec 1-Mar 1-May Day of Year

2,000 Three-Day 1,500

1,000

500 Pre-Merwin Dam Construction Flow (cfs) Flow Post-Merwin Dam Construction 0 1-Jul 1-Jan 1-Jun 1-Jan 1-Feb 1-Sep 1-Oct 1-Apr 1-Mar 1-Aug 1-Nov 1-Dec 1-May Day of Year

2,000 Ten-Day 1,500

1,000

500 Pre-Merwin Dam Construction Flow (cfs) Post-Merwin Dam Construction 0 1-Jul 1-Jan 1-Jun 1-Jan 1-Feb 1-Sep 1-Oct 1-Apr 1-Mar 1-Aug 1-Nov 1-Dec 1-May Day of Year

Figure 2.2-22. Base flow timing for Lewis River at Ariel (USGS Gage 14220500). Base flows were estimated annual minimum of daily average flow, 3-day running average flow, and 10-day running average flow. Peak flows for Lewis River at Ariel between 1910 and 1923 were estimated based on flood flows for Lewis River near Amboy.

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300 One-Day 250 200 150 100 Pre-Swift Dam Construction Flow (cfs) Flow 50 Post-Swift Dam Construction 0 1-Jul 1-Jan 1-Jun 1-Jan 1-Feb 1-Sep 1-Oct 1-Apr 1-Mar 1-Aug 1-Nov 1-Dec 1-May Day of Year

300 250 Three-Day 200 150 100 Pre-Swift Dam Construction Flow (cfs) 50 Post-Swift Dam Construction 0 1-Jul 1-Jan 1-Jan 1-Jun 1-Feb 1-Sep 1-Oct 1-Apr 1-Mar 1-Aug 1-Nov 1-Dec 1-May Day of Year

300 250 Ten-Day 200 150 100 Pre-Swift Dam Construction Flow (cfs) Flow 50 Post-Swift Dam Construction 0 1-Jul 1-Jan 1-Jun 1-Jan 1-Feb 1-Sep 1-Oct 1-Apr 1-Mar 1-Aug 1-Nov 1-Dec 1-May Day of Year

Figure 2.2-23. Base flow timing for Muddy River below Clear Creek (USGS Gage 14216500). Base flows were estimated annual minimum of daily average flow, 3-day running average flow, and 10-day running average flow.

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20 One-Day 15

10

5 Flow (cfs) Flow

0 1-Jul 1-Jan 1-Jun 1-Jan 1-Feb 1-Sep 1-Oct 1-Apr 1-Mar 1-Aug 1-Nov 1-Dec 1-May Day of Year

20 Three-Day 15

10

5 Flow (cfs)

0 1-Jul 1-Jan 1-Jan 1-Jun 1-Feb 1-Sep 1-Oct 1-Apr 1-Mar 1-Aug 1-Nov 1-Dec 1-May Day of Year

20 Ten-Day 15

10

5 Flow (cfs) Flow

0 1-Jul 1-Jan 1-Jun 1-Jan 1-Feb 1-Sep 1-Oct 1-Apr 1-Mar 1-Aug 1-Nov 1-Dec 1-May Day of Year

Figure 2.2-24. Base flow timing for Speelyai Creek near Cougar (USGS Gage 14219800). Base flows were estimated annual minimum of daily average flow, 3-day running average flow, and 10-day running average flow.

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2.2.5.4 Peak Flow Frequency

Peak flow frequency analyses were performed on 6 streamflow gages using the HECEXE program. This program computes peak flow frequency from annual instantaneous peak flows using the accepted U.S. Water Resources method (U.S. Water Resources Council 1981). The Lewis River gage at Ariel record is being analyzed as part of the flood studies (FLD 1, Section 11.1) and is not reported here. During the early years of the Amboy gage, flows were based on a single daily stage reading made by a local observer, so the peak flow values may be somewhat lower than later continuous gage measurements.

The results of the analysis are displayed in Table 2.2-2 and Figures 2.2-25 through 2.2-27. It should be noted that development of peak flow frequencies is a statistical procedure and is very sensitive to the period of record available and the magnitude of peak flows that occurred during the analysis period. A longer data record produces more reliable results, particularly for longer recurrence interval flows like the 50-100 years. The largest recorded peak flows in the watershed occurred during December 1917, December 1933, and February 1996. Since each of the gages analyzed had a different period of record that included some, all, or none of these large floods, the results of this analysis are not directly comparable between gage sites. The purpose of the following data is to provide information on peak flow frequencies. Analysis of flood control at the project is undertaken in a separate study (FLD 1, Section 11-1).

Table 2.2-2. Peak flow frequencies. Station, Analysis Period, and Number of Events Analyzed in Each Period Lewis River Lewis River above Lewis River Lewis Muddy Chance of flow near Trout Muddy near River near River below Speelyai Creek occurring in any Lake River Cougar Amboy Clear Creek near Cougar given year Re- (14213200) (14216000) (14218000) (14219500) (14216500) (14219800) currence 1927-1933, 1917, 1925- 1928-1934, interval 1958-1972 1955-1977 1975 1912-1931 1955-1997 1960-1997 (years) 14 28 48 20 41 39 1% 100 19,500 35,300 74,100 98,500 26,300 4,470 2% 50 16,800 30,300 61,800 87,600 22,000 4,020 5% 20 13,500 24,100 47,500 73,200 16,900 3,410 10% 10 11,100 19,600 37,900 62,100 13,600 2,940 20% 5 8,890 15,200 29,100 50,600 10,500 2,440 50% 2 5,890 9,240 18,100 33,600 6,720 1,680 80% 1.25 3,990 5,540 11,700 21,800 4,490 1,140 90% 1.11 3,280 4,220 9,430 17,200 3,710 916 95% 1.05 2,810 3,350 7,970 14,100 3,200 764 99% 1.01 2,120 2,170 5,910 9,590 2,470 538

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Lewis River at Sheep Bridge near Trout Lake (14213200, 1958-1972, n=14) 1000000

) 100000

Flow (cfs 10000

1000 1.01 1.05 1.11 1.5 2 5 10 20 50 100 Recurrence Interval (years)

Lewis River above Muddy River (14216000, 1927-1933, 1955-1977, n=28) 1000000

) 100000

Flow (cfs 10000

1000 1.01 1.05 1.11 1.5 2 5 10 20 50 100 Recurrence Interval (years)

Lewis River near Cougar (14218000) from 1917, 1925 to 1975 (n = 48) 1000000

) 100000

Flow (cfs 10000

1000 1.01 1.05 1.11 1.5 2 5 10 20 50 100 Recurrence Interval (years)

Figure 2.2-25. Peak flow hydrographs for USGS gages in the upper and middle Lewis River basin.

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Lewis River near Amboy (14219500) from 1912 to 1931 (n = 20) 1000000

) 100000

Flow (cfs 10000

1000 1.01 1.05 1.11 1.5 2 5 10 20 50 100 Recurrence Interval (years) Figure 2.2-26. Peak flow hydrographs for USGS gages in the lower Lewis River basin.

Muddy River below Clear Creek (14216500, 1928-1934, 1955-1997, n=41) 100000

)

10000

Flow (cfs

1000 1.01 1.05 1.11 1.5 2 5 10 20 50 100 Recurrence Interval (years)

Speelyai Creek near Cougar (14219800, 1960-1997, n=39) 10000

) 1000

Flow (cfs

100 1.01 1.05 1.11 1.5 2 5 10 20 50 100

Recurrence Interval (years) Figure 2.2-27. Peak flow hydrographs for USGS gages on tributaries in the Lewis River basin: Muddy River below Clear Creek and Speelyai Creek near Cougar.

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2.2.5.5 Peak Flow Timing

The timing of peak flows at each of the gages was also analyzed. The magnitude of each annual peak was plotted versus day of the year that the flow occurred (Figures 2.2-28 through 2.2-30). The highest flows at most gages occur in the November-February time period, indicating they are the result of heavy rain or rain-on-snow events. At some gages, particularly those in the upper watershed or that have drainage areas at high elevations, many of the lower peaks occur in the March-June period, indicating the signature of snowmelt-caused high flows on those stations.

2.2.5.6 Project Spill Events

Available information on spill events at the Swift No. 1, Yale, and Merwin powerhouse tailraces was collected. Data availability was limited prior to 1989. The data were graphed to show magnitude of spill versus date at each location (Figures 2.2-31 through 2.2-33).

2.2.5.7 Comparison of Total Water Year Runoff and Precipitation

The total annual water year runoff for the Lewis River near Ariel was compared to the total annual precipitation at the Vancouver 4 NNE weather station (Figure 2.2-34). This is the closest weather station to the basin with a long period of record.

Annual precipitation ranged from 26-62 inches (66 to 157 cm), and total runoff ranged from 1.9 to 5.4 million acre-feet. Runoff generally corresponds to precipitation, with lower runoff in years with lower precipitation and visa versa. No distinct cyclic patterns of precipitation or runoff were observed; the regionally accepted drier years around 1930 and from 1985-1994 show up, as does the wetter 1995-1999 period.

The average annual runoff was regressed with annual precipitation to determine how well they correlate (Figure 2.2-35). As evidenced in the plot by water year, there was a general correlation of runoff with precipitation, but the 2 did not correlate in all years.

2.2.6 Discussion

Streams in the Lewis River watershed have flow patterns characteristic of a wet maritime climate: low flows in the late summer and early fall when little precipitation falls; and high flows during the wet winter and spring months. Streams in the upper portions of the watershed, with drainage basins at high elevations, show a marked snowmelt runoff peak in May and June that is even higher than the winter peak (i.e. Figure 2.2-3, Lewis River near Trout Lake, and Figure 2.2-5, Muddy River). The spring snowmelt peak becomes more and more muted as flows move downstream in the watershed. Lower elevation streams do not show a snowmelt peak, but have high flows from November through April in response to winter rains (i.e. Figure 2.2-8, Speelyai Creek).

Baseflows for all streams studies occur during August, September, and October when little rain falls in the area. Baseflows vary with stream size, but are generally 1/3 to 1/4 of the average annual flow (Table 2.2-3). The exception to this is Speelyai Creek, a small

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Peak flows in the watershed occur in response to winter rain and rain-on-snow events between November and April (Figures 2.2-18 through 2.2-30). In some years, the annual peak flow at upper watershed gages occurs during the spring snowmelt season, but these peaks are lower than the large rain-on-snow events. At most studied gages, the 2-year peak flow is 8-12 times higher than the mean annual flow. The exception is again Speelyai Creek, which has much higher peak flows, with the 2-year peak 30 times higher than the mean annual flow, indicating a very flashy hydrologic regime.

2.2.6.1 Effects of Project Operations on Flow Regimes

The Lewis River projects affect flow regimes in 3 reaches: the Swift bypass reach (between Swift Dam and Yale Lake); Speelyai Creek downstream of the upper diversion; and the Lewis River downstream of Lake Merwin. The effects of project operations are very different in each of these reaches.

Under current normal operating conditions, Swift Dam diverts essentially all of the flow from the Lewis River into the Swift No. 2 canal. As a result, the only flow in the Swift bypass reach is a result of inflow from tributaries, groundwater, and canal leakage. However, during high runoff conditions, when the projects are operating to control floods in the basin or during operational emergencies, water is spilled into the reach from either the Swift Dam spillway or the canal spillway. As a result of these operational regimes, flow in the Swift bypass reach is very low (5-10 cfs) most of the time. Flows downstream of Ole Creek, near the downstream end of the reach, are higher as a result of inflows from the creek. Spill events occur sporadically, but in general spills of several thousand cfs or greater occur every few years. The largest spill was 45,000 cfs during the February 1996 event. The effects of the project on flows and aquatic resources are described in more detail in the Swift Bypass Synthesis Report (WTS 4).

Under current conditions, the upper diversion on Speelyai Creek diverts all water from the upper watershed into the Speelyai canal and Yale Lake. The primary objective for diverting flows is to protect water quality at the Speelyai Hatchery water intake from the effects of high flows; the water is also used for power production at Yale Dam. Flows downstream of the upper diversion are the result of groundwater inflow, and increase downstream to an average of 15-20 cfs at the hatchery intake. Flows downstream of the diversion are fairly constant throughout the year. A detailed discussion of the effects of the upper diversion on Speelyai Creek is included in the Speelyai Creek Connectivity and Hatchery Protection Study (AQU 9).

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Peak Flow Timing, Lewis River near Trout Lake (Gage #14213200) 20,000 16,000 12,000 8,000 4,000 0 Annual Peak Flow (cfs) Flow Peak Annual 1-Jul 1-Jan 1-Jun 1-Oct 1-Feb 1-Sep 1-Oct 1-Apr 1-Nov 1-Dec 1-Mar 1-Aug 1-May Day of Year

Peak Flow Timing, Lewis River above Muddy River (Gage #14216000) 30,000 24,000 18,000 12,000 6,000 0 AnnualPeak Flow (cfs) 1-Jul 1-Jun 1-Jan 1-Feb 1-Sep 1-Oct 1-Oct 1-Apr 1-Mar 1-Aug 1-Nov 1-Dec 1-May Day of Year

Peak Flow Timing, Lewis River near Cougar (Gage #14218000) 80,000

60,000

40,000

20,000

0 Annual Peak Flow (cfs) Flow Peak Annual 1-Jul 1-Jan 1-Jun 1-Oct 1-Feb 1-Sep 1-Oct 1-Apr 1-Nov 1-Dec 1-Mar 1-Aug 1-May Day of Year Figure 2.2-28. Peak flow timing in the upper and middle Lewis River basin.

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Peak Flow Timing, Lewis River near Amboy (Gage #14219500) 100,000 80,000 60,000 40,000 20,000 0 Annual Peak Flow (cfs) Flow Peak Annual 1-Jul 1-Jan 1-Jun 1-Feb 1-Oct 1-Sep 1-Oct 1-Apr 1-Mar 1-Nov 1-Dec 1-Aug 1-May Day of Year

Peak Flow Timing, Lewis River at Ariel (Gage #14220500) 150,000 120,000 Post-Merwin Dam Construction Pre-Merwin Dam Construction 90,000 60,000 30,000 0 Annual Peak Flow (cfs) Annual 1-Jul 1-Jan 1-Jun 1-Oct 1-Feb 1-Sep 1-Oct 1-Apr 1-Nov 1-Dec 1-Mar 1-Aug 1-May Day of Year

Figure 2.2-29. Peak flow timing in the lower Lewis River basin. Peak flows at Ariel prior to 1924 and 1925 were predicted from observed annual flood flow near Amboy.

Table 2.2-3. Summary of streamflow statistics for Lewis River stream gages. Annual 50% Average Baseflow: Peak: exceedence 1-day 2-year annual flow annual flow Stream Gage flow baseflow peak flow ratio ratio Lewis River near Trout Lake 500 113 5,890 0.23 12 Lewis River above Muddy River 917 283 9,240 0.31 10 Muddy River below Clear Creek 620 144 6,720 0.23 11 Lewis River near Cougar (pre-project) 2,185 687 18,100 0.31 8 Lewis River near Amboy 3,050 949 33,600 0.31 11 Speelyai Creek 56 4 1,680 0.07 30 Lewis River at Ariel (pre-project) 3,370 1,051 42,000 0.31 12 Lewis River at Ariel (with-project) 3,790 767 22,000 0.20 6

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Peak Flow Timing, Muddy River below Clear Creek (Gage #14216500) 35,000 28,000

21,000 14,000 7,000

(cfs) Flow Peak Annual 0 1-Jul 1-Jun 1-Jan 1-Sep 1-Oct 1-Feb 1-Oct 1-Apr 1-Aug 1-Mar 1-Nov 1-Dec

1-May Day of Year

Peak Flow Timing, Speelyai Creek above Diversion (Gage #14219800)

4,000 3,200 2,400 1,600

800

0 Annual Peak Flow (cfs) Flow Peak Annual

1-Jul 1-Jan 1-Jun 1-Feb 1-Sep 1-Oct 1-Oct 1-Apr 1-Mar 1-Aug 1-Nov 1-Dec 1-May Day of Year Figure 2.2-30. Peak flow timing for selected tributaries in the Lewis River basin.

Operation of the Lewis River projects in compliance with the current FERC license articles and voluntary measures to protect aquatic resources controls the flow of water in the Lewis River downstream of Merwin Dam. The projects are operated to produce power, manage peak (flood) flows, augment late summer flows, and minimize rapid water level fluctuations in the lower river. As a result of these constraints, mean flows during the late summer, fall, and winter are higher than under pre-project conditions due to flow augmentation for fish in late fall and reductions in reservoir levels for peak flow storage (Figure 2.2-9). Flows during the spring are lower than under pre-project conditions as the reservoirs are refilled for the summer recreation season. Operation of the projects has also reduced the frequency of flows in the 10,000-20,000 cfs range and changed the shape of the mid-range flow fluctuations (Figure 2.2-36). The Merwin facility has 3 units, 2 with flow capacities of 3,790 cfs and a third with a capacity of 3,890, for a total of 11,470 cfs when all 3 turbines are operating at full capacity. As a result, flows under with-project conditions have a more step-wise pattern as units are turned on or off and brought up to their full capacity and held constant. Under pre-project conditions, flow fluctuations had a spikier shape as flows increased to a peak and then decreased over the course of several days to weeks. During large peak flows, when reservoirs are filled,

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2.2.7 Schedule

The Streamflow Study is complete.

50,000 45,000

40,000

35,000

30,000

25,000

Spill Flow (cfs) 20,000

15,000

10,000

5,000

0 1959 1962 1965 1968 1971 1974 1977 1980 1983 1986 1989 1992 1995 1998 2001 Date

Figure 2.2-31. Spill events and magnitude (cfs) into the Swift bypass reach.

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140,000

120,000

100,000

80,000

60,000 Spill Flow (cfs) 40,000

20,000

0 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 Date

Figure 2.2-32. Spill events and magnitude (cfs) at Yale powerhouse tailrace. Note: Data were not available prior to1989.

200,000

180,000

160,000

140,000

120,000

100,000

80,000 Spill Flow (cfs)

60,000 40,000

20,000

0 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 Date

Figure 2.2-33. Spill events and magnitude (cfs) at Merwin powerhouse tailrace. Note: Data were not available prior to 1989.

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6 y = 0.075x + 0.544 2 R = 0.561 5

4

3 (Million Acre-Feet)

Annual Runoff in Lewis R. near Ariel 2

1

20 25 30 35 40 45 50 55 60 65 Annual Precipitation at Vancouver 4NNE (Inches)

Figure 2.2-34. Annual runoff at the Lewis River near Ariel gage and annual precipitation at Vancouver 4NNE weather station.

7 70 Precipitation Runoff

6 60

5 50

4 40 ear Ariel (Million Acre-feet) 3 30

2 20

Annual Precipitation at Vancouver 4 NNE (Inches) Vancouver at Precipitation Annual 1 10

Annual Runoff, Lewis R. n

0 0

9 4 9 4 9 4 9 4 9 4 9 4 9 4 9 4 9 4 9 4 9

9 0 0 1 1 2 2 3 3 4 4 5 5 6 6 7 7 8 8 9 9

8 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 Water Year (Oct-Sep)

Figure 2.2-35. Regression of annual runoff vs. precipitation.

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60000

CFS 1924 CFS 1925 CFS 1926 CFS 1927 50000 CFS 1928 CFS 1929 CFS 1930 CFS 1931

40000

30000

Flow (cfs) Flow

20000

10000

0

/1 5 9 2 6 /8 0 7 6 3 /4 2 0 1 /2 /11 /25 4 /22 5/6 2 6/3 /1 7/1 /15 /12 2 9/9 0/7 1 /16 /3 1/1 1/2 2/1 2 3 3 4 5/ 6 7 7/29 8 8/ 9/2 1 1 1/18 12/ 2 2 10/21 1 1 1 Date

60000

CFS 1988 CFS 1989 CFS 1990 CFS 1991 50000 CFS 1992 CFS 1993 CFS 1994 CFS 1995 CFS 1996 CFS 1997

40000

30000 Flow (cfs) Flow

20000

10000

0 1/1 4/8 5/6 6/3 7/1 9/9 1/15 1/29 2/12 2/26 3/11 3/25 4/22 5/20 6/17 7/15 7/29 8/12 8/26 9/23 10/7 11/4 12/2 10/21 11/18 12/16 12/30 Date Figure 2.2-36. Mean daily flows at the Lewis River at Ariel gage (USGS 14220500) under pre-project (top graph; 1924-31) and recent with-project (bottom graph; 1988-1997) conditions. (Graphs courtesy of Jennifer Sampson, 10,000 Years Institute).

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2.2.8 References

Linsley, R.K. Jr., M.A. Kohler, and J.L.H. Paulhus. 1982. Hydrology for Engineers. McGraw-Hill:New York.

Maidment, D.R. 1993. Handbook of Hydrology. McGraw-Hill:New York.

PacifiCorp and Cowlitz PUD. 1999 as amended. Study Plan Document for the Lewis River Hydroelectric Projects. Portland, OR. And Longview, WA. October 29, 1999, as amended.

U.S. Water Resources Council. 1981. Guidelines for determining flood flow frequency. Bulletin No. 17B of the Hydrology Committee.

This report was prepared by:

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2.2.9 Comments and Responses on Draft Report

This section presents stakeholder comments provided on the draft report, followed by the Licensees’ responses. The final column presents any follow-up comment offered by the stakeholder and in some cases, in italics, a response from the Licensees.

Page/ Commenter Volume Paragraph Statement Comment Response Response to Responses WDFW – 1 WTS 02 Ramping rate. Where is the characterization of the A discussion of ramping JIM BYRNE ramping rates? rates, originally intended for this study, was expanded to its own study and is reported in AQU 3. WDFW – 1 WTS 02-7 Flow Some of the figures have a frame Comment noted. KAREN – 17 Fig. exceedence around them and some don’t. They KLOEMPKE 2.2-3 to curves. should be consistent. N 2.2-16 WDFW – 1 WTS 02- Diverting I thought the primary objective for The original water right Are the words in quotes JIM BYRNE 30 flows. diverting flows was for additional application for the Yale referenced as the primary power generation at Yale. diversion stated the purpose objective? of the diversion was “to Licensees’ Response: The divert flood water away from quotation marks should not State Fisheries rearing have been used for this ponds” as well as power paraphrasing. Water right production. permit no. 14862 states that the primary purpose is to divert flow in the interests of fish propagation and to protect hatchery water quality from the effects of high flows. J. Kaje – 1 WTS 02- Scope of entire The discussion of project effects on While an in-depth analysis of Hydrologic impacts are not a Tech.Adv. for 30-33, section the flow regime is inadequate, pre- and with-project figment of the past in the way Cowlitz Tribe 2.2.6.1 particularly with respect to peak flow hydrologic conditions is that fish passage is considered timing and base flow below Merwin. possible, FERC guidelines to be by some parties. The report should include statistical for relicensing define Hydrologic changes are analysis to support the figures. For existing conditions as the happening continuously to this example, Figure 2.2-22 appears to baseline for analysis of the day. One only needs to look at

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Page/ Commenter Volume Paragraph Statement Comment Response Response to Responses indicate a clear post-project decrease effects of the new license. A the CURRENT hydrologic in the 1-day and 3-day base flow rate general discussion of the patterns above the project area at Ariel, but no statistics are differences between pre- to the CURRENT hydrologic provided. Also peak flow timing at project and with-project patterns below the area to Ariel is presented in Figure 2.2-29 conditions was provided, but recognize that fact. So, the and appears to indicate that a much further comparison is not “baseline” argument does not higher proportion peak flows occur required. hold water. We have asked that after Feb-15 during the post-project a thorough assessment of period. By visual inspection of the project effects on downstream graph, it looks like the pre-project era hydrology be performed – this had only one peak flow data point has not yet happened. We after Feb-15 compared to 18 between suggest using the Indicators of late October and mid February, Hydrologic Alteration whereas the post project ratio appears methodology and associated significantly different. Please Range of Variability Analysis provide a more thorough discussion (Richter et al.). Hydrologic of all project effects on the flow changes are among the most regime. fundamental, continuous impacts of dams. These should be quantified in the relicensing context. Licensees’ Response: Studies have been developed and performed that are consistent with the Commission’s guidelines defining baseline conditions. This guidance has been affirmed by the courts in American Rivers v. FERC, 103F.3d 1007 (9th Circuit 1999) and in Confederated Tribes of the Yakama Nation v. FERC, 746 F 2d 466 (9th Circuit 1984. Accordingly, we respectfully decline to conduct further

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Page/ Commenter Volume Paragraph Statement Comment Response Response to Responses analysis of pre-project hydrologic conditions. That being said, analyses using the Indicators of Hydrologic Alteration (IHA) methodology have been conducted. Hardin- Davis recently carried out a statistical analysis of hydrologic patterns below Merwin Dam, using the IHA. This analysis compares the past 18 years of daily flow records with and without the dams in place (without-dam flows were calculated based on recorded daily changes in reservoir volumes). The report, which includes statistics on peak and base-flow timing and magnitude, will be made available to the ARG. 1 WTS 02- “The net effect Interpretation of effects of the J. Sampson, 30 – 33 of the projects projects on flows downstream of the Technical is to dampen Merwin project is overly simplistic. Advisor to the range of By providing only the most general the flow types of hydrological statistics, the Conservation fluctuations… 2001 Technical Report (TR) is not Groups High flows are able to compare hydrologic variation lower and low before and after the projects at flows are higher temporal scales relevant to processes than under pre- which increase and support biological project and habitat diversity. Licensees’ Response: conditions” These figures have been We submit figures 1 and 2 as an included in the final report as illustration of how the projects Figure 2.2-36.

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Page/ Commenter Volume Paragraph Statement Comment Response Response to Responses suppress the multitude of peak flows between 1000 and 20,000 cfs in the reach downstream of Merwin dam. These figures were generated from daily mean flows reported by USGS on their website for the Ariel gage. These are the same data used for Figure 4.3-4 (AQU3). Figures 1 and 2 should be included side by side as Figure 2.2-36 (Figure 1 as 2.2-36a and Figure 2 as 2.2-36b) with the title “Comparison of daily mean flows at Ariel gage between 1924 and 1931, with those between 1988 and 1997.” The last sentence of WTS2 Section 2.2.6.1 should be deleted, and replaced with the following text:

“Figure 2.2-36 provides an illustration of how operation of the projects, even under the most recent license terms, reduce the day to day variation in flows between 1000 and 20,000 cfs in the reach downstream of Merwin dam. Where pre-project conditions provided many small floods to this reach, project operation tends to dampen peaks in this flow range, regardless of their size. As a result, the river is less often in contact with the riparian zone; that is, the connectivity of the system is diminished. Because of this fundamental change in flows, transfer

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Page/ Commenter Volume Paragraph Statement Comment Response Response to Responses of nutrients and materials between the riparian zone and the river is altered (Meyer et al. 1988; Gregory et al. 1991), changing patterns of productivity in the channel; biological diversity in the riparian zone may be reduced (Pollock et al. 1998; Pinay et al. 1990; Power et al. 1996); and riparian habitat diversity including development of wetlands and side channels is reduced Pollock et al. 1998). The fundamental process upon which habitat and biological diversity in the reach develop is the variation in flows (Pollock 1998 see also citations of Richter 1996, Richter et al. 1997). While non-project developments may have similar, localized impacts in the riparian zone, alteration of short term patterns of variation as illustrated by Figure 2.2-36, and changes in flow variation at other temporal scales, are results of project operations.”

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