REDWOOD VALLEY SUBAREA

Transcription

1 Independent Science Review Panel Conceptual Model of Watershed Hydrology, Surface Water and Groundwater Interactions and Stream Ecology for the Russian River Watershed Appendices A-1

2 APPENDIX A A-2

3 REDWOOD VALLEY SUBAREA Table A-1. Peak flows recorded at the USGS gage Russian River near Ukiah, West Fork Russian River. Date Stream flow (cfs) Nov. 06, ,600 Dec. 06, ,600 Jan. 17, ,280 Dec. 21, ,900 Jan. 20, ,340 Feb. 12, ,200 Jan. 12, ,590 Feb. 08, ,900 Feb. 11, ,610 Feb. 13, ,320 Jan. 31, ,800 Jan. 20, ,850 Dec. 22, ,900 Jan. 04, ,900 Jan. 20, ,300 Dec. 23, ,720 Jan. 23, ,000 Dec. 03, ,360 Jan. 11, ,320 Jan. 16, ,600 Mar. 21, ,200 Dec. 14, ,900 Jan. 11, ,780 Jan. 13, ,800 Nov. 23, ,300 Dec. 21, ,000 Nov. 17, ,390 Feb. 08, ,700 Feb. 17, ,300 Jan. 04, ,040 Nov. 22, ,730 Jan. 07, ,790 Jan. 20, ,700 A-3

4 Table A-1. Peak flows recorded at the USGS gage Russian River near Ukiah, West Fork Russian River (cont.). Date Stream flow (cfs) Jan. 08, ,700 Jan. 24, ,900 Jan. 01, ,600 Feb. 07, ,710 Feb. 09, ,730 Dec. 01, ,560 Dec. 16, ,100 Feb. 17, ,100 Dec. 08, ,720 Dec. 30, ,600 Feb. 10, ,680 Jan. 04, ,200 Feb. 23, ,220 Jan. 20, ,250 Dec. 28, ,800 Jan. 20, ,180 Dec. 02, ,700 A-4

5 Table A-2. Monthly mean discharge at USGS stream flow gage Russian River near Ukiah, West Fork Russian River. Year Monthly mean in cubic feet/second (cfs) (Calculation Period: > ) Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec , , , , , ,202 1, , ,196 1, , ,185 1, ,111 A-5

6 Table A-2. Monthly mean discharge at USGS stream flow gage ( ) Russian River near Ukiah, West Fork Russian River (cont.). Year Monthly mean in cfs (Calculation Period: > ) Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec , , , , ,342 1, , , , , Mean of monthly Discharge A-6

7 Table A-3. Mean daily discharge for USGS stream flow gage on Russian River near Ukiah, West Fork Russian River. Day of month Mean of daily mean values for each day for years of record, in cfs (Calculation Period > ) Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec A-7

8 Table A-4. Peak flows recorded at USGS gage , Russian River near Redwood Valley, West Fork Russian River. Date Streamflow (cfs) Jan. 20, ,500 Dec. 22, ,400 Jan. 04, ,390 Jan. 20, ,520 Jan. 09, ,060 Jan. 13, ,580 Jan. 23, ,350 Dec. 03, ,880 Jan. 22, ,160 Jan. 11, ,390 Jan. 16, ,660 Mar. 21, ,540 A-8

9 Table A-5. Mean of monthly discharge at USGS gage Russian River near Redwood Valley, West Fork Russian River. YEAR Monthly mean in cfs (Calculation Period: > ) Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Mean of monthly Discharge A-9

10 Table A-6. Mean daily discharge for USGS stream flow gage Russian River near Redwood Valley, West Fork Russian River. Day of month Mean of daily mean values for each day for 5-6 years of record, in cfs (Calculation Period > ) Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec A-10 Interactions and Stream Ecology for the Russian River Watershed.

11 Table A-6. Mean daily discharge for USGS stream flow gage Russian River near Redwood Valley, West Fork Russian River (cont.). Day of month Mean of daily mean values for each day for 5-6 years of record, in cfs (Calculation Period > ) Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec A-11 Interactions and Stream Ecology for the Russian River Watershed.

12 UKIAH VALLEY SUBAREA Table A-7. Peak flows recorded at the East Fork Russian River ( ) stream flow gage. Date Peak flow (cfs) Prior to Coyote Dam Mar. 15, ,500 Jan. 18, ,140 Dec. 01, ,980 Dec. 07, ,540 Jan. 17, ,300 Dec. 21, ,300 After Coyote Dam Dec. 19, ,200 Nov. 24, ,380 Dec. 30, ,780 Jan. 31, ,140 Jan. 22, ,060 Jan. 24, ,350 Dec. 04, ,390 Jan. 13, ,520 Jan. 17, ,320 Mar. 27, ,340 Jan. 20, ,260 Jan. 15, ,740 Feb. 16, ,530 Mar. 03, ,470 Feb. 18, ,700 Jan. 02, ,080 Jan. 19, ,880 Feb. 13, ,830 Feb. 10, ,020 Feb. 16, ,290 Jan. 02, ,880 Jan. 04, ,490 Mar. 28, ,290 A-12

13 Table A-8. Mean monthly discharge for the East Fork Russian River ( ) stream flow gage. YEAR Monthly mean in cfs (Calculation Period: ) Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec , , , , , , , ,177 1, , A-13 Interactions and Stream Ecology for the Russian River Watershed.

14 Table A-8. Mean monthly discharge for the East Fork Russian River ( ) stream flow gage (cont.). YEAR Monthly mean in cfs (Calculation Period: ) Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec , , , ,138 1, , , , ,299 1, A-14 Interactions and Stream Ecology for the Russian River Watershed.

15 Table A-8. Mean monthly discharge for the East Fork Russian River ( ) stream flow gage (cont.). YEAR Monthly mean in cfs (Calculation Period: ) Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec , Mean of monthly Discharge A-15 Interactions and Stream Ecology for the Russian River Watershed.

16 Table A-9. Mean daily discharge for for the East Fork Russian River ( ) stream flow gage. Day of month Mean of daily mean values for , in cfs (Calculation Period > ) Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec A-16 Interactions and Stream Ecology for the Russian River Watershed.

17 Table A-9. Mean daily discharge for for the East Fork Russian River ( ) stream flow gage (cont.). Day of month Mean of daily mean values for , in cfs (Calculation Period > ) Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec A-17 Interactions and Stream Ecology for the Russian River Watershed.

18 HOPLAND VALLEY SUBAREA Table A-10. Peak flows recorded at the USGS Hopland ( ) stream flow gage (in cubic feet per second or cfs). DATE PEAK FLOW (in cfs) COMMENTS Feb. 28, ,100 Pre-Coyote Dam Jan. 21, ,000 Pre-Coyote Dam Jan. 21, ,900 Pre-Coyote Dam Dec. 22, ,000 Pre-Coyote Dam Dec. 22, ,500 Post-Coyote Dam Jan. 16, ,700 Post-Coyote Dam Feb. 17, ,900 Post-Coyote Dam Dec. 31, ,600 Post-Coyote Dam Table A-11. Monthly mean, maximum and minimum data for the Hopland ( ) stream flow gage for water years (in cfs). Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Mean 1,759 1,733 1, ,152 Max 5,856 6,799 5,361 2,657 1, ,656 4,849 (WY) (1970) (1958) (1983) (2006) (2003) (1998) (1961) (1961) (1974) (2011) (1984) (1965) Min (WY) (1977) (1977) (1977) (1977) (1977) (1949) (1948) (2009) (1977) (1978) (1978) (1991) A-18

19 Table A-12 Mean daily discharge for at Feliz Creek USGS gage ( ) (in cfs). Day of Mean of daily mean values for each day for 8-9 years of record in, cfs (Calculation Period > ) month Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec A-19 Interactions and Stream Ecology for the Russian River Watershed.

20 Table A-12 Mean daily discharge for at Feliz Creek USGS gage (in cfs) (cont.). Day of Mean of daily mean values for each day for 8-9 years of record in, cfs (Calculation Period > ) month Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec A-20 Interactions and Stream Ecology for the Russian River Watershed.

21 NARROWS SUBAREA Table A-13. Largest peak flows recorded at the Russian River near Cloverdale ( ) USGS stream flow gage Date Peak Flows (in cfs) Comments Jan 17, ,300 pre-coyote Dam Dec 22, ,000 pre-coyote Dam Feb 24, ,100 pre-coyote Dam Dec 22, ,200 post Coyote Dam Jan 5, ,600 post Coyote Dam Jan 23, ,000 post Coyote Dam Jan 16, ,900 post Coyote Dam Jan 26, ,200 post Coyote Dam Feb 17, ,700 post Coyote Dam Jan 9, ,400 post Coyote Dam Dec 31, ,700 post Coyote Dam Table A-14. Monthly mean data for water years for Russian River near Cloverdale ( ) stream flow gage (in cfs). Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Mean 2,515 2,426 1, ,602 Max 8,324 9,790 7,015 4,034 1, ,636 6,398 (WY) 1,995 1,998 1,983 2,006 2,003 1,998 1,998 1,961 1,974 1,963 1,984 1,965 Min (WY) 1,977 1,977 1,977 1,977 1,977 2,007 2,009 2,009 1,977 1,978 1,992 1,991 A-21

22 ALEXANDER VALLEY SUBAREA Table A-15. Peak flows recorded at the Russian River at Healdsburg ( ) stream flow gage. Date Peak flow in cfs February 28, ,000 February 6, ,200 January 21, ,300 December 28, ,800 December 4, ,800 January 9, ,900 January 17, ,700 December 22, ,400 February 25, ,900 February 1, ,800 December 23, ,300 January 5, ,400 January 16, ,500 December 4, ,200 January 16, ,700 January 16, ,800 December 20, ,000 January 26, ,700 February 17, ,000 January 20, ,600 January 9, ,000 January 1, ,700 February 3, ,500 December 16, ,700 February 18, ,500 December 31, ,900 A-22

23 Table A-16. Monthly mean, maximum, and minimum data for water years in cfs, Healdsburg gage ( ). Jan Feb March April May June July August Sept Oct Nov Dec Mean Max WY Min WY Table A-17a. Peak flows recorded at Big Sulphur Creek USGS gages. Big Sulphur Creek near Cloverdale USGS Gage Date Peak flow in cfs December 22, ,000 December 22, ,700 January 4, ,100 January 21, ,100 January 13, ,200 January 23, ,000 *Peak flow data available for 1955 to Table A-17b. Big Sulphur Creek at Geysers Resort near Cloverdale USGS Gage Date Peak flow in cfs February 17, ,700 March 4, ,090 January 8, ,550 December 12, ,070 January 1, ,010 December 16, ,880 February 17, ,380 December 31, ,130 January 4, ,740 December 2, ,210 A-23

24 Table A-18. Discharge at Big Sulphur Creek at Geysers resort near Cloverdale station , in cfs. Year Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Mean of monthly Discharge A-24

25 Table A-19. Discharge at Big Sulphur Creek near Cloverdale station , in cfs. Year Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec , , ,395 1, , Mean of monthly Discharge A-25

26 KNIGHTS VALLEY SUBAREA Table A-20 Peak flows recorded at the Maacama Creek USGS gage ( ) Date Peak flows in cfs January 31, ,700 February 13, ,370 January 31, ,700 January 20, ,180 December 22, ,920 January 4, ,650 November 19, ,620 January 10, ,670 January 23, ,250 January 16, ,460 March 28, ,630 March 21, ,770 January 16, ,360 February 13, ,110 February 17, ,760 December 3, ,290 Table A-21 Monthly mean, maximum and minimum data for the Maacama Creek stream flow gage ( ) for water years and (in cfs). Maacama Creek Statistics of Monthly Mean Data for Water Years , By Water Year (WY) Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Mean Max (WY) (1963) (1974) (1965) (1970) (1969) (1974) (1963) (1963) (1967) (1963) (1963) (1963) Min (WY) (1977) (1981) (1977) (1977) (1977) (1977) (1977) (1977) (1977) (1977) (1977) (1964) A-26

27 Table A-22. Mean monthly discharge at the Maacama Creek gage ( ) for the period and the period of record. YEAR Monthly mean in cfs (Calculation Period: ) Jan Feb Mar Apr Ma y Jun Jul Aug Sep Oct Nov Dec Mean of monthly Discharg e YEAR Monthly mean in cfs (Calculation Period: ) Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Mean of monthly Discharge A-27

28 Table A-23. Mean daily discharge at the Maacama Creek gage ( ) for the period. Day of month Mean of daily mean values for each day for years of record, in cfs (Calculation Period ) Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec A-28

29 Table A-24 Peak flows recorded at the Franz Creek USGS gage ( ). Date Peak Flow in cfs December 22, ,130 February 24, ,400 February 8, ,400 February 13, ,030 January 5, ,780 January 21, ,280 January 23, ,320 January 16, ,490 Table A-25 Mean monthly discharge at the Franz Creek gage ( ) for the period Monthly mean in ft3/s YEAR (Calculation Period: ) Jan Feb Ma Apr Ma Jun Jul Aug Sep Oct Nov Dec r y Mean of monthly Discharge A-29

30 Table A-26 Mean daily discharge at the Franz Creek gage ( ) for the period. Mean of daily mean values for each day for 5-5 years of record, in cfs. (Calculation Period ) Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Day of month A-30

31 MARK WEST CREEK WATESHED SUBAREA Table A-27. Peak flows recorded at Mark West Creek near Windsor USGS stream flow gage ( ). Water Year Date Stream Flow (cfs) 2007 Dec. 26, , Jan. 04, ,970 Table A-28. Mean monthly discharge for Mark West Creek near Windsor USGS stream flow gage ( ). Monthly Mean in cfs YEAR (Calculation period: > ) JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC Mean of monthly Discharge A-31

32 TableA-29. Mean daily discharge for Mark West Creek near Windsor USGS stream flow gage ( ). Day of Month Mean of Daily Mean Values for Each Day for 2 Years of Record, in cfs. Calculation period: > JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC A-32

33 Table A-30. Peak flows recorded at the Mark West Creek near Mirabel Heights U.S. Geologic Survey stream flow gage ( ). Date Stream Flow (cfs) Dec. 31, ,300 Feb. 11, ,720 Jan. 05, ,960 Jan. 23, ,480 Dec. 24, ,200 Table A-31. Mean monthly discharge at Mark West Creek near Mirabel USGS stream flow gage ( ). YEAR Monthly mean in cfs Calculation Period: > Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec , , ,585 1, , , Mean of monthly Discharge A-33

34 Table A-32. Mean daily discharge for the Mark West Creek near Mirabel Heights USGS stream flow gage ( ) in cfs. Day of Month Mean of Daily Man Values for Each Day for 6-9 Years of Record, in cfs. Calculation period: > JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC , , , , , , , , , , , A-34

35 A-35

36 APPENDIX B Analysis of the Discharge at the Russian River near Ukiah, CA Stream Flow Gage (USGS ) B-1

37 Analysis of the Discharge at the Russian River near Ukiah, CA Stream Gage (USGS ) A statistical analysis of the annual and monthly discharge measured at the Russian River near Ukiah stream gage was done to shed light on the following hypothesis. Hypothesis: For the West Fork Russian River gage (Russian River near Ukiah ) to review the and then the 1952-present records for dry season water flows and determine if Coyote Dam and channel incision has led to lower water levels during the dry season. The above hypothesis has two parts: 1) Is the dry season stream flow changing over time at the Russian River near Ukiah stream gage (West Fork of the Russian River)? 2) If the dry season streamflow is changing over time, a) How is the stream flow changing? b) What is driving the change? c) Has there been a change in the annual rainfall? d) Does the existing data support a causal link between the change in flow and dam induced channel incision? Difficulty in Establishing a Causal Link Channel incision induced by the construction of Coyote Dam, which was completed in 1958, is hypothesized to cause lower water levels during the dry season. There are only 8 water years of predam discharge data available at the Russian River near Ukiah stream gage station. The small sample size may hamper the ability of statistical tests to show a clear change in discharge between pre-dam and post-dam during the dry season. Also, statistical tests cannot, by themselves, establish causality. Statistical tests can provided supporting evidence for proposed causal mechanisms. Another problem is that the construction of Coyote Dam is not the only factor linked to channel incision. In 1992, Dianne Chocholak, working for the Mendocino County Water Agency, interviewed long-term residents of the Ukiah Valley to document historical processes that may have altered the Russian River from its pre-settlement condition. The findings from her interviews are presented in, Early Conditions and History of The Upper Russian River. Chocholak s findings reveal that there was a significant level of gravel extraction from the Russian River and its tributaries in the late 1940 s and early 1950 s. For example on page 6 we find; B-2

38 Then in 1948 to 1950 Masonite built its hardboard plant in Ukiah and a paved logging road westward out to its 55,000 acres of newly purchased forestlands. Masonite used gravel from Ackerman Creek north of Ukiah to pave its highway. As a result, the State Highway Division in 1950 had to reinforce the Ackerman Bridge, because its foundations were weakened "as gravel from beneath the bridge was carried downstream. GRAVEL EXTRACTION The production of sand and gravel was the principal mining industry in Mendocino County in the early 1950s. In 1950, 254,413 short tons of sand and gravel were produced. Gravel from the Russian River streambeds was used for concrete construction and for building and repairing roads. It supplied the entire Bay Area, and the river was greatly overextracted. Chocholak also notes the US Army Corps of Engineers began channel stabilization projects on the Russian River in October of Channel stabilization has been linked to channel incision by various researchers. The extensive gravel extraction in the late 1940 s and early 1950 s may have started channel incision on the upper Russian River prior to the construction of Coyote Dam. If this is in fact the case, then only the discharge from the 1912 and 1913 water years at the Russian River near Ukiah stream gage could be considered pre-incision. Reliable statistical tests based on only two years of discharge data would be virtually impossible. Lower dry season flows could be the result of other factors such as increased water diversions, decreased rainfall, or increasing evapotranspiration from native vegetation. Lower dry season discharge could also be the result of increased wet season discharge from increased rainfall intensity, or from a decrease in permeability of the surface of the watershed from road construction and land use. The above factors are complex and require additional research to determine their role in any change in discharge at the Russian River near Ukiah stream gage. Such research is beyond the scope of this present study. Summary of the Statistical Analysis of Discharge The discharge record at the Russian River near Ukiah stream gage has daily records for 65 water years or 23,754 days. There are many ways of establishing if the discharge is changing over time. This analysis looks at only a few possible ways of measuring change over time. This analysis is not intended to be an exhaustive study of the change in discharge at the Russian River near Ukiah gaging station. We looked at two levels of change. First we examined if change could be detected in annual data. We also looked for change in monthly data. Change in Annual Data We use two approaches to determine if there has been a statistically significant change over time in the stream flow at the Russian River near Ukiah stream gage. The first method is to test is the rank-correlation between the water year and an annual discharge parameter such as the annual minimum discharge. A rank-correlation is performed by assigning each value in a series of observations a rank from smallest to largest. Then the correlation is performed B-3

39 between the two sequences of ranked values. Rank-correlation is less sensitive to extremes in the data sets. We use Kendall s tau to test if the rank correlation is statistically significant. Annual discharge data tends to have a large variance because both wet and dry years are sampled when the record length is long. The large variance of annual flow data, measured in acre-feet per year, can hide changes in discharge. One way to reduce the variance of streamflow data is to convert annual discharge data from acre-feet to inches by dividing the annual discharge in acre-feet by the number of acres in the watershed. Another way to reduce the variance of stream flow data is to account for the variability in rainfall data. We did this by performing a simple linear regression to predict annual runoff, in inches, from annual rainfall. The predicted value for each rainfall observation is then subtracted from the observed runoff. The resulting set of runoff residuals will be free of the influence of rainfall. If the runoff residuals change over time, it indicates that there is some time-dependent process that is acting on the annual discharge. Changes in land use, changes in diversion amounts, or increasing channel incision are examples of timedependent mechanisms that may influence the runoff residuals. The second method to detect change in annual discharge parameters is to divide the period of record into two or more time periods, and to test if there is a statistical difference between the various groups. The difference may be in the magnitude (location of the center of the data) or in the distribution of the values of the groups (dispersion or shape). We use both methods to explore if the dry season flows have decreased over time. Russian River near Ukiah Watershed The watershed above the Russian River near Ukiah (USGS ) stream gage (West Fork) covers about 100 square miles. Redwood Valley lies a short distance upstream of the gage. According to the USGS StreamStats website the West Fork watershed s average annual precipitation is about 46.6 inches. The basin has a mean slope of about 27.4% and a mean elevation of about 1,468 feet with a maximum elevation is about 3,338. Stream flow data is available for the 1912 and 1913 water years and from the 1953 water year to the present. A total of 65 years of streamflow data is available. Rainfall Data Rainfall data is available from the California Department of Water Resources CDEC (California Data Exchange Center) website and from NOAA s National Climatic Data Center. The Ukiah, CA station (GHCND:USC ) has monthly and daily rainfall data from The station essentially closed in However, monthly data after 2013 was available on the CDEC website. The Ukiah, CA rainfall data is missing more than 5 days of rainfall data in 16 of the last 60 years. Since 1999, several years had from one to nine months of daily data missing. The significant number of missing days of record after 1998 raises the question of whether the Ukiah rainfall data can be used to detect change in streamflow. B-4

40 The problem of extensive missing data was dealt with by comparing the monthly data from NOAA s NCDC website and DWR s CDEC website and using the larger of the two values for each month. The resulting annual rainfall series has a correlation of with the Russian River near Ukiah annual discharge series. The high correlation between rainfall and stream flow suggests that the Ukiah rainfall record constructed from the NCDC and CDEC data is a reasonable approximation of the actual rainfall, despite the significant number of days of missing record. The rainfall data for the Potter Valley Power House was also examined. The Potter Valley Power House is close to the northeastern edge of the West Fork watershed. It too had many days of missing record. The Potter Valley Power House rainfall data had a correlation of with the annual stream flow of the Russian River near Ukiah gage, which is slightly lower than the Ukiah rainfall data correlation. Combining the Ukiah and Potter Valley Power House rainfall data only increased the correlation with stream flow to Therefore, we only used the Ukiah rainfall data in this study. Figure 1 shows the annual Ukiah rainfall and the annual runoff of the Russian River near Ukiah (USGS ) stream gage. Both the annual rainfall and the annual runoff are shown in inches. The annual discharge in acre-feet can be obtained by multiplying the runoff in inches by the watershed area in acres. Potential Error in the Data On Figure 1, note that the 1956 water year runoff almost equals the 1956 water year rainfall. The near equality of rainfall and runoff in the 1956 water year signals a potential problem with either the rainfall data or the runoff data. We define runoff efficiency as the ratio of annual runoff to annual rainfall. A runoff efficiency of 1.0 means that all the annual rainfall was converted to annual runoff. A runoff efficiency of 0 means that none of the annual rainfall was converted to annual runoff. During the 1956 water year, the Ukiah rainfall total was 50.67" and the runoff from the Russian River near Ukiah gage was 49.79". These values give a runoff efficiency of 98%. A runoff efficiency of 98% is suggestive of an impervious surface. Therefore we re-examined the Ukiah rainfall data for errors. We also compared the 1956 Ukiah rainfall to the 1956 Potter Valley and Fort Bragg rainfall records. The 1956 water year rainfall was inches at the Potter Valley Power House and was inches at Fort Bragg on the coast. The Willits rainfall record started in 1960 and so it had no data for the 1956 water year. It is possible that a data entry error was made for the Ukiah rainfall for the 1956 water year. It is also possible that the 1956 Ukiah rainfall is correct but simply underestimates the true annual average rainfall over the watershed by roughly 12". The 1956 water year rainfall for the Potter Valley Power House was which is greater than the Ukiah rainfall for that year. Comparing the Potter Valley Power House rainfall (63.15 ) for the 1956 water year to the runoff at the Russian River near Ukiah steam gauge (49.79 ) gives a runoff efficiency of 78.8%, which is similar to other wet year runoff efficiencies. Another possibility is that there is a problem with the discharge data. The 1956 water year includes the flood of December In addition, the 1956 water year was before Coyote Dam was finished, so the storm runoff from the East Fork of the Russian River would not have been captured by the dam. Thus, B-5

41 there may have been a backwater effect from the confluence of the flood waters on the Russian River near Ukiah gage, which was about 0.6 miles further upstream from its present location. To assess this possibility we looked at the annual maximum peak flow record and graphed the peak against the stage. But the 1956 WY data looked consistent with the other data collected at that site, suggesting that backwater from the confluence does not explain the high runoff to rainfall ratio. B-6

42 Figure 1. The annual Ukiah rainfall and the annual runoff of the Russian River near Ukiah (USGS ) stream gage are shown in inches. The annual discharge in inches is obtained from the annual discharge in acre-feet by dividing the acre-feet of discharge by the watershed area in acres. Note that there was almost zero runoff in Also note that the 1956 water year runoff almost equaled the 1956 water year rainfall. The near equality of rainfall and runoff in the 1956 water year signals a potential problem with either the rainfall data or the runoff data. We decided to accept the 1956 water year Ukiah rainfall and runoff values at face value and proceed with the analysis. Some of the statistical methods used, for example rank correlation, are not sensitive to this type of possible error. The anomalously high runoff efficiency may affect some statistical tests, but since the tests of greatest concern are for the dry season the impact of the suspicious data may be minimal. Ukiah Rainfall Characteristics The Ukiah water year rainfall for the 65 year period corresponding to the available discharge data ( and ) ranged from a minimum of to a maximum of The average water year rainfall is 38.0 and the median is B-7