P

0 1. Trends and Fluctuations in Precipitation \ and Stream Runoff in the Queen I, Charlotte Islands Land Management Report NUMBER 40

ISSN 0702 9861

1t March 1986 FISH/FORESTRY INTERACTION PROGRAM

This study was undertaken as part of the Fish/Forestry Interaction Program, a multidisciplinary research studyinitiated in 1981. The programwas startedfollowing a series of major winter stormsin 1978 that triggered landslides over much of the Queen CharlotteIsland forest land base. Originatingon steep slopes, many slidesdeposited tonnes of debrisin streams and on valley flats. The events raised private andpublic concerns over loggingpractices on the islands and prompted the establishmentof the 5 year program. Overall objectives of FFlP were:

0 to study the extent and severityof mass wasting andto assess its impacts onfish habitat and forest sites. 0 to investigate thefeasibility of rehabilitating stream andforest sitesdamaged by landslides. 0 to assess alternative silvicultural treatments for maintaining and improving slope stability. 0 to investigate the feasibility and success of using alternative logging methods, including skylines, helicopters, and by logging planning, to reduce logging-related failures. The program is jointly funded by direct appropriations from the Canada Departmentof Fisheries and Oceans, the B.C. Ministryof Forests (Research Branch), and the B.C. Ministryof Environment (Fisheries Branch). Participating agencies include the Canadian Forestry Service (Pacific For- estry Centre) and the Forest Engineering Research Instituteof Canada (FERIC), Vancouver, B.C.

Program results are published through the B.C. Ministry of Forests, Land Management Report Series as well as papers presented at symposiums, conferences and through technical journals.

For information about the program contact Ministry of Forests, Research Branch, 1450 Gov- ernment Street, Victoria, B.C. V8W 3E7. Trends and Fluctuationsin Precipitation and Stream Runoff in the Queen Charlotte Islands

by Eero J. Karanka E.J. Karanka and Associates

Fish/Forestry Interaction Program 2153 West 46th Avenue Vancouver, B.C. V6M 2L2

March 1986

Ministry of Forests Canadian Cataloguing in Publication Data

Karanka, Eero, 1946- Trends and fluctuatlons in precipitation and stream runoff in the Queen Charlotte Islands

(Land management report, ISSN 0702-9861 ; no. 40)

Bibliography: p. ISBN 0-7718-8520-2

1. Precipitation variablilty - British Columbia - Queen Charlotte Islands. 2. Runoff - British Columbia - Queen Charlotte Islands. 3. Stream channelization - British Columbia - Queen Charlotte islands. 4. Mass-wasting - British Columbia - Queen Charlotte Islands. I. Fish/Forestry Interaction Program (B.C.) II. British Columbia. Ministry of Forests. Ill. Title. IV. Series.

QC 925.1.c3~761986 551.57'73'0971131 ca6-092123-9

1986 Province of British Columbia

Published by the information Services Branch Ministry of Forests Parliament Buildings Victoria, B.C. vaw 3~7

Copes of thls and other Mintstry of Forests titles are avatlable from Queen's Printer Publicattons. Parliament Butldings, Vlctorla. B.C. V8V 4R5. ABSTRACT

A number of indicators of climatic trends in the Queen CharlotteIslands are examined in thisreport. The purpose ofthe analysis is to determine extentof climatic influence on recent increases in theincidence of slope failures and streamchannel enlargement. Winter (October toApril) total rainfall,precipitation, and snowfall;winter mean temperature;water-year (Octoberto September) totalstream runoff; and the exceedance of daily precipitation amountswere studiedusing a variety of trend and data homogeneityanalysis techniques. Althoughthere was considerablelack of homogeneityfound in thevarious long-termdata sets available from the Queen CharlotteIslands, and a low regionalcoherence between the data sets, several consistent climatic fluctuations wereevident. The mostnotable are the periods of generally above-average winter rainfall and temperatures, 1923 to 1946, 1957 to 1964, and 1974 to 1984, with interveningperiods of generally below-average winter rainfall andtemperature, from 1946 to 1957 and 1964 to 1974. The most recent of these fluctuations (since 1946) appear to correspond with generalchanges in synoptic-scale circulation patterns across the northeastern Pacific Ocean area. The periodsince 1974, particularlysignificant to theFish/Forestry Interaction Program, includes 7 years of exceptionally high precipitation in at least some portion of the Queen Charlotte Islands. ACKNOWLEDGEMENTS

The authorwishes to acknowledge thefollowing helpful zontributions: Dr. MichaelChurch andGary Barrett of the University of British Columbia for having first brought to the author's attention a relatively unknown method of climateaata trend andhomogeneity analysis, which provedto be the key to a wholefamily of methoas, incluoing the regional indexing methodsused extensively in this report; Gary Schaefferof the Canadian Atmospheric EnvironmentService for aavice on obtaining computer analysis of exceedance frequencies of daily precipitation amountsand for encouragement in pursuing theregional indexing approach; Bob Marsh,Mauro Coligado, and Rod Davisof the B.C. Ministry of Environment for helpful technical comments, professional review, ana the provisionof microfiche data; and finally the financial, word processing, and graphicssupport of the B.C. Ministry of Forests and the Fish/ForestryInteraction Program, particularly Jim Schwab andVince Poulin.

- iv - TABLE OF CONTENTS

ABSTRACT ...... iii ACKNOWLEDGEME~TS...... iv

1 INTHODUCTIO I...... 1 1.1 StudyArea ...... 2

2 METHOUS ...... 5 .. ~.1Data Homogeneity Analysis ...... 9 2.1.1 Stationhistory analysis ...... 12 2.1.2 Residual mass curveanalysis ...... 13 2.1.3 Double mass curveresiduals analysis ...... 14 2.2 Analysisof Regional Data Coherence ...... 15 2.3 TrendAnalysis ...... 15 2.4Analysis of Trends in 1-Day Precipitation Amount and Frequency ...... 19

3 RESULTS ...... 21 3.1Data Homogeneity ...... 21 3.2 RegionalData Coherence ...... 34 3.2.1 Precipitationdata ...... 35 3.2.2 Snowfalldata ...... 35 3.2.3 Stream runoffdata ...... 37 3.2.4 Wintertemperature data ...... 37 3.3Regional Trends ...... 37 3.3.1Uctober to April precipitation trends ...... 39 3.3.2October to April rainfall trends ...... 42 3.3.3October to April snowfall trends ...... 42 3.3.4Water-year runofftrends ...... 44 3.3.5Winter (December to March) mean temperaturetrends ... 46 3.3.6 One-day precipitation trends ...... 48

-v- 4 DISCUSSION ...... 54

CONCLUSIONS ...... 60

LITERATURE CITED...... 61

APPENDICES 1 Exceedance frequencies of daily total precipitation ...... 63 2 Detailed histories of Queen Charlotte Islands climate stations .... 65 3 Winter precipitation (October to April)indices for long-term Ween Charlotte Islands stations...... 69

TABLES la Summary of long-term Queen Charlotte Islands meteorological station data and history...... 6 lb Summary of long-term Queen Charlotte Islands and southern Alaska Panhandle hydrometric station data and history...... 7 Sequence of analysis for individual station dataseries...... 10 Sequence of analysis for regionaldata...... 11 Interstation correlation coefficients for October to April precipitation on the Queen Charlotte Islands...... 36 5 Interstation correlation coefficientsof water-year runoff volume at Revillagigedo Island hydrometric stations...... 38 6 Annual maximum 1-day precipitation in theyears with the highest, middle, and lowest thirdsof total October to April precipitation ...... 53 7 Frequencies of 1-day precipitation greater than30 mm in the years with the highest, middle, and lowest thirdsof total October to April precipitation...... 53 8 Comparison of winter temperature and precipitation anomaliesin the Queen Charlotte Islands with temperature anomaly patterns in the North Pacific Oceanas identified by Namias...... 56

- vi - FIGURES

1 Major physiographic regionsof tne Queen Charlotte Islands...... 3 2 Location of stations used for Queen Charlotte Islands precipitation and runoff indices...... a 3 Cumulative percent aeviation of October to April precipitation at Masset andLangara ...... 22 4 Cumulative percent deviation of October to April precipitation at Dead Tree Point and Tlell...... 5 Cumulative percent deviation of October to April precipitation at Queen Charlotte City and Sandspit Airport...... 24 6 Cumulative percent aeviation of October to April precipitation at Cape St. James and Tasu Sound...... 25 7 Timing of changes of cumulative percent deviation graphsof October to April precipitation at Queen Charlotte Islands stations...... 27 13 Composite graph of double mass curve residualsfor Masset October to April precipitation data...... 28 Y Cumulative percent deviation of winter snowfall at Masset and Langara ...... 30 1G Cumulative percent deviationof winter snowfall at Cape St. James ana Tasu Sound...... 31 11 Cumulative percent deviationof winter snowfall at Dead Tree Point, Tlell, and Sandspit Airport ...... 32 12 Summary of station histories for Queen Charlotte Islands regional precipitation index...... 33 13 Cumulative percent deviation of water-year runoff volume in the Yakoun River andOld Tom Creek...... 40 14 October to April seasonal and cumulative precipitation indexfor central and northern Queen CharlotteIslands...... 41 15 October to April seasonal and cumulative rainfall index for central and northern Queen Charlotte Islands...... 43 16 Water-year and cumulative runoff volume indexfor Revillagigedo Island, Alaska...... 45

- vii - 17 December to March seasonal and cumulative mean temperature index for northern Queen Charlotte Islands...... 47 18 Cumulative percent deviationof annual maximum 1-day precipitation at Masset and Langara...... 49 19 Cumulative percent deviationof annual maximum 1-day precipitation at Queen Charlotte City, Sandspit, and Cape St. James ...... 50 20 October to April seasonal and cumulative indexfor rnaximum 1-day precipitation for central and northern Queen Charlotte Islands...... 51

- viii - 1 INTRODUCTION

Thisstudy was undertaken as part of the Fish/Forestry Interaction Program (FFIP), initiated in 1981 toevaluate the inter-relationships among logging practices,slope failure occurrences, andconsequent stream impacts in the Queen CharlotteIslands. In investigations of theimpacts on natural systems ofland usechanges such as logging,two questions should be posed about the condition of the natural systems:

1. Can any backgroundevents or rates of change thatcould affect the outcome ofthe land use changebe identified in the natural system?

2. If background ratesof change arepresent in thenatural systems, to what degreecould these be altered by the landuse change?

This report describes the results of astudy of background climatic and hydrologictrends in the Queen CharlotteIslands, dealing specifically with autumn/winterprecipitation, frequency of intenseprecipitation, and annual stream runoff. The findings of recent related investigations support this workon the Queen CharlotteIslands. Several studies onVancouver Island havesuggested that an increase in autumn/winterprecipitation from the late 1940's to the mid-1970's hasbeen paralleled by increases in channelwidths in bothunlogged and logged watersheds(Rollerson 1983; Karanka;'Karanka and Rollerson2 ). The rates of change in channelwidth were higher in thelogged watersheds, reflecting a combination of effects from rate of cut, logging practices adjacent to channels, and increasedsediment supply from bank erosion and slopefailures. lKaranka, E.J. 1983. A reviewof changes in streamchannel morphology in coastalBritish Columbiaas relatedto flood-plain logging. B.C. Min. Environ., Water Manage. Branch, Victoria, B.C. Unpubl.working report.

*Karanka, E. J. and T.P. Rollerson. 1984. Changes in streamchannel morphology on central Vancouver Island, British Columbia, in relation toclimate trends and logging. Paper presentedat AnnualMeeting, Can. Assoc.Geographers, Malaspina College, 22-25 May, 1984, Nanaimo, B.C. Church and Miles (1986) investigated the connection between a recent increase in the frequencyof slope failures on the Lower Mainlandof British Columbia and trenas in annual precipitation and annual maximum1-dsy precipitation. They concluded that the recent increase in slope failure occurrences coincidea with a periodof substantially higher than average annual precipitation and annualmaximurn 1-day precipitation. Similar studies have been undertaken in Oregon (Lyons and 1983),Beschta northern California (Kelsey1980; Lisle 198l), and New Zealand (Beschta 19832; 198313)- -- all mountainous areas with slope failure problems and biogeoclimatic similarities to the Queen Charlotte Islands. The objectives of this studywere: - to determine background trends in autumn/winter precipitation, frequency of heavy 1-day precipitation, and annual totalstrearn discharge in the Queen Charlotte Islands; and - to determine the synoptic context of any such trends.

1.1 Study Area The Queen Charlotte Islands are located approximately75-125 km off the northern British Columbia coast and extend 275about km between latitudes 52O and 54ON (Figure 1). The island chainis comprised of three physiographic zones: the Queen Charlotte Range, the Skidegate Plateau, and the Hecate Lowland (Holland1964). The Queen Charlotte Range, on the west coast of the Islands, is composed primarily of Triassic and early Jurassic volzanics, interspersed with several Jurassic granitic batholiths, particularly on Moresby Island. Heavily glaciated by local icecaps during the Pleistocene Epoch, the Queen Charlotte Range is indented by fjords. It is generally less than25 km wide, with a maximum relief of about 1250 m. Very steep slopes are common, increasing the potential for slope failure. The Skidegate Plateau, flanking the Queen Charlotte Rangeto the northeast, is comprisedof generally flat- or round-topped ridges underlain by early Jurassic volcanics dippingto the northeast. Elevations range -3-

I

FIGURE 1. Majorphysiographic regions of the Queen CharlotteIslands. -4- from 300 to 600 m over a widthof 20-25 km. The Plateau zone is present on thecentral and northernsections of the Queen CharlotteIslands. The SkidegatePlateau yrauually becomes thetiecate Lowland to thenortheast. Thislowland is a 10- to 40-km widecoastal plain, underlain by Tertiary sedimentaryrocks topped by Quaternaryglacial sediments. The elevation isgenerally less than 150 m. The Queen CharlotteIslands have a temperatecoastal varitime climate, with a moderatelyseasonal distribution 3f precipitation. Mean monthlytemgeratures range from 1.2-3.6OC in January to 13.2-14.5OC in Julyat stations near sea level. About 70-80% ofthe precipitation occurs in theautumdwinter months of October to Upril. Most ofthe high daily precipitation events occur during this period, particularly in Octoberand November. Mean wintersnowfall on thecoastal lowland varies from 60 to 80 cm, but snowpacks rarelypersist for more than a few weeks. The winter snowlinegenerally occurs at about 500-700 m. Precipitation gradients are highly influenced by orographic uplifting acrossthe Queen Charlotte Range. Mean annualprecipitation increases to 4500 mm within 20 km of the windwardouter coast, diminishing gradually acrossthe leewara slope of the Skidegate Plateau. The low-lying,leeward coastal plain has a fairly low precipitation gradient, with annual means varyingfrom 1200 mm alongthe coast to 1500 mm nearthe boundary with the SkidegatePlateau. Changes in maximum rainfall intensities parallel the changes in mean annualprecipitation across the Queen CharlotteIslands. One-day rainfall with a 5-year return period increases to 180-200 mm within 20 krn of the outercoast, then declines gradually to about 50 mm alongthe leeward innercoast facing Hecate Strait. -5-

2 METHODS

For analyzingclimate trends, The WorldMeteorological Organization (WMO) recommends theuse of the longest available homogeneous records,suggesting a 30-year minimum lengthof record. Only six records meet the minimum length criterion on the Queen CharlotteIslands (Table 1). Moreover,the distributionof the long-term stations is peripheral, with all located onthe exposed extremities of the Islands or the eastern fringe of the coastal lowland(Figure 2). Thereare no long-termstations in themountainous high precipitation zone which is thefocus of the Fish/Forestry Interaction Program. Thus, to maxirnize thedata available for analysis, two other climate station records and thehydrometric record from the Yakoun Rivergauging station wereused. 411 three haverecords between 19 and 25 years in length. Only the station at Tasu Sound, and to a lesserdegree the Yakoun River hydrometricstation, are representative of the high precipitation zone of the Queen CharlotteIslands. Hydrometricrecords from Prince of Wales andRevillagigedo islands in the southernAlaska Panhandle were alsoanalyzed, representing the longest coastal hydrometricdata series north of central Vancouver Island.(All of the active north coastal British Columbiahydrometric records are less than 30 years in length.) The southernAlaska stations are approximately 160 km northof the north coast of the Queen CharlotteIslands, and 220 km away fromthe Yakoun Rivergauging station. Otherprecipitation data series from northern Vancouver Island,central and north coastal British Columbia,and the Alaska Panhandle were also consulted -- as were wintertemperature and snowfall records from the Queen Charlotte Islands climate stations -- to aid synoptic interpretation of the Queen Charlotte Islands trends. The autumn/winterperiod (October to April) was usedas the base period for analysis of precipitationtrends, while the water year (October to September) was selected for analysis of totaldischarge volume at the hydrometricstations. These seasonalbase periods were selected in preference to the calendar year so that the integrity of eachannual maximal precipitationperiod, which begins in the fall andends in thespring, could bemaintained. -6-

TABLE la. Summary of long-term Queen CharlotteIslands meteorological station data and history

Years Total Mean Oct. Mean Oct. Mean Oct. Mean Dec. with years of to Apr. to Apr. to Apr. to Mar. S tation records recordrecords Station ppt. rain snow temp . Cape St. James 1925-1940; 54 1117 mm 1082 mm 35 cm 1944-

DeadPoint Tree 1939-1958 19 809 884 75

Langara 1936- 113648 1219 83 3.5 c

Masset 1897-1951; 82 1023 948 75 3.0 (combined) 1952-1968; 1971-

Queen Charlotte 1914-1939; 33 1397 City 1940-1948

Sa nds pit AirportSandspit 1945-1946; 37 1013 80 933 1948-

Tasu Sound21 1963- 3287 3211 76

Tlell34 1950- 782 841 59

Source:Atmospheric Environment Service Climate Normals 1951-1980 -7-

TABLE lb. Summary oflong-term Queen CharlotteIslands and southern AlaskaPanhandle hydrometric station data and history

Y ears Tot a1 Tot Years Mean annual with years of waterequivalent S tation records records runoffrecords records Station (mm/unit area)

Fish Crk. 1916-1935; 65 4524 (Revillagigedo I.) 1939-

Manoney Crk. 1921-1925; 26 6343 (Revillagigedo I. ) 1926-1933; 1948-1957; 1978-1981.

Manzanita Crk. 1928-1937; 30 4843 (Revillagigedo I. ) 1948-1967. Old Tom Crk. 1950- 34 70 22 (Prince of kales I.)

NinstanleyCrk. 1937-1938; 30 3535 (Revillagigedo I. ) 1948-1975.

Yakoun River 1962- 21 2061 (Graham I. )

Sources:United States Geological Survey Anchorage Office

Water Survey of Canada Historical Streamflow Summary and Annual Surface Water Data -a-

\\ " L.

Q*Cape St. James

FIGURE 2. Location of stations used for Queen Charlotte Islands precipitation and runoff indices. -9-

The hydroclimaticvariables analyzed for trend in this study were:

1. October toApril total precipitation. 2. October toApril total rainfall. 3. October toApril snowfall. 4. Water-year(October to September) totalrunoff volume. 5. October toApril frequencies of 1-day precipitationgreater than 30 ana 50 mm, respectively.

The winter (December to March) mean temperatureseries from three stations were used forsynoptic analysis. Dataanalysis was aimed atdetermining: the homogeneity of data at each station, the coherence ofregional data, trends in precipitation andstream runoff, and thesynoptic context of any trendsfound. The methods of analysis were generallythe same for all variables except 1-day precipitation amountsand frequencies,which required a different approach. A specific sequence of analyses was developedfor evaluating the database, beginning with analyses of individual data series and leading up to regionaldata matrices. Tables 2 ana 3 outlinethe sequencesand summarize therationale for eachstep. The entire sequence was not done for all variables, notably October to April snowfall andOctober 'to April rainfall. These twovariables are subsets of October to April precipitation, andwere coverea by the sequencedone for theprecipitation data. However, snowfall and rainfall data were analyzedfor specific interpretive purposes, to help clarify some features of the total precipitation data series.

2.1 DataHomogeneity Analysis A key condition for analysis of climate trends from individual station records is the homogeneity of the data by station location, exposure,and instrumentationduring the period of record. If thedata are not homogeneous, at-a-station trend analysis may show spurioustrends and maymask or distortgenuine trends. Evaluation of data homogeneity involves three types of analysis: - 10 -

TABLE 2. Sequence of analysis for individual station data series

Procedure Rationale 1. station history analysis - identify potential long-term and supplementary records - provide an initial screeningof data series for homogeneity problems Source documents: Canada Atmospheric Environment Service (AES) station catalogue; annual lists of station operators and postal addresses; station inspection reports.

2. Compile October to April - unify the data series for each autumn/winter precipitation, rainfall, period (as opposed to splitting each maximal andsnowfall series. precipitation period when calendar year is CompileDecember Used) to March mean temperature series. Compile water Source docurnents: Printouts of monthly yearrunoff series. precipitation, rainfall, ana temperature. Air Studies Branch to1976. Climate of B.C. Air Studies Branch,1977 to 1982 (Microfiche). Monthly climate summaries. Canada AES, post-1982 (Microfiche). Historical Streamflow Summary, British Columbia to 1982. Water Survey of Canada, 1983. Surface Water Data. British Columbia 1983. Water Survey of Canada1984. Alaska Water Data to 1982/83. Water year compiled by United States Geological Survey Anchorage Office. Daily precipitation amount/frequency data supplied by the Canadian Climate Centre. 3. Compute mean and - these parameters are used in all subsequent standarddeviationanalyses - log normal distribution was used for water-year run0 f f

4. Compute residual mass - carry out first statistical analysis and test curve series (cumulative of data series homogeneity or trend percent deviation series) - 11 - TABLE 3. Sequence of analysis for regional data

Procedure Rationale 1. Compute interstation - indicate the degree of regional coherence correlationmatrix between dataseries - can also indicate data homogeneity changes at individual stations 2. Compute double mass - identify data homogeneity changes at curve residuals specific stations 3. Identify homogeneous - eliminate the most obvious non-homogeneous data series data from further analysis. Procedure is based on steps 1 and 4, Table 2, and steps 1 and 2, Table 3. 4. Compute regional indices - pool regional data to maximize common regional trend components in homogeneous data sets - minimize local variability components in data series 5. F-test for significance - test the regional index matricesfor signifi- of time versus regional cance of temporal versus geographic variations variations in regional data series - 12 -

1. Station history analysis. 2. Statistical testing of homogeneity, using various forms of the residual mass curve(WMO 1966), otherwise known as cumulative deviation curves (Buishand1982), in combination with various tests of significance. 3. Analysis of double mass curve residuals.

2.1.1 Station history analysis The primary source material for analysisof climate station history is the Station Catalogueof the Canadian Atmospheric Environment Service, which maintains allof the long-term climate stations in the Queen Charlotte Islands. The catalogue lists periods of station operation, location co-ordinatesby latitude and longitude, and changesin location and instrumentation, and cross references any station name changes. Any changes listed in the catalogue, particularly location changesor interruptions of operation, are potential sourcesof non-homogeneity in the data series. The catalogue does not, however, include all the significant changes that have occurred at a station, particularly in the early years of station operation. This information can sometimesbe found from periodic station inspection reports, and occasionallyby compiling lists of station operators and matching their postalor residential addresses against the location co-ordinates in the station catalogue. One specific, uncatalogued change in instrumentation has occurred at eachof the three synoptic stations in the Queen Charlotte Islands. Coastal synoptic stations are located at airports or lighthouses, and transmit observations dailyby radio as part of the weather forecasting service. Since 1960, all synoptic stations have had Nipher-shielded snow gauges installed. Snow catch efficiency may be enhanced considerably over the older snowboard, particularly in windy locations. The snow measurements at Nipher-shielded snow gauges are also affectedby a change in the - 15 -

method of' calculating water equivalent. The snow catchis melted and measured volumetrically at the hipher-shielded gauges. With the use of a snowboara, the snow water equivalent is assumed to be l/lOth of the snow depth, which generally underestimates the volumetric value. The combined effectof the increased catch efficiency and greater volumetric measurement of water equivalent resultis an enhanced snowfall measurement at the hipher-shielded snow gauges over the snowboard measurements, which maybe sufficiently large to affect the homogeneity of the total precipitation data series at some stations.

2.1.2 Residual mass curve analysis Resiaual mass curves, also knownas cumulative deviation curves, are a familyof related methods used primarily for data homogeneity analysis. Although included by the WMO in the listof methods not recommended for analysisof climate trends, Buishand(1982) found the curves useful in analyzing changes in data homogeneity. This study uses one formof this method -- the cumulative percent deviation curve as developea by Barrett 3 and applied by him -- to analysis of hydroclimatic trends in British Columbia. The cumulative percent deviation methodis based on the sequential deviations of annual (or seasonal) precipitation amounts from the mean for the periociof record, expressed in percent. The sequential annual deviations are accumulated to determine the value for a given year, according to equation(1):

3Barrett, G.E. 1979. Changes in the discharge of selected rivers in British Columbia during the periodof instrumental records. Univ. of B.C., Dep. of Geography, Vancouver, B.C. Unpubl. honours essay. - 14 -

where yi = cumulative percent departure from the meanto year i of therecord x i = the precipitation value for year i and x = the mean for periodof record.

One of the attractions of this method is that it provides an excellent graphic representation of trends in the data series, particularly the timing of changes. It detects the timing and direction of changes in trend in data series, regardless of the source of the change. Thus, a change due to climate trend is indistinguishable from a change due to transferof the station to another location or exposure. Separation of changes that are due to climate trends from other sources of change requires the analysisof double mass curve residuals.

2.1.3 Double mass curve residuals analysis The analysisof double mass curve residuals compares the cumulative ratiosof precipitation amounts at a base station assumed to have a homogeneous record, to a remote station with unknown data homogeneity, according to equation(2) (Craddock 1979).

where si = cumulative deviationof the observed total precipitation volume (mass) at the remote station upto the year i, from the expected total volume (mass), based theon ratio of annual means for the period of record at the base and remote stations and the observed total precipitation volume (mass) up to the yeari at the base station. - x = base station mean for the periodof record - 15 -

7 = remotestation mean forthe period of record

x = base stationprecipitation for year i i

and y. = remotestation precipitation for year i. 1

Us with thecumulative percent deviation method,good graphiz representationof apparent changes in datahomogeneity can be derived from thisanalysis. Changes in datahomogeneity appear as a persistent change in the slope of the cumulative deviation graph. Analyses of severalremote-base station relationships should be done to confirm changes in datahomogeneity. The homogeneity of the Yakoun Riverhydrometric record could not betested against other regional hydrometric records because none were available. The Yakoun Riverrecord was thereforetested against themeteorological stations (Tasu Sound, Sandspit,Tlell) having the best correlation of October to April precipitation and the total water-yearrunoff, expressed in basinarea-depth equivalents, using thedouble mass curveresidual analysis technique.

2.2 Analysisof Regional Data Coherence An interstation data correlation matrix was determined for all long-term and supplementaryprecipitation data. Correlation coefficients were calculated with a stockprogram on a TI 59 programmable calculator. Yakoun Riverwater-year runoff data were also used, after the total runoff volume was convertedinto basin-area water depth equivalents.

2.3 TrendAnalysis Precipitation trends in the Queen Charlotte Islands were previously analyzed by Crowe (1960,1963) andPowell (1966). Bothanalyzed the Masset precipitation series using the method of 'In-yearmoving means", with 5- and 30-year base periods. Crowe concludedthat ''except for a minordecrease in the last twodecades [1940's and 195O's], little - 16 -

variation hasoccurred at Masset since 1915."Powell included Massetas one of three stations in an "OuterCoast" region, and concludedthat annual precipitation on the outer coast had decreased from the period, 1901-1930, tothe period, 1931-1960, in contrastto all other regions of British Columbia. Bothof these pioneering studies are, in retrospect,flawed by "hidden"data homogeneity problems at some ofthe stations selected, and by the methodused foranalysis. Both Crowe andPowell assumed thattheir datasets were homogeneous, and escheweda more rigorous analysis of homogeneity. The Massetdata series hasa 9-yearperiod from 1904 to 1912 duringwhich recorded precipitation is suspiciouslylow. Moreover, the other two stationsselected by Powell for the outer coast region (Clayoquot and Quatsino)have much more flagrant homogeneityproblems, renderinghis analysis invalid for this region. The n-yearmoving mean method was, in all fairness to Crowe and Powell,the principal methodused for climate trend analysis in British Columbia prior to 1979. Sincethen, its usehas falleninto disfavour as a result of a re-evaluation of its efficacy relative to newermethods. The moving mean is one of the methods listed as"not recommended" for analysisof climatic trends by the WMO (1966). The main criticismsof the 4 methodare, as summarized by Barrett:

. The choiceof llnll isoften arbitrary, yet it determines to a considerabledegree the appearance of the smoothed record. Thus, records smoothedby different n-yearmoving mean filters will not be directly comparable.

. The use of moving means tendsto obscure the timing of changes in stationarity.

. A singleexceptional year in a stationaryseries may perturbthat series for 2n - 1 yearsbefore and after the exceptional year.

4Barrett, 1979. - 17 -

Use of the moving averageprocess may inducean apparent periodicity of n-years,even in a random series.

. The effective lengthof record is reduced by (n-1)/2 years at either endof the record, and before and after any gaps in the record; i.e., there is a loss of n-1 years perrecord and n-1 years pergap.

To the above criticisms shouldbe added a caution applicable to all methodsof analysis based on a single series ofdata: the assumption of data homogeneity. If the record has significantchanges in homogeneity as a result of changesin station location, exposure, or instrumentation, thenany method of at-a-station analysis can show spurious,exaggerated, or diminished "climatic" trends,depending on the natureand timing of the changein homogeneity. The analysesof data homogeneity (Section 2.1) andregional data coherence(Section 2.2) suggestedthat the Queen Charlotte Islands precipitationrecords are susceptibleto misinterpretation if at-a-station methods, such as then-year moving mean andcumulative percent deviation curves, were reliedon exclusively fortrend analysis. Therefore, a regionalprecipitation indexing methoddeveloped by Kraus (1977) was used instead. This indexingmethod is particularlyappropriate in regions with relatively low interstationcorrelation, high incidence of changes at stations,and a generallyfragmented long-term data base. By poolingthe data baseto maximize the common regionaltrend components and minimize localvariations, regional indexing reduces the risk of identifying spurioustrends and trend distortions The indexingmethod preferred by Kraususes precipitation data normalized by equation (3):

where = the normalizedOctober to April precipitation value at 'ij station i for year j x = theOctober to April precipitation station i in ij at the year j - 18 - - = the i x i mean forthe perioa of record at station and 0 i = thestandard deviatim for the periodofrecord at station i.

The regionalprecipitation index for each season is calculated by averagingthe normalized precipitation values of all stations having a record for thatseason, according to equation (4).

a = l/Ij fpij j

where a = theregional precipitation index forthe year j j 1 = the number of regionalstations operating in theyear j j and Pij as defined previously.

Statisticaltests for the significance of year to year variations in inaexvalues are based on standardanalysis of variance methods. In ?articular, an F-test is used todetermine the significance oftime variance versus regionalvariance, according to the varianceestimates in equations (5) ana (6):

.2 Variance(time) = XIi . a . (5) 3-1 where J = the number ofyears in theperiod of analysis and I previouslyas a. defined. j' J

2 Variance(regional) = lu - XI * a (6) uN-J where N = C.1 . = CiJi (thetotal number of stationyears) JJ and I previouslyas a. defined. j' J

Thesame regional indexing procedure was used forwinter temperature and water-yearrunoff volume data. In thelatter instance, log transformeddata were used, to reduce the effects ofskewness of the distribution of thedata on thenormalization procedure. - 19 -

2.4 Analysis of Trends in 1-Day Precipitation Amount andFrequency Mostslope failures and streamchannel changes occur during short periodsof more intenseprecipitation or streamflow. Such events do not necessarilyoccur during periods of generally above-average annual precipitation or streamrunoff such as are identified by the analyses in Section 2.3. In the Queen CharlotteIslands, the shortest duration for which long-term precipitation data are available is the daily observation period(usually 0800 to 0800 hours). The fixeddaily observation period usually masks the amount of the greatest 24-hour precipitation, by dividing it betweentwo dailyobservation periods. At some non-synoptic stations run byvolunteer observers, moreover, the daily observation schedule may lapsefrom time to time. For example, thedaily schedule may bemaintained only from Monday toFriday or Saturday.Precipitation duringthe period from the last observation on Friday or Saturday is combined in thefirst observation on Monday. This results in four or five legitimate 1-day precipitation measurements plus one readingwhich combinesthe precipitation over a 2- or 3-day period. The total precipitationrecorded at such stations remains a homogeneous series, but the 1-day precipitation series is nolonger useable, if thelapse in daily schedulepersists over a period of time. Fourmethods were used for the analysis of changes in the amountsand frequenciesof 1-day precipitation. Three ofthe methodsused the seasonal(October to April) maximum 1-day precipitation. Themaximum 1-day precipitation series from each station(except Tasu Sound, Dead Tree Point, and Tlell) were analyzedusing the cumulative percent deviation methodand theindexing methoddescribed in Section 2.3 for analysis of seasonal(October toApril) total precipitation. Log-transformed data were used for the indexing method to reduce the effects of skewness of the distribution of the data on the analysis. The third method for analysis of maximum October to April 1-day precipitation involved a comparisonbetween the maxima fromthe years with thehighest, middle, andlowest thirds of seasonal (October to April) totalprecipitation amounts at eachstation. The 1-day maxima from the - 20 - years in thethree classes were tested for significance of differences betweenthe means of the classes with a standardF-test. Sporns (1962) used a regionalindex of severe storm occurrences, based on the number ofdays in a year on which precipitation exceeded 100 mrn at one or more observing stations in thelower Fraser Valley. Churchand Miles (1986) updated this work. Applicationof this method to the Queen Charlotte Islands required lowering the 1-day precipitation defining a severestorm because of the different precipitation characteristicsat the Queen CharlotteIslands stations. Exceedance thresholds for 1-day precipitation greater than 30 and 50 mm duringeach October to April seasonwere chosen arbitrarily to represent moderately frequent 1-day precipitation (occurring at least twice a yearon average) and infrequent 1-day precipitation (occurring less than oncea year on average) atthe leeward coastal stations on the Queen CharlotteIslands. The analysis of 1-day precipitation exceedancefrequencies required tallies of exceedanceevents (provided by the Canadian Climate Centre, AtmosphericEnvironment Service) as cumulativefrequency tables of 1-day precipitation amounts,by month and yearfor each station (Appendix 1). The October to April frequencies of 1-day precipitationexceeding 30 rnm werecompared between theyears with thehighest, middle, and lowest third of October to April total precipitation amounts at each station. Themeans of frequencies of events in eachclass were tested for significance of differences using a standardF-test. - 21 -

3 RESULTS

The dataanalyses indicated that several of themeteorological stations on the Queen Charlotte Islands and the Yakoun River hydrometric station have questionabledata homogeneity. Moreover, the entire Queen CharlotteIslands region has a relativelylow coherence between stations. The homogeneity test results reinforced the validity of usingthe regional indexing approach for analysisof trends and fluctuations in hydroclimate variables in the Queen CharlotteIslands.

3.1 DataHomogeneity The basicsources of informationabout data homogeneity are the detailedstation histories (Appendix Z), cumulativepercent deviation graphs, and analyses of double mass curveresiduals. All mustbe combined for a comprehensiveevaluation. The meteorologicalstation catalogue, if consideredalone, suggests that of theeight long-term andsupplementary stations available on the Queen CharlotteIslands, three havehad no changes in their location (Langara,Sandspit Airport, and Dead TreePoint). Three others have had interruptions of operation and possible location changes(Tasu Sound, Cape St. James, and Queen CharlotteCity). The remainingtwo, Tlell and Masset,have had location changes ofseveral kilometres. Although not listed in thecatalogue, Nipher-shielded snow gaugeswere installed at Langara, Cape St. James, and SandspitAirport in the mid-1960's. The cumulative percent deviation graphs for precipitation data (Figures 3, 4, 5, and 6) show periodsof below-, near-, andabove-normal precipitation aschanges in theslope of theline. Periods of below-normal precipitation have a negativeslope (downwards to the right); periods of above-normal precipitation have a positive slope (upwards to the right) ; near-normalperiods have a zeroslope. Points of change in the slope of the line identify the timing of changesbetween the various periods. The points of change fromthe various graphs have been plotted - 22 -

a) MassetStation (combined) .ti00 . .. -0 ..- .-loo C* .. .*e . .*. ..*...... *.* 0...... * .. L 0. .. . .-200 ..

1 1 "300 1 30 1900 1910 1920 1930 1940 1950 1960 1970 1980

b) Langara

...... :e.. . .* 0 .. . ** ...=. .. -1 00 -. f 2..

- 200

-300 ! I 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980

FIGURE 3. Cumulativepercent deviation of October to April precipitation at Masset and Langara. - 23 -

a) DeadTree Point + 100 ..

*. 0. '0

.- 100

,-200

"300 1890 19'00 1910 1d20 1930 19'40 1950 1960 1970 1980

b) Tlell + 100

0 ..-...... * " .. .-. 0. . -100 ..

- 200

FIGURE 4. Cumulative percent deviationof October to April precipitation at Dead Tree Point and Tlell. - 24 -

a)Queen Charlotte City

b) SandspitAirport

+70' 9.. *'...... -100 1 *.*e .. '

FIGURE 5. Cumulative percentdeviation of October to April precipitationat Queen Charlotte City and Sandspit Airport. - 25 -

a) Cape St. James ,+loo .. 0 **. .-• 5 .. -100 0... .. *.

-200

-300 la90 1900 1910 1920 1930 1940 1950 1960 1970 1980

b) Tasu Sound +loo

0

- 100

- 200

-300

FlGURE 6. Cumulative percent deviationof October to April precipitation at Cape St. James and Tasu Sound. schematically in Figure 7 to show thecoincidences a;l[J disagr,?ements between thegraphs. The major coincidencesare the Seginninys of belaw-normal periods in 1918, 1332, i946, and 1964, and above-normai periods in 1522, 1936, 1458, ana 1Y74. The agrement ammy a number of stations on th?sedates indicates that the changes areprubaoly -1imati:: in origiq. The vaindisagreemmts ;Ire at Quee;lCharlotte City in 1427 and 1942; Cape St. James in 1949, 1955, and 1969; Dead Tree P3iqt in 1952; arid Tlell in 1970 ant] 1979. In theseinstances the changeappears tn have occurreo in isolatiorl. In addition,there is t.he major perturbation in t4asset data pri,x to 19i3. 9lthoucJh theseisolated changes are suspicious,the curnulative percent frequency graphs do not, by t,hemselves, inai-ate whether thechanges are due to localzli-nate fluctuat.ions or to station changes that have altered%he homogeneity of the data series. Furtheranalysis with double mass curveresiduals and reference to the detailedstation nistories are required to resolvethis distinction. Figure 8 illustrates a composite example of Uouble mass curve residualsanalysis, and uses Masset asthe remote station with unknown data hornogeneity and a variety of base stations 3ssumed to be iioqoyeneous. As on the graphs of cumulativepercent deviation, changes in theslope of the line and the points of zhange arethe interpretive featlures on the graph. The poir7ts of change indicateshifts in the relationship of pecipitation amountsbetween remote and base stations. In Figure 8, suchchanges appear to occur at Masset in 1904, 1913, and iiii3. Only the change in 1913 is coincident with a known change in station location. Composite graphs of double mass residuals were not produced for the otherstations; analysis was done numerically. This indicated that in audition to theearly Masset data(pre-19131, the Queen Charlotte City data after 1443 and theentire Tlell record should be rejected as non-homogeneous. Analysis of double mass curveresiduals also questioned the homogeneity of the Yakoun Riverhydrometric record. The annual runoff of the Yakoun Riverchanges in relation to the precipitation at both Tasu Sound ana Sandspit in 1968. (Tlell was not used for analysisbecause the - 17 -

I--

A 3 7 ;-I- rn- r C 0 -c,

A I I

I cn -c na a k I-- cx 0 7 3 0 0 0- 0 7 v) 0 I A- I I

mzD 1 ? 0 0 0 c. Q DO m NO a 90 a I 5 I I L mc I- 120 "I o u 4-io 00

0 0 ? I - 28 -

3 -a 4 4 4 1 1 4 ‘4 4 k 4 aa Q < a Q 0 c, k al _o 0 ‘a u 8 0 a .. 0 010 u >> al a2 cn cn qa m aa z k 1 0 a L

I r \ -*0 Q) ? r f al> k 3 0

e e e al 4 r a \ 3 e - 0 0 (u -0 e Q) e r cc. e om

e e e e 8 e e e 0 e

r W . X 7

dY G - 29 - homogeneity of the Tlell record was already rejected above.) The change coincided with an 8-month gap in the Yakoun River record, which suggested changes in either the channel transector the water level gauging station when the station was re-established. The effects of Nipher-shielded snow gauge installations at Langara, Sandspit Airport, and Cape St. James were examined with cumulative percent deviation curves for winter snowfall at all the Queen Charlotte Islands stations (Figures 9, 10, and 11). The snowfall data show that the largest effects have occurred at Langara and especially at St.Cape James, while little effect has been observed at Sandspit Airport. This result is not surprising, since Langara and Cape St. James are undoubtedly the windiest meteorological stations on the Queen Charlotte Islands, and the catch efficiency of the Nipher gauge compared to snowboards increases with windspeed. Although snowfall accounts for only3 and 7% of total October to April precipitation over the periodsof record at Cape St. James and Langara, respectively, a comparisonof the pre- and post-Nipher gauge installation periods shows a substantial increase in snowfallas a portion of total precipitation at these two stations. At CapeSt. James, snowfall increased from 1.6 to 5.9% of total October to April precipitation, while the increase at Langara was from4.9 to 9.3%. Changes for the same perioos at Sandspit Airport were from7.1 to 8.4%, and at Masset from 6.8 to 7.6%. The October to April rainfall (precipitation minus snowfall) records at Langara and Cape St. James are probablymore homogeneous than the total precipitation records. The detailed station histories and resultsof data homogeneity analysis with the cumulative percent deviation graphs and double mass curve residuals are summarized in Figure12. This shows that the only station on the Queen Charlotte Islands that has not changed during its operation is Dead Tree Point, which has a relatively short record and was discontinued in 1958. In summary, the following changes in Queen Charlotte Islands stations and data homogeneity have been inferred: .*"r

9.

.* c Zm

I 00000000~000000 00000 000000000 ?"'Dt" "troro ++++ I I 11-O2!9?$ + II Ill

.'

3.' .' .' '

c *' ,. m m .* m 6 5 n 6 t

** . .* - 31 -

-

0 00 0) l- 0 h 0) f 0 :(0 0 0 10 C 0) 3 f 0 v) *0 a m fn 7 m 0 I- m h m n r 0 N 0) f 0 l- ? 0 0 m r 0 rn m 0 3- 0 0 04 I

0 00000 0 00000 0000000000 00000 00000NdW00 0 f00'Dthl CU'Q'D00fff-f hl t+t++OI IllI I I I I I I 1 1 I I

0 00 m ? 0 h .* m l- 0 W s1 0 :v) 0 v .* m m 7 0 .* m .* 0) r 0 N m r 0 l- (I, r 0 0 .. c 0) zfn 7 0 m b) I f - 32 -

0 m UJ c 0 rc

c L 0 n L u .- m U .-c n

(I) or c 0 r a, F 0 0

I I 1 I- 0000000000000000 om(Dt(U00000 0000000000 '++++ ,l-rrl-rCU + I I I I I I

0 000000 00000 0000000000 00000 0000 tW(0601 NtfDcO ::2:2: ++if+I Ill I1 I I I I I I t

I' f .* *..* .**. c. -c 0 n 0 m_ m- r C 0 '4 4.J m 0 c, t. t. m " 3-

0 W m " r

0 u) m " r 1 cn H a, 0 c, t " c, m 0 c 4 k Lco 0

0 C m " aJ m (u r 3 CT

0 01 m " c

0 " rn c 0 4 c, m CI cn 0 0- cc m 0 r x

0 mi m v W L W m N C ?I m -1 rrW - 34 -

Ut Masset,the 1904-1913 data are much toolow even for a dry period. The post-1971data should have -- butapparently did not -- become progressively drier as the station location moved furthereast. At Langara, Cape St. James, and SandspitAirport the installation of Nipher-shielded snow gauges in the1960's increased the amount of snowfallrecorded, and probablyhas affected the homogeneity of precipitationdata at Langara and Cape St. James. TheQueen Charlotte City station was apparently moved further west in 1943, significantlyincreasing the recorded precipitatiort. The Tlell station hasbeen moved severaltimes, and was for a period located in a badexposure (R. Marsh, pers. comm.) The Yakoun River hydrometric station apparently had achange in the channeltransect or thewater level gauging station in 1968.

On the basis of the above information,three records were rejected for inclusion in theregional precipitation index for analysis of trends. The pre-1914Masset record was rejected because it appears to be much too lowduring a 9-yearperiod from 1904 to 1913,and cannot be corroborated by other Queen CharlotteIslands data. After 1913, the Queen Charlotte Citydata provide a reasonablebackup. TheQueen CharlotteCity data after 1943 were rejected because of the station's apparent move to a much wetterlocation. Finally, the entire Tlell record was rejected becauseof several moves, including one to a poorraingauge exposure.

3.2Regional Data Coherence Correlationsbetween stations can indicate the scale of processes thataffect regional precipitation, while anomalies in correlationscan indicatedata homogeneity problems at individual stations. Interstation correlations weredone forOctober to April precipitation, water-year runoff volume,and wintertemperature. Regional coherence of snowfall was analyzed by examiningthe cumulative percent deviation graphs. - 35 -

3.2.1 Precipitationdata The Queen Charlotte Islands, like much of north coastal British Columbia,has relatively low correlation of precipitation between stations,particularly when compared to Vancouver Island.October to Apri.1 precipitation correlation coefficients greater than r=0.7 are rare among thelong-term Queen CharlotteIslands stations, and occur mainlybetween some olderdata sets from 1915 to 1957(Table 4). The bestoverall coherence occurs among the northeast coastal stations betweenMasset and Sandspit Airport. The average ofthe correlation coefficients of stations in this area is about r=0.65, in a low-lying areaabout 90 km long,covering a narrow strip along the eastern coast. By comparison,the long-term stations on northern Vancouver Island havean average correlation coefficient of about r=0.85, in an areaabout 90 km longbut including both leeward andwindward stations. In fact, on northern Vancouver Island,correlation coefficients less than r=0.75 werea fairly reliable indicator of a datahomogeneity problem in one of thedata sets. The relatively low correlation coefficients on the Queen CharlotteIslands suggests that trends in the precipitation data from theleeward east coastal stations may not be representative of trends in thewindward west coast area. Moreover, they suggest that small scale local influences on autumdwinter precipitation are more important on the Queen CharlotteIslands than onVancouver Island, which is amore coherent unit.

3.2.2 Snowfalldata Correlation coefficients were notcalculated for snowfall data. Examination of the cumulative percent deviation graphs for snowfall (Figures 9, 10, and 11) shows thatgeneral periods of below- and above-normal snowfallhave occurred concurrently at most stations. The exceptionsare Langara and Cape St. James, where trendsare dominated by the change in catch efficiency resulting from the installation of Nipher-shielded snow gauges. - 36 -

TABLE 4. Interstationcorrelation coefficients for October to April precipitation on the Queen CharlotteIslands

+ indicatesinsufficient data ( lessthan 10 values - 37 -

3.2.3 Stream runoffdata Analysisof regional coherence was notpossible for the stream-gaugingstations on the Yakoun River on Graham Island and Old Tom Creekon Prince of Wales Island because of their isolation from otherlong-term hydrometric stations. The Yakoun Riverwater-year runoff volumeswere converted to basin depth equivalents for comparison with the October to April precipitation at the meteorologicalstations. Correlation coefficients were in the same range(0.5-0.7) as between the precipitation data (Table 4). Correlation coefficients on RevillagigedoIsland are comparable to October to April precipitation coefficients on northern Vancouver Island,ranging from r=0.78 tor=0.91 (Table 5). It is apparentthat runoff is fairly coherent on Revillagigedo Island.

3.2.4 Wintertemperature data Mean temperatures,especially during a4-month period (December to March) aregenerally coherent across a widerarea than is precipitation.Correlation coefficients betweenLangara, Masset, Port Simpson,and PrinceRupert ranged from 0.86 to 0.96 formonthly mean temperatures in December, January,February, and March.

3.3 RegionalTrends Climatetrends in the Queen Charlotte Islands are shown as regional indices for October to April precipitation and rainfall, and December to March mean temperature.Water-year runoff volumeon RevillagigedoIsland is also shown as a regionalindex. Both the annual (seasonal) and cumulativeindex values are shownon the graphs. The cumulativevalue illustrates trends in the sameway ascumulative percent frequency curves do: a negativeslope indicates below-average conditions, a positiveslope indicates above-average conditions, and a neutralslope indicates average conditions. - 30 - TABLE 5. Interstation correlation coefficients of water-year runoff volume at Revillagigedo Island hydrometric stations - 39 -

A regionalindex could not be constructedfor snowfall data because ofthe extremeskewness ofthe data. Old Tom Creek,being relatively isolatedfrom the other hydrometric stations, was excludedfrom the RevillagigedoIsland regional runoff volume index.Trends in thesnowfall data and theexcluded set of runoff volumes are interpreted from their individualcumulative percent deviation graphs (Figures 9-11, 13).

3.3.1October toApril precipitation trends The precipitation index for the Queen Charlotte Islands was calculatedfrom the stations at Masset (excludingpre-1914 data), Queen CharlotteCity (excluding post-1943 data), Dead TreePoint, SandspitAirport, Langara, andTasu Sound. Tlell was excluded because of the data homogeneityproblem at this station, and Cape St. Jameswas excludedbecause of its isolation fromthe other stations and poor correlation coefficients with most of the other data series. The precipitation index is shown in Figure14, and the matrix of indexvalues is in Appendix 3. The cumulativeprecipitation index shows that the central and northern Queen Charlotte Islands haveundergone fiveepisodes since 1914. The precipitationfor the 30-year periodfrom 1914/15 to 1945/46approximated the long-term mean, as was suggestedearlier by Crowe (1960).During this period there were fourshort periods with above-normal precipitation: 1915/16-1918119;1923/24-1926/27; 1930/31-1931/32;and 1938/39-1941142. Periodsof below-normal precipitationintervened. Five of the 10 highestindex values occurredduring these short periods of above-normal precipitation. Two longerperiods of below- andabove-normal precipitation have alternatedsince 1945/46. The two drierperiods occurred from 1946/47 to 1957/58and from about 1964/65 to 1973/74.October to April precipitation averagedbetween 7 and 12% belowthe long-term mean duringthese periods. The periodsof above-normal precipitation occurredfrom 1958/59 to 1963/64and from 1974/75 to 1983/84. Autumdwinterprecipitation has averaged from 8 to 19%above the long-term mean duringthese periods. Since 1974/75, the central and - 40 -

a) Yakoun River

+ 1oc

C

-100

b) Old Tom Creek - 200 (Prince of Wales Island)

-300 7 1 1 I 1890 19001910 1920 1930 1940 1950 1960 1970 1980

FIGURE 13. Cumulative percent deviation of winter-year runoff volumein the Yakoun River and Old TomCreek. - 41 -

999 rN:*V)q) aN- 99 999 ++COI I I I I

U C m 1 m k c, C a, 0 k 0 L X a, U C '4 C 0

H 1 ma, KO oc, cno m1 a,k "E

9 C? 9 0 9 m N F F 2 + + + I I - 42 - northern Queen Charlottes havebeen experiencing the longest sustainedperiod of above-normal precipitation since the beginning of records.Included in thisperiod are 3 yearsthat werewet throughoutthe area covered by theindex (1974/75, 1975/76, and 1980/81).During 4 ofthe years in this period, index values were highestalong the north coast of Graham Island (1977/78-1979/80, and 1981/82).During the most recent 2 years(1982/83-1983/84), the locus of highest indices shifted to the east coast betweenSandspit andMasset. Three ofthe 10 highestregional index values have occurred during this period. The Massetdata prior to 1914/15 suggest a lengthydry period occurredfrom 1898 to 1913. Whilethese data have been rejected on the basis of homogeneityanalysis, other data from north coastal British Columbiaand the AlaskaPanhandle corroborate the occurrence of a dryperiod, but one not as severeas that implied by theMasset data.

3.3.2 October toApril rainfall trends The regionalindex for October to April rainfall (Figure 15) shows one differencefrom the precipitation index. Although the same shortfluctuations between below- andabove-normal periods were evidentfor both indices between 1914/15and 1945/46, theperiod from 1923/24 to 1945/46on the wholehad above-normal rainfall. The above-normal rainfall is particularly evident from1938/39 to 1945/46.

3.3.3October toApril snowfall trends All of the meteorological stations on the Queen Charlotte Islandsare located at less than 200 m elevation.Snowfall trends at theselow-elevation stations do notnecessarily represent trends at elevations above the semi-permanent wintersnowline at around 500-700 m. The cumulativepercent deviation graphs of winter snowfallindicate periods of below-normal snowfall from 1919/20 to 1945/46,1956/57 to 1963/64, and 1976/77 to 1983/84.Above-normal - 43 - - 44 - periodsintervened from 1946/47 to 1955/56 and 1964/65 to 1975/76. Langaraand Cape St. James were excluded from analysis of snowfall trends because of the perturbation causedby installation of Nipher-shielded snow gauges in themid-1960's.

3.3.4 Water-year runoff volume trends RevillagigedoIsland The water-yearrunoff volume indexfor Revillagigedo Island (Figure16) shows both similarities to and differencesfrom the precipitation and rainfall indices for the Queen CharlotteIslands. The main similarities are:

. The periodfrom 1915/16 to 1939/40 has runoff volumesnear the long-term mean overall, with short fluctuations betweenbelow- andabove-normal amounts thatcorrespond to those of Queen Charlotte Islands precipitation. . The periodfrom 1940/41 to 1957/58 has below-normal runoff volumes. Thisperiod isinterrupted by 3 yearsof above-normal runoff,which are not distinguishable in the Queen Charlotte Islands precipitation/rainfall indices. . The periodfrom 1958/59 to 1963/64has runoff much abovenormal, correspondingto the Queen CharlotteIslands data. The majordifferences between the Queen Charlotte Islands precipitation/rainfall indices and the Revillagigedo Island runoff indexhave occurred since 1963/64. TheQueen CharlotteIslands precipitation and rainfallare below normal from 1964/65 to 1973/74 andabove normal since 1974/75. By contrast,the runoff index for RevillagigedoIsland remains near normal from 1964/65 to 1973/74, but hasbeen below normal since 1973/74, except for the 3 years 1974/75, 1975/76,and 1980/81.

Yakoun River The Yakoun Riverhydrometric record was rejected on the basis of datahomogeneity analysis. The trends shown in thecumulative - 45 -

999 99999 mcuc -(urntin m Y cn >m

k 0 4-

e, E 3 -i 0 >

c, m 3 - 46 - percent deviation graph (Figure 13a)- of runoff volume are contrary to thetrends in both the regional precipitation index and the cumulativepercent deviation graphs of precipitation at individual stations.

Prince of Wales Island Trends in the cumulative percent deviation graph of runoff volumes in Old Tom Creek, Prince of Wales Island (Figure 13b),- differ fromRevillagigedo. Runoff volumeswere generally below the long-term mean from1949/50 (beginning of records) to 1965/66. The above-normal periodfrom 1958/59 to 1963/64, which is a feature in both the Queen Charlotte Islands precipitation index and the RevillagigeaoIsland runoff index, is nearly absent from the Old Tom Creek data. On the other hand, the above-normal period of runoff from1974/75 to 1980/81 in Old Tom Creek duplicates the trend in the Queen Charlotte Islands precipitation index, but is in sharpcontrast to trends in runoff volumeson Revillagigedo Island.

3.3.5 Winter (December to March) mean temperaturetrends The temperaturerecords from Langara, Masset, Port Simpson,and PrinceRupert werecombined to construct a wintertemperature index for the northern Queen Charlotte Islands - northern British Columbia coastarea (Figure 17). The cumulativeindex shows periodsof above-normaltemperature from 1896/97 to 1905/06,1911/12 to 1914/15, 1925/26 to 1931/32,1937/38 to 1945/46,1957/58 to 1963/64,and 1976/77 to 1983/84. All of the post-1914/15 periodscoincide with periods of above-normal precipitation or rainfall and below-normal snowfall on the Queen CharlotteIslands. The periodsof below-normal temperatures(1915/16 to 1922/23,1932/33 to 1936/37,1946/47 to 1956/57,and 1964/65 to 1975/76) coincide with periods of below-normal precipitation and rainfall, and above-normal snowfall. The coincidental timing is discussed further in Section 4.1. - 47 -

(s)!un*a*S) xepul eAllalnurn3 - 9999 ?????? WON- -(UmtlDw ++++ON I I I I I

C k aJ f c, k 0 C k cc0

-0 Cm

w 4

1 I I ? ? 9 0 ? ? 9 O 01 l- c N O + + + I I I - 48 -

3.3.6 One-day precipitationtrends Trends in 1-day maximum precipitation were analyzed for Masset, Langara, Queen CharlotteCity, Sandspit, and Cape St. James.The Tlell, pre-1914 Masset,and post-1943 Queen CharlotteCity data were deletedto ensure data consistency as previously discussed. The data fromMasset Canadian Forces Station (CFS) andTasu Sound also had to be deletea from the 1-day precipitationanalysis. It was determined that some irregularities in thedata series from the latter two stations weredue to changes in thedaily observation schedules. Tasu Souna changed from a schedule of regular twice-daily observations to a schedule of Monday to Friday twice-daily observations in 1980. Weekend precipitation amountswere recorded thereafter asa cornbinea Fridayevening to Monday morning total. Thus, the Tasu Sound record becomes unusable for analysis of daily precipitationafter 1980. Similarly,the Masset CFS record has periods with no weekend readings, as well as irregular,longer combinations of daily precipitation amounts beginning in 1978. The cumulative percent deviation graphs of the annual maximum 1-day precipitation (Figures 18 and 19) indicate periods of greater thanaverage annual maxima from 1914/15 to 1923/24,1933/34 to 1935/36,1950/51 to 1953/54 (southonly), 1957/58 to 1962163 (north only), 1969/70 to 1972/73 (Langaraonly), and 1978/79 to 19831’84. All of theseperiods, except the period beginning in 1950/51 coincide with periods of greater than average October to April precipitation. The regionalindex of annual maximum 1-day precipitation for the central ana northern Queen Charlotte Islands (Queen Charlotte City, Masset,Sandspit, and Langara)indicates general periods of above-averageannual maxima from 1914/15 to 1935/36 and 1977/78 to 1983/84. A longperiod of generally below-average maxima intervenes (Figure 20). The most notablefeature of the regional index is that 5 out of the 18 highestvalues have occurred since 1978/79, an unbrokenconcentration unprecedented in thevalidated record. While other concentrations of high indices haveoccurred from 1914/15 to - 49 -

.e*'.. .' .* ..*.0.

6 L 6 CI c m i n n

0 0 0 0 0 0 0 0 0 m 01 c 01 --"-t t ? 0 I I

c m m m 6 f n 6 - so -

C W e, 3 W

0 0 0 0 0 0 s! E N m 0 l I t . .* .’. ** I . *: .. . -* - 51 -

x m -0 I 4 E '4 .rlC X m E - 52 -

1923/24,1933/34 to 1935/36,1958/59 to 1961/62,these periods have been shorterand/or broken by intervening years of below-normal maxima. F-testsindicated that the means of annual maximum 1-day precipitationfrom the years with thehighest, middle, and lowest thirds of total October to April precipitation differed significantly at only two of five stations at the 95% level(Table 6). Frequencies of 1-day precipitation greater than 30 mm were also comparedbetween theyears with thehighest, middle, and lowest thirdsof total October toApril precipitation. F-tests indicated that the mean frequencies differed significantly at the 95% level at fourout of thefive stations (Table 7). Frequencies of 1-day precipitation greater than 50 mm are concentrated in theperiods from 1915/16 to 1923/24, 1933/34 to 1936/37,1957/58 to 1959/60,and 1978/79 to 1982/83. - 53 -

TABLE 6. Annual maximum 1-day precipitation in theyears with thehighest, middle,and lowest thirds of total October to April precipitation

Mean annual maximum 1-day precipitation (mm)

Highest Middle Lowest third of third of third of F-testLevel of Station years years years score significance score years years years Station

Cape St. James7.79 36.2 42.7 47.3 ’ 99%

4 9.4 47.5 46.6 0.25 Langara 46.6 47.5 49.4 < 90%

Masset38.7 42.5 47.1 2.11 < 90%

Queen CharlotteCity 49.958.9 60.9 1.21 < 90% Sa ndsp it AirportSandspit 50.8 41.5 41.1 3.64 96%

TABLE 7. Frequencies of 1-day precipitationgreater than 30 mm in theyears with the highest,middle, and lowest thirds of totalOctober to April precipitation

Mean annual maximum frequency of days with precipitation greater than 30 mm

Highest Middle Lowest third of third of third of F-testLevel of Station years years years score Significance score years years years Station

Cape St. James 13.6 10.6 6.1 20.5 > 99%

Langara 10.2 1.65.1 3.7 > 99%

Masset1.9 2.9 2.9 1.90 < 90%

Queen CharlotteCity 2. 7.2 7.4 a 2.77 92%

Sa ndsp it AirportSandspit 4.8 3.7 7.4 2.0 > 99% - 54 -

4 DISCUSSION

Tne most striking feature of the climatological data from the Queen CharlotteIslands since 1914115 is analternation, with some overlap and short-termfluctuation, between periods having generally above-normal autumn/winter rainfall and temperature,but below-normal snowfall (Type I), and periodshaving belaw-normal rainfall and temperature,but above-normal snowfall(Type 11). Type Iperiods occurred from 1923/24 to 1945/46,1958/59 to 1963/64, and 1974/75 to 1983/d4. Type I1 periodsintervened from 1946/47 to 1956/57 and 1964/65 to 1974/75. No overalltrend is apparent in the fluctuations. The climatic fluctuations in the Queen CharlotteIslands appear to be related to persistent changes in atmosphericpressure patterns and gradients over the northern Pacific Ocean and the adjacent Siberian and NorthAmerican land masses, with associatednorth-south shifts in the mean position(s) of the autumn/winterstorm track(s) across the northeastern Pacific Ocean. Such synoptic-scale changes have been studied by Namias (1969; 1971; 1972a;- 1972b;- 1978;and 1980) and Namias and Born (1972) forthe period from 1947 to 1979. The keyoccurrences in thesynoptic scenario described byNamias are reversals of oceantemperature patterns in the central and eastern North Pacific Ocean and their atmospheric linkages. Namias(1972a) - described two quasi-stable oceantemperature patterns: 1. coolerthan normal in thenorth-central Pacific Ocean, combined with warmer thannormal in the northeastern Pacific, and 2. thereverse of pattern 1. Pattern 1 corresponds with warm, generally wet winters in westernNorth America. The locus of the warmest, wettestconditions can shift north and south,depending on the location of the storm track. Pattern 2 corresponds with cool,generally dry winters in westernNorth America. The ocean temperature patterns are linked to climate through changes in the relative strength and position of the semi-permanent Aleutian Low and North Pacific Highpressure systems, which in turn affect the position of the storm tracks across the Pacific. - 55 -

Duringthe period of analysis from 1947 to 1979, pattern 2 (cool,dry westernNorth America) dominated from 1947 to 1958and was re-established in 1971-72. Pattern 1 (warm, wet westernNorth America) dominated from 1958 to 1971,and was re-established in 1976. The reversals in 1958and 1976, which resulted in theestablishment of pattern 1 oceantemperatures, are both associated with the El Nino phenomenon of the tropical Pacific Ocean. Basically,the El Ninoresults in theincursion of warm oceanwaters into the northeasternPacific Ocean alongthe margin of blorthAmerica. A similar,very strong,incursion occurred during the El Ninoof 1982. The 1947 to 1979 period of Namias'analyses included 2 fluctuations between Type I (warm, wet)and Type 11 (cool,dry) winter climate regimes in the Queen CharlotteIslands. Winters on the Queen CharlotteIslands since 1946were classified by theirtemperature and precipitation indices and compared with the ocean temperaturepatters identified by Namias (Table8). Sixclasses wereused in classifying the winters on the Queen Charlotte Islanas: - I: temperature and precipitation indices are both in thehighest thirdof index values since 1914/15. - i: eitherthe temperature or precipitation index is in thehighest third of indexvalues, while the other index is in themiddle third of index values since 1914/15. - 0: bothtemperature and precipitation indices are in themiddle third of index values since 1914/15. - ii: eitherthe temperature or precipitation index is in thelowest thirdof index values, while the other index is in themiddle third of index values since 1914/15. - 11: temperatureand precipitation indices are both in thelowest thirdof index values since 1914/15. - 111: temperature and precipitation indices are in the opposite highest or lowestthird of index values since 1914/15. - 56 -

TABLE 8. Comparison of winter temperature and precipitation anomalies in the Queen Charlotte Islands with temperature anomaly patterns in the North Pacific Oceanas identified by Namias

Ocean Winter Winter One-day Winter temp Winter One-day Winter Winter . tempertureprecipitation maximum climateppt. anomaly index index index regime type pattern type regime index Winter index index 1946-47 -0.23 -1.37 -0.34 ii 2 1947-48 -0.09 -0.21 -0.20 0 2 1948-49 -1.28 -G. 27 -0.67 ii 2 1949-50 -2.00 -0.78 +O. 34 I1 2 1950-51 -0.62 -0.63 -0.42 I1 2 1951-52 -0.51 +O. 23 +O. 56 ii 2 1952-53 +O. 03 -0.69 -0.10 ii 2 1953-54 -0.47 +O. 28 -0.25 I11 2 1954-55 +o. 01 +O. 08 -0.55 0 2 1955-56 -1.59 -0.52 -1.50 I1 2 1956-57 -0.68 -1.81 -0.70 I1 2 1957-58 +l. 30 -0.88 +O. 05 I11 2 1958-59 +o. 22 +O. 36 +O. 96 i 1 1959-60 +O. 66 +2.22 +l. 29 I 1 1960-61 +l. 31 +O. 80 -1.00 I 1 1961-62 +O. 14 +O. 03 +O. 51 0 1 1562-63 +l. 19 -0.66 +o. 11 I11 1 1963-64 +O .52 +o. 99 -0.34 I 1 1964-65 -1.08 -1.08 -0.65 I1 1 1965-66 -0.46 +o. 73 -0.53 I11 1 1966-67 -0.06 -0.50 -0.15 ii 1 1967-68 +O. 03 -1.02 +O. 31 ii 1 -2.47 -0.87 -1.30 1968-69-0.87 -2.47 I1 1 1969-70 +O. 92 +O. 08 +l. 24 i 1 1970-71 -1.30 -0.49 -0.27 I1 1 1571-72 -1.97 -0.12 +O. 16 ii 2 1972-73 -0.37 -0.71 -0.20 ii ? 1973-74 -0.62 -0.08 -0.41 ii ? 1974-75 -0.61 +O. 62 +o. 10 I11 ? 1975-76 -0.19 +l. 25 -0.05 i ? 1976-77 +l. 33 -0.15 -0.37 i 1 1977-78 -0.39 +o. 22 -0.26 0 1 1978-79 -0.49 -0.14 +1.30 ii 2? 1979-80 +O. 14 +o. 79 +l.16 i ? 1980-81 +l. 50 +l. 65 +O. 55 I ? -0.83 -0.08 -0.33 -0.081981-82 -0.83 ii l? 1982-83 +l. 69 +O. 62 +1.54 I l? 1983-84 +O .83 +l. 00 +O. 78 I l? - 57 -

Table 8 shows that changes from predominantly Type I1 (cool,dry) winters topredominantly Type 1 (warm, wet)winters in 1958/59and 1975/76 correspond to the changes in oceantemperature patterns in the same yearsnoted by Namias. Both changes areassociated with the El Nino phenomenon. Another El Ninooccurred in 1982,which resulted in two exceptionallystrong Type 1 winters in the Queen CharlotteIslands. One theother hand, the Namias hypothesisaoes not account for the changeover from Type Ito Type I1 winters whichoccurred in the Queen CharlotteIslands in 1964/65. Accordingto Namias (1472b),- this changeover was in the middle of a long period of ?attern 1 ocean temperatureanomalies which persisted until 1971. On theother hand, precipitation on northern Vancouver Island,which also became aboveaverage after 195W59,remained above average until themid-19701s, throughout the periodsuggested by the synoptic model proposed byNamias. The discrepancy between the Namiasmodel and actual precipitation fluctuations on the Queen CharlotteIslands may be a reflection of local variability which is too subtle in scale for a synopticmodel that covers the entire north Pacific Oceanand Nestern North America. Trends in annualrunoff volumeson Prince of Wales Island in thesouthern Alaska Panhandle are similar to precipitation trends in the central and northern Queen CharlotteIslands. On theother hand, neitherthe Yakoun River runoff data nor the Revillagigedo Island runoff data show anincrease since 1975/76. The homogeneity ofthe Yakoun Riverdata hasalready been questioned in Section 3.1. The RevillagigedoIsland data, however,cannot be rejected on the basis of homogeneitybecause of the high correlation between the stations. The discrepancybetween the Queen CharlotteIsland precipitation dataand the Revillagigedo Island stream runoff data cannot be resolvedfrom the available information. The twoperiods from 1958/59 to 1963/64and 1974/75 to 1983/84have had the most consistent clustering of heavy1-day precipitation events since 1947 atthe Queen CharlotteIslands meteorological stations. The period of greater-than-averagefrequency of 1-day precipitation exceeding 30 mm between 1958and 1964 was localized to northern Graham Island(Langara and Masset), onlybriefly affecting Sandspit to the south. Nine of 25 1-day precipitation - 58 - amounts exceeding 50 mm occurredduring this period at Langara. Above-average frequencies of 1-day precipitation greater than 30 mm havebeen more widespreadthroughout the Queen CharlotteIslands since 1974/75.Moreover, one-half of all 1-day precipitation events exceeding 50 mm have occurred during this period at Cape St. James and SandspitAirport, while seven of 25 suchevents have occurredat Langara beginning in 1978. October to April precipitation indices from southern Vancouver Island to theAlaska Panhandle suggest the following synoptic changes areassociated with the Type I and I1 periods identified in the Queen CharlotteIslands.

1. Type Iperiod from 1923/24 to 1945/46coincides with a periodof oelow-normal precipitation across Vancouver Island and above-normal precipitationacross the Alaska Panhandle, indicating anorthward shiftof the autumn/winterstorm track in thenortheast Pacific. The Queen CharlotteIslands, in betweenthese two anomalies, show above-normal rainfall,but near-normal precipitation. This period is markedby considerableshort-term fluctuation. 2. Type I1 periodfrom 1946/47 to 1957/58 coincideswith a periodof above-normal precipitation across southern Vancouver Island and below-normal precipitation from northern Vancouver Island to the AlaskaPanhandle, indicating a persistent southerly shift in the autumdwinter storm track. 3. Type Iperiod from 1957/58 to 1963/64 coincides with a periodof above-normal precipitationthroughout the northeast Pacific area, especiallyfrom the central British Columbia mainland coast to the AlaskaPanhandle. 4. Type I1 periodfrom 1964/65 to 1975/76 coincides with a periodof above-normal precipitation onVancouver Island and below-normal precipitation from the Queen CharlotteIslands to the Alaska Panhandle, indicating a persistent southerly shift of the autumdwinterstorm track. - 59 -

5. Type I perioa from1975/76 to 1983/84 coincides with a period of fluctuatiny, but generally below-normal precipitation on Vancouver Island and above-normal precipitationin the Queen Charlotte Islands and the northern Alaska Panhandle, indicatinga persistent northerly snift in the autumn/winterstorm track. - 60 -

5 CONCLUSIONS

1. Long-term precipitationdata from the Queen CharlotteIslands haslow regional coherence, with interstationcorrelations for October to Aprilprecipitation generally less than r=0.7. Thus, trends and fluctuations at anyone station my not beapplicable in anotherarea of tne queen Charlotte Islands.

2. Most ofthe long-term Queen CharlotteIslands data sets have changes in homogeneity resultingfrom changes in station location or instrumentation.Results of single-stationtrend analyses, such as eumdativepercent deviation graphs or n-yearmoving means mustbe interpretedcautiously with respect to climatic trends or fluctuations.

3. Queen CharlotteIslands climate data show an alternation between periodsof above-normalautumdwinter rainfall and temperature,but below-normalsnowfall (Type I>; and periods with below-normal autumdwinterrainfall andtemperature, but above-normalsnowfall (Type11). These fluctuationsapparently result from persistent shifts in the mean position of theautumn/winter stormtrack across thenortheastern Pacific. Type I periodsoccurred from 1923/24 to 1945/46,1957/58 to 1963/64,and 1974/75 to 1983/84. Type I1 periods intervenedfrom 1946/47 to 1956/57and 1964/65 to 1973/74.

4. The above-normal precipitation in the Queen CharlotteIslands since 1976/77 is not reflected in runoffdata from the Yakoun River or on RevillagigedoIsland. Runoff trends in Old Tom Creekon Prince of Wales Island,on the other hand, showa similar trend to Queen CharlotteIslands precipitation.

5. The most likelyperiods during which stream channel enlargement occurredon the Queen CharlotteIslands because of above-normal precipitation and runoffare: 1938-1946,1958-1964, and 1975-1984. - 61 -

6 LITERATURE CITE13 deschta, R.L. 1983a. Channel changes following storm-induced hillslope erosion in-the Upper Kowai Basin,Torlesse Range, New Zealand. J. Hyarol., W. Zealand. Vol. 22!2):93-111. . 1983b. Long-term changes in channel widths of the Kowai River, Torlesse-Ranqe, New Zealana. J. Hydrol . , N. Zealand. Vol. 22(2) :112-122. - tjuishand, T.A. 1982. Som? :nethods for testingthe homogeneity of rainfall records. J. Hydrol. 58:ll-27.

Church, M. and M.J. Miles.[1986]. Meteorological antecedents to debris flow in southwestern British Columbia: some cases studies. Geol. SOC. QmericaSpecial Papers. In press. Boulder,Colorado.

Craddock, J.M. 1,079. Methods of comparing annual rainfallrecords for climaticpurposes. Weather 34:332-346.

Crowe, R.B. 1960.Recent precipitationfluctuations and trends for the british Columbia coast. Canada Dep. Transport,Meteorol. Branch, Circ. 3309 Tech. 318. 10 p. . 1963. Recenttemperature and precipitationfluctuations along the British Columbia coast. 3. App. Meteorol.(2):114-118.

Holland, S.5. 1964. Landforms of British Columbia, a physiographic outline. B.C. Min. Mines PetroleumResources. Bull. 48.

Kelsey, H.M. 1480. 4 seaimcntbudget and an analysis of geomorphic process in the Van Ouzen River basin, north coastalCalifornia, 1941-1975: Summary. Geol. 50C. America Bull. Part I, Vol. 91, pp. 190-195.

Kraus, E.B. 1977. Subtropicaldroughts and cross-equatorialenergy transports. Monthly Weather Review 105(8):1009-1018.

Lisle, T.E. 1981. The recovery of aggradedstream channels at gauging stations in northernCalifornia and southern Oregon. IAHS-AISH Publ. 132, pp. 189-211.

Lyons, J.K. ana R.L. Beschta. 1983. Land use, floods, and channelchanges: upper Middle Fork WillametteRiver, Oregon (1936-1980) Water ResourcesHesearch 19(2) :463-471. Namias, J. 1969. Seasonalinteractions between the North Pacific Oceanand the atmosphere during the1960's. Monthly Weather Review 97(3) ~173-192. - 62 - . 1971. The 1968-69 winteras an outgrowthof sea and air coupling during antecedentseasons. J. Phys. Oceanog. 1(2):65-81. . 1Y72a. Large-scale and long-term fluctuations in some atmospheric and oceanicvariables. -In hobel Symposium 20. David Dyrssen and DanielJagner (editors). Almqvist and Wiksell, Stockholm, pp. 27-48 . 1972b. Experiments in objectivelypredicting some atmospheric and oceanicvariables for the winter of 1971-72. 3. AppliedMeteorol. 11(8):1164-~74. . 1978. Multiplecauses of the horth American abnormal winter of 1976-77. Monthly Weather Review 106(3):279-295. . 1980. Causes of some extreme Northern Hemispheric climatic anomalies from summer 1978 through the subsequent winter. Monthly Weather Review .108(9) :1333-1346. hamias, J. and H.M. Born. 1972. Empiricaltechniques applied to large- scale and long-periodair-sea interactions: a preliminary report. SI0 Ref. 72-1, ScrippsInstitution of Oceanography, 47 p. Powell, J.M. 1966. Annual ana seasonaltemperature and precipitationtrends in 8ritish Columbia since 1890. Can. Dep. Transport,Meteorol. Yranch, Circ. 4296, CtI-34.

Rollerson, T.P. 1983. Channel stability in natural and logged river systems (northern Vancouver Island). Land Use PlanningAdvisory Team, MacMiilan Bloedel Ltd.

Sporns, U. 1962. The occurence of severe storms in the Lower FraserValley British Columbia. Can. Dept. Trans.,Meteorol. Branch, Circ. 3631, TEC-404. 11 p.

World MeteorologicalOrganization. 1966. Climaticchange. Tech. Note 79. - 63 -

APPENDIX 1

Exceedance Frequenciesof Daily Total Precipitation

(Sample pageof computer printout) - 64 -

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c.) oooooooooooodcm md 0000OOOOOOrtN~W~mD 2 rtm dA 4

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z 00000000000000~In0 OOVOO+dNNNNUC*m ma 3 m d rtw -I

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c 0 c

0 b-

1111~111111111111

0moooobooooooooo~ oLloooouooooooooo...... SOy1O&nOU'~~0~CmNdO OmNN4rtOOOOOU0000 0000000000000000 - 65 -

APPENDIX 2

Detailea Historiesof Queen Charlotte Islands

Climate Stations - 65 -

1. Masset

- station opened JJne 1897. - many short gaps in earlyrecord to 1901,again in 1904 and 1910.

- possiblelocation change in 1909.

- definitelocation change by 1913; station now reported at an elevation Jf 3 rn instead of theprevious 9 rn. The evidencesuggests the change actuallyoccurred in 1909, when theobserver is known to have changed his residence to a location lower in elevation.

- first observer retires in 1.919; coincides with a suspected change in station homogeneity.

- stationcloseu October 1951 to ivlarch 1952; may have reopened in a differentlocation.

- station closed in March 1968.

- station reopened in November 1971 as Masset CFS (CanadianForces Station), 4' lonyitude (5 kin) furthereast.

- precipitationdata become erraticafter 1976. - stationclosed in February1981.

- station reopened in September 1981 as Masset Tow Hill, a further6' longitude (7 krn) furthereast.

2. LangaraLighthouse

- station opened in July 1936.

- Nipher-shielded snow gauge installed in 1965.

3. Sandspit Airport

- station opened in September 1945.

- stationclosed in March 1946.

- station reopenea in August 1948.

- Nipher-shielded snow gauge installed in 1966. - 67 -

4. Llueen CharlotteCity

- station openea in October 1914.

- no snowfallrecordea from 1931 to 1937. Winterprecipitation should bereaucea from 80 to 160 mm lessthan expected during this period.

- stationclosed in October 1939. - station reopened at or near old location in April 1940.

- station wasmovea in 1943, to a locationabout 3 km further west. Since this is a highgraaient rainfall area, the new station location wasmuch wetter.

- stationclosed in December 1448.

5. Tlell

- station opened in January 1950. - stationlocation changed in June1954, to 1' longitude (1.5 km) further east.

- stationlocation changed in November 1966, to about4' latitude (6 km) further south.

- stationlocation changed in November 1971, to a further 2' latitude (3 km) furthersouth.

- Bob Marsh (B.C. Ministry of Environment)reports the rain gauge to havebeen in toosmall a clearing, in fact,under a tree.

6. Dead TreePoint

- station opened in February 1939. - stationclosed in January1958.

7. TasuSound

- station opened in January 1963.

- location changed in August 1966. - 68 -

8. Cape St. James Lighthouse - station opened in August 1925.

- many short data gaps inwinter months frm 1925 to 1940.

- station closed in April 1440. - station reopenea in December 1944.

- hipher-shielded snow gauge installedin 1964. - 69 -

APPEND I X 3

Winter Precipitation (October to April) Indices for Long-Term Queen Charlotte Islands Stations - 70 -

..

+ II

11++1++1+11+11

4 4101 N 44 4 4 1+1+1111+++++111++1+l+l++ 1+1

4m-i 4 4d 44 1 1+1++1111++1+111++11+111++1+1+++1111 - 71 -

...... -4 N 4 4 4 -4 4 I+l++lll++++l+l+llI+IIII++I+I++I++ ...... N -id -4 +1+111+1111+++11++11+

1 4 1 Id 4 N IN 111+1111+++11+1+ 1111+11++++1++1++

1111+111++++1+1+11111+1++++++++++1

I 111111+++11+1+11 11+++1+1+++++