Ash River Project Water Use Plan - BC Hydro - Power smart · PDF file ·...

Ash RiverProject

Water Use Plan

4 October 2004

B

Revised for Acceptanceby the Comptroller ofWater Rights

Ash River Project Water Use Plan

Revised for Acceptance by the Comptroller of Water Rights

Generation 4 October, 2004

Ash River Project - Water Use Plan

Generation 4 October 2004

Ash River ProjectWater Use Plan

Revised for Acceptance by the Comptroller of Water Rights

Cam MathesonManager, Operations

Ash River Project - Water Use Plan Page i


Table of Contents

1.0 INTRODUCTION ............................................................................................... 1

2.0 DESCRIPTION OF WORKS............................................................................. 1

2.1 Location ..................................................................................................... 12.2 Existing Works ........................................................................................... 2

3.0 HYDROLOGY OF THE ASH RIVER BASIN ................................................ 4

4.0 OPERATING CONDITIONS FOR FACILITY .............................................. 4

4.1 Role of Facility in BC Hydro's System....................................................... 44.2 Use of Water for Power Generation at the Ash River

Hydroelectric Facility................................................................................ 54.3 Emergencies and Dam Safety .................................................................... 54.4 Conditions for the Operation of Works for Diversion and Use

of Water...................................................................................................... 54.4.1 Elsie Dam 54.4.2 Ramp Rates 64.4.3 Ash River Generating Station 6

5.0 PROGRAM FOR ADDITIONAL INFORMATION ....................................... 6

6.0 IMPLEMENTATION OF RECOMMENDATIONS....................................... 7

7.0 EXPECTED WATER MANAGEMENT IMPLICATIONS ........................... 7

7.1 Riparian Rights .......................................................................................... 77.2 Fisheries..................................................................................................... 77.3 Wildlife Habitat.......................................................................................... 77.4 Flood Control ............................................................................................ 87.5 Recreation.................................................................................................. 87.6 Water Quality............................................................................................. 87.7 Industrial Use of Water.............................................................................. 87.8 First Nations Considerations..................................................................... 87.9 Power Generation...................................................................................... 9

8.0 RECORDS AND REPORTS .............................................................................. 9

8.1 Compliance Reporting ............................................................................... 98.2 Non-compliance Reporting ........................................................................ 98.3 Monitoring Program Reporting................................................................. 9

Ash River Project - Water Use Plan Page ii


9.0 PLAN REVIEW ...................................................................................................9

10.0 NOTIFICATION PROCEDURES.....................................................................9

List of Tables

Table 4–1: Rate of Change in Release from Elsie Dam Low Level Outletinto Ash River ............................................................................................6

List of Figures

Figure 2-1: Place Names in Ash River Water Use Plan ...............................................2

List of Appendices

Appendix 1: Ash River Basin Hydrology



Preface

The water use planning process for BC Hydro's Ash River facility was initiated inSeptember 2000 and completed in June 2002.

The proposed conditions in this Water Use Plan, for the operation of BC HydroAsh River hydroelectric facility reflect the June 2002 consensus recommendations of theAsh River Water Use Plan Consultative Committee. On 8 May 2003, Hupacasath FirstNation sent a letter to BC Hydro declaring that they were withdrawing acceptance of theconsensus recommendations of the Consultative Committee on 25 June 2002.

BC Hydro thanks all those who participated in the process that led to the production ofthis Water Use Plan, for their effort and dedication. The proposed conditions for theoperation of BC Hydro’s facilities will not come into effect until implemented under theWater Act.

Ash River Project - Water Use Plan Page 1


1.0 INTRODUCTION

The proposed conditions in this Water Use Plan, for the operation of BC Hydro’sAsh River hydroelectric facility reflect the June 2002 consensusrecommendations of the Ash River Water Use Plan Consultative Committee. Theproposed terms and conditions to be authorized under the Water Act for thebeneficial use of water at the Ash River hydroelectric facility are set out in thisdocument.

The proposed conditions would change current operations and are expected toresult in:

• Increased rearing and spawning habitat for fish in the Ash River includinga nearly 14-fold increase in steelhead parr rearing habitat belowElsie Dam

• Increased opportunities for fish to migrate past Lanterman Falls andDickson Falls

• Increased minimum flows in the Ash River

• Increased riparian habitat around Elsie Lake Reservoir

• Potential change in the type of or a reduction in the quality of therecreation experience at Elsie Lake Reservoir

• Increased power generation

A monitoring study and a review period is proposed which will study keyuncertainties to enable improved operating decisions in the future. Refer to theAsh River Water Use Plan: Report of the Consultative Committee datedJune 2003 for details on the consultative process, interests, objectives,performance measures, values associated with operating alternatives, and detailsof the proposed monitoring program.

2.0 DESCRIPTION OF WORKS

2.1 Location

The Ash River is located within the Regional District of Alberni-Clayoquot oncentral Vancouver Island (Figure 2-1). The Ash River flows south, betweenStrathcona Park to the west and the Beaufort mountain range to the east, into theStamp and Somass Rivers, and eventually into the Alberni Inlet.



Ash River Project

Figure 2-1: Place Names in Ash River Water Use Plan

(Map courtesy of Fisheries and Oceans Canada)

The Ash River hydroelectric facility is a one reservoir system. Elsie LakeReservoir is approximately 40 km north west of Port Alberni. Water flows froman intake on the south side of the reservoir through 7.9 km of tunnels andpenstocks to the powerhouse on the north shore of Great Central Lake. Flows arealso released from Elsie Dam to maintain fish habitat in the Ash River.

2.2 Existing Works

The current physical structures comprising the Ash River project include:

• Main Dam: This primary dam is located at the eastern end of Elsie LakeReservoir. The earthfill dam is 189.2 m long and 30.5 m high with a crestelevation of 334.37 m above sea level

• Saddle Dam 1: Earthfill dam 438.1 m long and 18.3 m high


• Saddle Dam 3: Earthfill dam 130 m long and 3 m high




• Low level outlet: The low level outlet located at the base ofSaddle Dam 1 is a 2.44 m diameter steel conduit 60 m long encased inconcrete. The sill of the low level outlet (invert elevation) is at 313.33 m.At the downstream end of the conduit is a hollow cone valve to controlsupply of water to the Ash River. When the reservoir is at full pool(330.71 m) the low level outlet has a maximum discharge capacity ofapproximately 55 m3/s.

• Freecrest overflow spillway: The freecrest overflow spillway is locatedbetween Saddle Dams 1 and 4. The left, centre and right spillway crestelevations are 330.71 m, 331.45 m and 331.14 m respectively. Atelevations above 330.71 m, water flows over the freecrest overflowspillway and into the Ash River. The freecrest overflow spillway has adischarge capacity of approximately 1280 m3/s when the reservoirelevation is at 334.37 m (dam crest).

• Spillway sluicegate: In 2001, as part of the ongoing dam safety upgradeprogram, BC Hydro constructed a new spillway sluicegate betweenSaddle Dams 1 and 4. The spillway sluicegate has a discharge capacity ofapproximately 35 m3/s when the reservoir is at full pool and is intended tosupply water for fish in the Ash River in the event the low level outlet isout of service for maintenance.

• Power Intake: The power intake is located at the south shore ofElsie Lake Reservoir, 5 km southwest of the Main Dam with a sill (invert)elevation at 309.88 m. The power intake is a 3.35 m x 3.35 m concretelined tunnel opening and is comprised of 2 trashracks, a steel operatinggate and a bulkhead gate.

• Ash River Powerhouse: The Ash River powerhouse is located on thenorth shore of Great Central Lake and contains a single 27 MW capacityvertical shaft Francis turbine generator unit. Water is delivered through a1.6 km upper tunnel, 2.46 km lower tunnel, 3.37 km woodstave penstock,and 0.5 km steel penstock. Once through the turbine, the water isdischarged from the Ash River Generating Station intoGreat Central Lake.

• Elsie Lake Reservoir: Elsie Dam impounds Elsie Lake Reservoir. Thereservoir covers approximately 658 ha (6.58M m2) at full pool. Thenormal operating range of the reservoir is between 315.47 m and330.71 m. At elevations above 330.71 m, water flows over the freecrestoverflow spillway. The maximum quantity of water which may bediverted from Elsie Lake Reservoir and used at the Ash River GenerationStation and discharged into Great Central Lake ranges between 13.6 m3/sand 15.01 m3/s depending on reservoir elevation.



3.0 HYDROLOGY OF THE ASH RIVER BASIN

Appendix 1, Ash River Water Use Plan Hydrology Memo highlights thephysiography, climate, and hydrology of the Ash River basin. The Ash Riverbasin is in the transition zone between the wet west coast and drier east coastclimates of Vancouver Island. The basin is affected by frontal storms arrivingfrom the southwest off the Pacific Ocean with strong, moist winds that bringheavy precipitation for durations of a few hours to four days. Very often a seriesof cyclonic storms are carried in the flow of air separated by hours or days.

The west-facing mountain slopes of Vancouver Island are usually cloud-coveredand wet during the winter because of the lifting of warm, moist air flowinginland. Prolonged and heavy rains can fall on these slopes when a Pacific cycloneapproaches. The east faces of these mountains experience the spillover effect ofthese winds. Precipitation formed by the lifting of the moisture-laden winds iscarried over the mountain barrier. The climate tends to be less rainy on the eastcoast of the island because the descending air tends to disperse clouds and lessenthe cyclonic rainfall.

During these large winter storms the air temperature may be above freezing at allaltitudes in the basin. Consequently, the accumulated snowpack may varyappreciably at low elevations. Typically, a period of cooler weather in which thesnowpack increases may be followed by a large Pacific disturbance that raisestemperatures and melts a portion of the snowpack.

The memo also describes daily inflow and seasonal volume inflow forecastingprocedures. The supporting network of hydrometeorological stations in the areais described. A summary of the inflow hydrograph for Elsie Lake Reservoir isprovided.

4.0 OPERATING CONDITIONS FOR FACILITY

4.1 Role of Facility in BC Hydro's System

The Ash River generating station is part of BC Hydro’s integrated generationsystem which is described in BC Hydro’s publication ‘Making the Connection’.

In addition to generating electricity, the Ash River powerhouse provides ancillarysupport to electricity supply on Vancouver Island. The generating station isequipped with a back-up diesel generator and batteries. Following an outage, theAsh River hydroelectric facility can be started without any external supply ofelectricity ("black start" capability). Once restarted, electricity from theAsh River generation plant can provide electricity to restart other plants onVancouver Island and provide voltage support for the electricity transmissionsystem.



The Ash River hydroelectric facility contributes approximately 6% ofBC Hydro’s Vancouver Island hydroelectric generation, or about 0.27% ofBC Hydro’s total hydroelectric generation.

4.2 Use of Water for Power Generation at the Ash River Hydroelectric Facility

The Ash River hydroelectric facility is classified as a “coastal reservoir” whichmeans that the majority of inflow results from seasonal rainstorms and springsnowmelt.

Water stored in Elsie Lake Reservoir is diverted to the Ash River powerhouse onthe north shore of Great Central Lake. The Ash River generating plant isnormally operated as a base load plant running at relatively constant output fordays or weeks at a time. At maximum generating plant output of 27 MW, turbinedischarge ranges between 13.6 m3/s and 15.01 m3/s depending on reservoirelevation.

4.3 Emergencies and Dam Safety

Emergencies and dam safety requirements shall take precedence over theproposed conditions outlined in this Water Use Plan. Emergencies include, butare not limited to, actual and potential loss of power to customers. Dam safetyrequirements for operations are outlined in the document titled Ash River:Operation, Maintenance and Surveillance Requirements (OMS) for Dam Safetywhich is issued by BC Hydro's Director of Dam Safety.

4.4 Conditions for the Operation of Works for Diversion and Use of Water

BC Hydro will plan the operation of its water in accordance with the proposedconditions outlined below. BC Hydro may not be able to operate within theseconstraints during extreme hydrological events.

4.4.1 Elsie Dam

From 1 May to 31 October a minimum flow of 3.5 m3/s will be released fromElsie Dam into the Ash River. From 1 November to 30 April a minimum flow of5 m3/s will be released from Elsie Dam into the Ash River.

Between 1 August and 30 September, two separate pulse flows of 10 m3/s fortwo days, measured at the Moran Creek Water Survey of Canada gauge, will bereleased from Elsie Dam into the Ash River. Each pulse flow release will betimed when adult steelhead are holding at the base of Dickson Falls, asdetermined by direct observation in season, with each pulse coinciding withnatural increases from precipitation.



4.4.2 Ramp Rates

Ramp rates for flow releases from Elsie Dam into the Ash River will be inaccordance with Table 4–1 and no ramp rates are required for changing flowsgreater than 30 m3/s.

Table 4–1: Rate of Change in Release from Elsie Dam Low Level Outlet into Ash River

Ramp Up Rate Ramp Down Rate

Discharge Rate of Change Discharge Rate of Change

Ramp Rate Metric 0-2.8 cms =

2.8-5.7 cms =

5.7-8.5 cms =

8.5-14.2 cms =

14.2-19.8 cms =

19.8-26.9 cms =

27-30 cms =

1.1 cms/hr

2.3 cms/hr

2.8 cms/hr

3.4 cms/hr

4.0 cms/hr

4.5 cms/hr

5.1 cms/hr

30-27 cms =

27.0-19.8 cms =

19.8-17.0 cms =

17.0-14.2 cms =

14.2-8.5 cms =

8.5-5.7 cms =

5.7-3.5 cms =

3.5-0 cms =

2.5 cms/hr

2.3 cms/hr

2.0 cms/hr

1.8 cms/hr

1.0 cms/hr

0.9 cms/hr

0.3 cms/hr

0.2 cms/hr

Note: Elsie Dam low level outlet valve openings will be changed a minimum of every fifteen minutes.

Flow releases at Elsie Dam will normally be provided through the Low LevelOutlet, but may be provided using the Sluicegate or the Sluicegate incombination with the Low Level Outlet. The ramp rates apply to the combinedflow releases from the Low Level Outlet and the Sluicegate.

4.4.3 Ash River Generating Station

The Consultative Committee did not recommend any constraints on the diversionflows for the Ash River Generating Station. BC Hydro shall make informationavailable respecting actual and planned discharges from Ash River GeneratingStation.

5.0 PROGRAM FOR ADDITIONAL INFORMATION

Development of proposed conditions for the Ash River hydroelectric facility wascomplicated by uncertainties and information gaps. The June 2002 consensusrecommendations of the Consultative Committee was contingent on theimplementation of the monitoring program to reduce these uncertainties overtime and an ongoing management program to address priority issues related tooperational impacts.

Accordingly it is recommended that the Comptroller of Water Rights directBC Hydro to undertake a monitoring program that will:

• evaluate the effectiveness of the new operating conditions on steelheadmigration, and



• provide additional steelhead information on which to base decisions aboutfuture operating conditions.

The primary management question for the Adult Steelhead Migration MonitoringProgram is "will pulse flow releases in the Middle Ash River maximize the rate ofadult steelhead migration"?

Details and costs of the proposed monitoring program are provided in theAsh River Water Use Plan: Report of the Consultative Committee.

6.0 IMPLEMENTATION OF RECOMMENDATIONS

The proposed conditions and monitoring program in this Water Use Plan will beimplemented after BC Hydro receives direction from the Comptroller of WaterRights.

7.0 EXPECTED WATER MANAGEMENT IMPLICATIONS

Implications for the provincial interests considered during the preparation of thisWater Use Plan are expected outcomes based on the best available information.After BC Hydro has been directed to implement the proposed conditions,BC Hydro will be responsible for meeting the operational parameters, but not forachieving the expected outcomes.

7.1 Riparian Rights

The proposed conditions in this Water Use Plan are not expected to affectriparian rights associated within the Elsie Lake Reservoir or the Ash River belowthe facilities.

7.2 Fisheries

The proposed conditions in this Water Use Plan are expected to increase troutrearing habitat in tributaries to Elsie Lake Reservoir. It is also expected that therewill be increased rearing and spawning habitat for fish in the Ash River includinga nearly 14-fold increase in steelhead parr rearing habitat just below Elsie Damfrom increased minimum flows. The migration pulse flows may provideincreased opportunities for fish to migrate past Lanterman Falls andDickson Falls.

7.3 Wildlife Habitat

The proposed conditions in this Water Use Plan are expected to increase riparianhabitat around Elsie Lake Reservoir.



7.4 Flood Control

The proposed conditions in this Water Use Plan are not expected to affect floodrouting associated with Elsie Lake Reservoir operations or Ash River below thefacilities.

7.5 Recreation

The proposed conditions in this Water Use Plan are expected to hold Elsie LakeReservoir at lower elevations during 24 May to 15 October. This may change thetype of or reduce the quality of the recreation experience at the reservoir.

7.6 Water Quality

The proposed conditions in this Water Use Plan are not expected to affect waterquality associated within Elsie Lake Reservoir or Ash River below the facilities.

7.7 Industrial Use of Water

The proposed licence conditions in this Water Use Plan are not expected to affectindustrial use of water associated within Elsie Lake Reservoir or Ash Riverbelow the facilities.

7.8 First Nations Considerations

BC Hydro's Ash River hydroelectric facility lies within the claimed traditionalterritory of Hupcasath First Nation and Tseshaht First Nation. First Nations havean interest in:

• protection of First Nation archaeological resources in Elsie LakeReservoir drawdown zone from unauthorized collection

• protection of an archaeological site in Elsie Lake Reservoir from waveerosion

• opportunities for study and traditional use in the Elsie Lake Reservoirdrawdown zone

• traditional use in the Ash River

At the June 2002 Consultative Committee meeting, an Archaeological Artifactsin the Elsie Lake Reservoir Monitoring Program was proposed. A number ofactivities have been undertaken, during and following the Ash River Water UsePlan to address these archaeological and traditional issues. BC Hydro, FirstNations and the provincial Archaeology Planning and Assessment Branch arecurrently reviewing the results of the activities completed to date. It is expectedthat the review of the results of the archaeological management work completedto date will help both BC Hydro and First Nations establish what steps may



remain to be taken to complete the post Ash River Water Use Plan monitoringactivities.

7.9 Power Generation

The proposed conditions in this Water Use Plan are expected to increase powergeneration associated with the Ash River hydroelectric facility.

8.0 RECORDS AND REPORTS

8.1 Compliance Reporting

BC Hydro will submit data as required to the Comptroller of Water Rights todemonstrate compliance with the conditions conveyed in the Water Licences.The submission will include records of:

• Elsie Dam discharges

• Elsie Lake Reservoir levels

8.2 Non-compliance Reporting

Non-compliance with operating conditions required by the water licence, oranticipation thereof, will be reported to the Comptroller of Water Rights in atimely manner.

8.3 Monitoring Program Reporting

Reporting procedures will be determined as part of the detailed terms ofreference for each study or undertaking.

9.0 PLAN REVIEW

Five years after the implementation of this Water Use Plan, BC Hydro willreview the results of the monitoring study and assess the need to review theAsh River Water Use Plan. A review of the Water Use Plan could be triggeredsooner if significant risks are identified that could result in a recommendation tochange operations.

10.0 NOTIFICATION PROCEDURES

Notification procedures for floods and other emergency events are outlined in the"SOUTH ISLAND GENERATION Power Supply Emergency Plan (PSEP) forthe Ash River Project". This document is filed with the Office of the Comptrollerof Water Rights.



Appendix 1Ash River Water Use Plan Hydrology Memo

Water Use Plan 4 October 2004

Inter-office memo

TO: Eric Weiss 8 March 2002

FROM: Mike Homenuke File: PSE 151.0

SUBJECT: Ash River WUP - Hydrology of Ash River Basin

1 INTRODUCTION

The Ash River system encompasses one hydroelectric project with the following general

characteristics:

• Elsie Lake Reservoir is impounded by one Main Dam and four Saddle

Dams.

• Power releases are diverted through a 7.4-km tunnel and pipeline to

the 27 MW Ash powerhouse on Great Central Lake.

• Spill and other non-power releases from Elsie Lake discharge into the

Ash River.

This report highlights the hydrology of the Ash River hydroelectric system.

Physiography and climatology are reviewed for the Ash River watershed.

Methods used to calculate reservoir inflows, such as BC Hydro’s FLOCAL

program, are discussed. Typical inflow hydrographs and summaries are

provided. Flow records for the Ash River system referred to in this report were

used in power studies conducted for the Ash River Water Use Plan.

Procedures used to provide daily and seasonal volume inflow forecasts are also

described.

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2

2 Physiography1

The Ash River system is located in the central portion of Vancouver Island about

40 km northwest of Port Alberni. The upper basin is dominated by high

mountains up to 2000 m high which form the boundary between the Ash,

Campbell and Comox basins. Several small areas of permanent snowpack exist.

The Ash River has its source in these mountains and then flows into Oshinow

Lake after a drop of 1200 m and a run of 12 km. Oshinow Lake is a natural lake

with a length and width of 5 km and 0.6 km respectively at an elevation of

410 m. Approximately 30% of the basin area lies above Oshinow Lake.

The drainage basin for the Ash River system is shown in Figure 1.

Figure 1: Watershed Map and Hydrometeorological Stations

1 BC Hydro. March 1987. “Ash River Project: Probable Maximum Flood”, BC Hydro Hydroelectric Engineering

Division, Report No. H1903.

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3

After discharging from Oshinow Lake, the Ash River runs a further 13 km to

Elsie Lake, falling 80 m in the process. This downstream portion of the basin has

lower relief than the upper basin, with a maximum height of about 1350 m. Elsie

Lake has a length of approximately 7 km and an average width of 1 km at an

elevation of approximately 30 m.

The mean basin elevation is 700 m and the total basin area is 239 km2, distributed

as shown in the hypsometric curve for the basin (Figure 2).

Approximately 20 km downstream from Elsie Lake, the Ash River joins the

Stamp River which then flows a further 15 km into the Somass River. Finally,

the Somass River runs 8 km to its mouth on Alberni Inlet, near Port Alberni.

Hypsometric Curve for Ash River BasinFrom BCH Report No. H1903

200

400

600

800

1000

1200

1400

1600

1800

2000

0 10 20 30 40 50 60 70 80 90 100

Percent of Basin Area

Elev

atio

n (m

)

Figure 2: Hypsometric curve for the Ash River System

Figure 3 shows the elevation-storage relationship for Elsie Lake Reservoir within

its normal reservoir operating ranges. Between its normal maximum and

minimum operating elevations Elsie Lake has a storage capacity of

approximately 900 cms-days (78 million m3).

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4

Elsie Lake Stage-Storage CurveBased on photogrammetry survey conducted 2001 for the Water Use Plan

305

310

315

320

325

330

335

0 200 400 600 800 1000

Storage Volume (cms-days)

Res

ervo

ir El

evat

ion

(m)

Minimum Normal Operating Level El. 315.47 m

Maximum Normal Operating Level El. 330.71 m

Figure 3: Stage-storage relationship for Elsie Lake Reservoir

3 Climatology2

The Ash River basin is in the transition zone between the wet west coast and

drier east coast climates of Vancouver Island. The basin is affected by frontal

storms arriving from the southwest off the Pacific Ocean with strong, moist

winds that bring heavy precipitation for durations of a few hours to four days.

Very often a series of cyclonic storms are carried in the flow of air separated by

hours or days.

The west-facing mountain slopes of Vancouver Island are usually cloud-covered

and wet during the winter because of the lifting of warm, moist air flowing

inland. Prolonged and heavy rains can fall on these slopes when a Pacific

cyclone approaches. The east faces of these mountains experience the spillover

effect of these winds. Precipitation formed by the lifting of the moisture-laden

winds is carried over the mountain barrier. The climate tends to be less rainy on

2 BC Hydro. March 1987. “Ash River Project: Probable Maximum Flood”, BC Hydro Hydroelectric Engineering

Division, Report No. H1903.

- -


5

the east coast of the island because the descending air tends to disperse clouds

and lessen the cyclonic rainfall.

During these large winter storms the air temperature may be above freezing at all

altitudes in the basin. Consequently, the accumulated snowpack may vary

appreciably at low elevations. Typically, a period of cooler weather in which the

snowpack increases may be followed by a large Pacific disturbance that raises

temperatures and melts a portion of the snowpack.

There are no long-term meteorological stations within the Ash River basin.

However, stations in the Alberni valley and the Myra Creek station in the

adjacent Campbell River basin are indicative of the basin climate.

Figure 4 shows maximum, average and minimum monthly precipitation at Myra

Creek AES to highlight the year-to-year variations in precipitation conditions.

Mean, Maximum and Minimum Monthly Precipitation at Myra Creek AES

(1979-1997)

0

100

200

300

400

500

600

700

800

900

1000

October December February April June August

Mon

thly

Pre

cipi

tatio

n (m

m)

El. 354 m

Figure 4: Maximum and minimum monthly precipitation at Myra Creek AES

Figure 5 shows the maximum, mean, and minimum daily temperatures at Myra

Creek AES.

- -


6

Mean, Maximum and Minimum Daily Temperatures at Myra Creek AES(1979-1997)

-20

-10

0

10

20

30

40


Tem

pera

ture

(°C

)

El. 354 m

Figure 5: Maximum, mean and minimum daily temperature at Myra Creek AES

Figure 6 shows the normal monthly snow water equivalent at Upper Thelwood

Lake snow course (3B10), located at El. 980 m.

Mean, Maximum and Minimum Monthly Snow Water EquivalentUpper Thelwood Lake Snow Course (1958-2001)

0

500

1000

1500

2000

2500

3000

February March April May

Snow

Wat

er E

quiv

alen

t (m

m)

El. 980 m

Figure 6: Maximum, mean and minimum monthly snow water equivalent at Upper Thelwood

Lake snow course (3B10)

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7

4 Inflow calculations

Reservoir inflow calculations: Inflow is the volume of water entering a reservoir

within a given period of time. Reservoir inflows are calculated rather measured

directly. Daily inflows may be derived from mean daily discharge from the

reservoir and change in reservoir storage over a period of 24 hours. The generic

formula is:

INFLOW = OUTFLOW + ∆ STORAGE......................... (1)

where INFLOW = average inflow over a one - day period

OUTFLOW = average outflow over a one - day period

∆ STORAGE = S2 - S1, where

S2 = reservoir storage at the end of the day

S1 = reservoir storage at the end of the previous day

Reservoir storage for a specific reservoir elevation is derived from a stage –

storage curve unique to each reservoir.

The nature of the calculation of inflows can result in “noisier” hydrographs than

observed at unregulated, natural river channels. Noisy inflows can arise due to

various sources of error, such as wind set up on the reservoir, resolution of

elevation measurements, errors in reservoir elevation readings, errors in outflow

measurements through turbines, spillways or valves, errors in stage-storage

curves and errors in the rating curves for various outlet facilities. The impact of

noise tends to reduce as the time interval over which inflow is computed

increases.

Storage relationships: The Storage relationship used to determine the volume of

water in Elsie Lake Reservoir is shown in Figure 3.

Outflow relationships: Flow through the turbine at the Ash powerhouse is

computed based on megawatt output and hydraulic head. “Hydraulic head” is a

measure of the vertical distance between the water level in the reservoir and the

water level immediately below the turbine outlet. Power output is proportional to

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8

head and turbine discharge. A generic relationship between these variables is

shown in Figure 7.

G e n e r ic re la t io n s h ip b e tw e e n f lo w , g e n e ra t io n a n d h e a d fo r a tu rb in e

In c re a s in g G e n e ra t io n

Incr

easi

ng F

low

In c re a s in g H e a d

Figure 7: Generic relationship between flow, generation, and head for a turbine

“Rating curves” show the relationship between flow, opening, and elevation fora given release device. A rating curve for spill facilities at Elsie Lake is shown inFigure 8.

Elsie Lake Rating Curve for all Spill Discharge Facilities Fully OpenFrom BC Hydro CRO Database

310

315

320

325

330

335

0 200 400 600 800 1000 1200

Discharge (cms)

Res

ervo

ir El

evat

ion

(m)

Crest of Main Overflow Weir El. 330.71 m

Crest of Main Dam El. 334.37 m

Sill of Low Level Outlet Works El. 313.33 m

Sill of Undersluice Box Culvert El. 323.80 m

Maximum turbine discharge capacity ~ 13.5 cms inaddition to spill capacity shown.

Figure 8: Rating curve for Elsie Lake with all spill discharge facilities open3

3 The section of the rating curve above El. 330.71 m is taken from modelling results following the reconfiguration of

the Elsie Lake spillway in November 2001.

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9

Data records: BC Hydro computes inflow using a computer program called

FLOCAL. Specifically;

Inflows to Elsie Lake Reservoir are computed based on equation (1).

Various information, including gate openings, reservoir and tailwater elevations,

energy, spill, turbine flows, and inflows are stored in FLOCAL. A FLOCAL

configuration for the Ash River system is shown in Figure 9.

Figure 9: Schematic of the FLOCAL configuration for the Ash River system

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10

5 Reservoir inflow characteristics

Figures 10 shows “spaghetti plots” of historical inflows to the Ash project. The

10th, 50th and 90th percentile inflows are shown in bold.

Daily Inflow Hydrographs to Elsie Lake ReservoirBased on BC Hydro PDSS Data 1963-1999

0

50

100

150

200

250

300

350

400

450

Oct-1 Nov-1 Dec-1 Jan-1 Feb-1 Mar-1 Apr-1 May-1 Jun-1 Jul-1 Aug-1 Sep-1

Dai

ly In

flow

(cm

s)

10th, 50th and 90th Percentiles Shown in Bold

Figure 10: Historical Daily Inflows to Elsie Lake Reservoir

Figure 11 and Table 1 summarize the daily inflows by month. Average monthly

and maximum and minimum daily inflows are shown to highlight the variability

of inflows to the project.

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11

Mean, Maximum and Minimum Daily Inflow to Elsie Lake Reservoir

0

50

100

150

200

250

300

350

400

450


Dai

ly In

flow

(cm

s)

Figure 11: Variability in Ash Project’s daily inflows

Table 1: Ash Project’s daily inflows (1963-1999)

Mean Maximum Minimum

October 21 233 <1

November 32 280 1December 29 390 <1January 25 323 1February 24 313 <1March 21 225 2April 24 152 4May 28 133 6June 24 91 3July 13 118 1August 7 151 <1September 7 213 <1

A “flow duration curve” indicates the percent of time that a flow is greater than a

given discharge. Figure 12 shows a flow duration curve of daily inflows for the

years 1963-1999. The figure again illustrates the large range and variability of

inflows.

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12

Duration Curve of Daily Inflows to Elsie Lake Reservoir(1963-1999)

0

50

100

150

200

250

300

350

400

450

0 10 20 30 40 50 60 70 80 90 100

Percentage of Time Inflow is Greater than Shown (%)

Dai

ly In

flow

(cm

s)

Figure 12: Duration curves of daily inflows to the Ash Project

Figure 13 shows a duration curve for annual flows.

Duration Curve of Annual Inflows to Elsie Lake Reservoir(1963-1999)

0

2000

4000

6000

8000

10000

12000

0 10 20 30 40 50 60 70 80 90 100

Percentage of Time Inflow is Greater than Shown (%)

Annu

al In

flow

(cm

s-da

ys)

Figure 13: Duration curve of annual inflows to the Ash Project

- -


13

Figure 14 shows a comparison between the mean annual local inflow and total

live storage available at a number of project reservoirs. The Ash Project is

highlighted and shows that the average annual inflow is about 7 times the

available storage.

The ratio of average annual inflow to available reservoir storage provides a

qualitative indication of how the inflow regulation and spill management

capability varies from project to project; the higher the ratio, the lower the

regulation capability. Figure 14 also shows the relative contribution of Elsie

Lake Reservoir to BC Hydro’s total reservoir storage capability.

- -


14

Notes Each graph has it's own scale Inflows are based on 1961-1990 normals Ability to route flows through a reservoir also depends on turbine and gate discharge c

Total storage may not always be available due to reservoir operating constaints. All numbers expressed in millions of cubic meters

Lower Mainland

Bridge

Coastal

Vancouver Island

Interior

Kootenay

Columbia

Peace

Comparison of project annual local inflow to reservoir storage

throughout BC Hydro's system

0

10000

20000

30000

40000

Wahleach

0

100

200

300

400

Inf low Stor age

Duncan

0

1000

2000

3000

4000

Inflo

w

Stor

age

Jordan Div

0

100

200

300

400In

flow

Stor

age

Alouette

0

200

400

600

800

Inf low Stor age

Ash

0

200

400

600

800

Inflo

w

Stor

age

Coquitlam

0

200

400

600

800

Inf low Stor age

Comox

0

300

600

900

1200

Inflo

w

Stor

age

Clowhom

0

300

600

900

1200

Inflo

w

Stor

age

Lajoie

0

400

800

1200

1600

Inflo

w

Stor

age

Sugar

0

400

800

1200

1600

Inflo

w

Stor

age

Daisy

0

500

1000

1500

2000

Inflo

w

Stor

age

Strathcona

0

1000

2000

3000

4000

Inflo

w

Stor

age

Carpenter

0

500

1000

1500

2000

Inflo

w

Stor

age

Corra Linn

0

4000

8000

12000

16000

Inflo

w

Stor

age

Stave

0

1000

2000

3000

4000

Inf low Stor age

Whatshan

0

100

200

300

400

Inflo

w

Stor

age

Mica

0

5000

10000

15000

20000

Inflo

w

Stor

age

Williston

0

10000

20000

30000

40000

Inflo

w

Stor

age

Arrow

0

3000

6000

9000

12000

Inflo

w

Stor

age

0

500

1000

1500

2000

Alo

uette

Coqu

itlam

Stav

e

Wah

leac

h

Lajo

ie

Carp

ente

r

Dais

y

Clow

hom

Stra

thco

na

Com

ox

Ash

Jord

an D

iv

Suga

r

Dunc

an

Corr

a Li

nn

Wha

tsha

n

Mic

a

Reve

lsto

ke

Arr

ow

Willi

ston

Small scale

Large scale

Revelstoke

0

2000

4000

6000

8000

Inflo

w

Stor

age

Live Storage (MCM)

Live Storage (MCM)

Seton

0

250

500

750

1000

Inflo

w

Stor

age

Figure 14: Comparison of project annual inflows to reservoir storage throughout BC Hydro’s

system

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15

6 Operational Inflow Forecasting

BC Hydro’s Resource Management produces two main types of hydrologic

forecasts: daily inflow and seasonal volume inflow forecasts for the Ash River

projects.

Daily inflow forecasts: Daily inflow forecasts are short-term forecasts that

indicate the inflow expected over the next few days. An in-house conceptual

watershed model, FLOCAST, is currently used to produce these forecasts. Each

morning of each working day, Resource Management enters observed and

forecast precipitation, temperature, and freezing level data into the model to

forecast inflow over each of the next five days.

Volume inflow forecasts: Volume inflow forecasts estimate the volume of water

that is expected to flow in to the Ash River system during a given period. BC

Hydro typically produces forecasts for the period February through September.

The ability to forecast seasonal runoff for this period lies in the fact that much of

the runoff during the forecast period is the product of snowmelt runoff. By

measuring snow water equivalent in the mountain snowpack, as well as other

parameters such as precipitation and streamflow up to the forecast date, a more

accurate estimate of future runoff can be made than one based on historical

inflow data alone. Volume inflow forecasts are issued beginning January 1 of

each year and forecasts are updated on the first of each month until August 1.

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16

7 Hydrometeorologic Network

Hydrometeorological data is required to plan, monitor, and operate facilities in

the Ash River system’s watershed. Characteristics of the hydrometeorological

data collection stations used for forecasting and operations are summarized in

Table 2.

Table 2: Hydrometeorological stations used for inflow forecasting and operations

Station Type ID Elev (m) Latitude Longitude Characteristics

Comox A AES 1021830 24 49.72 124.90 Climate

Campbell River A AES 1021261 106 49.95 125.27 Climate

Elk River DCP ELK 270 49.86 125.81 Climate

Cruickshank River DCP CRU 150 49.58 125.20 Climate

Wolf (Upper) River DCP WOL 1490 49.68 125.74 Climate, Snow

Elsie Forebay DCP ASH 340 49.93 125.14 Climate

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