TAS – Review Load and Hydro Shapes for use in TEPPC 2026 Common Case

Kevin Harris, ColumbiaGridTEPPC\Hydro Modeling Task Force -

Chair

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Overview

• Compare unimpaired Run-Off• Compare Hydro generation• Compare Load Shapes• Wind vs. Water Year• Northwest Export to California• Perspective• Summary

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Unimpaired Run-Off• The chart show 85 calendar years of unimpaired run-off at The Dalles

– Unimpaired Run-Off: Natural flow without regulation (dams), municipal or agriculture use• Observations:

– Annual peak flow: Jun– 2nd highest flow: May– 3rd highest flow: Jul – 4th highest flow: Apr

Northern CA run-off: Average 23.6 MAFMedian 21.5 MAF

Clearly June is the peak flow month

Black dash line: Coincident Avg Shape (11 Years)+/- 5 years around annual average

Monthly rank order (sorted) then avg/un-sorted

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Averaging Monthly Shape• Issue: With weather dependent systems the peak can occur on

one of several month. Hydro flow is no different, a simple average or median of the data will distort - compress the fundamental shape.

• The, unimpaired run-off, peak flow on the Columbia River occurs on during May or Jun based on 86 years of water year data

• The average flow for May and June is 87% and 90%

• Averaging results in the loss of 10% of the peaking flow for the peak month

Historic Occurrence of Peak Flow MonthPeak Flow

Month2nd

Highest Flow

Month

3rd Highest

Flow Month

Net Average Flow as % of Annual

PeakMay 44% 52% 3% 100% 87%Jun 56% 43% 1% 100% 90%Typical Flow (% of Annual Peak)

100% 79% 54%

Averaging reduces monthly volatility

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Compare 2008 and 2009 Flow

Unimpaired Run-Off(No regulation of flow)

• Typical peak flow occurs in Jun and around 30.5 MAF• 2008: Peak flow of 31.6 MAF; Summer flow in-line with historic• 2009: Peak flow of 25.7 MAF; Lower summer flow

2009 is not in the 11 years around long-term

flow

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NW Forecasted Hydro Generation• Hydro generation from the 2014 Biological Opinion for the Core Projects on

the Columbia River– Coulee – Bonneville (11 Projects) for 79 years of operation (1929-2007)

• Observations:– Annual peak Gen: Jun– 2nd highest Gen: May– 3rd highest Gen: Jul – 4th highest Gen: Apr

Calendar year 2008 and 2009 is not included

2014 Bio Opinion

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Compare Hydro GenerationIn favor of 2008 In favor of 2009

• John Fazio (NW Council) recommends 2008 as the best year to represent normal Hydro generation in the NW

• For NW, a clear spring peak in June while 2009 has a muted peak

• For NW, 2008 normal Jul-Sep generation while 2009 has a muted -2,250 aMW

• For CA, the 2009 has more generation in the Q3 and Q4• For CA, 2009 has a more pronounced generation in the

spring coinciding with spring run-off

Northwest Hydro generation is 4.11 times that of California’s.

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Impact of Modeling 2009 over 2008• The net change in Hydro gen: -48 aMW• Significant reduction in NW Hydro Jun-Sep (below normal 2008)• Relative monthly change in CA Hydro is minor when compared to the NW

West wide the monthly impact of

using 2009 over 2008 is significant

5 months where the net swing is greater

than 1,500 aMW

The net swing in:Jun: -2,300 aMWJul: -3,200 aMW

Aug: -2,300 aMW

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Load Shape

• 2008 has a uniform seasonal shape• 2009 has a muted June

Not a primary concernGrowing load with monthly peak and demand eliminate

any non-conforming seasonal shape

Background: Monthly load f(CCD) & peak f(day-day temp) CEC uses 60-30-10%

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California Monthly Wind• Stable annual generation with monthly volatility

greater than the annual• 2008: Median spring/summer• 2009: Above median spring

CA peak wind gen May-Aug

CA Wind (2008-14)Gen %Ch(Avg)

Avg 1,618StDev 78 +/-4.8%Min 1,477 -8.7%Max 1,731 7.0%2008 1,731 7.0%2009 1,671 3.3%

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Northwest Monthly Wind• Stable annual generation with monthly volatility

greater than the annual• 2008: Peak wind in Jun coinciding with peak Hydro• 2009: Peak wind in Mar and below median in spring

NW Wind (2008-14)Gen %Ch(Avg)

Avg 3,463StDev 227 +/-6.5%Min 3,209 -7.4%Max 3,870 11.7%2008 3,870 11.7%2009 3,309 -4.5% NW peak wind gen Apr

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NW Export Shape to CA• The operating range on the Core Columbia River

generation has narrowed starting in 2011• The hourly export shape to CA has also narrowing

starting in 2011

Charts: Average hourly weekday shape to California (Path 65 & 66)

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Perspective

WECC modeled Hydro generation is 2.2 times that of modeled Wind/Solar

(From 2024 WECC 1.4 dataset)

Selecting a reasonable Hydro year has a greater impact on transmission flow that modeled

Wind/Solar

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Summary2008 2009

NW Hydro Normal Hydro genClear spring peak (Jun)Normal summer gen

Muted spring run-off: -10%Week summer gen

Q3 -2,250 aMWCA Hydro 2008 is lower than 2009 Closer to normal

but still a below normalNet Monthly Hydro The normal NW Hydro shape

out weighs the negative impact of CA Hydro

Significant negative impact to gen: Jun-Sep

Improved gen in AprLoad Shape Growing load with monthly peak and energy instead of annual

results in this being a secondary issueNW Wind Annual gen high: 11.7% Annual gen low: -4.5%

Monthly Strong spring w/spike in Jun Week spring

CA Wind Annual gen high: 7% Annual gen high: 3.3%Monthly Close to median High in spring

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Kevin Harris Harris@columbiagrid.org

(503) 943-4932

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Modeled Solar WECC 1.5• On average California Solar serves 10% of it’s load

Breakdown of California Load Served by Solar in WECC 1.5 Dataset (GWh)Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

CA Solar 1,330 1,728 2,622 2,978 3,126 3,171 3,189 2,968 2,837 2,544 2,033 1,812CA Load 25,354 22,693 24,684 23,793 26,023 27,040 30,742 30,846 28,024 25,889 24,098 25,685Solar/Load 5.2% 7.6% 10.6% 12.5% 12.0% 11.7% 10.4% 9.6% 10.1% 9.8% 8.4% 7.1%