TAS – Review Load and Hydro Shapes for use in TEPPC 2026 Common Case Kevin Harris, ColumbiaGrid TEPPC\Hydro Modeling Task Force - Chair

Overview Compare unimpaired Run-Off Compare Hydro generation Compare Load Shapes Wind vs. Water Year Northwest Export to California Perspective Summary 2

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 – 2 nd highest flow: May – 3 rd highest flow: Jul – 4 th highest flow: Apr 3 Northern CA run-off: Average 23.6 MAF Median 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

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 4 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 Averaging reduces monthly volatility

Compare 2008 and 2009 Flow 5 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

NW Forecasted Hydro Generation 6 Hydro generation from the 2014 Biological Opinion for the Core Projects on the Columbia River – Coulee – Bonneville (11 Projects) for 79 years of operation ( ) Observations: – Annual peak Gen: Jun – 2 nd highest Gen: May – 3 rd highest Gen: Jul – 4 th highest Gen: Apr Calendar year 2008 and 2009 is not included 2014 Bio Opinion

Compare Hydro Generation 7 In favor of 2008In 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.

Impact of Modeling 2009 over 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 aMW Jul: -3,200 aMW Aug: -2,300 aMW

Load Shape 2008 has a uniform seasonal shape 2009 has a muted June 9 Not a primary concern Growing load with monthly peak and demand eliminate any non-conforming seasonal shape Background: Monthly load f (CCD) & peak f (day-day temp) CEC uses %

California Monthly Wind Stable annual generation with monthly volatility greater than the annual 2008: Median spring/summer 2009: Above median spring 10 CA peak wind gen May-Aug

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 11 NW peak wind gen Apr

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

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 13

Summary NW HydroNormal Hydro gen Clear spring peak (Jun) Normal summer gen Muted spring run-off: -10% Week summer gen Q3 -2,250 aMW CA Hydro2008 is lower than 2009Closer to normal but still a below normal Net Monthly HydroThe normal NW Hydro shape out weighs the negative impact of CA Hydro Significant negative impact to gen: Jun-Sep Improved gen in Apr Load ShapeGrowing load with monthly peak and energy instead of annual results in this being a secondary issue NW WindAnnual gen high: 11.7%Annual gen low: -4.5% Monthly Strong spring w/spike in JunWeek spring CA WindAnnual gen high: 7%Annual gen high: 3.3% Monthly Close to medianHigh in spring

15 Kevin Harris (503)

Modeled Solar WECC 1.5 On average California Solar serves 10% of it’s load 16