Energy Link Limited 1/10/2020 Waitaki

Thursday, 01 October 2020 Issue: 1224

A weekly summary relating to hydro storage and inflows. Compiled by Energy Link Ltd. Storage Summary South Island South Island North Island Total Storage Controlled Uncontrolled Total Taupo Current Storage (GWh) 984 756 1740 255 1994 Storage Change (GWh) 132 96 228 102 330 Note: SI Controlled; Tekapo, Pukaki and Hawea: SI Uncontrolled; Manapouri, Te Anau, Wanaka, Wakatipu Transpower Security of Supply South Island North Island New Zealand Current Storage (GWh) 1567 255 1822 Note: These figures are provided to align with Transpower's Security of Supply information. However due to variances in generation efficiencies and timing, storage may not exactly match Transpower's figures. New Zealand Summary Total storage increased 330.2 GWh over the last week. South Island controlled storage increased 15.4% to 984 GWh; South Island uncontrolled storage increased 14.6% to 756 GWh; with Taupo storage increasing 67.3% to 255 GWh.

New Zealand Storage and Inflow Summary 5000 2000

4500 1750 4000 1500 3500 1250 3000 2500 1000 Clutha 2000

750 Storage (GWh) Storage 1500 (GWh) Inflows 500 1000 250 500

0 0 May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr Month Taupo Inflows (2020/21) South Island inflows (2020/21) South Island 2019/20 South Island 2020/21 Waikato 2019/20 Waikato 2020/21 New Zealand Storage (2020/21) New Zealand Storage (2019/20) Average SI Storage (15/16-19/20)

Thursday, 01 October 2020 Manapouri Clutha Waitaki Waikato NZ Storage (GWh) This Week 583 244 913 255 1994 Last Week 512 197 803 152 1664 % Change 13.9% 23.7% 13.7% 67.3% 19.8%

Inflow (GWh) This Week 281 142 193 129 745 Last Week 234 123 172 50 579 % Change 20.2% 15.6% 12.1% 158.3% 28.8% Subscribe at www.energylink.co.nz/publications

Ph (03) 479 2475 Consultancy House Email: [email protected] Hydro Watch Dunedin Energy Link Limited 1/10/2020 Lake Levels and Outflows

Catchment Lake Level Storage Outflow Outflow (m. asl) (GWh) (cumecs) Change Manapouri Manapouri 179.03 188 346 250 Te Anau 203.50 395 Clutha Wakatipu 310.29 79 277 59 Wanaka 277.97 94 323 63 Hawea 340.00 71 11 -1 Waitaki Tekapo 705.32 309 Pukaki 523.11 604 Waikato Taupo 356.47 255

Inflow Summary The two charts below represent where current inflows are in relation to historic inflow patterns. The percentile values have been calculated using all inflows since 1931.

South Island Inflows - The past four weeks of S. I. inflows rank as the 8th wettest on record.

South Island Inflow Percentile Data 4 week running average 1200 99%ile

1000 95%ile

75%ile 800 Median 600

25%ile GWh

400 5%ile

1%ile 200 4week 0 inflow

Month

North Island Inflows - The past four weeks of N. I. inflows rank as the 34th driest on record.

North Island Inflow Percentile Data 4 week running average 140 99%ile 120 95%ile

100 75%ile

80 Median 25%ile

GWh 60 5%ile 40 1%ile

20 4week inflow 0

Month

Waikato System

Ph (03) 479 2475 Consultancy House Email: [email protected] Hydro Watch Dunedin Energy Link Limited 1/10/2020 Waikato System

Lake Taupo Levels and Inflows 357.50 250 Maximum Lake level

357.00 200

356.50 150

356.00 100

Minimum Lake level Lake Lake level (m) 355.50 50 (GWh)Inflows

355.00 0 May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr Month Taupo Inflows (2020/21) 2015/16 2016/17 2017/18 2018/19 2019/20 2020/21 Average Maximum Lake Levels

Lake Levels - Lake Taupo storage increased to 44.6% of nominal full at 255 GWh.

Inflows - Inflows increased 158.3% to 129 GWh.

Generation - Average generation decreased 6.2% to 273.4 MW.

Tekapo

Lake Tekapo Levels and Inflows 712 220 200 Maximum Lake level 710 180 160 708 140 120 706 100 80 704

60

Inflows (GWh)Inflows Lake Lake Level(m) 702 40 Minimum Lake level 20 700 0 Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr Month Tekapo Inflows (2020/21) 2015/16 2016/17 2017/18 2018/19 2019/20 2020/21 Average (Last 5 Years) Maximum Lake Levels Minimum Lake Levels Lake Levels - ended the week 43% nominally full with storage increasing to 309 GWh.

Inflows - Inflows into tekapo increased 35.6% to 79 GWh.

Generation - Average Tekapo generation increased 30% to 88 MW.

Hydro Spill - Lake Tekapo did not spill.

Ph (03) 479 2475 Consultancy House Email: [email protected] Hydro Watch Dunedin Energy Link Limited 1/10/2020 Waitaki System

Lake Pukaki Levels and Pukaki/Ohau Inflows 535 240

533 220 Maximum Lake level 200 531 180 529 160 527 140 525 120

523 100 80

521 Inflows(GWh)

Lake Lake Level(m) 60 519 40 Minimum Lake level 517 20 515 0 Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr Month Pukaki/Ohau Inflows (2020/21) 2015/16 2016/17 2017/18 2018/19 2019/20

Lake Levels - Lake Pukaki ended the week 34% nominally full with storage increasing to 604 GWh.

Inflows - Inflows into the Waitaki System increased 0.2% to 115 GWh.

Generation - Average Waikati generation increased 8.2% to 547.2 MW.

Hydro Spill - Lake Pukaki did not spill.

River Flows - Flows from the Ahuriri River increased to 63.3 cumecs while flows were higher than last week averaging 252.1 cumecs.

Clutha System

Lake Hawea Levels and Inflows 347 Maximum Lake level 34 32 345 30 28 26 343 24 22 341 20 18 16 339 14 12

337 Normal Minimum 10 Inflows (GWh) Inflows Lake Level Lake Level (m) 8 Emergency Minimum Lake 6 335 4 2 333 0 Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr Month Hawea Inflows (2020/21) 2015/16 2016/17 2017/18 2018/19 2019/20

Total storage for the Clutha System increased by 23.7% to 244 GWh.

Ph (03) 479 2475 Consultancy House Email: [email protected] Hydro Watch Dunedin Energy Link Limited 1/10/2020 Lake Levels - Total storage for the Clutha System increased by 23.7% to 244 GWh. Lakes Hawea, Wanaka and Wakatipu ended the week 24.1%, 82.1% and 74.3% nominally full respectively. Inflows - Total Inflows into the Clutha System 15.6% higher at 142 GWh.

Generation - Average generation was 4.1% higher at 583 MW.

Hydro Spill - Estimate Spill is 84.6 cumecs.

River Flows - Total outflows from the lakes and Shotover River increased to 717.8 cumecs. This comprised of 11 cumecs from Lake Hawea, 323 cumecs from Lake Wanaka, 277 cumecs from Lake Wakatipu and 107 cumecs from the Shotover River.

Lake Wanaka Levels and Inflows

281 100

90 280 80

70 279 60

278 50

40 277

30

Inflows (GWh)Inflows Lake Lake Level(m) 20 276 10

275 0 Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr Month Wanaka Inflows (2020/21) 2015/16 2016/17 2017/18 2018/19 2019/20

Lake Wakatipu Levels and Inflows 100 311.8 90 311.4 80 70 311 60 310.6 50 310.2 40 30

Lake Lake Level(m) 309.8 Inflows(GWh) 20 309.4 10 309 0 Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr Month Wakatipu Inflows (2020/21) 2015/16 2016/17 2017/18 2018/19 2019/20

Ph (03) 479 2475 Consultancy House Email: [email protected] Hydro Watch Dunedin Energy Link Limited 1/10/2020

Manapouri System

Lake Manapouri Levels and Manapouri/Te Anau Inflows 182 400 360 181 320 180 280

Upper Operating Level 179 240 200 178 160

177 120

Inflows(GWh) Lake Lake Level(m) Lower Operating Level 80 176 40 175 0 Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr Month Manapouri/Te Anau Inflows(2020/21) 2015/16 2016/17 2017/18 2018/19 2019/20 2020/21 Average Upper Operating Level Lower Operating Level

Lake Levels - Total storage for the Manapouri System increased by 13.9% to 583 GWh with Lake Manapouri ending the week 115.9% nominally full and Lake Te Anau ending the week 143.5% nominally full. Inflows - Total inflows into the Manapouri System increased 20.2% to 281 GWh.

Generation - Average generation was 3.2% lower at 738 MW.

Hydro Spill - Estimated spill at the Mararoa Weir was 346 cumecs.

Operating Range - Lakes Manapouri and Te Anau are operating in the middle of their respective 'High operating range'.

Lake Te Anau Levels 205

204

Upper Operating Level 203

202

Lake Lake Level(m) Lower Operating Level 201

200 Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr Month 2015/16 2016/17 2017/18 2018/19 2019/20 2020/21 Average Upper Operating Level Lower Operating Level

Ph (03) 479 2475 Consultancy House Email: [email protected] Hydro Watch Dunedin