Soggy summer keeps hydro dams pumping
As it cancelled holiday plans, near-constant summer rain meant the North Island hydropower stations received little respite. The grid had its greenest start to the year since 1996, according to Ministry of Business, Innovation and Employment data. After skyrocketing in 2021, coal-fired power generation has stayed low. Most of the country had a warm, very wet start to the year. Niwa found that Auckland, Northland, Bay of Plenty and Hawkes Bay experienced their wettest summer since records began. Storms and cyclones produced extreme flooding, which took lives and damaged properties. Consequently, the North Island lakes and rivers feeding hydropower stations have stayed consistently full. At the same time, southern and western regions of the South Island had less rain than normal. Some large dammed lakes in these areas held less water than normal. But the North Island power stations more than compensated for this shortfall, according to the Ministry of Business, Innovation and Employments Mike Hayward. Between January and March, just over 87% of all power on the grid came from renewable power stations including hydro dams, Hayward said, with wind generation also playing a role. Coal units at the Huntly power station generated just 2% of all power between January and March one-sixth of the energy they produced during the notoriously dry start to 2021. Solar added 1% to the grid, about a third more than panels contributed a year ago. Hydro scientist Earl Bardsley warned that massive amounts of water would also have been spilled and not used to generate electricity by power stations after extreme rainfall. The South Island-based Waitaki dams recently spilled water that could have generated more than 500MW, he said. Thats about half the capacity of our largest power station, Huntly. Hydro stations can preemptively run hard and lower their lake levels when a forecast for a big storm is issued, but typically the notice period isnt long enough to avoid the need to spill, Bardsley said. In addition, the electricity market can financially disincentivise this type of thing. The weather pattern continued through autumn. Last month was the warmest May on record, according to Niwa with average temperatures in seven cities 2C above average. While April was relatively dry in many places, the rains returned in May. The warmer, wetter run-up to winter offers a good forecast for renewable electricity. With the lakes in both islands relatively full , hydro generation is expected to stay high, while less demand for heating will delay the seasonal ramp-up of fossil-fuelled power units. Our weekly email newsletter, by the Forever Project's Olivia Wannan, rounds up the latest climate events. Sign up here .