Hydro lakes future in focus over summer

Anxiously watching the levels of the country's hydropower lakes is something of a New Zealand tradition. Hydro - unlike geothermal - can be turned on and off at will, meaning it can supplement variable wind and solar generation, for a clean and, ideally affordable electricity system. But the water flows that feed the lakes supplying more than HALF the nation's electricity are changing in not-entirely predictable ways, as Climate Change Correspondent Eloise Gibson reports.