We went to Zealandia. When we got there the water in the lower dam was only 4 or 5 meters deep. They are emptying it because of the perch (kokopu). Perch are not a New Zealand species of fish and they are eating the very tiny animals which were supposed to be eating the algae, so the water turned a nasty green colour and it was poisonous. They are emptying the water so they can get rid of the perch. Instead, they will reintroduce New Zealand native species.
Where they have emptied the water, there are cracks on the muddy ground.