Even water has to be treated differently in NZ#

by Hermann Maurer

When hiking in Europe or the Americas in the mountains one basic rule is: „Make sure that your shoes never get wet“.

So when I did my first major three day hike in the Urewera National Park Uruwera National Park, NZ with my dear friend Mike Lennon, he surprised me when when we got to the first stream we had to cross: without hesitation he just waded with his heavy mountain boots into the water.

He just smiled „forget it!“ when I made attempts to take off my boots to go barefoot and keep my boots dry. However, it does not take long to understand why crossings are handled this way. The national park has almost no trails. Hence a typical hike means following a stream upwater until you reach the highest point (usually close to the timber line at 2.000 meters), cross over to where the next stream starts (having climbed a medium sized peak before) and follow the stream dwonward until you eventually reach a road again.

This takes usually 2-4 days. As you follow a creek, the bush is often so dense that you cannot walk through, or rocks are blocking your way, so you have to walk in the stream, along sand-bars, changing the side of the stream again and again, sometimes climbing through a small waterfall: if you tried to do this barefoot, your feet (particularly after some time when soft because of the water) would certainly be hurt, but worse, you would be bound to slip and fall into the water.

Hence: You keep your boots on!

It does rain a bit almost everyday in NZ, particularly on the North Island. Never call it rain: Rather follow the Irish and enjoy it, calling it „liquid sun“. The liquid sun also changes how you spend your day. You do not stop for coffee or lunch when you feel like it, but you stop when the liquid sun starts. By the time you have finnished your coffee or snack the sun is out again. There is a good reason for the saying: „If you don‘t like the weather, just wait a few minutes.“

There are many other curiosities about water in NZ: even from crystal clear streams you better filter the water or use some tablet to kill tiny eggs of worms (a type of Schistosoma) in the water that migrate through your blood into all kinds of organs and start to destroy them. However, one often quoted fact is NOT true: water rotation in home bathrooms under normal circumstances is not related to the Coriolis effect or to the rotation of the earth, and no consistent difference in rotation direction between toilet drainage in the Northern and Southern Hemispheres can be observed.

The formation of a vortex over the plug hole may be explained by the conservation of angular momentum: The radius of rotation decreases as water approaches the plug hole, so the rate of rotation increases, for the same reason that an ice skater's rate of spin increases as they pull their arms in. Any rotation around the plug hole that is initially present accelerates as water moves inward.

Only if the water is so still that the effective rotation rate of the earth is faster than that of the water relative to its container, and if externally applied forces are very small the Coriolis effect may determine the direction of the vortex. Otherwise, the Coriolis effect is much smaller than various other influences on drain direction.