21 April, 2011

Living in the Rain Shadow.

Wind roars across the southern oceans west to east bearing vast amounts of moisture.  Then smashes into the west side of our mountains, the 'Southern Alps". dumping a lot of rain in a very small area. That leaves a dry 'rain shadow' to the eastern side.   The difference  is remarkable.  Over just 60-80 kilometers, a saturated rain forest changes to bone dry desert like land.

The same effect occurs in southern Chile, which has rainforest as the weather dumps on the western side of the southern Andes mountains.  The eastern side of the Andes are dry, forming the magnificent and distinctive landscapes of Patagonia, southern Argentina.

For a more scientific explanation try this link to Wikipeadia which says in part - On the South Island of New Zealand is to be found one of the most remarkable rain shadows anywhere on Earth.  

It's dry in the 'rain shadow' but huge rivers flow out of the mountains and across the dry places.  Here the Kawarau river flows out of it's gorge past the back gate of "The Field of Gold".  It's no small river with an average flow of 218 Cumecs (Cubic Meters per Second).
The 'Field of Gold' is on the right of the river as it flows out of the gorge.  Near the white Cherry nets.
Living in the rain shadow means we also have bright sunny days most of the time.  Here at Bannockburn we have the driest place in New Zealand which would usually make it hard to grow things.  But we have access to vast amounts of water.

But it's not like the United States where 25 million people rely on equivalent rivers like the Colorado with no alternative.  Here fewer people than 50,000 people rely on the local rivers, the Kawarau, the bigger Clutha, and their huge cousin the Waitaki river, just over the hill.

A few years ago this was dry barren rocky land.  Now vineyards.  Because of the application of water.
This photo joins the one above.  Lake Dunstan, fed by two major rivers.  The Kawarau and the Clutha.
There were some storms and floods in the mountains, not that we knew much about it as the rain did not reach us in any quantity.  In the news we saw a rare event, the Benmore Dam on the Waitaki was spilling.  A rare event which only happens about once a year.

So we had a day out.  Up over and down the Lindis pass about 150 Kilometers.

It was spectacular.
This dam is huge.  That's a couple of Kilometers away.  ( more than a mile)
Disturbing at a distance. Scary up close.
There were certainly a lot of people there.  Many had come hundreds of kilometers to the middle of the nowhere to see this.

The Waitaki river averages about 340 cumecs.  Running in these photos at about 1200 cumecs although a lot of that is going through the power turbines and not down the spillway.  The spillway can handle 3400 cumecs.  The day that happens I am not coming anywhere near the frightening thing. 


  1. If that sucker blows, what with the 50km of water behind it you would not want to be under the thing downstream. Just as well there is not a big town below.
    You'd have to say there was a good bit of balls with the fellows that designed and built the thing given you are as, if not more, active than Japan.

  2. Very nice Benmore spillway shots Kerry.

    Keep up the good work.



  3. It's hard to understand the concept of a rain shadow, but interesting how powerful water is. Ithink more people realized that during the recent tsumani. nothing to take for granted.

    I don't know if I'd ever go white water river rafting for that reason.

  4. Hi Sue
    A rain shadow. Around here the wet weather comes from one direction. But there are huge mountains between us and the wet dumps there. Leaving us dry - like when there is a big object between you and the sun. You don't get the sun. You are in a 'shadow".

  5. Vince. You are keen on those maps. Yep. It's a worry. Earthquakes - we have a thing called "the alpine fault" Mmmmh. But a good rainfall would do it. Once that dam overtops - then it's an earth dam. And will wash away like sand.

  6. Kerry, It’s a very rainy Spring day so I thought it would be a good time to check in on you and the other Blogs I follow. Can not be out in the dirt so I am here at the computer. Your photos are very nice. gives me an idea of your surrounding area. Like that. As for the blowing winds, we get a lot of wind here too but not as wild as yours. Some of our storms hit 60 mph form the Northeast coming in off the lake. Yesterday I walked the beach to see what blew up from last week's storm and to check if anything is turning green yet this Spring after all the snows we have had. Posted a few pictures this morning so I have a record that life is beginning again here along Lake Michigan - finally. Jack

  7. Nature never, ever ceases to amaze me. Nor does mankind's efforts to control/live with it.

    Thank you for leaving a message on my blog. I have been so behind lately - well, for nearly a year actually, as Moon Over Martinborough just reminded me.

    PS I love your lavender hedge. I planted one a couple of years ago, but I must admit, it hasn't quite turned out as I had planned. I can see that yours will be fine and it's a great idea for creating a boundary between the "tame" and the wild.

  8. Yes Casalba.
    The lavender Hedge seems to be turning out well. A long way to go yet but you can just tell it's going to be good.
    Mostly I see rows of Lavender that look very scrappy and failures in part.
    So I guess the very careful setup and input of work has made the difference.


I would love to hear from you on any of these posts. This blog is not daily news and I will respond to comments even on backdated posts.