Saturday, 22 September 2007

Pie charts and pistachios

You cannot look at the route Mark has been following for the last couple of days without noticing the effect that the availability of irrigation has on the landscape ...The ribbons of green stand out clearly in this otherwise arid landscape. To understand how significant they are, you need to bear in mind that this area IS a desert - with average monthly totals of precipitaion in mm as follows (Jan to Dec in Kerman)
29.0, 26.7, 32.0, 19.5, 8.6, 0.5, 0.7, 0.6, 0.3, 0.7, 5.1, 18.6 . This adds up to an annual total of just 142.1 mm. Now, as all good students of Geography should know, anywhere receiving less that 250mm is officially a desert! So Kerman is not just a desert but it is a very dry desert. To put Kerman's annual rainfall total into context, Glasgow receives 1500mm of rain annually while the east coast of Scotland has about 750mm.

142mm of rain (much of it falling when high temperatures will instantly evaporate it), is just not enough rain to sustain cultivation. Thus , our ribbons of green will be entirely dependent on irrigation. So where does the water come from? You have to remember that this area is surrounded by mountains which rise to between 2000m and 3000m. Snow will accumulate there in the winter and melt in spring so there will be surface water available which can be stored in mountain dams and released down the valleys at various times during the year. Here, for example, is a dam I 'found' by scanning the mountains just south of Rafsanjan.

In addition to the surface water,there are also ground water sources which can be tapped.

When roaming over the area between Rafsanjan and Kerman, I also came across these features which, for once, I can explain....

What looks like pie charts are actually centre pivot irrigation systems. So what is all this irrigation for? What crops are producing the ribbons of green on the map? Well, it seems that this part of Iran produces pistachios .... a LOT of them. Iran is in fact the largest producer of pistachios in the world and the desert border through which Mark is currently cycling is the main area for production. Clicking here will take you to a website entirely devoted to information about Iranian pistachios! From what I have read, it would seem that this part of Iran has the ideal climate for pistachio production..... short cold winters, long very hot summers, low humidity and the possibility of infrequent irrigation.

And in case you are wondering how they grow, here are some fruiting pistachios. They look like pink flowers but the nuts are inside the pink shells. When fully ripe, the shells are blanched by the sun and split open.

Mark cycled through the city of Kerman today but probably had little time for sight seeing. We, though, do have the chance to soak in some of the sights of the city.

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