Center Pivot Irrigation Explained

Sunday, 24 June 2012

Discover Kuriositas
If you have been in a plane over a large agricultural hub you may have casually glanced out of your window. And then you may have performed a very, very quick double take. What on earth are those circular shapes below? They are not the alien crop circles of infamy that’s for sure – in fact whole fields seem to be circular in shape. There are way too many of them, too, to have been done as some sort of practical joke. So, what are they? Welcome to the world of center pivot irrigation.

As the name suggests, this is a method of irrigation, but it is one which, after the initial setup, does not need the touch of human hand half as much as traditional methods. Imagine the middle of a field and place a great big pivot at its heart. To this pivot attach sprinklers and equipment to rotate them. As the pivot turns, so do the sprinklers – in a circular motion (the system is also called circle irrigation). The explanation is as simple as that, even if sometimes the patterns are not wholly circular -some can look like part of a giant Pacman game.

When do you think it started? Although it did not take off on a truly industrial scale until later the credit for this remarkable method of irrigation goes to a 1940s Texan farmer, Frank Zybach.  His farm could be found near the town of Dalhart, which had the misfortune of being smack bang in the middle of the very dry Texas panhandle. It was vital that the distribution of water to the fields be improved upon and this solution is what Mr Zybach came up with in 1949.

They are quite simply spectacular. Yet to elucidate further we need to go from a bird’s eye view to that of a scarecrow. Ironically, given the ubiquity of air travel, many more people get to see them from great heights than on the ground. So, here they are.

Segments of aluminum or galvanized steel pipe (the number varies according to manufacturer) are connected together and supported by a system of trusses. They are then mounted upon wheeled towers – with sprinklers along their length. The role of the pivot is, not to put too fine a point on it, pivotal.

The picture above shows the pivot and the squat thing below is the water pump which feeds it. The water is fed through to the sprinklers and the whole leviathan is then set in motion.  The motion is slow, to say the least – if you wanted to capture a single cycle through stop motion you would have to be patient – it normally takes around three days to complete an entire circle. The idea is to irrigate, after all, not to drown!

It is the sets of wheels on the periphery which set the pace. Modern technology plays its part.  Sensors are placed on the segments which detect if and when they are losing alignment and this keeps all of the pieces perfectly straight. Without them a slight bend could turn in to a steel bending catastrophe.

As such the entire length of a center pivot rarely exceeds 1600 feet (around 500 meters) and the most common is around a quarter of a mile in diameter.  You may be wondering why the water at the center of the field is not much wetter than that along its radius as the inner towers do not travel as far as those on the outside. The answer is, again, simple. The nozzles which spray the water are smaller on the inside than those farther out, so ensuring that water is delivered equally to all areas of the field.

From satellites to planes, the patterns which are created fascinate and intrigue. Yet all this would not be possible without one vital if humble component- the  sprinkler nozzle. They are crucial to the success of the center pivot irrigation system and many different types have been developed over the years by bespoke manufacturers. Nowadays, as you can see here, most nozzles are suspended from a pipe called a gooseneck meaning they can be positioned just a few feet above the crop. As evaporation and wind could divert a lot of water otherwise, this proximity is imperative in arid areas.

The water can even be dropped straight on the ground using a LEPA (which is a Low Energy Precision Application), involving a mini damming process which is very high tech and a twenty first century innovation.  It must be said that since its invention in 1949 the center pivot system has come a long way. Back in Mr Zybach’s time this type of irrigation was water powered, eventually replaced by hydraulic systems.  Today most systems have an electric motor on each of the towers.

For obvious reasons you cannot put this sort of irrigation system on a steep hill.  However, although the ground has to be fairly flat, it can undulate.  The machinery can cope with small ripples in the ground which beforehand had been difficult to farm. As you can see from these pictures, some nooks and crannies which were previous very difficult to farm can now yield crops. Farmland can now extend right up to where hills abruptly begin.

In parts of the Middle East and Africa it has been a huge success, conserving water which would otherwise have been wasted. And yet... of course there is a downside. As with any mechanization, fewer people are needed to produce the same amount of goods. Yet bear in mind that without center pivot irrigation the crop may never have been planted in the first place let alone become a harvest. However, many environmentalists are also concerned that with previously inaccessible areas now being farmed, whole ecosystems may be destroyed. Above, previously untouched ecosystems in the Sahara Desert in Libya and on the island of Madagascar are given the center pivot treatment.

So next time you are in a plane, peering down to the earth below and you see a strange collection of circles, you know exactly what they are and how they were created. You may even feel a sudden desire to tap the stranger next to you and bore them for a while with your wisdom!


Acknowledgements
Kuriositas would like to thank the following Flickr Photographers for their kind permission to use their images: Tresijas, Sky Schemer, Patrick Huber, Robert Love Taylor and Ute Hagen. Please visit their amazing photostreams by clicking the links.

Ute Hagen also has an eponymous website featuring her lovely artwork.

Share on Facebook Share on Twitter

Amung Feedjit