Every month on Earth Matters, we offer a puzzling satellite image. The February 2017 puzzler is above. Your challenge is to use the comments section to tell us what part of the world we are looking at, when the image was acquired, what the image shows, and why the scene is interesting.
How to answer. Your answer can be a few words or several paragraphs. (Try to keep it shorter than 200 words). You might simply tell us what part of the world an image shows. Or you can dig deeper and explain what satellite and instrument produced the image, what spectral bands were used to create it, or what is compelling about some obscure speck in the far corner of an image. If you think something is interesting or noteworthy, tell us about it.
The prize. We can’t offer prize money or a trip to Mars, but we can promise you credit and glory. Well, maybe just credit. Roughly one week after a puzzler image appears on this blog, we will post an annotated and captioned version as our Image of the Day. After we post the answer, we will acknowledge the person who was first to correctly ID the image at the bottom of this blog post. We may also recognize certain readers who offer the most interesting tidbits of information about the geological, meteorological, or human processes that have played a role in molding the landscape. Please include your preferred name or alias with your comment. If you work for or attend an institution that you want us to recognize, please mention that as well.
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Releasing Comments. Savvy readers have solved some of our puzzlers after only a few minutes or hours. To give more people a chance to play, we may wait between 24-48 hours before posting the answers we receive in the comment thread.
Good luck!
Editor’s Note: Congratulations to Gareth Renowden for being the first reader to solve the puzzler on the Earth Observatory site, and to Mark Baumgartner for answering first on Facebook. See a labeled version of the February puzzler here.
Tags: puzzler
We’re looking down on the Canterbury Plains on the East coast of New Zealand’s South Island, to the West of Christchurch – specifically the Eyrewell Forest area. Giveaways: the Waimakariri River running across the image from West to East – a “braided” river of many streams running in a wide gravel bed, common in NZ – and the the bright green circles caused by large centre-pivot irrigation systems installed during the rapid expansion of dairy farming in the region.
This image shows irrigation agriculture along the banks of a braided river system. The round fields are irrigated by center-pivot sprinklers that extract water from the aquifer. There are non-irrigated fields, pastures and forests, as well, and green vegetation along the river, so it is most probably not a desert region.
Braided rivers typically occur where we have high sediment loads, considerable slope in longitudinal profile and strong variations of water flow e.g. due to pronounced rainy seasons or nival systems (snowmelt). The pattern of channels, point bars and cut-banks shows that the river flows from west to east.
The combination of irrigation agriculture and braided river point to a region of relatively dry climate at the eastern edge of a high mountain range with snow cover in winter or even glaciers. The field pattern suggests that it is not North America (where everthing is nearly always pressed in squares). So; there were not too many regions left in the world to search: It is the area of Eyrewell Forest, west of Christchurch on New Zwaland’s South Island (around 620 mm annual precipitation). The river is the Waimakariri, which originates in the Southern Alps to the west of the image area.
Sorry; typo: west of Christchurch on New ZEALAND’s South Island, of course!
Coordinates: 43°26’14.5″S 172°18’29.3″E
Location: Eyrewell Forest, Waimakariri District, Canterbury Region, New Zealand.
Description: The dark green alternating stripes of north-east & south-west oriented forest is most probably the subject of discussion in this subset of Landsat 8 – True Color Composite Satellite Image acquired with the OLI Sensor. Eyrewell Forest in the Canterbury plains of New Zealand has had a long and tumultuous history. Originally planted by the government in the late ’20s and early ’30s due to absence of native forests in the region, these exotic trees of Eyrewell mostly consists of Pinus Radiata (a coniferous evergreen tree) surrounded mainly by center-pivot irrigation and the braided River Waimakariri with shingle beds in the south of the image. There are meticulously planned reasons why the once dense and lush green Eyrewell forest has been stripped to its current orientation and form. Chief among them are the disastrous winds from the north-west and south-east that have been causing extensive damage to the forest. ‘Windthrow’ or ‘blowdown’ are constant terms used in this context. Contentious forest design practices of Eyrewell are heavily debated even to the present day. (Reference: NZFS)
Historical satellite images (Source: Google Earth) of the region suggests that the center-pivot irrigation systems started becoming commonplace in the beginning of the 21st century, a much later development as compared to the Eyrewell forest that were planted in the early 20th century. It has been observed through decades of study that frequent attempts to save the forest have not yielded expected results.
Braided, sediment-rich rivers – South Island of New Zealand, Canterbury Plains?
Time to face the music armed with this great intomrafion.
Low density of farm facilities, pivot irrigation and large unfenced plots of land; this place should be an area with intensive agriculture. I might be wrong but both grasand cereal can be grown and even reach different growth stages at the time the pic was taken (rather temperate climate)? This means soil quality has to be quite high (also due to riparian location). The area might be suffering from occasional drought events (low river flow, farm ponds) but the river footprint/sediment colour looks like mountains are near. California, Pacific Northwest, Chile maybe.
The image is from the north bank of the Waimakariri River on the Canterbury Plains in New Zealand at 43.44 S 172.31 E. I’ll highlight the key ecological and geological features of the image, which include the riparian verges on the braided river, and the imprint of paleo-channels on the plain. In the bottom left of the image (in the area with scattered tree cover) is a just visible set of paleo-channels, which record evidence of how the river has moved across the very flat landscape to help construct this part of the Plains. Also visible are some remnant floodplain verges (dark tree cover near the river) which to the detriment of their function of flood mitigation and wildlife refuges, are under threat from ‘reclamation’ by encroaching farmland (green circles and stripes) ((http://www.radionz.co.nz/news/national/323934/'they've-basically-stolen-public-land‘)
The view of the Waimakariri River just west of Christchurch, on the South Island of New Zealand, is a textbook example of a braided river. Braided rivers are found where mountains are growing and eroding rapidly, putting a huge burden of sediment into the channel and keeping it unstable. The multiple channels are always shifting whenever flows go up after rainfall or when the heavy snows melt in the upper reaches of the watershed. The light blue tint of the water is suspended rock flour from the glacial source in the Southern Alps.
The human presence is visible in the form of large centre pivot irrigation structures, plantation forestry, roads and holding ponds. The Canterbury Plains are a productive agricultural region and were once the “breadbasket” of the country, but over the past two decades a massive shift to intensive dairy has brought irrigated pasture and forage crops to the landscape. Farmers draw large quantities of water from the rivers and the underground aquifers to keep their paddocks green in the face of hot, dry foehn winds coming from the northwest. The striking pattern of the Eyrewell forestry blocks puts them athwart these winds and may help protect seedling trees in the lee of maturing stands.
Braided rivers and their ecosystems are a precious habitat for many rare and endemic species of plants, birds, fish and invertebrates. They have been in the New Zealand news recently as the Department of Conservation and the regional council overseeing resource use have warned farmers about the legality of encroachment into the channels of these waterways: http://www.stuff.co.nz/environment/88605503/over-the-line-rivers-being-whittled-away
Location: West of Christchurch, South Island, New Zealand.
https://www.google.ch/maps/place/43%C2%B027'42.6%22S+172%C2%B019'29.2%22E/@-43.4302333,172.2885078,10625m/data=!3m1!1e3!4m5!3m4!1s0x0:0x0!8m2!3d-43.461826!4d172.324789?hl=en
Time: Guessing this winter from sparse mountain snowcaps.
Significance: The Waimakariri River basin is almost dry, I’m guessing from lack of snow combined with over-irrigation of the adjacent farmland?A
I noticed the river, is it just a dry bed due to the agricultural use lowering the water table? If looks like a dry bed with only small tracks of water. Plus all the land is developed and nothing looks untouched.
Average flow is ~120cumecs. Highest flows in spring to early summer as the winters snows on the southern alps melt. Lowest flow, about now actually!
Northern Italy, near the Alps. The image was taken in the spring. Braided river full of water. Image show agriculture, both cows and crops. The scene is interesting, because there seems to be plenty water, but they still store water in man-made ponds. The area is highly cultivated with erosive rivers nearby which bring fertile soil in times of flooding.
Clearly a very fertile area with intensive irrigation, as indicated by the pivots and by several pollution control dams downslope of the fields. The land therefore is sloping gently down from left to right, the dams being at the lower end of the fields. That the gradient is very small is also indicated by the intense meandering of the river. Not much evidence of human habitation, no houses. Could this be somewhere on the central plains in the US or Canada?
I’m guessing it’s New Zealand because of the braided river with the blue colour of glacial/snow melt water. It’s probably South Island, Otago region. It must have been taken in summer during crop harvest. Maybe late summer or early autumn. So February/March.
Landbrugskollektiv i Rusland
A braided stream of glacial melt-water flows across the bottom of the photo, with many small and larger farm plots adjacent, some shaped and irrigated by circular spray systems. The varied colors of land may be due to varied planting and fallow cycles, and different crops grown. I am guessing this is near the Himalaya range.
This is the Eyrewell Forest area of Canterbury, NZ (43°25’22.9 S, 172°18’27.9 E) and it is the first puzzler I’ve found!
The river (the Waimakariri) is a braided channel, with a white-blue colour typical of glacial rivers – which led me to this part of the world.
I think the striped pattern is a forestry plantation. The area was planted with forests in the 1900s but they were hazard-prone (mainly a fire risk) and following a big storm that blew many of the trees down in 1975 they were not widely replaced.
The circular patterns are a result of centre-pivot irrigation. The Canterbury Plains are one the driest areas of NZ, so the intensive arable/mixed agriculture there depends on irrigation.
Congratulations and credit to you, Mark. I looked for braided rivers in Europe, Zimbabwe and even New Zealand, but couldn’t find the right spot.
Cheers,
Stephan.
lisbon
The image is probably from a developed country (1st world) because of the high techicity of the ariculture and the compactness of the cultures. Probably a country with little land or high inhabitants per area. The circular plots are irrigated from artesian wells that are depleting the nearby river (grey area). Black areas are probably munching and beige area indicate poor soil, probably desertic like areas. My guess would be either Israel or the Almeria region. When this picture was taken is difficult to say, but if this picture was taken years ago, this area is completely water depleted today and there is no agriculture anymore. The interessting fact about this picture is the fact that the artesian wells have almost completely desertified a big river, that now is recluded to small flows.
The satellite image shows a section of the Canterbury Plains, northwest of Christchurch, New Zealand. The Canterbury Plains are a product of erosion from the nearby southern alps. The land is mainly used for extensive dairy farming. Due to the low precipitation, a vast amount of water is needed for irrigation which is being pumped out of the braided rivers, also typical for this region (such as Waimakariri River on the image). The dark diagonals and lines are pine trees which are typical for the Canterbury Plains to prevent erosion of the strong winds coming from the mountain valleys.
Surpiisrngly well-written and informative for a free online article.
I would not have guessed New Zealand as the actual site, but that makes sense. I suggest a developed country (evidence: the center-pivot irrigation pattern in some of the fields – which I hope will change as the developed world realizes the need to conserve water, not let 80 – 90% of irrigation water evaporate away).
What are the small cerulean blue irregular polygons just to the lower right of the center (& 1 more triangular one towards the upper right)? Are they bodies of water? Do you know what purpose they serve, if any?