{"id":5148,"date":"2012-09-12T00:56:37","date_gmt":"2012-09-12T00:56:37","guid":{"rendered":"http:\/\/blogs.agu.org\/landslideblog\/?p=5148"},"modified":"2012-09-12T01:00:13","modified_gmt":"2012-09-12T01:00:13","slug":"landslides-and-the-red-yangtze-river","status":"publish","type":"post","link":"https:\/\/blogs.agu.org\/landslideblog\/2012\/09\/12\/landslides-and-the-red-yangtze-river\/","title":{"rendered":"Landslides and the red Yangtze River"},"content":{"rendered":"

An interesting story coming out of China today concerns the Yangtze River at Chongqing, upstream of the Three Gorges Dam.\u00a0 To the understandable consternation of local people, on Thursday the river developed an intense red colouration.\u00a0 Various news agencies have images of this phenomenon, but the Daily Mail has the best photo compilation<\/a> that I’ve seen so far (and, as an aside, it is accompanied by the most amusing comments at the bottom of the page):<\/p>\n

\"\"<\/a>

http:\/\/www.dailymail.co.uk\/news\/article-2199800\/The-river-DID-run-red-Residents-Chinese-city-left-baffled-Yangtze-turns-scarlet.html?ito=feeds-newsxml<\/p><\/div>\n

Inevitably, there is a great deal of speculation as to the cause of this change in colour, ranging from a “red tide” algal bloom (unlikely as this is marine phenomenon), pollution such as a toxic chemical spill (also unlikely given the scale – the Yangtze is a huge river at this point, such that this would need to be a huge input of chemicals), the Yunnan earthquake (again unlikely given the location of the affected area), or sediment generated by soil erosion and landslides.\u00a0 Incidentally, it is also being interpreted as an indicator of momentous events in China, with links being made to the forthcoming change in leadership of the country.\u00a0 It is slightly dispiriting that such interpretations are still made.<\/p>\n

By far the mostly likely cause of the change of colour is a large-scale input of iron-rich sediment to the river.\u00a0 It is notable that a large flood wave passed down the river last week<\/a>, caused by heavy rainfall in Sichuan Province.\u00a0 This was reportedly the largest flood wave for two decades.\u00a0 Thus, I would hypothesise that the intense rainfall caused extensive sediment mobilisation both in terms of landslides on slopes and debris already in the river, and that this has caused the change in water colour.<\/p>\n

Of great interest to me is the question of where this sediment mobilisation occurred.\u00a0 One leading candidate might be the Wenchuan Earthquake area<\/a>, where we know that very large quantities of sediment were released from the slopes<\/a>.\u00a0 Could it be that this is the main part of that sediment plume passing downstream?\u00a0 If so, I am surprised that it has taken so long, but it could be that a portion of the sediment has been stored in the channel and only mobilised during this extreme rainfall event.\u00a0 An alternative hypothesis that has been proposed is that this was caused by landslides on the banks of the Three Gorges reservoir<\/a>, where we know that extensive mass movements are occurring.\u00a0 However, this appears to have occurred upstream of the Three Gorges reservoir, so that is highly unlikely.\u00a0 Alternatively, it could be that there is some other area in the Yangtze catchment that is suffering extensive landsliding, although it is not clear where and why this might be occurring.<\/p>\n

None of the newspaper reports indicate that this change in river colour has a precedent in Chongqing, indicating that something out of the ordinary has occurred.\u00a0 It will be interesting to discover the nature of the causal event. But in the meantime, it is interesting to note that at time of writing this change in water-colour does not seem to feature on Xinhua News<\/a>, the official Chinese news agency website.<\/p>\n","protected":false},"excerpt":{"rendered":"

The Yangtze River has changed colour – suddenly becoming red – in the city of Chongqing. The likely cause is landslides associated with heavy rainfall in the catchment, although exactly where this occurred is not clear.<\/p>\n","protected":false},"author":22,"featured_media":5149,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":"","_members_access_role":[],"_members_access_error":""},"categories":[3],"tags":[16,23,469,365,615,643],"class_list":["post-5148","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-landslide-report","tag-china","tag-earthquake","tag-featured","tag-sediment","tag-three-gorges","tag-yangtze"],"_links":{"self":[{"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/posts\/5148","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/users\/22"}],"replies":[{"embeddable":true,"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/comments?post=5148"}],"version-history":[{"count":0,"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/posts\/5148\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/media\/5149"}],"wp:attachment":[{"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/media?parent=5148"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/categories?post=5148"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/tags?post=5148"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}