Three Gorges Dam, Yangtze River, China under construction below and nearly complete top
Source: NASA Earth Observatory
When it was proposed and during construction of the Three Gorges Dam, many commentators said it would fail to stem the floods for which the Yangtze is notorious. Since its completion the rains of summer 2010 mark the first season of precipitation greatly in excess of long-term averages, and events of the past two months would seem to prove their point. There has been substantial flooding both above and below the dam. Although the Chinese authorities claim the dam itself is sound, it has been able to hold back only a small part of the additional flow of the massive river. Devastating flooding has wiped out towns and villages, farm fields, and transportation facilities both up and downstream from the world's largest barrage. Built for all four of the magic goals of dams, for the foreseeable future the Three Gorges Dam may fail at three of them, flood control, navigation, and hydroelectric generation, while the rains make the final one, irrigation, unnecessary.
Much of the detritus caused by the flooding, it turn, has washed into the river, and the dam has blocked that material coming from upstream in much the same way that it blocks silt in periods of normal flow. Upstream of the dam the accumulating trash in the reservoir, already about a meter thick and strong enough to form islands capable of supporting a person, could clog a floodgate and threaten the integrity of the dam itself, but more likely is blockage of the navigation locks (right hand side of the pictures) and fouling of the water flowing over and through the dam with trash that makes downstream use difficult. There are dire predictions about navigation dangers on the river, a crucial route for Chinese commerce, due to the accumulated trash. Upstream, the immense city of Chongqing (Chongqing (重庆; Chóngqìng formerly spelled Chungking), may have to draw water into its public supply that has been fouled by industrial and agricultural chemicals, farm waste, and human sewage. Rapid flow would serve to dilute those pollutants if the river had been left undammed, but the slack water behind dams results in far less mixing of waters and dilution of pollutants.
Meanwhile, at the opposite end of the rainfall spectrum, the severe drought and excessive heat that have plagued European Russia for most of the summer of 2010 have resulted in some serious problems of heat and smoke in the capital. Moscow, a city where air conditioning is rare because in the past it has been needed infrequently, has suffered multiple days with 35+ degrees Celsius. In addition to the heat, Muscovites are breathing air with dangerous levels of smoke, soot and other pollutants, a consequence of field, brush and forest fires, some of them burning down into the layers of peat beneath birch woods and brush lands surrounding the city. Peat, used as a fuel in several parts of the world, can smolder and burn for a long time once ignited, and until drenching rains or the winter cold begins, smoke will continue to plague Moscow even when temperatures moderate.
Most Russian grain is rain-fed with no supplemental irrigation, and the combination of drought and fires have devastated the 2010 crop. World grain prices have soared because analysts expect the grain crop in Russia to be far smaller than usual, and that country has banned grain exports. Increases in grain prices could spark serious food problems worldwide.Should the Argentinian and Australian grain areas suffer serious drought in the 2010-11 growing season, the year of 2011 could have a food crisis.
Temperature anomalies in Russia, Summer 2010
Source: NASA Earth Observatory
As always one must remember that the events of a single summer say nothing about climate change, but the flooding in Pakistan and China and the drought and heat in Russia are precisely the kinds of conditions that warmer earth temperatures point toward. Those include long spells of hot weather in many northern hemisphere cities, redistribution of precipitation with increases in some areas and deficits in others, and an increasing frequency of extreme weather events including both drought and torrential rainfall.
