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Proof Point: Drought in the Yangtze River Basin

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Proof Point: Drought in the Yangtze River Basin

4 April 2025

In this series, we detail current weather-related events, their impacts on the affected region, and the historical accuracy of the Water Security Indicator Model (WSIM) forecasts. 

Description of the Event: Insufficient rainfall causes drought, wildfire risk in Yangtze River Basin

Date of Event: December 2024 - February 2025

What happened, where and when? 

Since late January, portions of the Yangtze River Basin, specifically in the Jiangxi province, have faced significant drought as the region experiences lack of rainfall and unevenly distributed precipitation. Average rainfall has been significantly below past levels, especially in southern Jiangxi. At the end of January, over 90% of Jiangxi was at extreme fire risk, while 66.7% of its counties were in severe drought. 

In addition to Jiangxi, several other provinces within the basin report continuous drought and insufficient rainfall. As of January 17, many areas from the middle and lower reaches of the Yangtze River to central and northern South China have reached severe drought levels, and areas such as Jiangxi, eastern Hunan, western Fujian, northwestern Guangdong, central and northeastern Guangxi have reached extreme drought levels.

The drought conditions prompted authorities to induce artificial rainfall. These efforts alleviated drought conditions in some regions, decreasing the amount of counties affected by drought by 55.9%, and fire risk levels dropped in many areas. However, 26 counties in southern Jiangxi still face significant fire risk. As of February, artificial rainfall operations continue. 

In the coming flood season, the Yangtze River Basin is expected to experience both drought and flooding, though overall conditions are expected to remain dry. Middle reaches of the Poyang Lake systems, as well as northern areas of the Dongting Lake systems, may face droughts while rainfall in the northern reaches could lead to mountain torrents and mudslides. 

The forecast maps (below) show the WSIM’s historical forecast accuracy of these events in more detail. 

WSIM analyses of seasonal (3 month) surface water anomalies for December 2024 through February 2025 as forecast in early September 2024 (left) and subsequently computed using observed data through February 2025 (right). The black ovals highlight regions around Poyang and Dongting lakes in the Yangtze River Basin, northeastern and western China, and the Russian Republic of Buryatia as described in the text.

In early September 2024, WSIM produced a forecast of seasonal (3 month) surface water anomalies for December 2024 through February 2025 using observed data from ERA5 through August 2024 and an ensemble of 28 NOAA CFSv2 forecasts issued the last week of August 2024 as shown on the left in the figure above. This forecast, produced 4-6 months in advance, captures the major features of surface water anomalies subsequently computed with observed data from ERA5 through February 2025 as shown on the right in the figure above.  

The forecast accurately captures the extent of deficits in the Yangtze River basin in areas surrounding Poyang and Dongting lakes as described in the text above, but understates the severity. It also accurately depicts the extent and severity of deficits in the Russian Republic of Buryatia (east of Lake Baikal) and most of the surpluses in western and northeast China.  However, the forecast is not perfect. For example, it misses surpluses in Taiwan and forecasts deficits in South Korea that did not materialize. Each of these errors were corrected in forecasts subsequently issued in early December 2024 with lead times of 1-3 months as shown in the figure below. Also note that the 1-3 month lead time forecast also better represents the severity of the drought in the Yangtze River Basin and the surpluses in China north of the border with North Korea.

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Many analyses reported in ISciences-authored blog posts are based on data generated by the ISciences Water Security Indicator Model (WSIM). Other sources, if used, are referenced in footnotes accompanying individual posts. WSIM is a validated capability that produces monthly reports on current and forecast global freshwater surpluses and deficits with lead times of 1-9 months at 0.25°x0.25° resolution. This capability has been in continuous operation since April 2011 and has proven to provide reliable forecasts of emerging water security concerns in that time-frame. WSIM has the ability to assess the impacts of water anomalies on people, agriculture, and electricity generation. Detailed data, customized visualizations, and reports are available for purchase.

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