We have identified three groups of problems in the context of which human societies intersect with the two conditions related to water mentioned above: 1) the natural environment/phenomena, 2) production/life, and 3) movement/distribution. In addition, 1876-78, 1918-20, and 1931 are marked as benchmark years among the project members because of the abnormal climate caused by El Niño during these years. In this context, three projects have been promoted: "Natural Disasters and Social Change," in relation to the Problem Groups 1) and 2), and "Inter-hydrospheric Connections and Virtual Water Trade" with regard to 1) and 3).
How did the flood in 1931 cause such an unprecedented disaster? To answer this question, this project reconstructs the flood process and examines its socio-economic impacts.
Figure 1. Image of the records from Weather Monthly 『気象月刊』March 1931
Figure 2. Observation sites reported in Weather Monthly
As Figure 3 shows, Chinese Maritime Customs regularly observed the level of water and the flow rate of the rivers (for the archives of Chinese Maritime Customs, see Data & Archives: Interview with Takeshi Hamashita).
Figure 3. Daily water levels of Yangzi River at Hankou（Chinese Maritime Customs, Returns of Trade and Trade Reports 1869）
Source: Harvard-Yenching Library, https://nrs.harvard.edu/urn-3:FHCL:5164957
By constructing a meteorological database from these long-overlooked contemporary observations and then applying hydrological models and analysis methods to the data, we can reconstruct the natural environment at a time when socioeconomic activities can be examined. This project is particularly focused on flood analysis. Flood analysis is a technique that uses rainfall distribution, topographical data such as elevation and land usage, and river cross-sectional data to calculate the excess rainfall, effluence, and flooding in the river basins. Figure 4 explains Rainfall-Runoff-Inundation (RRI) model that this project employs for flood analysis. The elevation data used here are derived from HydroSHEDS and provided by the United States Geological Survey (USGS). Weather observation data measured by Chinese Maritime Customs at the time were added to the 2°grid rainfall data of the last 150 years, which have been provided by the U.S. National Oceanic and Atmospheric Administration, (NOAA) to obtain precipitation data.
The investigation reported that among the causes of death during the flood, the rate of sickness (70 percent) was observed to be higher than that of drowning (24 percent). To investigate the lives in the hydrosphere, Chinese Maritime Customs also paid much attention to the relationships among water, health, and diseases (see Data & Archives: Interviews to Takeshi Hamashita).
The rice price index indicates that the failure of the crop in Hunan, which is a major rice-growing area (Figure 5), impacted the regions along the Yangzi River (Figure 6) through the domestic rice market. (Tomoko Shiroyama)
Figure 5. Rice price index in Hunan (June 1931=100）
Figure 6. Rice price index in the cities along the Yangzi River（June 1931=100）