Marco Gemmer

Precipitation, temperature and runoff analysis from 1950 to 2002 in the Yangtze basin, China / Analyse des précipitations, températures et débits de 1950 à 2002 dans le bassin du Yangtze, en Chine

Abstractn Abstract Monthly precipitation and temperature trends of 51 stations in the Yangtze basin from 1950–2002 were analysed and interpolated. The Mann-Kendall trend test was applied to examine the monthly precipitation and temperature data. Significant positive and negative trends at the 90, 95 and 99% significance levels were detected. The monthly mean temperature, precipitation, summer precipitation and monthly mean runoff at Yichang, Hankou and Datong stations were analysed. The results indicate that spatial distribution of precipitation and temperature trends is different. The middle and lower Yangtze basin is dominated by upward precipitation trend but by somewhat downward temperature trend; while downward precipitation trend and upward temperature trend occur in the upper Yangtze basin. This is because increasing precipitation leads to increasing cloud coverage and, hence, results in decreasing ground surface temperature. Average monthly precipitation and temperature analysis for the upper, middle and lower Yangtze basin, respectively, further corroborate this viewpoint. Analysis of precipitation trend for these three regions and of runoff trends for the Yichang, Hankou and Datong stations indicated that runoff trends respond well to the precipitation trends. Historical flood trend analysis also shows that floods in the middle and lower Yangtze basin are in upward trend. The above findings indicate that the middle and lower Yangtze basin is likely to face more serious flood disasters. The research results help in further understanding the influence of climatic changes on floods in the Yangtze basin, providing scientific background for the flood control activities in large catchments in Asia.

Observed precipitation trends in the Yangtze river catchment from 1951 to 2002

The monthly, seasonal, and annual precipitation trends in the Yangtze river catchment have been detected through analysis of 51 meteorological stations’ data between 1950–2002 provided by National Meteorological Administration. Results reveal that: 1) Summer precipitation in the Yangtze river catchment shows significant increasing tendency. The Poyanghu lake basin, Dongtinghu lake basin and Taihu lake basin in the middle and lower reaches are the places showing significant positive trends. Summer precipitation in the middle and lower reaches experienced an abrupt change in the year 1992; 2) The monthly precipitation in months just adjoining to summer shows decreasing tendency in the Yangtze river catchment. The upper and middle reaches in Jialingjiang river basin and Hanshui river basin are the places showing significant negative trends; 3) Extreme precipitation events show an increasing tendency in most places, especially in the middle and lower reaches of the Yangtze river catchment.

Dynamic inundation risk identification and estimation of the potential loss in Honghu flood diversion area,China

Under the background of global change and the rapid development of economy,the Yangtze River basin is confronted with rising pressure to prevent flood.The identification of inundation risks and the evaluation of poten- tial flood losses are of great significance in the Yangtze river basin.This study performs the identification of the in- undation risk in Honghu flood diversion area with a hydrological-hydraulic model based on raster data integrated into Arcview3.x.It processes an evaluation of the potential less in terms of land use types and damage functions,and finally builds an dynamic database of potential loss which can serve as scientific base for the management of Honghu flood diversion area.The identification of inundation risks is carried out based on a digital elevation model,calibra- ted with the waterstage-time curve derived from the summer flood in 1998 and manning roughness of each land use type.