| Minjiang river is the major tributary of the Yangtze river, and the upper reach of the river supplies plentiful water resources for Chengdu plain through Dujiangyan Irrigation Project. But the runoff of upper reach of Minjiang river have extremely declined since 1930's , and the geological disasters, such as debris flow, landslide and serious soil erosion break out frequently owing to climate change and the influence of human activities. To analyze the hydrological characteristics of this drainage basin are not only the basis for water cycle and soil erosion's research, but also can provides beneficial supports to avoid geological and flood hazard.This research extracted the river network, drainage divide, sub-basins of upper reach of Minjiang river and calculated the drainage area and river length of each sub-basins using Geographic Information System (GIS) technology from digital evaluation model (DEM) with 90m resolution. Then, the drainage density, main-stream channel longitudinal profiles and stream fractal dimension of the whole basin and sub-basins were analyzed and compared quantitatively. After made a detailed study of the geometrical hydrology characteristics which have been mentioned above, I analyzed the fluctuation and seasonal change of the precipitation and discharge of upper reach of Minjiang river by correlatively analyzing and linear regressing, and the precipitation and runoff data were respectively observed in Songpan, Dujiangyan meteorology stations and Zipingpu hydrological station from 1955 to 2003. Further more, this study acquired the area rainfall of the basin by Kriging interpolation method based on the 21 scattered stations'precipitation from 1982 to 1987. Finally, the runoff coefficients of whole upper Minjiang river basin and the sub-basins were calculated with the area rainfall data and runoff data observed in 8 hydrological station of upper Minjiang area. The results show that:Firstly, the mean annual runoff coefficient of the whole drainage basin is 0.77 from 1982 to 1987, the Zhenjiang-guan sub-basin is 0.55, Heishui-he is 0.73, Jiangshe-ba is 0.88. And the coefficients of 3 sub-basins increase one by one from the whole drainage basin's north to south. Drainage density of the study area is 0.172km/km2, and the 3 sub-basins'drainage densities are 0.177km/km2, 0.173km/km2 and 0.171 km/km2 which decrease one by one from north to south. The negative correlation coefficient between drainage density and runoff coefficient is -0.98, which shows that the higher drainage density increase, the less runoff coefficient is.Secondly, the length of upper reach of Minjiang river is 344.2km, the stream gradient of the river is 9.7‰, both gradient and curvature of longitudinal profiles of main-stem stream of five sub-basins increase one by one from the north to south, and the shape of main channel profile affected by tectonic movement significantly. By analyzing the fractal dimension of river network and the most proper fitting function of main stream profile, I speculate that the landform evolution of the study area has developed into early mature stage.Thirdly, the mean annual runoff of upper reach of Minjiang river is 14.34 billion m3 from 1955 to 2003, equivalent to runoff depth of 635.5mm, and the coefficient of variation of the discharge is 0.11. The surface precipitation of the study area is decrease from the north, west and south to east, and the rainfall declines 90.9mm with the elevation drop 100m for Heishui-he sub-basin, the Zagu-nao decreases 17.8mm per 100m , the south side of Longmen mountain falls 43.2mm per 100m, and the stream valley of the river decrease 21.7mm per 100m. |
PDF Full Text Request