Estimation of areal precipitation in the Qilian Mountains based on a gridded dataset since 1961

Based on a 0.5°×0.5° daily gridded precipitation dataset and observations in mete- orological stations released by the National Meteorological Information Center, the interan- nual variation of areal precipitation in the Qilian Mountains during 1961-2012 is investigated using principal component analysis （PCA） and regression analysis, and the relationship be- tween areal precipitation and drought accumulation intensity is also analyzed. The results indicate that the spatial distribution of precipitation in the Qilian Mountains can be well re- flected by the gridded dataset. The gridded data-based precipitation in mountainous region is generally larger than that in plain region, and the eastern section of the mountain range usu- ally has more precipitation than the western section. The annual mean areal precipitation in the Qilian Mountains is 724.9×108 m3, and the seasonal means in spring, summer, autumn and winter are 118.9×108 m3, 469.4×108 m3, 122.5×108 m3 and 14.1×108 m3, respectively. Summer is a season with the largest areal precipitation among the four seasons, and the proportion in summer is approximately 64.76%. The areal precipitation in summer, autumn and winter shows increasing trends, but a decreasing trend is seen in spring. Among the four seasons, summer have the largest trend magnitude of 1.7×108 m3-a-1. The correlation be- tween areal precipitation in the mountainous region and dry-wet conditions in the mountains and the surroundings can be well exhibited. There is a negative correlation between drought accumulation intensity and the larger areal precipitation is consistent with the weaker drought intensity for this region.

Extraction and Application of Small and Middle River Basins in Jiangxi Province

[Objective] The study aimed to develop the forecasting and early waming system of floods in small and middle river basins. [Methed] Taking small and middle rivers in Jiangxi Province as the research object, using the Hydro ArcTools module of arcgisl0, the digital drainage network and basin boundaries of Jiangxi Province were extracted from the 1：50 000 digital elevation model （ DEM） of Jiangxi Province. Afterwards, the geo- graphic information database of small and middle rivers were established, and areal precipitation in Chongyi region was calculated using Thiessen polygon method based on precipitation data during June 20 -22, 2012. [Resttlt] When the threshold was 78 65,5, the extracted river systems and basin boundaries could meet the demand of actual application and could be used as the basic parameters of areal precipitation prediction model. The areal precipitation in Chongyi region was higher than 7 mm, and it was higher in the east compared with the west. [ Conclusion] The research could provide scientific references for the control and prevention of flood in future.

Runoff Simulation of Three Gorges Area in the Upper Yangtze River during 1998 Flood Season

The contribution of areal precipitation of the catchment from Cuntan toYichang (Three Gorges area) to eight flood peaks of the Upper Yangtze River (the upper reaches ofthe Yangtze River) is diagnosed for 1998 flood season. A rainfall-runoff model is employed tosimulate runoffs of this catchment. Comparison of observed and simulated runoffs shows that therainfall-runoff model has a good capability to simulate the runoff over a large-scale river and theresults describe the eight flood peaks very well. Forecast results are closely associated with thesensitivity of the model to rainfall and the calibration processes. Other reasons leading tosimulation errors are further discussed.