Abstract:

To study temporal and spatial variations of precipitation in Jinshajiang River basin, some typical precipitation indices on long time scale and some typical rainy days were analyzed in present research, by applying the MannKendall test and Empirical Orthogonal Function method based on daily precipitation data during 1961-2010 in Jinshajiang River basin. The results shows that annual areal rainfall had a certain increasing tendency without passing the significance test, while annual rainfall in the lower reach of the basin decreased weakly. Precipitation in the flood season had no obvious changes, while monthly rainfall through a year (except rainfall in September and December) had a weak increasing tendency. In addition, annual rainfall showed obvious spatial differences, and the higher rainfall area is located in the lower basin especially in Hengduan Mountain area. Rainfall in the flood season showed more obvious regional characteristics, and the higher value area is also located in Hengduan Mountain area. At the same time, rainy days for light level and moderate level increased weakly in the upper and middle regions, while they decreased weakly in the lower basin, without passing the significance test. Rainy days for heavy rain grade increased in the most of the whole basin, but it had unobvious decreasing tendency in the head region and around Dege station without passing the significance test. The number of no rain days and the number of consecutive no rain days in one year showed the similar spatial change patterns and had obvious decreasing tendency in the upper and middle basin, while they had obvious increasing tendency in the lower basin, especially that the number of no rain days in one year increased dramatically around Zhaojue, Zhaotong and Huize stations with passing the significance test. However, the number of consecutive rainy days in one year almost decreased in the whole basin, and decreased significantly in a small part of the lower basin. Moreover, as far as decadal changes were concerned, the number of no rain days and the number of consecutive no rain days in one year were the biggest in 2000s, while the number of consecutive rainy days was the smallest in 2000s, which was consistent the recent frequent occurrences of drought events in WestSouth China. The temporal changes of the typical precipitation indices may confirm the possible increasing tendency for occurrence of drought events in the downstream of Jinshajiang River basin