Intra-annual distribution and decadal change in extreme hydrological events in Xinjiang, Northwestern China

We examined intra-annual characteristics and decadal change of extreme hydrological events occurring from 1901 to 2010 in Xinjiang, China, using concentration degree, concentration index, and Mann–Kendall tests. The results indicated that the concentration index in Xinjiang reached a maximum in summer for all areas, demonstrating that extreme hydrological events occurred mainly during summer (although Altay also showed a high winter concentration index). Intra-annual distribution was most concentrated in Turpan and Urumqi, followed by Kuytun–Shihezi and Aksu, with the concentration degree smallest in Altay. The frequency of extreme hydrological events exhibited an obvious increasing trend from 1901 to 2010, particularly post 1970s. Based on the results obtained in this study, the frequency, magnitude, and intensity of extreme hydrological events are expected to increase over time. In addition, the concentration degree and concentration index used to analyze intra-annual distribution of extreme hydrological events were proven to be reliable and will be useful for future studies.