Abstract: To obtain the development law of runoff and sediment relations in the Yarkant River Basin, the variation point of runoff and sediment relation was diagnosed using the method of modulus coefficient, moving t-test, and moving correlation coefficient based on the data of runoff and sediment of the Kagun and Langan hydrologic stations. The two-dimensional joint distribution model of runoff and sediment was constructed by Copula function. Results manifest that: 1) The relationship between runoff and sediment changed dramatically around 1993. 2) The correlation between runoff and sediment in 1993-2015 was stronger than that in 1954-1992. 3) In different periods, the frequency of synchronous water and sediment was always larger than that of asynchronous water and sediment. The probability of “high water and low sediment” as well as “low water and high sediment” was both zero. 4) The frequency of synchronous water and sediment reached 58.97% from 1954 to 1992, and 82.61% from 1993 to 2015, and ever increased after 1993. The research conclusions offer theoretical basis for the operation and management of water resource in the Yarkant River Basin.

Key words: runoff-sediment relationsship, Copula function, runoff, sediment, Yarkant River