Synchronous-Asynchronous Encounter Probability Analysis of High-Low Runoff for Jinsha River, China, using Copulas*

Abstract

Synchronous-asynchronous encounter probability analysis of high-low runoff, which requires a description of the probabilistic properties of hydrological variables, is important in regional water resources management. This study aims to investigate this encounter probability for Jinsha River and its tributary Yalong River in southwest China. A bivariate distribution is used to model the runoff variables of the two rivers based on Copula theory. The Copula is a function that links the univariate marginal distributions to form the bivariate distribution. The bivariate distribution is then employed to determine joint and conditional probabilities. The study results indicate the encounter probability of mainstream runoff and tributary runoff in different periods, also illustrate the mainstream runoff distribution under the condition of knowing the tributary runoff distribution.