Multivariate Copula-Based Joint Probability Distribution of Water Supply and Demand in Irrigation District

Based on the data series of rainfall, reference crop evapotranspiration and irrigation water from 1970 to 2013 in the Luhun irrigation district of China, the multivariate joint probability of water supply and demand are constructed with student t-copula function. The results show that student t-copula function can indicate the associated dependence structure amongst these variables well, and the constructed multivariate copula-based joint probability distribution reveal the statistical characteristics and occurrence probability of different combinations of water supply and water demand. Moreover, the trivariate joint probability distribution is more reasonable than the bivariate distribution to reflect the water shortage risk, and these joint distribution values of different combinations of water supply and demand can provide the technological support for water shortage risk evaluation in the irrigation district.