Method for Analyzing Copula-Based Water Shortage Risk in Multisource Water Supply Cities

Based on the data series location water, Yellow River water, and the South-to-North Water Diversion water which were obtained from 1985 to 2017 in Zhengzhou, China, a joint probability distribution (JPD) model and encounter probability (EP) were established using the optimized t-copula function. The EP was combined, and a risk analysis was performed based on the water shortage situation of each user in different encounters. The results showed that (1) the trivariate JPD could reflect the probability of multisource water supply more precisely than the bivariate JPD; (2) the asynchronous EP was 76.6%, higher than the synchronous EP by 53.2%, indicating that the three water sources were complementary, and the local water exhibited the most significant impact on water supply system in Zhengzhou; and (3) the maximum EP for S1 was 11.7%, all users in S27 experienced varying degrees of water shortage, and the domestic water shortage was (−0.271, −0.33) billion m3. The reservoirs should be converted into joint dispatch, and water rights trading and other water resource management measures should be adopted. The amount of extracted groundwater may be increased if necessary to maintain the urban water supply system.