Inclusion of Ecological Water Requirements in Optimization of Water Resource Allocation Under Changing Climatic Conditions

Meeting ecological water requirements (EWRs) is important for maintaining watershed system stability in many arid and semi-arid areas. Rainfall–runoff relationships under changing climate conditions could have many adverse effects on EWRs. The inherent uncertainties in water resource management and potential variations in EWRs should be considered to obtain suitable water allocation strategies under climate change. In this study, an integrated approach was proposed through incorporation of copula functions and a Markov Chain Monte Carlo (MCMC) simulation into a chance-constrained programming (CCP) model. The proposed approach had several advantages for water resource allocation under variable climatic conditions with respect to the following: (a) tackling correlated features of rainfall and watershed inflow under climate change based on copula–MCMC simulations, (b) obtaining runoff distributions using the copula sampling method under multiple climate change scenarios, (c) analyzing fluctuations in EWRs based on variable monthly flows and diverse runoff distributions, and (d) obtaining desired water allocation strategies through the developed CCP model with consideration of EWRs and water shortage risk. Application of the developed method to water resource management in the city of Dalian (China) indicated that the EWRs in the watersheds of Dalian would exhibit large variations under changing climatic conditions. Moreover, in comparison with the supply in 2025, an increase in water supply transferred from the Dahuofang Reservoir (Hun River) would be 6942–33,772, 6942–25,472, and 2849–14,259 Mt with risk tolerance levels of 20%, 50%, and 80%, respectively.