A Copula-based Approach for Multivariate Dependence Analysis of Precipitation and River flow Changes and Attributions of Anthropogenic Activities and Climate Change to River flow

Abstract

Abstract The two major factors influencing river flow change in basins are anthropogenic activities and climate change (AACC), and separating the attribution of each can be crucial for managing water resources as well as economic, political, and social activities. In this study, a hydrologic model simulation was used to separate AACC attributions to river flow change in the southwest of Iran's Karkheh basin. The trend of annual potential evapotranspiration, precipitation, river flow, and air temperature was determined by the Mann-Kendall (MK) test. Multivariate dependence analysis was performed for precipitation changes, river flow changes, attributions of AACC to river flow change by different copula functions. The finding showed that the point of change in the annual river flow series by the double cumulative curve (DCC) and Pettitt test occurred in 1999. Thus, the pre-and post-change periods are before and after 1999, respectively. When compared to the pre-change period, the average annual river flow has decreased by 42.3%. The results of the hydrologic model simulation showed that anthropogenic activities and climate change have reduced river flow by 63.1% and 36.9%, respectively. The results showed that the attributions of AACC to river flow each year could be obtained based on the dependence analysis between precipitation changes, river flow changes, and the attributions of AACC to river flow change with copula functions. The study results can be a reference for developing, operating, and managing water resources and environmental conservation.