Yali Ma, Zuirong Niu, Dongyuan Sun
Changes in external environmental conditions include surface conditions and climate, the process of water and sediment transport also exhibit non-steady-state characteristics, nonlinear and low-correlation characteristics, leading to a more complex interaction mechanism between water and sediment transport. It is worth exploring whether the water-sediment relationship is coordinated. The study was conducted on the changes and causes of water-sediment relationships in the Taohe River Basin in this paper. The results showed that: (1) The water and sediment transport in the Taohe River have significantly decreased. The annual average runoff and sediment discharge have decreased by 25.41% since 1987 and by 72% since 1995 respectively. (2) There is a positive correlation between water and sediment in the Taohe River. After 2009, the situation with less water and more sediment has changed to a situation with more water and less sediment. The water-sediment relationship became increasingly coordinated. (3) The water and sediment exhibit a symmetrical joint distribution characteristic, and the Frank-Copula function has the best fitting effect. The water-sediment synchronization and asynchronous probabilities are 85.62% and 14.38%, respectively, and the water-sediment synchronization probability is significantly greater than the water-sediment asynchronous probability. (4) Climate change has respectively led to a reduction of 24% to 47% in runoff and a decrease of 5% in sediment discharge, while that of human activities is 53% to 76% and 95% respectively. Human activities are the dominant factor causing these reductions, and they have a greater impact on the reduction of sediment discharge. The results provide scientific basis for the regulation and disaster prevention of water and sediment, and the management of water resources. • The patterns and correlations of water and sediment changes are revealed. • The marginal and joint distributions of water and sediment have both been constructed. • The risks of abundance and scantiness encountering of water and sediment have been assessed. • The partial differential equations for attribution have been constructed under six Budyko hypotheses.