Interannual runoff variation and statistical characteristics of wet and dry years in upper reaches of Yellow River

Abstract

[Objective] The upper reaches of the Yellow River contribute approximately two-thirds of the water volume of the entire river basin and four-fifths of its reservoir storage capacity, serving as the major water-producing area and interannual runoff regulation area for the river basin. However, the significant interannual variation of runoff and its difficulties in accurate prediction have constrained the effectiveness of reservoirs in the upper reaches in “storing water in wet years to compensate for dry years” and undermined the security of water resources. [Methods] To further enhance the understanding of runoff, naturalized runoff data at major cross-sections along the Yellow River's mainstream from 1956 to 2022(Tangnaihai, Lanzhou, Lijin) and archaeological runoff data from 1736 to 1911(Qingtongxia) were collected. Multivariate statistical method such as Copula function and non-consistency tests were employed to explore the contribution of the upper reaches to the runoff of the entire river basin, interannual variation patterns of runoff in the upper reaches, and statistical characteristics of wet and dry years. [Results] The synchronous probability of wet, normal, and dry years of runoff at the Lanzhou cross-section and the entire river basin was 71.5%, with the probabilities of coincident dry or wet years being 32.2% and 20.3%, respectively. The probabilities of single dry or wet year at the Lanzhou cross-section were 43.3% and 26.9%, respectively. Specifically, the probability of an extremely wet year was 7.5%, with no extremely dry year observed during the study period. The probabilities of two consecutive dry or wet years were 19.7% and 12.1%, respectively, while three consecutive dry or wet years showed probabilities of 7.7% and 4.6%, respectively. The probability of transition between wet and dry years was 16.7%. [Conclusion] To effectively cope with the adverse effects of extremely wet or dry years, as well as consecutive wet or dry years, it is imperative to improve the long-term runoff prediction capabilities while fully leveraging the interannual regulation capacity of the Longyangxia Reservoir, and to accelerate the construction of the “one-route and seven-reservoir” water network system in the Yellow River Basin.

Keywords

runoff / extremely wet/dry years / consecutive wet/dry years / Copula function / non-consistency test / upper reaches of the Yellow River / influencing factors