The Impacts of Reservoirs on Runoff in the Upper Yellow River, China

Abstract

River runoff is an important link in the water cycle that can be adversely affected by the construction of reservoirs. Based on the runoff data from 1950 to 2009 at eight stations in the upper Yellow River, this study investigated on the impacts of the combined operation of Longyangxia Reservoir and Liujiaxia Reservoir on river runoff. The measured series of runoff data for the period after the commencement of combined operation of two reservoirs were restored by adjusting for water balance. The intra-annual characteristics of observed and restored runoff at Lanzhou station and Xiaheyan station were analyzed using Mann-Kendall test and wavelet analysis. There was a significantly downward trend in both runoff series, with abrupt changes in 1986 in the observed data and in 1989 in the restored data. Periodic oscillations in the observed and restored runoff series occurred at temporal scales of 3–5-year, 6–9-year, 14–19-year, and 22–27-year. The observed runoff series at Lanzhou station and Xiaheyan station had periodicities of 25-year, 16-year, 8-year, and 4-year. The restored runoff series at Lanzhou station had periodicities of 23-year, 8-year, and 4-year, and at Xiaheyan station had periodicities of 24-year, 4-year, and 8-year. The results show that the combined operation of Longyangxia Reservoir and Liujiaxia Reservoir contributed to the decreasing trend of river runoff, and leaded to runoff abrupt changes and alterations in the periodic variation.