Temporal and spatial distribution characteristics and fluxes of dissolved organic carbon in the upper Yellow River (Longyangxia-Liujiaxia) under cascade hydropower development
Aiming at the problem of riparian biogenic material cycles brought upon by cascade hydropower development, the cascade hydropower development section of the upper Yellow River (Longyangxia-Liujiaxia section, a total of five reservoirs) was selected as the research area, and dissolved organic carbon (DOC) as the main research object. The distribution characteristics of DOC and physicochemical indicators were analyzed by sampling monitoring method, then the DOC transport flux in each reservoir was estimated based on the static box algorithm model. The results showed that DOC and conventional physicochemical indicators presented obvious spatiotemporal heterogeneity, and the concentration of DOC in the flood season (5.37-7.00 mg/L) was higher than that in the non-flood season (2.90-5.56 mg/L). Moreover, due to the vertical water temperature stratification of the reservoir, the DOC showed the characteristics of fluctuated change along the vertical direction of the water depth in the flood season. During the sampling year, the total input of DOC in the Long-Liu section was 258.53 kt, the total output was 192.23 kt, and the interception rate was 25.6%. The reservoirs which played the role of interception were Longyangxia, Gongboxia and Liujiaxia, and the rest were all transporters.