Analysis of Variation Trend and Driving Factors of Baseflow in Typical Yellow River Basins.

Baseflow is a stable part of streamflow and the main component of streamflow during the dry season. Baseflow plays an important role in the water cycle, and in ecological environment protection of the Yellow River basin (YRB). Taking the Zuli, Kuye, and Tuwei basins, and the Jingle sub-basin as examples, the baseflow was separated using a recursive digital filtering method. The intra-annual, inter-annual, and chronological characteristics of baseflow and the baseflow index (BFI) were analyzed, and driving factors were analyzed from the perspective of climate-change and human-impact factors. The results showed that: (1) The annual baseflow of the basins mainly declined, trending downward in all four test basins, while the BFI increased in two of the basins and remained nearly constant in the other two basins; however, the distributions of baseflow and the BFI were more uniform. (2) The intra-annual patterns for baseflow and the BFI showed changes between earlier and later periods. (3) Precipitation and soil and water conservation measures were the primary driving forces of baseflow change in the basins. The influence of the former weakened while the latter strengthened, and coal mining in the Kuye River and Tuwei River basins also influenced baseflow significantly. (4) When the normalized difference vegetation index (NDVI) < 0.375, the BFI of test watersheds gradually decreased with the increase in the NDVI. When 0.375 < NDVI < 0.65, the BFI of the basins gradually increased with the increase in the NDVI and the underlying surface continued to improve. When NDVI > 0.65, the increase rate of the BFI decreased and the soil and water conservation capacity of the underlying surface tended to be stable. [ABSTRACT FROM AUTHOR]

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