Evaluation of baseflow processes in the Yellow River Basin, China

Yellow River is the mother river of the Chinese nation. It has provided available water resources for more than 5000 years and makes the Yellow River Basin (YRB) a significant grain-producing in China. Recently, promoting the high-quality development of the YRB has been proposed as a Chinese national strategy, highlighting the high status of the YRB in China. However, covering a large area of the arid and semi-arid region, hydrometeorological extremes such as droughts have often occurred in historical periods in the YRB, with prolonged effects on agricultural production. In addition, water conflicts (i.e., water shortage) between human beings’ needs and water resource availability have been much more severe due to population growth and global warming, affecting the ecological health of basins and challenging the lives of riparian residents. Baseflow is a stable flow during the drought season to discharge total streamflow from the groundwater and other delayed sources, which is significant for maintaining the ecological health of river basins and promoting sustainable economic development in arid and semi-arid catchments. Therefore, it is urgent to investigate baseflow characteristics and their determinants for understanding the hydrological processes better and provide scientific foundations for mitigating water shortage problems in the YRB.

Based on that, we collected the daily streamflow records from the main catchments in the YRB. The daily ensembled mean baseflow records derived from Lyne-Hollick, Chapman-Maxwell, Eckhardt and United Kingdom of Institute Hydrology (UKIH) separation algorithms were obtained after the 21^st century to reduce simulation uncertainties. Dynamics hydrological signatures were extracted to investigate baseflow spatiotemporal variations and their determinants. Catchments’ physical properties, including topography, vegetation, soil and human activities, were selected. The stepwise model was conducted to see how these catchments’ properties influence the hydrological signatures variability and the ranking of their importance. Our findings showed significant spatial distribution patterns of hydrological signatures in the YRB. Most of them had higher values in upstream and downstream reaches, while low values were in the middle reaches. The magnitude of temporal variation of hydrological signatures was strongly correlated with the catchment topography, vegetation conditions and cropland coverage. It is challenging to discover one single controlling property influencing hydrological signatures for all catchments across the YRB. For most of the hydrological signatures, soil textures, precipitation and vegetation conditions are the most significant influencing factors, indicating the baseflow processes are influenced by a synergistic effect in the YRB.

This study comprehensively investigated the baseflow characteristics in the whole YRB. It can not only provide scientific foundations for water resources management in the YRB but also take an example of how to quantitively evaluate the baseflow characteristics in large semi-arid and arid catchments.