Climatic and Landscape Controls on Long‐Term Baseflow

다국어 초록 (Multilingual Abstract)

For evaluating the climatic and landscape controls on long‐term baseflow, baseflow index (BFI, defined as the ratio of baseflow to streamflow) and baseflow coefficient (BFC, defined as the ratio of baseflow to precipitation) are formulated as functions of climate aridity index, storage capacity index (defined as the ratio of average soil water storage capacity to precipitation), and a shape parameter for the spatial variability of storage capacity. The derivation is based on the two‐stage partitioning framework and a cumulative distribution function for storage capacity. Storage capacity has a larger impact on BFI than on BFC. When storage capacity index is smaller than 1, BFI is less sensitive to storage capacity index in arid regions compared to that in humid regions; whereas, when storage capacity index is larger than 1, BFI is less sensitive to storage capacity index in humid regions. The impact of storage capacity index on BFC is only significant in humid regions. The shape parameter plays an important role on fast flow generation at the first‐stage partitioning in humid regions and baseflow generation at the second‐stage partitioning in arid regions. The derived formulae were applied to more than 400 catchments where storage capacity index was found to follow a logarithmic function with climate aridity index. The role of climate forcings at finer timescales on baseflow were quantified, indicating that seasonality in climate forcings has a significant control especially on BFI.
Baseflow is a portion of streamflow from delayed storage such as groundwater, and it is crucial for human water supply and ecological environments. Studies have indicated both climate and catchment landscape have impacts on baseflow generation. However, their respective roles on mean annual baseflow are not fully understood. This study derives new functions to analyze the mediation effects of soil water storage capacity on the process of precipitation partitioning, and uses numerical simulations to evaluate the role of climate forcings at finer timescales on mean annual baseflow. Two widely used baseflow metrics are focused on here: baseflow index (BFI), defined as the ratio of baseflow to total streamflow; and baseflow coefficient (BFC), defined as the ratio of baseflow to precipitation. Our results show that the spatial variability of soil water storage capacity plays an important role in baseflow generation, and the impact of soil water storage capacity on BFI spreads across regions with different climates, while its impact on BFC is only significant in humid regions. Numerical simulation shows that seasonality in climate forcings has a vital influence on BFI. Our study advances our knowledge of physical controls on baseflow generation.



Derived baseflow index (BFI) and baseflow coefficient (BFC) as functions of aridity index, storage capacity index, and a shape parameter

When storage capacity index is small (large), BFI is less sensitive to climate aridity index in arid (humid) regions

The control of climate variability (particularly seasonality) on BFI is strong, but not for BFC


Derived baseflow index (BFI) and baseflow coefficient (BFC) as functions of aridity index, storage capacity index, and a shape parameter
When storage capacity index is small (large), BFI is less sensitive to climate aridity index in arid (humid) regions
The control of climate variability (particularly seasonality) on BFI is strong, but not for BFC