The Impact of an Open Water-balance Assumption on the Understanding of
the Factors that Control the Long-term Streamflow Components
Abstract
Understanding how streamflow and its components, baseflow and quickflow,
vary spatially according to climate and landscape characteristics is
fundamental for dealing with different water-related issues. Analytical
formulations have been proposed to investigate their long-term behavior
and additional influencing factors, suggesting that they are mainly
controlled by the aridity index ( Φ). Nevertheless, these studies assume
the catchment as a closed water balance system, neglecting
inter-catchment groundwater flow (IGF). This simplification makes the
analysis of the long-term streamflow components and their main control
mechanisms challenging, given that many catchments cannot be considered
as closed hydraulic entities. Here, we assessed the controls of the
mean-annual streamflow components and their behavior under an open water
balance assumption, using observed data of 731 Brazilian catchments with
diverse hydroclimatic conditions. Our results indicate that indeed
streamflow components are primarily controlled by at the mean annual
timescale. The consideration of an open water-balance significantly
improved the performance of the functional forms to describe streamflow
components while also elucidating the assessment of other influencing
factors on the streamflow behavior. Land cover, groundwater, climate
seasonality and topographic attributes appeared as the main control
mechanisms beyond aridity. Overall, our study provides new insights of
the main control mechanism of the streamflow behavior at the mean-annual
scale, while shedding light on the importance of the open water-balance
assumption for model development and water resources management.