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Title: Functional approach to exploring climatic and landscape controls on runoff generation. 2. Timing of runoff storm response

Hortonian overland flow, Dunne overland flow and subsurface stormflow are the three dominant mechanisms contributing to both the volume and timing of streamflow. A previous study quantified the climatic and landscape controls on the relative dominance of the volumes of the different runoff components. In this paper we explore the impacts of climate, soil and topography on the timing of these runoff components in small catchments within the framework of the Connected Instantaneous Response Functions (CIRF). The CIRF here is viewed as a probability density function of travel times of water droplets associated with a given runoff generation mechanism (from the locations where they are generated to the catchment outlet). CIRF is a refinement of the traditional catchment IRF in that it explicitly accounts for variable contributing areas: only those partial areas of runoff generation which are hydrologically connected to the outlet are regarded as contributing areas. The CIRFs are derived for each runoff mechanism through the numerical simulations with a spatially distributed hydrological model which accounts for spatially distributed runoff generation and routing, involving all three mechanisms, under multiple combinations of climate, soil and topographic properties. The advective and dispersive aspects of catchment’s runoff routing response are captured throughmore » the use of, respectively, the mean travel times and dimensionless forms of the CIRFs (i.e., scaled by their respective mean travel times). It was found that the CIRFs, upon non-dimensionalization, collapsed to common characteristic shapes, which could be explained in terms of the relative contributions of hillslope and channel network flows, and especially of the size of the runoff contributing areas. The contributing areas are themselves governed by the competition between drainage and recharge to the water table, and could be explained by a dimensionless drainage index which quantifies this competition. On the other hand, the mean residence times were vastly different in each case, and are governed by relative lengths of the flow pathways, flow velocities (and their variability) and the study also revealed simple indicators based on landscape properties that can explain their magnitudes in different catchments.« less
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Journal Article
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Journal Name: Water Resources Research, 50(12):9323–9342
Research Org:
Pacific Northwest National Laboratory (PNNL), Richland, WA (US)
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Country of Publication:
United States
runoff components, travel times, component instantaneous response function, distributed modeling