Abstract Hydrologists and engineers may choose from a range of semidistributed rainfall‐runoff models such as VIC, PDM, and TOPMODEL, all of which predict runoff from a distribution of watershed properties. However, these models are not easily compared to event‐based data and are missing ready‐to‐use analytical expressions that are analogous to the SCS‐CN method. The SCS‐CN method is an event‐based model that describes the runoff response with a rainfall‐runoff curve that is a function of the cumulative storm rainfall and antecedent wetness condition. Here we develop an event‐based probabilistic storage framework and distill semidistributed models into analytical, event‐based expressions for describing the rainfall‐runoff response. The event‐based versions called VICx, PDMx, and TOPMODELx also are extended with a spatial description of the runoff concept of “prethreshold” and “threshold‐excess” runoff, which occur, respectively, before and after infiltration exceeds a storage capacity threshold. For total storm rainfall and antecedent wetness conditions, the resulting ready‐to‐use analytical expressions define the source areas (fraction of the watershed) that produce runoff by each mechanism. They also define the probability density function (PDF) representing the spatial variability of runoff depths that are cumulative values for the storm duration, and the average unit area runoff, which describes the so‐called runoff curve. These new event‐based semidistributed models and the traditional SCS‐CN method are unified by the same general expression for the runoff curve. Since the general runoff curve may incorporate different model distributions, it may ease the way for relating such distributions to land use, climate, topography, ecology, geology, and other characteristics.
Abstract Field hydrology is on the decline. Meanwhile, the need for new field‐derived insight into the age, origin and pathway of water in the headwaters, where most runoff is generated, is more needed than ever. Water Resources Research (WRR) has included some of the most influential papers in field‐based runoff process understanding, particularly in the formative years when the knowledge base was developing rapidly. Here we take advantage of this 50th anniversary of the journal to highlight a few of these important field‐based papers and show how field scientists have posed strong and sometimes outrageous hypotheses—approaches so needed in an era of largely model‐only research. We chronicle the decline in field work and note that it is not only the quantity of field work that is diminishing but its character is changing too: from discovery science to data collection for model parameterization. While the latter is a necessary activity, the loss of the former is a major concern if we are to advance the science of watershed hydrology. We outline a vision for field research to seek new fundamental understanding, new mechanistic explanations of how watershed systems work, particularly outside the regions of traditional focus.
Southwestern Quebec lies between the boreal forest to the north and the Ottawa River in the west and in the south. Its mixed and deciduous forests are high in biodiversity but are virtually unprotected. At risk is the fate of the Dumoine—the only intact watershed left in western Quebec. The Dumoine River watershed is home to a representative sample of native wildlife, as well as the largest remnant of intact southern boreal forest in the province of Quebec. It represents a wealth of soil, water, and other important natural resources.
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