1) is global in nature, the local response to frequent large-scale meteorological forcing results from global phenomena acting at local scales in response to local conditions. Therefore, a wide variety of different hydrologic models exist, which are inadequate and falsifiable in all but the most simple situations. The practice of hydrologic modeling is greatly hampered by uncertainties in process and the overwhelming influence of heterogeneities ( Troch et al., 2009) and other poorly understood and ill-described natural phenomena. Typically, model selection tends to be more a function of familiarity than appropriateness ( Addor and Melsen, 2019). For this reason and others, the practice of hydrologic modeling has, in general, included too much reliance on mathematics at the expense of true knowledge, and suffers from a need for more rigorous evaluation of appropriateness ( Klemeš, 1997). ![]() Rather, there are many plausible solutions, depending on purpose and needed complexity. Because of the nature of environmental predictions, there is no single best model. Hydrologic modeling is used to answer environmental transport questions where water excess, scarcity, or dissolved or solid content is of primary importance ( Burges, 1986). ![]() Ogden, in Encyclopedia of Geology (Second Edition), 2021 Introduction Studies in similar runoff source areas could utilize this approach and create their specific surrogate models.Fred L. Thus, the small-scale nonlinear physics that determines the soil’s water flow rate before equilibrium is reached were irrelevant when the time step is one day. In our case, the quasi-static equilibrium was restored within a day. The surrogate model accurately predicted daily discharge and water table height using climatic data and a literature-based water retention function. Based on these observations, a simple spreadsheet-based surrogate model was developed to calculate the air-filled pore volume by accounting for daily precipitation and evaporation. Runoff was generated by saturation excess and equaled the rainfall minus the empty pore volume. The soil–water retention function determined the soil water distribution and the drainable porosity. It indicated that a quasi-static equilibrium had been established, in which the capillary pressure decreased linearly with depth to zero at the shallow groundwater. Measurements showed that the outflow was negligible 24 h after a rain event. Perched water table depths at five locations and the outflow were measured continuously. The site chosen was a 5.4-ha, periodically saturated runoff source area with a shallow perched water table and a humid temperate climate. This study seeks to find the soil physical parameters governing the hydrology of runoff source areas in humid climates and use them in a surrogate simulation model to predict the runoff and the perched water table height. The limitation is that input values are not known a priori. ![]() However, the self-organization of complex hydrological systems makes it possible to simplify watershed models by considering the landscape functions. Numerically modeling water fluxes in the source areas is quite complex. Understanding the hydrology of runoff source areas is crucial for predicting floods and evaluating chemical transport.
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