The role of macropores and multi-resolution soil survey datasets for distributed surface–subsurface flow modeling

Improving the representation of hydrologic processes in Earth System Models

“…Table 3 identifies candidate areas to improve the representation of hydrologic processes in land models. The key areas are (1) improve simulations of the storage and transmission of water in the soil matrix, obtained through (a) implementing the mixed form of Richards' equation [Celia et al, 1990;Maxwell and Miller, 2005] and (b) explicitly representing macropore flow [Beven and Germann, 1982;Weiler, 2005;Nimmo, 2010;Yu et al, 2014]; (2) improve representation of hydraulic gradients throughout the soil-plantatmosphere continuum to improve simulations of root water uptake and evapotranspiration [Baldocchi and Meyers, 1998;Mackay et al, 2003;Bonan et al, 2014]; (3) improve representation of groundwater dynamics across a hierarchy of spatial scales, including improving ''among grid'' and ''within grid'' groundwater representations [Famiglietti and Wood, 1994;Troch et al, 2003;Miguez-Macho et al, 2007]; and (4) improve simulations of streamflow, by explicitly representing stream-aquifer interactions and improving parameterizations of channel/floodplain routing [Qu and Duffy, 2007;Shen and Phanikumar, 2010;MiguezMacho and Fan, 2012a;Pappenberger et al, 2012]. Underpinning all of these areas is the need to improve data sets on geophysical attributes, especially data on bedrock depth and permeability [Tesfa et al, 2009;Fan et al, 2015] and data sets on the physical characteristics of rivers [Getirana et al, 2013;Mersel et al, 2013;Gleason and Smith, 2014].…”

“…Moving forward, there is an opportunity to improve representation of storage and transmission of soil water in land models, while maintaining computational efficiency in mind, by (1) explicitly representing variably saturated flow, as is possible in the mixed form of Richards' equation [Celia et al, 1990;Maxwell and Miller, 2005;Kumar et al, 2009], to improve simulations of shallow groundwater dynamics; (2) explicitly represent airflow (vapor diffusion) through the soil to improve simulations of bare soil evaporation [Parker et al, 1987;Painter, 2011;Zeng et al, 2011;Smits et al, 2012]; and (3) explicitly represent macropore flow to simulate the nonuniform wetting of the soil matrix and the heterogeneity of flow paths at larger spatial scales Germann, 1981, 1982;SimunEk et al, 2003;Weiler, 2005;McDonnell et al, 2007;Maxwell and Kollet, 2008a;Nimmo, 2010;Yu et al, 2014]. Some integrated models have incorporated these processes-for example, the coupling of ParFlow and CLM represents threedimensional variably saturated flow and has now been applied at continental scales [Maxwell et al, 2015], CLM now parameterizes the diffusion of water vapor through a dry surface layer to improve simulations of bare soil evaporation [Swenson and Lawrence, 2014], and the LM3 model has a simple representation of macropores .…”

Scale dependent parameterization of soil hydraulic conductivity in 3D simulation of hydrological processes in a forested headwater catchment

“…Topography is one of the main factors governing hydrological dynamics and a change of scale (grid size) in topographic discretization means that hydraulic parameters, such as saturated soil hydraulic conductivity (K s ) must be upscaled/recalibrated (Grayson and Blöschl, 2000). Many modelling studies demonstrated the importance of correct parametrization of K s and preferential flow on the simulation of soil moisture, evapotranspiration, groundwater dynamics, runoff, solute transport and erosion (Bogena and Diekkrüger, 2002;Simunek et al, 2003;Weiler, 2005;Maxwell and Kollet, 2008;Yu et al, 2014).…”

Flood response for the watersheds of the Fernow Experimental Forest in the central Appalachians

“…Important themes include mechanisms promoting ''hydrologic connectivity'' [Hopp and McDonnell, 2009;Wienhoefer and Zehe, 2014;Kim, 2014;Harel and Mouche, 2014;Bachmair and Weiler, 2014], threshold-dependent runoff production mechanisms [Tromp-van Meerveld and McDonnell, 2006] and the role of spatial heterogeneity of soil properties for runoff production [Harel and Mouche, 2014;Yu et al, 2014]. Significant progress has also been made in linking hillslope processes to catchment scale processes [McGuire et al, 2005;Bachmair and Weiler, 2014].…”