Development and Application of an Interactive Coupling Rainfall-Runoff Model According to Soil Texture

In this study, we developed a model that simulates surface and subsurface flows for rainfall-runoff analyses using an interactive coupling method. To characterize the interaction between the surface and subsurface flows, we studied the coupling analysis model. The proposed model was designed following comparisons with existing models. For the analysis of the surface and subsurface flows, a governance equation was constructed. The goodness of fit of the model was also tested. To examine the sensitivity of the input parameters, simulations were performed while changing the major parameters of the model according to the soil texture. The developed model showed high applicability to actual watersheds after adjustment of the parameters. This model can be applied to the extension module for channel analysis; therefore, it can be used efficiently in urbanized watersheds wherein the upstream and downstream parts are pervious and impervious watersheds, respectively.

Physical Modelling of Wave-Driven Groundwater Flows in a Sand Beach Using Transparent Soil

<p>The characteristics of waves breaking on a beach can have significant impacts on how water infiltrates and influences coastal groundwater flows. The effects of continuous wave action on groundwater in coastal aquifers is important to understand to predict subsurface flows in beaches. This investigation will study how coastal wave dynamics in the swash zone impact the groundwater table using physical laboratory modelling and detailed image analysis that allows for high density spatial and temporal resolution degree of saturation measurements using unsaturated transparent soil as illustrated in Figure 1. Transparent soil methods will be applied to observe simulated wavedriven subsurface flows in a cross-section of a sandy beach. The objective of this study is to extend the current knowledge of how waves drive groundwater fluctuations by experimentally quantifying the time and length scales of flow within a beach.</p><p><img src="https://contentmanager.copernicus.org/fileStorageProxy.php?f=gnp.37e54696a70064314111161/sdaolpUECMynit/12UGE&app=m&a=0&c=abbe0b116f2bfbac393fa27b5fbd2c00&ct=x&pn=gnp.elif&d=1" alt=""></p><p>Figure 1.</p><p>Transparent soil can be used to experimentally measure subsurface fluid/air flow and is used to quantify spatial and temporal saturation conditions every few seconds during an experiment. Digital image analysis allows for millimeter spatial resolution throughout the domain. Transparent soil is formed are applied by using crushed quartz rock in place of sand and an oil mixture with an identical refractive index to the grains (Peters et al. 2011). When the pores of the crushed quartz are saturated with the oil, the mixture appears transparent. When dry, the crushed quartz appears opaque. Change in colour is quantified, through digital image analysis, to measure degree of saturation throughout the domain (Sills et al. 2017)</p><p>This study applied transparent soil techniques in its first application to understand coastal processes by observing how incident waves infiltrate beaches and induce groundwater table fluctuations. Four tests are reported with variations in beach slope and wave properties, and the images are processed to quantify spatial and temporal degree of saturation variation. In each test, the swash interacted with the groundwater table by forming a partially saturated zone above the saturated zone of the beach. This partially saturated mound followed a consistent shape, that varied in size and rate of change primarily due to beach slope. The partially saturated zone is formed by a combination of capillary forces and downward infiltration, forming a continuously dampened zone in the beach. Finally, the results show a strong inverse correlation between the wetting front formed in a beach and the slope of the swash zone. Steeper slopes displayed much larger partially saturated mounds and were observed to do so in a slower manner compared to flatter slopes.</p><p> </p><p>Peters, S. B., Siemens, G., and Take, W. A. (2011). “Characterization of Transparent Soil for Unsaturated Applications.” Geotechnical Testing Journal, 34(5).</p><p>Sills, L.-A. K., Mumford, K. G., and Siemens, G. A. (2017). “Quantification of Fluid Saturations in Transparent Porous Media.” Vadose Zone Journal, 16(2), 1–9.</p>

The era of infiltration

Inspired by a quotation from Howard Cook in 1946, this paper traces the evolution of the infiltration theory of runoff from the work of Robert Horton and LeRoy Sherman in the 1930s to the early digital computer models of the 1970s and 1980s. The reasons for the popularity of the infiltration theory are considered and its impact on the way in which hydrological responses were perceived by several generations of hydrologists. Reconsideration of the perceptual model for many catchments, partly as a result of the greater appreciation of the contribution of subsurface flows to the hydrograph indicated by tracer studies, suggests a more precise utilisation of hydrological terms and, in particular, that the use of runoff and surface runoff should be avoided.

Modelling ground displacement and gravity changes with the MUFITS simulator

We present an extension of the MUFITS reservoir simulator for modelling the ground displacement and gravity changes associated with subsurface flows in geologic porous media. Two different methods are implemented for modelling the ground displacement. The first approach is simple and fast and is based on an analytical solution for the extension source in a semi-infinite elastic medium. Its application is limited to homogeneous reservoirs with a flat Earth surface. The second, more comprehensive method involves a one-way coupling of MUFITS with geomechanical code presented for the first time in this paper. We validate the accuracy of the development by considering a benchmark study of hydrothermal activity at Campi Flegrei (Italy). We investigate the limitations of the first approach by considering domains for the geomechanical problem that are larger than those for the fluid flow. Furthermore, we present the results of more complicated simulations in a heterogeneous subsurface when the assumptions of the first approach are violated. We supplement the study with the executable of the simulator for further use by the scientific community.