Watershed Scale Physically Based Water Flow, Sediment and Nutrient Dynamic Modeling System

2013 ◽  
pp. 145-171
Author(s):  
Billy E. Johnson ◽  
Zhonglong Zhang ◽  
Charles W. Downer
Keyword(s):  
Water Flow ◽  
Dynamic Modeling ◽  
Watershed Scale ◽  
Nutrient Dynamic ◽  
Physically Based

The Daisy agroecological system model: A physically based model for preferential water flow and solute transport in drained agricultural fields

2021 ◽  
Author(s):  
Efstathios Diamantopoulos ◽  
Maja Holbak ◽  
Per Abrahamsen
Keyword(s):  
Solute Transport ◽  
Water Flow ◽  
Preferential Flow ◽  
Column Experiment ◽  
Soil Matrix ◽  
Physically Based Model ◽  
Physically Based ◽  
Rapid Transport ◽  
Preferential Water

<p>Preferential water flow and solute transport in agricultural systems affects not only the quality of groundwater but also the quality of surface waters like streams and lakes. This is due to the rapid transport of agrochemicals, immediately after application, through subsurface drainpipes and surface water. Experimental evidence attributes this to the occurrence of continuously connected pathways, connecting the soil surface directly with the drainpipes. We developed a physically-based model describing preferential flow and transport in biopores and implemented it in the agroecological model Daisy. The model simulates the often observed rapid transport of chemicals from   the upper soil layers to the drainpipes or to deeper layers of the soil matrix. Based on field investigations, biopores with specific characteristics can be parameterized as classes with different vertical and horizontal distributions. The model was tested against experimental data from a column experiment with an artificial biopore and showed good results in simulating preferential flow dynamics. We illustrate the performance of the new approach, by conducting five simulations assuming a two-dimensional simulation domain with different biopore parametrizations, from none to several different classes. The simulation results agreed with experimental observations reported in the literature, indicating rapid transport from the soil to the drainpipes. Furthermore, the different biopore parametrizations resulted in distinctly different leaching patterns, raising the expectation that biopore properties could be estimated or constrained based on observed leaching data and direct measurements.</p>

scholarly journals Development of physically based liquid water schemes for Greenland firn-densification models

2019 ◽  
Vol 13 (7) ◽  
pp. 1819-1842 ◽  
Author(s):  
Vincent Verjans ◽  
Amber A. Leeson ◽  
C. Max Stevens ◽  
Michael MacFerrin ◽  
Brice Noël ◽  
...  
Keyword(s):  
Water Flow ◽  
Liquid Water ◽  
Preferential Flow ◽  
Greenland Ice Sheet ◽  
Single Domain ◽  
Richards Equation ◽  
Retention Capacity ◽  
Water Percolation ◽  
Physically Based ◽  
Dual Domain

Abstract. As surface melt is increasing on the Greenland Ice Sheet (GrIS), quantifying the retention capacity of the firn layer is critical to linking meltwater production to meltwater runoff. Firn-densification models have so far relied on empirical approaches to account for the percolation–refreezing process, and more physically based representations of liquid water flow might bring improvements to model performance. Here we implement three types of water percolation schemes into the Community Firn Model: the bucket approach, the Richards equation in a single domain and the Richards equation in a dual domain, which accounts for partitioning between matrix and fast preferential flow. We investigate their impact on firn densification at four locations on the GrIS and compare model results with observations. We find that for all of the flow schemes, significant discrepancies remain with respect to observed firn density, particularly the density variability in depth, and that inter-model differences are large (porosity of the upper 15 m firn varies by up to 47 %). The simple bucket scheme is as efficient in replicating observed density profiles as the single-domain Richards equation, and the most physically detailed dual-domain scheme does not necessarily reach best agreement with observed data. However, we find that the implementation of preferential flow simulates ice-layer formation more reliably and allows for deeper percolation. We also find that the firn model is more sensitive to the choice of densification scheme than to the choice of water percolation scheme. The disagreements with observations and the spread in model results demonstrate that progress towards an accurate description of water flow in firn is necessary. The numerous uncertainties about firn structure (e.g. grain size and shape, presence of ice layers) and about its hydraulic properties, as well as the one-dimensionality of firn models, render the implementation of physically based percolation schemes difficult. Additionally, the performance of firn models is still affected by the various effects affecting the densification process such as microstructural effects, wet snow metamorphism and temperature sensitivity when meltwater is present.

Field measurement of soil water repellency and its impact on water flow under different vegetation

Biologia ◽  
2007 ◽  
Vol 62 (5) ◽  
Author(s):  
L’ubomír Lichner ◽  
Paul Hallett ◽  
Debbie Feeney ◽  
Olívia Ďugová ◽  
Miloslav Šír ◽  
...  
Keyword(s):  
Hydraulic Conductivity ◽  
Forest Soil ◽  
Soil Water ◽  
Water Flow ◽  
Water Repellency ◽  
Water Repellent ◽  
Dry Spell ◽  
Physically Based ◽  
Low Levels ◽  
The Impact

AbstractNumerous recent laboratory studies have shown that vegetation can influence soil water flow by inducing very low levels of water repellency. In this study we extended on this previous research by developing a field-based test using a miniature infiltrometer to assess low levels of water repellency from physically based measurements of liquid flow in soil. The field-based test was verified through a simple laboratory experiment and then applied to determine the impact of vegetation and antecedent soil water content. The soil hydraulic properties determined were hydraulic conductivity, sorptivity, as well as the persistence and index of water repellency. Tests were conducted following a dry spell and wet spell on (1) forest soil (0 cm depth), (2) glade soil (0 cm depth) and (3) glade soil (50 cm depth). It was found that both the persistence and index of water repellency, R, decreased in the order as follows: forest soil > glade soil (0 cm) > glade soil (50 cm) for both dry and wet spell. The range of values of R was 0.28 (wettable) to 360 (highly water repellent), which affected hydraulic conductivity k r(−2 cm). R increased and hence k r(−2 cm) decreased in the order: forest soil < glade soil (0 cm) < glade soil (50 cm) for both the dry and wet spell. There were clear interactions between vegetation and changes to water flow caused by presence of repellency.

Dynamic Modeling of Organic Rankine Cycle Power Systems

2013 ◽  
Vol 135 (4) ◽  
Author(s):  
Francesco Casella ◽  
Tiemo Mathijssen ◽  
Piero Colonna ◽  
Jos van Buijtenen
Keyword(s):  
Power Systems ◽  
Dynamic Modeling ◽  
Power Plants ◽  
Dynamic Models ◽  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Operating Conditions ◽  
Design And Optimization ◽  
Physically Based ◽  
Key Variables

New promising applications of organic Rankine cycle (ORC) technology, e.g., concentrated solar power, automotive heat recovery and off-grid distributed electricity generation, demand for more dynamic operation of ORC systems. Accurate physically-based dynamic modeling plays an important role in the development of such systems, both during the preliminary design as an aid for configuration and equipment selection, and for control design and optimization purposes. A software library of modular reusable dynamic models of ORC components has been developed in the MODELICA language and is documented in the paper. The model of an exemplary ORC system, namely the 150 kWe Tri-O-Gen ORC turbogenerator is validated using few carefully conceived experiments. The simulations are able to reproduce steady-state and dynamic measurements of key variables, both in nominal and in off-design operating conditions. The validation of the library opens doors to control-related studies, and to the development of more challenging dynamic applications of ORC power plants.

scholarly journals Röthlisberger channel theory: its origins and consequences

2010 ◽  
Vol 56 (200) ◽  
pp. 1079-1086 ◽  
Author(s):  
Joseph S. Walder
Keyword(s):  
Surface Water ◽  
Conceptual Model ◽  
Water Flow ◽  
Keen Interest ◽  
Surface Water Hydrology ◽  
Physically Based ◽  
Flow Through ◽  
First Time ◽  
Channel Theory

AbstractThe theory of channelized water flow through glaciers, most commonly associated with the names of Hans Röthlisberger and Ron Shreve and their 1972 papers in the Journal of Glaciology, was developed at a time when interest in glacier-bed processes was expanding, and the possible relationship between glacier sliding and water at the bed was becoming of keen interest. The R-channel theory provided for the first time a physically based conceptual model of water flow through glaciers. The theory also marks the emergence of glacier hydrology as a glaciological discipline with goals and methods distinct from those of surface-water hydrology.

Modeling Ground Water Flow in Alluvial Mountainous Catchments on a Watershed Scale

Ground Water ◽  
2008 ◽  
Vol 46 (5) ◽  
pp. 695-705 ◽  
Author(s):  
Jens Wolf ◽  
Roland Barthel ◽  
Jürgen Braun
Keyword(s):  
Ground Water ◽  
Water Flow ◽  
Watershed Scale ◽  
Ground Water Flow ◽  
Mountainous Catchments

Numerical calculation of secondary discharge peak from a small watershed using a physically based watershed scale infiltration simulation

2007 ◽  
Vol 12 (3) ◽  
pp. 201-208 ◽  
Author(s):  
Katsushige Shiraki ◽  
Yoshiki Shinomiya ◽  
Rieko Urakawa ◽  
Hiroto Toda ◽  
Kikuo Haibara
Keyword(s):  
Numerical Calculation ◽  
Watershed Scale ◽  
Small Watershed ◽  
Physically Based

scholarly journals BrAHMs V1.0: a fast, physically based subglacial hydrology model for continental-scale application

2018 ◽  
Vol 11 (8) ◽  
pp. 3497-3513 ◽  
Author(s):  
Mark Kavanagh ◽  
Lev Tarasov
Keyword(s):  
Water Flow ◽  
Regime Switching ◽  
Water Pressure ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Staggered Grid ◽  
Overburden Pressure ◽  
Continental Scale ◽  
Hydrology Model ◽  
Physically Based

Abstract. We present BrAHMs (BAsal Hydrology Model): a physically based basal hydrology model which represents water flow using Darcian flow in the distributed drainage regime and a fast down-gradient solver in the channelized regime. Switching from distributed to channelized drainage occurs when appropriate flow conditions are met. The model is designed for long-term integrations of continental ice sheets. The Darcian flow is simulated with a robust combination of the Heun and leapfrog–trapezoidal predictor–corrector schemes. These numerical schemes are applied to a set of flux-conserving equations cast over a staggered grid with water thickness at the centres and fluxes defined at the interface. Basal conditions (e.g., till thickness, hydraulic conductivity) are parameterized so the model is adaptable to a variety of ice sheets. Given the intended scales, basal water pressure is limited to ice overburden pressure, and dynamic time stepping is used to ensure that the Courant–Friedrichs–Lewy (CFL) condition is met for numerical stability. The model is validated with a synthetic ice sheet geometry and different bed topographies to test basic water flow properties and mass conservation. Synthetic ice sheet tests show that the model behaves as expected with water flowing down gradient, forming lakes in a potential well or reaching a terminus and exiting the ice sheet. Channel formation occurs periodically over different sections of the ice sheet and, when extensive, displays the arborescent configuration expected of Röthlisberger channels. The model is also shown to be stable under high-frequency oscillatory meltwater inputs.

Dynamic Modeling and Simulation of Saturators for Humid Air Turbine Cycle

2004 ◽  
Author(s):  
Yongwen Liu ◽  
Ming Su
Keyword(s):  
Modeling And Simulation ◽  
Water Flow ◽  
Dynamic Modeling ◽  
Gas Flow ◽  
Simulation Software ◽  
Inlet Temperature ◽  
Humid Air ◽  
Spray Tower ◽  
Air Turbine ◽  
Number Of Segments

This paper describes the dynamic modeling and simulation of spray tower saturator using one-dimensional flow control volume method, as a part of study for dynamic modeling of the humid air turbine cycle. The mass, energy and momentum exchanges between gas flow and water flow, as well as their conservations, are taken into consideration. Separate modules are built for gas flow and water flow, and are put into an application library of EASY5, which is general-purpose simulation software. Modular structure and mathematical causality needed by explicit modeling are maintained for the modules in the application library. Then spray tower saturators can be divided into arbitrary number of segments, and each one is modeled by a gas flow module and a water flow module. To exemplify the modeling method, two dynamic models with different number of segments are built for a spray tower saturator. For steady state analysis, quantity variations with tower height at design point are illustrated, and the results of the two models are compared. For dynamic analysis, two dynamic simulations are run to obtain response to 10% step increase of the gas and water inlet temperature respectively. Estimation of the dominant time constants by linearized model is also discussed.

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