scholarly journals Simulating nitrogen long-term fate and transport processes at a regional scale with a surface and subsurface fully-coupled watershed model

2015 ◽  
Keyword(s):  
Regional Scale ◽  
Fate And Transport ◽  
Transport Processes ◽  
Watershed Model ◽  
Fully Coupled

Study on transport upscaling of Advection or Diffusion dominated process

2020 ◽  
Author(s):  
Zhilin Guo ◽  
Rich Pauloo ◽  
Graham E. Fogg ◽  
Christopher Henri ◽  
Chunmiao Zheng
Keyword(s):  
Mass Transfer ◽  
Transient Flow ◽  
Flow Direction ◽  
Regional Scale ◽  
Breakthrough Curves ◽  
Transport Processes ◽  
Late Time ◽  
Flow Conditions ◽  
Primary Flow

<p>Regional scale transport models are needed to support the long-term evaluation of groundwater quality and to develop management strategies aiming to prevent serious groundwater degradation. The transport dominant process, advection or diffusion, was identified for flow fields with different primary flow directions. The capacities of Multi-Rate Mass Transfer (MRMT) and adaptive Multi-rate Mass Transfer (aMMT), modified from MRMT by updating mass transfer rates with changing velocities, to adequately describe the main solute transport processes, including the capture of late-time tails under changing boundary conditions were evaluated. Advective-dispersive contaminant transport simulated in a 3D heterogeneous medium was used as a reference solution. Equivalent transport under homogeneous flow conditions was then evaluated by applying the MRMT or aMMT models for upscaling. Results indicated that for advection-dominated transport, both the MRMT and aMMT methods can upscale the anomalous transport dynamics affected by sub-grid heterogeneity under transient flow conditions. Whereas, for diffusion-dominated systems, the MRMT model failed to capture the tails of tracer breakthrough curves (BTCs) after the boundary condition changed, but the results from the aMMT model were significantly improved. However, if the overall flow direction changed, both MRMT and aMMT failed to represent the BTC tail generated by the heterogeneous system. In this study, an indicator that describe the primary flow direction in anisotropic heterogeneous domain was developed, and the relationship between the flow direction and the dominant transport process was investigated. The ranges of the indicator, within which the advection or diffusion is dominant, are determined. Therefore, this study not only show the capability of upscaling methods on describing the transport that dominated by different processes, but provides a guide on choosing upscaling methods in field site, which supports long-term management of groundwater.</p>

scholarly journals Integrating current and historical water chemistry data with long-term piezometric records to develop a regional-scale conceptual flow model: Las Salinas spring, Medina del Campo, Spain

2021 ◽  
Vol 34 ◽  
pp. 100781
Author(s):  
A. De la Hera-Portillo ◽  
J. López-Gutiérrez ◽  
C. Marín-Lechado ◽  
P. Martínez-Santos ◽  
A. Ruíz-Constán ◽  
...  
Keyword(s):  
Water Chemistry ◽  
Flow Model ◽  
Regional Scale ◽  
Chemistry Data

Assessment of groundwater contamination by chlorpyrifos using the PWC model in Valencia Region (Spain)

2021 ◽  
Author(s):  
Ricardo Pérez Indoval ◽  
Javier Rodrigo-Ilarri ◽  
Eduardo Cassiraga
Keyword(s):  
Reactive Transport ◽  
Management Practices ◽  
Fate And Transport ◽  
Environmental Modeling ◽  
Transport Processes ◽  
Negative Effects ◽  
Advection Dispersion ◽  
Agricultural Applications ◽  
Transformation Processes ◽  
Mass Transport Equation

<p>Chlorpyrifos is commoly used as an pesticide to control weeds and prevent nondesirable grow of algae, fungi and bacteria in many agricultural applications. Despite its highly negative effects on human health, environmental modeling of this kind of pesticide in the groundwater is not commonly done in real situations. Predicting the fate of pesticides released into the natural environment is necessary to anticipate and minimize adverse effects both at close and long distances from the contamination source. A number of models have been developed to predict the behavior, mobility, and persistence of pesticides. These models should account for key hydrological and agricultural processes, such as crop growth, pesticide application patterns, transformation processes and field management practices.</p><p>This work shows results obtained by the Pesticide Water Calculator (PWC) model to simulate the behavior of chlorpyrifos. PWC model is used as a standard pesticide simulation model in USA and in this work it has been used to  simulate the fate and transport of chlorpyrifos in the unsaturated zone of the aquifer. The model uses a whole set of parameters to solve a modified version of the mass transport equation considering the combined effect of advection, dispersion and reactive transport processes. PWC is used to estimate the daily concentrations of chlorpyrifos in the Buñol-Cheste aquifer in Valencia Region(Spain).</p><p>A whole set of simulation scenarios have been designed to perform a parameter sensitivity analysis. Results of the PWC model obtained in this study represents a crucial first step towards the development of a pesticide risk assessment in Valencia Region. Results show that numerical simulation is a valid tool for the analysis and prediction of the fate  and transport of pesticides in the groundwater.</p>

Long-term modeling of soil loss and fluvial transport processes in a mountainous semi-arid basin, southern Spain

2020 ◽  
pp. 1733-1740 ◽  
Author(s):  
A. Millares ◽  
J. Herrero ◽  
M. Bermúdez ◽  
J.F. Leiva ◽  
M. Cantalejo
Keyword(s):  
Soil Loss ◽  
Transport Processes ◽  
Southern Spain ◽  
Fluvial Transport ◽  
Semi Arid

scholarly journals Evaluating the Performance of a Forest Succession Model to Predict the Long-Term Dynamics of Tree Species in Mixed Boreal Forests Using Historical Data in Northern Ontario, Canada

Forests ◽  
2021 ◽  
Vol 12 (9) ◽  
pp. 1181
Author(s):  
Guy R. Larocque ◽  
F. Wayne Bell
Keyword(s):  
Populus Tremuloides ◽  
Boreal Forests ◽  
Forest Ecosystems ◽  
Forest Succession ◽  
Regional Scale ◽  
Abies Balsamea ◽  
Forest Growth ◽  
Northern Ontario ◽  
Phase Dynamics

Environmental concerns and economic pressures on forest ecosystems have led to the development of sustainable forest management practices. As a consequence, forest managers must evaluate the long-term effects of their management decisions on potential forest successional pathways. As changes in forest ecosystems occur very slowly, simulation models are logical and efficient tools to predict the patterns of forest growth and succession. However, as models are an imperfect representation of reality, it is desirable to evaluate them with historical long-term forest data. Using remeasured tree and stand data from three data sets from two ecoregions in northern Ontario, the succession gap model ZELIG-CFS was evaluated for mixed boreal forests composed of black spruce (Picea mariana [Mill.] B.S.P.), balsam fir (Abies balsamea [L.] Mill.), jack pine (Pinus banksiana L.), white spruce (Picea glauca [Moench] Voss), trembling aspen (Populus tremuloides Michx.), white birch (Betula papyrifera Marsh.), northern white cedar (Thuja occidentalis L.), American larch (Larix laricina [Du Roi] K. Koch), and balsam poplar (Populus balsamefera L.). The comparison of observed and predicted basal areas and stand densities indicated that ZELIG-CFS predicted the dynamics of most species consistently for periods varying between 5 and 57 simulation years. The patterns of forest succession observed in this study support gap phase dynamics at the plot scale and shade-tolerance complementarity hypotheses at the regional scale.

Global random walk solvers for fully coupled flow and transport in saturated/unsaturated porous media

2021 ◽  
Author(s):  
Nicolae Suciu ◽  
Davide Illiano ◽  
Alexander Prechtel ◽  
Florin Radu
Keyword(s):  
Finite Element ◽  
Porous Media ◽  
Random Walk ◽  
Transport Processes ◽  
Richards Equation ◽  
Unsaturated Porous Media ◽  
Coupled Flow ◽  
Flow And Transport ◽  
Coupled Flow And Transport ◽  
Fully Coupled

<p>We present new random walk methods to solve flow and transport problems in saturated/unsaturated porous media, including coupled flow and transport processes in soils, heterogeneous systems modeled through random hydraulic conductivity and recharge fields, processes at the field and regional scales. The numerical schemes are based on global random walk algorithms (GRW) which approximate the solution by moving large numbers of computational particles on regular lattices according to specific random walk rules. To cope with the nonlinearity and the degeneracy of the Richards equation and of the coupled system, we implemented the GRW algorithms by employing linearization techniques similar to the <em>L</em>-scheme developed in finite element/volume approaches. The resulting GRW <em>L</em>-schemes converge with the number of iterations and provide numerical solutions that are first-order accurate in time and second-order in space. A remarkable property of the flow and transport GRW solutions is that they are practically free of numerical diffusion. The GRW solvers are validated by comparisons with mixed finite element and finite volume solvers in one- and two-dimensional benchmark problems. They include Richards' equation fully coupled with the advection-diffusion-reaction equation and capture the transition from unsaturated to saturated flow regimes.  For completeness, we also consider decoupled flow and transport model problems for saturated aquifers.</p>

Forecasting long-term shoreline evolution in highly antrhopized coastal areas

2021 ◽  
Author(s):  
Moisés Álvarez-Cuesta ◽  
Alexandra Toimil ◽  
Iñigo J. Losada
Keyword(s):  
Climate Models ◽  
Regional Scale ◽  
Mediterranean Coast ◽  
Multiple Time Scales ◽  
Multiple Time ◽  
Coastal Zones ◽  
Climate Data ◽  
Shoreline Evolution ◽  
Automated Technique

<p>A new numerical model for addressing long-term coastline evolution on a local to regional scale on highly anthropized coasts is presented. The model, named IH-LANS (Long-term ANthropized coastlines Simulation tool), is validated over the period 1990-2020 and applied to obtain an ensemble of end-of-century shoreline evolutions. IH-LANS combines a hybrid (statistical-numerical) deep-water propagation module and a shoreline evolution model. Longshore and cross-shore processes are integrated together with the effects of man-made interventions. For the ease of calibration, an automated technique is implemented to assimilate observations. The model is applied to a highly anthropized 40 km stretch located along the Spanish Mediterranean coast. High space-time resolution climate data and satellite-derived shorelines are used to drive IH-LANS. Observed shoreline evolution (<10 meters of root mean square error, RMSE) is successfully represented while accounting for the effects of nourishments and the construction and removal of groynes, seawalls and breakwaters over time. Then, in order to drive the ensemble of end-of-century shoreline evolutions, wave and water level projections downscaled from different climate models for various emissions scenarios are employed to force the calibrated model. From the forecasted shoreline time-series, information from multiple time-scales is unraveled yielding valuable information for coastal planners. The efficiency and accuracy of the model make IH-LANS a powerful tool for management and climate change adaptation in coastal zones.</p>

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