scholarly journals Simulation of Flow and Agricultural Non-Point Source Pollutant Transport in a Tibetan Plateau Irrigation District

Water ◽  
2019 ◽  
Vol 11 (1) ◽  
pp. 132 ◽  
Author(s):  
Yuqing Li ◽  
Zuhao Zhou ◽  
Kang Wang ◽  
Chongyu Xu
Keyword(s):  
Transport Processes ◽  
Lateral Flow ◽  
Irrigation District ◽  
Distributed Model ◽  
Flow And Transport ◽  
Growing Period ◽  
Subsurface Lateral Flow ◽  
Nitrogen Concentrations ◽  
Simulated Flow ◽  
Highland Barley

Flow and transport processes in soil and rock play a critical role in agricultural non-point source pollution (ANPS) loads. In this study, we investigated the ANPS load discharged into rivers from an irrigation district in the Tibetan Plateau and simulated ANPS load using a distributed model. Experiments were conducted for two years to measure soil water content and nitrogen concentrations in soil and the quality and quantity of subsurface lateral flow in the rock and at the drainage canal outlet during the highland barley growing period. A distributed model, in which the subsurface lateral flow in the rock was described using a stepwise method, was developed to simulate flow and ammonium nitrogen (NH4+-N) and nitrate nitrogen (NO3−-N) transport processes. Sobol’s method was used to evaluate the sensitivity of simulated flow and transport processes to the model inputs. The results showed that with a 21.2% increase of rainfall and irrigation in the highland barley growing period, the average NH4+-N and NO3−-N concentrations in the soil layer decreased by 10.8% and 14.3%, respectively, due to increased deep seepage. Deep seepage of rainfall water accounted for 0–52.4% of total rainfall, whereas deep seepage of irrigation water accounted for 36.6–45.3% of total irrigation. NH4+-N and NO3−-N discharged into the drainage canal represented 19.9–30.4% and 19.4–26.7% of the deep seepage, respectively. The mean Nash–Sutcliffe coefficient value, which was close to 0.8, and the lowest values of root mean square errors, the fraction bias, and the fractional gross error indicated that the simulated flow rates and nitrogen concentrations using the proposed method were very accurate. The Sobol’s sensitivity analysis results demonstrated that subsurface lateral flow had the most important first-order and total-order effect on the simulated flow and NH4+-N and NO3−-N concentrations at the surface drainage outlet.

scholarly journals Simulation of Flow and Agricultural Non-Point Source Pollutant Transport in a Tibetan Plateau Irrigation District

2018 ◽  
Author(s):  
Yuqing Li ◽  
Zuhao Zhou ◽  
Kang Wang ◽  
Chongyu Xu
Keyword(s):  
Transport Processes ◽  
Lateral Flow ◽  
Irrigation District ◽  
Distributed Model ◽  
Flow And Transport ◽  
Growing Period ◽  
Surface Drainage ◽  
Subsurface Lateral Flow ◽  
Simulated Flow ◽  
Highland Barley

Flow and transport processes in soil and rock play a critical role in agricultural non-point source pollution (ANSP) loads. In this study, we investigated the ANPS load discharged into rivers from an irrigation district in the Tibetan Plateau, and simulated ANPS load using a distributed model involving detailed descriptions of flow and ANPS transport and transformation processes in the soil and rock. Experiments were conducted for two years to measure soil water content and nitrogen concentrations and the quality and quantity of lateral flow in the rock and at the drainage canal outlet during the highland barley growing period. A distributed model, in which the subsurface lateral flow was described using a step-wise method, was developed to simulate flow and ammonium nitrogen and nitrate nitrogen transport. Sobol’s method was used to evaluate the sensitivity of simulated flow and transport processes to model inputs. The results showed that, with a 21.2% increase of rainfall and irrigation in the highland barley growing period, the average NH4+-N and NO3--N concentrations in the soil layer decreased by 10.8% and 14.3%, respectively, due to increased deep seepage. Deep seepage of rainfall water accounted for 0–52.4% of total rainfall, whereas deep seepage of irrigation water accounted for 36.6–45.3% of total irrigation. NH4+-N and NO3--N discharged into the drainage channel represented 19.9–30.4% and 19.4–26.7% of the deep seepage, respectively. The mean Nash-Sutcliffe coefficients, root mean square errors, and cumulative deviations between the measured and simulated flow rates and NH4+-N and NO3--N concentrations at the surface drainage canal outlet were 0.694, 0.081, and 0.242, respectively, indicating that the proposed method can effectively describe the hydrological and ANPS pollution migration in the plateau irrigation zone. The Sobol’ sensitivity analysis results demonstrated that subsurface lateral flow had the most important first order and total effect on the simulated flow and NH4+-N and NO3--N concentrations at the surface drainage outlet.

scholarly journals Simulation and validation of concentrated subsurface lateral flow paths in an agricultural landscape

2009 ◽  
Vol 13 (8) ◽  
pp. 1503-1518 ◽  
Author(s):  
Q. Zhu ◽  
H. S. Lin
Keyword(s):  
Agricultural Landscape ◽  
Subsurface Flow ◽  
Lateral Flow ◽  
Soil Profiles ◽  
Clay Layer ◽  
Large Area ◽  
Flow Paths ◽  
Subsurface Lateral Flow ◽  
Simulated Flow ◽  
Water Flow Paths

Abstract. The importance of soil water flow paths to the transport of nutrients and contaminants has long been recognized. However, effective means of detecting concentrated subsurface flow paths in a large landscape are still lacking. The flow direction and accumulation algorithm based on single-direction flow algorithm (D8) in GIS hydrologic modeling is a cost-effective way to simulate potential concentrated flow paths over a large area once relevant data are collected. This study tested the D8 algorithm for simulating concentrated lateral flow paths at three interfaces in soil profiles in a 19.5-ha agricultural landscape in central Pennsylvania, USA. These interfaces were (1) the interface between surface plowed layers of Ap1 and Ap2 horizons, (2) the interface with subsoil water-restricting clay layer where clay content increased to over 40%, and (3) the soil-bedrock interface. The simulated flow paths were validated through soil hydrologic monitoring, geophysical surveys, and observable soil morphological features. The results confirmed that concentrated subsurface lateral flow occurred at the interfaces with the clay layer and the underlying bedrock. At these two interfaces, the soils on the simulated flow paths were closer to saturation and showed more temporally unstable moisture dynamics than those off the simulated flow paths. Apparent electrical conductivity in the soil on the simulated flow paths was elevated and temporally unstable as compared to those outside the simulated paths. The soil cores collected from the simulated flow paths showed significantly higher Mn content at these interfaces than those away from the simulated paths. These results suggest that (1) the D8 algorithm is useful in simulating possible concentrated subsurface lateral flow paths if used with appropriate threshold value of contributing area and sufficiently detailed digital elevation model (DEM); (2) repeated electromagnetic surveys can reflect the temporal change of soil water storage and thus is a useful indicator of possible subsurface flow path over a large area; and (3) observable Mn distribution in soil profiles can be used as a simple indicator of water flow paths in soils and over the landscape; however, it does require sufficient soil sampling (by excavation or augering) to possibly infer landscape-scale subsurface flow paths. In areas where subsurface interface topography varies similarly with surface topography, surface DEM can be used to simulate potential subsurface lateral flow path reasonably so the cost associated with obtaining depth to subsurface water-restricting layer can be minimized.

scholarly journals Simulation and validation of subsurface lateral flow paths in an agricultural landscape

2009 ◽  
Vol 6 (2) ◽  
pp. 2893-2929 ◽  
Author(s):  
Q. Zhu ◽  
H. S. Lin
Keyword(s):  
Soil Water ◽  
Water Flow ◽  
Agricultural Landscape ◽  
Lateral Flow ◽  
Soil Profiles ◽  
Clay Layer ◽  
Flow Paths ◽  
Subsurface Lateral Flow ◽  
Simulated Flow ◽  
Water Flow Paths

Abstract. The importance of soil water flow paths to the transport of nutrients and contaminants has long been recognized. However, effective means of detecting subsurface flow paths in a large landscape is still lacking. The flow direction and accumulation algorithm in GIS hydrologic modeling is a cost effective way to simulate potential flow paths over a large area. This study tested this algorithm for simulating lateral flow paths at three interfaces in soil profiles in a 19.5-ha agricultural landscape in central Pennsylvania, USA. These interfaces were (1) the surface plowed layers (Ap1 and Ap2 horizons) interface, (2) the interface with subsoil clay layer where clay content increased to over 40%, and (3) soil-bedrock interface. The simulated flow paths were validated through soil hydrologic monitoring, geophysical surveys, and observable soil morphological features. The results confirmed that subsurface lateral flow occurred at the interfaces with the clay layer and the underlying bedrock. At these two interfaces, the soils on the simulated flow paths were closer to saturation and showed more temporally unstable moisture dynamics than those off the simulated flow paths. Apparent electrical conductivity in the soil on the simulated flow paths was elevated and temporally unstable as compared to those outside the simulated paths. The soil cores collected from the simulated flow paths showed significantly higher Mn contents at these interfaces than those away from the simulated paths. These results suggest that (1) the algorithm is useful in simulating possible subsurface lateral flow paths if used appropriately with sufficiently detailed digital elevation model; (2) repeated electromagnetic surveys can reflect the temporal change of soil water storage and thus is an indicator of soil water movement over the landscape; and (3) observable Mn content in soil profiles can be used as a simple indicator of water flow paths in soils and over the landscape.

scholarly journals A Novel Physically Based Distributed Model for Irrigation Districts’ Water Movement

Water ◽  
2021 ◽  
Vol 13 (5) ◽  
pp. 692
Author(s):  
Boyu Mi ◽  
Haorui Chen ◽  
Shaoli Wang ◽  
Yinlong Jin ◽  
Jiangdong Jia ◽  
...  
Keyword(s):  
Soil Water ◽  
Water Movement ◽  
Regional Scale ◽  
Irrigation District ◽  
Distributed Model ◽  
Efficiency Coefficient ◽  
Good Correspondence ◽  
Groundwater Movement ◽  
Irrigation Districts ◽  
Physically Based

The water movement research in irrigation districts is important for food production. Many hydrological models have been proposed to simulate the water movement on the regional scale, yet few of them have comprehensively considered processes in the irrigation districts. A novel physically based distributed model, the Irrigation Districts Model (IDM), was constructed in this study to address this problem. The model combined the 1D canal and ditch flow, the 1D soil water movement, the 2D groundwater movement, and the water interactions among these processes. It was calibrated and verified with two-year experimental data from Shahaoqu Sub-Irrigation Area in Hetao Irrigation District. The overall water balance error is 2.9% and 1.6% for the two years, respectively. The Nash–Sutcliffe efficiency coefficient (NSE) of water table depth and soil water content is 0.72 and 0.64 in the calibration year and 0.68 and 0.64 in the verification year. The results show good correspondence between the simulation and observation. It is practicable to apply the model in water movement research of irrigation districts.

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>

Characterization of hydraulic properties in the upper vadose zone for two aquifers in Slovenia

2021 ◽  
Author(s):  
Vesna Zupanc ◽  
Matjaž Glavan ◽  
Miha Curk ◽  
Urša Pečan ◽  
Michael Stockinger ◽  
...  
Keyword(s):  
Stable Isotopes ◽  
Soil Water ◽  
Water Flow ◽  
Vadose Zone ◽  
Hydraulic Properties ◽  
Isotope Composition ◽  
Transport Processes ◽  
Precipitation Event ◽  
Water Fluxes ◽  
Flow And Transport

<p>Environmental tracers, present in the environment and provided by nature, provide integrative information about both water flow and transport. For studying water flow and solute transport, the hydrogen and oxygen isotopes are of special interest, as their ratios provide a tracer signal with every precipitation event and are seasonally distributed. In order to follow the seasonal distribution of stable isotopes in the soil water and use this information for identifying hydrological processes and hydraulic properties, soil was sampled three times in three profiles, two on Krško polje aquifer in SE Slovenia and one on Ljubljansko polje in central Slovenia. Isotope composition of soil water was measured with the water-vapor-equilibration method. Based on the isotope composition of soil water integrative information about water flow and transport processes with time and depth below ground were assessed. Porewater isotopes were in similar range as precipitation for all three profiles.  Variable isotope ratios in the upper 60 cm for the different sampling times indicated dynamic water fluxes in this upper part of the vadose zone. Results also showed more evaporation at one sampling location, Brege. The information from stable isotopes will be of importance for further analyzing the water fluxes in the vadose zone of the study sties. <br>This research was financed by the ARRS BIAT 20-21-32 and IAEA CRP 1.50.18 Multiple isotope fingerprints to identify sources and transport of agro-contaminants.  </p>

Inferring saline tracer transport characteristics from time-lapse GPR experiments

2021 ◽  
Author(s):  
Peter-Lasse Giertzuch ◽  
Alexis Shakas ◽  
Bernard Brixel ◽  
Joseph Doetsch ◽  
Mohammadreza Jalali ◽  
...  
Keyword(s):  
Electrical Conductivity ◽  
Velocity Field ◽  
Nuclear Waste ◽  
Time Lapse ◽  
Transport Processes ◽  
Nuclear Waste Repository ◽  
Tracer Transport ◽  
Tracer Injection ◽  
Flow And Transport ◽  
Conductivity Sensor

<p>Monitoring and characterization of flow and transport processes in the subsurface has been a key focus of hydrogeological research for several decades. Such processes can be relevant for numerous applications, such as hydrocarbon and geothermal reservoir characterization and monitoring, risk assessment of soil contaminants, or nuclear waste disposal strategies.</p><p>Monitoring of flow and transport processes in the subsurface is often challenging, as they are usually not directly observable. Here, we present an approach to monitor saline tracer migration through a weakly fractured crystalline rock mass by means of Ground Penetrating Radar (GPR), and we evaluate the data quantitatively in terms of a flow velocity field and localized difference GPR breakthrough curves (DRBTC).</p><p>Two comparable and repeated tracer injection experiments were performed within saturated rock on the decameter scale. Time-lapse single-hole reflection data were acquired from two different boreholes during these experiments using unshielded and omnidirectional borehole antennas. The individual surveys were analyzed by difference imaging techniques, which allowed ultimately for tracer breakthrough monitoring at different locations in the subsurface. By combining the two complimentary GPR data sets, the 3D tracer velocity field could be reconstructed.</p><p>Our DRBTCs agree well with measured BTCs of the saline tracer at different electrical conductivity monitoring positions. Additionally, we were able to calculate a DRBTC for a location not previously monitored with borehole sensors. The reconstructed velocity field is in good agreement with previous studies on dye tracer data at the same research locations. Furthermore, we were able to resolve separate flow paths towards different monitoring locations, which could not be inferred from the electrical conductivity sensor data alone. The GPR data thus helped to disentangle the complex flow field through the fractured rock.</p><p>Out technique can be adapted to other use cases such as 3D monitoring of fluid migration (and thus permeability enhancement) during hydraulic stimulation and tracing fluid contaminants – e.g. for nuclear waste repository monitoring.</p>

The Modelling of Multiphase Flow and Transport Processes in Porous Media

1995 ◽  
pp. 221-222
Author(s):  
Vincent Lagendijk ◽  
Axel Braxein ◽  
Christian Forkel ◽  
Gerhard Rouvé
Keyword(s):  
Porous Media ◽  
Multiphase Flow ◽  
Transport Processes ◽  
Flow And Transport
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