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

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.

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

Hydrology and Earth System Sciences Discussions ◽

10.5194/hessd-6-2893-2009 ◽

2009 ◽

Vol 6 (2) ◽

pp. 2893-2929 ◽

Cited By ~ 1

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.

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Large-scale lateral saturated soil hydraulic conductivity as metric for the connectivity of the subsurface flow paths at hillslope scale

10.22541/au.163896913.32177523/v1 ◽

2021 ◽

Author(s):

Mario Pirastru ◽

Massimo Iovino ◽

Hassan Awada ◽

Roberto Marrosu ◽

Simone Di Prima ◽

...

Keyword(s):

Soil Moisture ◽

Hydraulic Conductivity ◽

Spatial Scale ◽

Water Table ◽

Subsurface Flow ◽

Lateral Flow ◽

Saturated Soil ◽

Flow Paths ◽

Soil Hydraulic Conductivity ◽

Hillslope Scale

Lateral saturated soil hydraulic conductivity, Ks,l, is the soil property governing subsurface water transfer in hillslopes, and the key parameter in many numerical models simulating hydrological processes both at the hillslope and catchment scales. Likewise, the hydrological connectivity of lateral flow paths plays a significant role in determining the intensity of the subsurface flow at various spatial scales. The objective of the study is to investigate the relationship between Ks,l and hydraulic connectivity at the hillslope spatial scale. Ks,l was determined by the subsurface flow rates intercepted by drains, and by water table depths observed in a well network. Hydraulic connectivity of the lateral flow paths was evaluated by the synchronicity among piezometric peaks, and between the latter and the peaks of drained flow. Soil moisture and precipitation data were used to investigate the influence of the transient hydrological soil condition on connectivity and Ks,l. It was found that the higher was the synchronicity of the water table response between wells, the lower was the time lag between the peaks of water levels and those of the drained subsurface flow. Moreover, the most synchronic water table rises determined the highest drainage rates. The relationships between Ks,l and water table depths were highly non-linear, with a sharp increase of the values for water table levels close to the soil surface. Estimated Ks,l values for the full saturated soil were in the order of thousands of mm h-1, suggesting the activation of macropores in the root zone. The Ks,l values determined at the peak of the drainage events were correlated with the indicators of synchronicity. The sum of the antecedent soil moisture and of the precipitation was correlated with the indicators of connectivity and with Ks,l. We suggest that, for simulating realistic processes at the hillslope scale, the hydraulic connectivity could be implicitly considered in hydrological modelling through an evaluation of Ks,l at the same spatial scale.

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

Water ◽

10.3390/w11010132 ◽

2019 ◽

Vol 11 (1) ◽

pp. 132 ◽

Cited By ~ 2

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.

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

10.20944/preprints201812.0025.v1 ◽

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.

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Quantifying Subsurface Lateral Flow along Sloping Horizon Boundaries in Soil Profiles of a Hummocky Ground Moraine

Vadose Zone Journal ◽

10.2136/vzj2017.05.0106 ◽

2018 ◽

Vol 17 (1) ◽

pp. 170106 ◽

Cited By ~ 5

Author(s):

Vilim Filipović ◽

Horst H. Gerke ◽

Lana Filipović ◽

Michael Sommer

Keyword(s):

Lateral Flow ◽

Soil Profiles ◽

Ground Moraine ◽

Subsurface Lateral Flow

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Collaborative Experiment for Pulsed Radar Visualization of Water Flow Paths in Snow

10.21236/ada393212 ◽

2000 ◽

Cited By ~ 1

Author(s):

M. W. Williams ◽

W. T. Pfeffer ◽

M. Knoll

Keyword(s):

Water Flow ◽

Flow Paths ◽

Water Flow Paths

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Form and function in hillslope hydrology: characterization of subsurface flow based on response observations

Hydrology and Earth System Sciences ◽

10.5194/hess-21-3727-2017 ◽

2017 ◽

Vol 21 (7) ◽

pp. 3727-3748 ◽

Cited By ~ 26

Author(s):

Lisa Angermann ◽

Conrad Jackisch ◽

Niklas Allroggen ◽

Matthias Sprenger ◽

Erwin Zehe ◽

...

Keyword(s):

Preferential Flow ◽

Explanatory Power ◽

Subsurface Flow ◽

Time Lapse ◽

Storm Event ◽

Monitoring Methods ◽

Catchment Scale ◽

Flow Paths ◽

Form And Function ◽

And Function

Abstract. The phrase form and function was established in architecture and biology and refers to the idea that form and functionality are closely correlated, influence each other, and co-evolve. We suggest transferring this idea to hydrological systems to separate and analyze their two main characteristics: their form, which is equivalent to the spatial structure and static properties, and their function, equivalent to internal responses and hydrological behavior. While this approach is not particularly new to hydrological field research, we want to employ this concept to explicitly pursue the question of what information is most advantageous to understand a hydrological system. We applied this concept to subsurface flow within a hillslope, with a methodological focus on function: we conducted observations during a natural storm event and followed this with a hillslope-scale irrigation experiment. The results are used to infer hydrological processes of the monitored system. Based on these findings, the explanatory power and conclusiveness of the data are discussed. The measurements included basic hydrological monitoring methods, like piezometers, soil moisture, and discharge measurements. These were accompanied by isotope sampling and a novel application of 2-D time-lapse GPR (ground-penetrating radar). The main finding regarding the processes in the hillslope was that preferential flow paths were established quickly, despite unsaturated conditions. These flow paths also caused a detectable signal in the catchment response following a natural rainfall event, showing that these processes are relevant also at the catchment scale. Thus, we conclude that response observations (dynamics and patterns, i.e., indicators of function) were well suited to describing processes at the observational scale. Especially the use of 2-D time-lapse GPR measurements, providing detailed subsurface response patterns, as well as the combination of stream-centered and hillslope-centered approaches, allowed us to link processes and put them in a larger context. Transfer to other scales beyond observational scale and generalizations, however, rely on the knowledge of structures (form) and remain speculative. The complementary approach with a methodological focus on form (i.e., structure exploration) is presented and discussed in the companion paper by Jackisch et al.(2017).

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