scholarly journals Water flow in the active layer along an arctic slope – An investigation based on a field campaign and model simulations

2017 ◽  
Author(s):  
Sebastian F. Zastruzny ◽  
Bo Elberling ◽  
Lars Nielsen ◽  
Karsten H. Jensen
Keyword(s):  
Water Flow ◽  
Active Layer ◽  
Preferential Flow ◽  
Breakthrough Curves ◽  
Travel Times ◽  
Field Site ◽  
Arctic Ecosystems ◽  
Data Set ◽  
Discontinuous Permafrost ◽  
Geophysical Surveys

Abstract. As climate conditions change, the hydrological regime in the active layer is subject to change too. This influences the transport of solutes and the availability of nutrients, e.g. nitrogen particularly, along slopes. There is a lack of understanding the pathways and travel times of water and nutrients along slopes in discontinuous permafrost regions and how to scale changes along transects to the rest of the landscape. This study presents a comprehensive data set of a field site in Disko Island in Greenland aiming at constructing a hydrological model of the area. Data from automated weather stations, geophysical surveys, soil samples and soil sensors and tracer experiments are combined to describe the spatial variability in the field and to serve as input to a two-dimensional model (SUTRA) for simulating water and solute transport in the summer period. The model is calibrated and validated against volumetric water content and breakthrough curves of the applied tracers. Observed and simulated results suggest that the flow velocity in the active layer is directly influenced by annual precipitation patterns leading to water flow during the summer and rapid movement at the end of summer. Yearly travel times for the specific field site are simulated to be approximately 14 m/a and the highest peak velocities are most likely caused by preferential flow paths. The spatial heterogeneities linked to the frost topography seem to control the direction and velocity of flow. The observed discontinuous movement of a conservative tracer suggests that the movement of dissolved nitrogen compounds such as nitrate, being released along the slope in consequence of permafrost thawing, could possibly quickly influence nitrogen cycling at the end of the slope. This may trigger a feedback of climate changes in terms of increasing carbon sequestration due to additional plant growth in these otherwise nitrogen-limited Arctic ecosystems.

scholarly journals Travel-time-based thermal tracer tomography

2016 ◽  
Vol 20 (5) ◽  
pp. 1885-1901 ◽  
Author(s):  
Márk Somogyvári ◽  
Peter Bayer ◽  
Ralf Brauchler
Keyword(s):  
Hydraulic Conductivity ◽  
Grid Method ◽  
Early Time ◽  
Thermal Conditions ◽  
Breakthrough Curves ◽  
Injection Rate ◽  
Staggered Grid ◽  
Travel Times ◽  
Data Set ◽  
Technical Parameters

Abstract. Active thermal tracer testing is a technique to get information about the flow and transport properties of an aquifer. In this paper we propose an innovative methodology using active thermal tracers in a tomographic setup to reconstruct cross-well hydraulic conductivity profiles. This is facilitated by assuming that the propagation of the injected thermal tracer is mainly controlled by advection. To reduce the effects of density and viscosity changes and thermal diffusion, early-time diagnostics are used and specific travel times of the tracer breakthrough curves are extracted. These travel times are inverted with an eikonal solver using the staggered grid method to reduce constraints from the pre-defined grid geometry and to improve the resolution. Finally, non-reliable pixels are removed from the derived hydraulic conductivity tomograms. The method is applied to successfully reconstruct cross-well profiles as well as a 3-D block of a high-resolution fluvio-aeolian aquifer analog data set. Sensitivity analysis reveals a negligible role of the injection temperature, but more attention has to be drawn to other technical parameters such as the injection rate. This is investigated in more detail through model-based testing using diverse hydraulic and thermal conditions in order to delineate the feasible range of applications for the new tomographic approach.

Evaluating travel time distributions of macroporous hillslope

2020 ◽  
Author(s):  
Jaromir Dusek ◽  
Tomas Vogel
Keyword(s):  
Travel Time ◽  
Soil Water ◽  
Preferential Flow ◽  
Hydrological Regime ◽  
Breakthrough Curves ◽  
Travel Times ◽  
Antecedent Soil Moisture ◽  
Modeling Methodology ◽  
Biogeochemical Transformations ◽  
The Individual

<p>Residence and travel times of water in headwater catchments and hillslopes represent important descriptors of hydrological regime. In this study, travel time distributions were evaluated for a montane forest hillslope site using a two-dimensional dual-continuum model. The model was used to simulate the seasonal soil water regime and selected major rainfall–runoff events observed at the hillslope site. In particular, it was used to generate hillslope breakthrough curves of a fictitious conservative tracer applied at the hillslope surface in the form of the Dirac impulse. The simulated tracer breakthroughs allowed us to estimate the travel time distributions of soil water associated with the episodic subsurface stormflow, deep percolation and transpiration, yielding partial travel time distributions for the individual discharge processes. The travel time distributions determined for stormflow were dominated by the lateral component of preferential flow. The event-based stormflow median travel times ranged from 1 to 17 days. The estimated travel times were significantly affected by the temporal rainfall patterns and antecedent soil moisture distributions. The applied modeling methodology can be used for the evaluation of runoff dynamics at the hillslope and catchment scales as well as for the quantification of biogeochemical transformations of dissolved chemicals.</p>

Preferential flows and the legacy of Peter F. Germann (1944-2020)

2021 ◽  
Author(s):  
Majdi R. Abou Najm ◽  
Keith Beven
Keyword(s):  
Soil Water ◽  
Water Flow ◽  
Preferential Flow ◽  
Research Work ◽  
Soil Physics ◽  
Data Set ◽  
Wide Range ◽  
University Of Bern ◽  
The University ◽  
Preferential Flows

<p>Peter Germann died on December 6<sup>th</sup> 2020 in Bern, Switzerland. Known for a wide range of contributions to the physics of soil-water interactions and flow, his name (along with Keith Beven, his career-long collaborator and fiend) is recognized by an entire generation of soil physicists and hydrologists who studies macropore and preferential flows. They both co-authored the classic, and highly cited 1982 review paper in Water Resources Research on Macropores and Water Flow in Soils. Peter’s PhD work between 1976-1980 was a study of soil-water relations based on maintaining a network of 35 nests of tensiometers at 10 different depths down to 3m. At that time, these were still manual tensiometers coupled to mercury manometers that were read every 2 to 3 days for 3 years. One of the features that this remarkable data set revealed was that during infiltration, wetting in some cases occurred at depths, apparently by-passing the tensiometers above. This is what we all now know as preferential flow. Another was the large heterogeneity in responses between sites and between wetting events. For the major part of his research career, Peter was a strong advocate for a reconsideration of the physics of water flow through soils and, in particular, for the limitations of the Darcy-Buckingham-Richards flow theory. Peter later developed the kinematic wave approach into a theory of viscosity (rather than capillarity) dominated film flows subject to Stokes’ law during infiltration. He summarised his research work in his 2013 book on the subject published by the University of Bern. Peter held academic positions at the University of Virginia in Charlottesville, at Rutgers University, and at the University of Bern back in Switzerland where he stayed until he retired in 2009, and held an Emeritus position until 2015.   He continued to publish papers until shortly before his death which followed 2 major strokes. In this talk, we will go over Peter’s main contribution and research highlights in the area of macropores and preferential flows. Peter was no stranger to EGU, and many know him and have met him in this session or others. For those who knew Peter, they will miss his enthusiasm, his critical mind, his genuine care for the state of soil physics, his thoughtful responses, and his humour. He was a great source of inspiration to us and many others. Peter will be missed by many in soil science.</p>

Groundwater age from multi-level bores: What it can tell about the aquifers

2021 ◽  
Author(s):  
Uwe Morgenstern ◽  
Zara Rawlinson
Keyword(s):  
Groundwater Flow ◽  
Groundwater Recharge ◽  
Sea Level ◽  
Preferential Flow ◽  
Groundwater Age ◽  
Geological Processes ◽  
Recharge Sources ◽  
Transient Electromagnetic ◽  
Geophysical Surveys ◽  
Multi Level

<p>Geologic data to provide information on the functioning of aquifers is often scars. For the aquifers underlying the Heretaunga Plains, Hawkes Bay, one of New Zealand’s most important groundwater systems, we used groundwater age (tritium, SF6, 14C) to inform the geologic model and to provide information on groundwater flow through alternating strata of permeable river gravel beds and fine impermeable beds that form an interconnected unconfined–confined aquifer system with complex groundwater flow processes.</p><p>The aquifers are a result of geological processes responding to climate change cycles from cold glacial when sea level was more than 100m below present sea level, to warm interglacial periods with sea level similar to present day. Glacial climate strata are river gravel, sand and silt deposits and include the artesian aquifers. The interglacial strata form the aquicludes and are marine sand, silt, and clay deposits with interbedded estuarine, swamp and coastal fluvial silt, clay, peat and gravel deposits.</p><p>We have re-visited tracer data sampled during the drilling of multi-level observation well in the early 1990s, and collected new samples from these multi-level bores in order to understand in 3D the groundwater recharge sources, groundwater recharge and flow rates, connection to the rivers, and potential groundwater discharge out to sea. Consistently young water (c. 25 years) at depth greater than 100m indicates preferential flow paths, likely related to paleo-river channels. The flow pattern obtained from the water tracer data improves the geologic information from the drill-holes, and fits with information from recent airborne transient electromagnetic (SkyTEM) geophysical surveys.</p>

scholarly journals Effects of freezing on soil temperature, freezing front propagation and moisture redistribution in peat: laboratory investigations

2012 ◽  
Vol 16 (2) ◽  
pp. 501-515 ◽  
Author(s):  
R. M. Nagare ◽  
R. A. Schincariol ◽  
W. L. Quinton ◽  
M. Hayashi
Keyword(s):  
Water Content ◽  
Active Layer ◽  
Water Movement ◽  
Peat Soil ◽  
Soil Column ◽  
Initial Period ◽  
Soil Freezing ◽  
Permafrost Soil ◽  
Freezing Front ◽  
Discontinuous Permafrost

Abstract. There are not many studies that report water movement in freezing peat. Soil column studies under controlled laboratory settings can help isolate and understand the effects of different factors controlling freezing of the active layer in organic covered permafrost terrain. In this study, four peat Mesocosms were subjected to temperature gradients by bringing the Mesocosm tops in contact with sub-zero air temperature while maintaining a continuously frozen layer at the bottom (proxy permafrost). Soil water movement towards the freezing front (from warmer to colder regions) was inferred from soil freezing curves, liquid water content time series and from the total water content of frozen core samples collected at the end of freezing cycle. A substantial amount of water, enough to raise the upper surface of frozen saturated soil within 15 cm of the soil surface at the end of freezing period appeared to have moved upwards during freezing. Diffusion under moisture gradients and effects of temperature on soil matric potential, at least in the initial period, appear to drive such movement as seen from analysis of freezing curves. Freezing front (separation front between soil zones containing and free of ice) propagation is controlled by latent heat for a long time during freezing. A simple conceptual model describing freezing of an organic active layer initially resembling a variable moisture landscape is proposed based upon the results of this study. The results of this study will help in understanding, and ultimately forecasting, the hydrologic response of wetland-dominated terrain underlain by discontinuous permafrost.

scholarly journals Derivation and analysis of a high-resolution estimate of global permafrost zonation

2011 ◽  
Vol 5 (3) ◽  
pp. 1547-1582
Author(s):  
S. Gruber
Keyword(s):  
High Resolution ◽  
Land Surface ◽  
Permafrost Region ◽  
Large Area ◽  
Data Set ◽  
Regional Patterns ◽  
Actual Surface ◽  
Interesting Insight ◽  
Air Temperatures ◽  
Discontinuous Permafrost

Abstract. Permafrost underlies much of Earths' surface and interacts with climate, eco-systems and human systems. It is a complex phenomenon controlled by climate and (sub-) surface properties and reacts to change with variable delay. Heterogeneity and sparse data challenge the modeling of its spatial distribution. Currently, there is no data set to adequately inform global studies of permafrost. The available data set for the Northern Hemisphere is frequently used for model evaluation, but its quality and consistency are difficult to assess. A global model of permafrost extent and dataset of permafrost zonation are presented and discussed, extending earlier studies by including the Southern Hemisphere, by consistent data and methods, and most importantly, by attention to uncertainty and scaling. Established relationships between air temperature and the occurrence of permafrost are re-formulated into a model that is parametrized using published estimates. It is run with a high-resolution (<1 km) global elevation data and air temperatures based on the NCAR-NCEP reanalysis and CRU TS 2.0. The resulting data provides more spatial detail and a consistent extrapolation to remote regions, while aggregated values resemble previous studies. The estimated uncertainties affect regional patterns and aggregate number, but provide interesting insight. The permafrost area, i.e. the actual surface area underlain by permafrost, north of 60° S is estimated to be 13–18 × 106 km2 or 9–14 % of the exposed land surface. The global permafrost area including Antarctic and sub-sea permafrost is estimated to be 16–21 × 106 km2. The global permafrost region, i.e. the exposed land surface below which some permafrost can be expected, is estimated to be 22 ± 3 × 106 km2. A large proportion of this exhibits considerable topography and spatially-discontinuous permafrost, underscoring the importance of attention to scaling issues and heterogeneity in large-area models.

scholarly journals Spatial variation of physicochemical parameters in a constructed wetland for wastewater treatment: An example of the use of the R programming language

2021 ◽  
Vol 13 (1) ◽  
pp. 15
Author(s):  
Junior Pastor Pérez-Molina ◽  
Carola Scholz ◽  
Roy Pérez-Salazar ◽  
Carolina Alfaro-Chinchilla ◽  
Ana Abarca Méndez ◽  
...  
Keyword(s):  
Wastewater Treatment ◽  
Spatial Variation ◽  
Water Flow ◽  
Programming Language ◽  
Constructed Wetland ◽  
Physicochemical Parameters ◽  
Preferential Flow ◽  
Oxygen Demand ◽  
R Programming Language ◽  
R Programming

Introduction: The implementation of wastewater treatment systems such as constructed wetlands has a growing interest in the last decade due to its low cost and high effectiveness in treating industrial and residential wastewater. Objective: To evaluate the spatial variation of physicochemical parameters in a constructed wetland system of sub-superficial flow of Pennisetum alopecuroides (Pennisetum) and a Control (unplanted). The purpose is to provide an analysis of spatial dynamic of physicochemical parameters using R programming language. Methods: Each of the cells (Pennisetum and Control) had 12 piezometers, organized in three columns and four rows with a separation distance of 3,25m and 4,35m, respectively. The turbidity, biochemical oxygen demand (BOD), chemical oxygen demand (COD), total Kjeldahl nitrogen (TKN), ammoniacal nitrogen (N-NH4), organic nitrogen (N-org.) and phosphorous (P-PO4-3) were measured in water under in-flow and out-flow of both conditions Control and Pennisetum (n= 8). Additionally, the oxidation-reduction potential (ORP), dissolved oxygen (DO), conductivity, pH and water temperature, were measured (n= 167) in the piezometers. Results: No statistically significant differences between cells for TKN, N-NH4, conductivity, turbidity, BOD, and COD were found; but both Control and Pennisetum cells showed a significant reduction in these parameters (P<0,05). Overall, TKN and N-NH4 removal were from 65,8 to 84,1% and 67,5 to 90,8%, respectively; and decrease in turbidity, conductivity, BOD, and COD, were between 95,1-95,4%; 15-22,4%; 65,2-77,9% and 57,4-60,3% respectively. Both cells showed ORP increasing gradient along the water-flow direction, contrary to conductivity (p<0,05). However, OD, pH and temperature were inconsistent in the direction of the water flow in both cells. Conclusions: Pennisetum demonstrated pollutant removal efficiency, but presented results similar to the control cells, therefore, remains unclear if it is a superior option or not. Spatial variation analysis did not reflect any obstruction of flow along the CWs; but some preferential flow paths can be distinguished. An open-source repository of R was provided. 

scholarly journals Active layer thermal regime in two climatically contrasted sites of the Antarctic Peninsula region

2016 ◽  
Vol 42 (2) ◽  
pp. 457 ◽  
Author(s):  
F. Hrbáček ◽  
M. Oliva ◽  
K. Laska ◽  
J. Ruiz-Fernández ◽  
M. A. De Pablo ◽  
...  
Keyword(s):  
Active Layer ◽  
Antarctic Peninsula ◽  
Thermal Regime ◽  
Active Layer Thickness ◽  
Mean Annual Temperature ◽  
Climate Trends ◽  
Ground Temperatures ◽  
Air Temperatures ◽  
Discontinuous Permafrost ◽  
The Antarctic

Permafrost controls geomorphic processes in ice-free areas of the Antarctic Peninsula (AP) region. Future climate trends will promote significant changes of the active layer regime and permafrost distribution, and therefore a better characterization of present-day state is needed. With this purpose, this research focuses on Ulu Peninsula (James Ross Island) and Byers Peninsula (Livingston Island), located in the area of continuous and discontinuous permafrost in the eastern and western sides of the AP, respectively. Air and ground temperatures in as low as 80 cm below surface of the ground were monitored between January and December 2014. There is a high correlation between air temperatures on both sites (r=0.74). The mean annual temperature in Ulu Peninsula was -7.9 ºC, while in Byers Peninsula was -2.6 ºC. The lower air temperatures in Ulu Peninsula are also reflected in ground temperatures, which were between 4.9 (5 cm) and 5.9 ºC (75/80 cm) lower. The maximum active layer thickness observed during the study period was 52 cm in Ulu Peninsula and 85 cm in Byers Peninsula. Besides climate, soil characteristics, topography and snow cover are the main factors controlling the ground thermal regime in both areas.

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

&lt;p&gt;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&amp;#160;&amp;#160; 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.&lt;/p&gt;

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