Controls on the spatial distribution of soil moisture and solute transport in a sloping reclamation cover

2008 ◽  
Vol 45 (3) ◽  
pp. 351-366 ◽  
Author(s):  
Chris Kelln ◽  
S. Lee Barbour ◽  
Clara Qualizza
Keyword(s):  
Spatial Distribution ◽  
Soil Moisture ◽  
Preferential Flow ◽  
Salt Transport ◽  
Soil Matrix ◽  
Groundwater Flux ◽  
Through Diffusion ◽  
Moisture Conditions ◽  
Lower Slope ◽  
Upper Slope

A detailed field study was conducted to map the spatial distribution of soil moisture and salt transport within a sloping clay-rich reclamation cover overlying a saline-sodic shale overburden landform. The soil moisture data suggest that: lower-slope positions are wetter in spring due to the down-slope movement of surface run-off; infiltration occurs via preferential flow paths while the ground is frozen; and, interflow occurs along the cover–shale surface when the ground thaws. Soil moisture conditions also remain wetter in lower-slope positions throughout the summer and fall. Salt transport from the shale into the overlying cover is affected predominantly by soil moisture conditions and lateral groundwater flux. Quasi one-dimensional modelling of in situ profiles of pore-water Na+ concentration demonstrate that: (i) increased soil moisture conditions in lower-slope positions accelerate salt transport into the cover through diffusion; (ii) snow melt infiltration water bypasses the soil matrix higher in the cover profile; (iii) drier conditions in the mid- and upper-slope positions limit salt transport through diffusion; (iv) advection accelerates upward salt transport in lower-slope positions; and, (v) interflow and (or) deep percolation are key mechanisms mitigating vertical salt movement in lower- and upper-slope positions.

scholarly journals Effects of preferential flow on snowmelt partitioning and groundwater recharge in frozen soils

2019 ◽  
Vol 23 (12) ◽  
pp. 5017-5031 ◽  
Author(s):  
Aaron A. Mohammed ◽  
Igor Pavlovskii ◽  
Edwin E. Cey ◽  
Masaki Hayashi
Keyword(s):  
Soil Moisture ◽  
Groundwater Recharge ◽  
Preferential Flow ◽  
Frozen Soil ◽  
Time Lags ◽  
Runoff Generation ◽  
Frozen Ground ◽  
Soil Matrix ◽  
Frozen Soils ◽  
Flow Through

Abstract. Snowmelt is a major source of groundwater recharge in cold regions. Throughout many landscapes snowmelt occurs when the ground is still frozen; thus frozen soil processes play an important role in snowmelt routing, and, by extension, the timing and magnitude of recharge. This study investigated the vadose zone dynamics governing snowmelt infiltration and groundwater recharge at three grassland sites in the Canadian Prairies over the winter and spring of 2017. The region is characterized by numerous topographic depressions where the ponding of snowmelt runoff results in focused infiltration and recharge. Water balance estimates showed infiltration was the dominant sink (35 %–85 %) of snowmelt under uplands (i.e. areas outside of depressions), even when the ground was frozen, with soil moisture responses indicating flow through the frozen layer. The refreezing of infiltrated meltwater during winter melt events enhanced runoff generation in subsequent melt events. At one site, time lags of up to 3 d between snow cover depletion on uplands and ponding in depressions demonstrated the role of a shallow subsurface transmission pathway or interflow through frozen soil in routing snowmelt from uplands to depressions. At all sites, depression-focused infiltration and recharge began before complete ground thaw and a significant portion (45 %–100 %) occurred while the ground was partially frozen. Relatively rapid infiltration rates and non-sequential soil moisture and groundwater responses, observed prior to ground thaw, indicated preferential flow through frozen soils. The preferential flow dynamics are attributed to macropore networks within the grassland soils, which allow infiltrated meltwater to bypass portions of the frozen soil matrix and facilitate both the lateral transport of meltwater between topographic positions and groundwater recharge through frozen ground. Both of these flow paths may facilitate preferential mass transport to groundwater.

scholarly journals Impacts of rainfall features and antecedent soil moisture on occurrence of preferential flow: A study at hillslopes using high-frequency monitoring

2016 ◽  
Author(s):  
Zhenyang Peng ◽  
Hongchang Hu ◽  
Fuqiang Tian ◽  
Qiang Tie ◽  
Sihan Zhao
Keyword(s):  
Soil Moisture ◽  
High Frequency ◽  
Preferential Flow ◽  
Rainfall Amount ◽  
Average Intensity ◽  
Wetting Front ◽  
Antecedent Soil Moisture ◽  
Soil Matrix ◽  
Surface Cover ◽  
Frequency Monitoring

Abstract. In order to evaluate influences of rainfall features and antecedent soil moisture on occurrence of preferential flow, observation was conducted at 12 sites within a 7-km2 catchment, by applying the high-frequency monitoring approach. Totally 65 rainfall events were selected to compare among sites, and preferential flow was inferred when (i) responses of soil moisture did not follow a linear sequence with depth, or (ii) penetration velocity of wetting front in at least one horizon exceeded the threshold, which was set to be 5–10 times of the saturated hydraulic conductivity of soil matrix at different depths. Results showed that frequency of preferential flow was 40.7 % in average, but varied from 17.9 % to 74.3 % among the sites. Correlations between the frequency and rainfall features, i.e. rainfall amount, duration, maximum and average intensity, were well fitted by logarithmic curves. Rainfall amount, which was most prominently correlated with frequency (R2 = 0.93), was regarded as the dominant driving factor of preferential flow, while average intensity was in second (R2 = 0.90). Antecedent soil moisture was also significantly correlated with the frequency. However, this should largely be attributed to the differences of soil moisture among sites, since varying range of soil moisture at a specific site was not wide enough to influence the frequency significantly. Further examination suggested that topography and surface cover (dead leaves and humus) were the controlling factors of both infiltration amount and occurrence of preferential flow, as water was more readily to infiltrate into soils and preferential flow was more readily to occur when slope gradient was small and surface cover was thick, while soil moisture was more likely to be a consequence of water storage capacity, rather than an inducer of preferential flow. This knowledge could be helpful in understanding the partitioning of surface runoff and infiltration, as well as runoff processes in catchments with complex topography and underlying conditions.

scholarly journals Effects of preferential flow on snowmelt partitioning and groundwater recharge in frozen soils

2019 ◽  
Author(s):  
Aaron A. Mohammed ◽  
Igor Pavlovskii ◽  
Edwin E. Cey ◽  
Masaki Hayashi
Keyword(s):  
Soil Moisture ◽  
Groundwater Recharge ◽  
Preferential Flow ◽  
Frozen Soil ◽  
Time Lags ◽  
Runoff Generation ◽  
Frozen Ground ◽  
Soil Matrix ◽  
Frozen Soils ◽  
Flow Through

Abstract. Snowmelt is a major source of groundwater recharge in cold regions. Throughout many landscapes snowmelt occurs when ground is still frozen, thus frozen soil processes play an important role in snowmelt routing, and, by extension, on the timing and magnitude of recharge. This study investigated the vadose zone dynamics governing snowmelt infiltration and groundwater recharge at three grassland sites in the Canadian Prairies over the winter and spring of 2017. The region is characterised by numerous topographic depressions where ponding of snowmelt runoff results in focused infiltration and recharge. Water balance estimates showed infiltration was the dominant sink (35–85 %) of snowmelt under uplands (i.e. areas outside depressions), even when ground was frozen, with soil moisture responses indicating flow through the frozen layer. Refreezing of infiltrated meltwater during winter melt events enhanced runoff generation in subsequent melt events. At one site, time lags of up to 3 days between snowcover depletion on uplands and ponding in depressions demonstrated the role of shallow subsurface flow through frozen soil in routing snowmelt to depressions. At all sites, depression-focused infiltration and recharge began before ground thaw and a significant portion (45–100 %) occurred while the ground was partially frozen. Relatively rapid infiltration rates and non-sequential soil moisture and groundwater responses, observed prior to ground thaw, indicated preferential flow through frozen soils. The preferential flow dynamics are attributed to macropore networks within the grassland soils, which allow infiltrated meltwater to bypass portions of the frozen soil matrix and facilitate both lateral transport of meltwater between topographic positions and groundwater recharge through frozen ground. Both of these flowpaths may facilitate preferential mass transport to groundwater.

scholarly journals Linking soil moisture balance and source-responsive models to estimate diffuse and preferential components of groundwater recharge

2012 ◽  
Vol 9 (7) ◽  
pp. 8455-8492
Author(s):  
M. O. Cuthbert ◽  
R. Mackay ◽  
J. R. Nimmo
Keyword(s):  
Soil Moisture ◽  
Groundwater Recharge ◽  
Water Table ◽  
Preferential Flow ◽  
Numerical Models ◽  
Balance Model ◽  
Shallow Water Table ◽  
Soil Matrix ◽  
Moisture Balance ◽  
Soil Moisture Balance

Abstract. Results are presented of a detailed study into the vadose zone and shallow water table hydrodynamics of a field site in Shropshire, UK. A conceptual model is developed and tested using a range of numerical models, including a modified soil moisture balance model (SMBM) for estimating groundwater recharge in the presence of both diffuse and preferential flow components. Tensiometry reveals that the loamy sand topsoil wets up via macropore flow and subsequent redistribution of moisture into the soil matrix. Recharge does not occur until near-positive pressures are achieved at the top of the sandy glaciofluvial outwash material that underlies the topsoil, about 1 m above the water table. Once this occurs, very rapid water table rises follow. This threshold behaviour is attributed to the vertical discontinuity in the macropore system due to seasonal ploughing of the topsoil, and a lower permeability plough/iron pan restricting matrix flow between the topsoil and the lower outwash deposits. Although the wetting process in the topsoil is complex, a SMBM is shown to be effective in predicting the initiation of preferential flow from the base of the topsoil into the lower outwash horizon. The rapidity of the response at the water table and a water table rise during the summer period while flow gradients in the unsaturated profile were upward suggest that preferential flow is also occurring within the outwash deposits below the topsoil. A variation of the source-responsive model proposed by Nimmo (2010) is shown to reproduce the observed water table dynamics well in the lower outwash horizon when linked to a SMBM that quantifies the potential recharge from the topsoil. The results reveal new insights into preferential flow processes in cultivated soils and provide a useful and practical approach to accounting for preferential flow in studies of groundwater recharge estimation.

Influence of trees and topography on soil water content in semi-arid region, the case of an agro-silvo-pastoral ecosystem dominated by Faidherbia albida (Senegal)

2021 ◽  
Author(s):  
Djim Diongue ◽  
Didier Orange ◽  
Waly Faye ◽  
Olivier Roupsard ◽  
Frederic Do ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Moisture Content ◽  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Soil Layer ◽  
Rainfall Infiltration ◽  
Faidherbia Albida ◽  
Lower Slope ◽  
Upper Slope

<p>Vegetation strongly affects the water cycle, and the interactions between vegetation and soil moisture are fundamental for ecological processes in semiarid regions. Therefore, characterizing the variation in soil moisture is important to understand the ecological sustainability of cropping systems towards food security. The present study aims at exploring factors and mechanisms influencing soil moisture variability in the Faidherbia albida (FA) parkland at Sob basin located in the center of Senegal [1]. Volumetric soil moisture content at multiple depths was monitored at 15 locations distributed along a transect (upper slope, mid-slope and lower slope) and different FA tree position (under, at the limit and outside canopy) from August to October 2020. A portable TRIME Time Domain Reflectometry (TDR) Tube Probe (IMKO, Germany) was used to determine soil volumetric moisture content while being placed at specific depth intervals inside a PVC access tube set up at each location. Soil moisture was monitored at 10 cm interval from 20 to 420 cm during the rainy season from July to October 2020. Results of soil moisture profiles along the transects exhibit two main zones based on the standard deviation (SD) and the inflection of the coefficient of variation (CV): shallow soil moisture (SSM) and deep soil moisture (DSM). For SSM observed at 20-60 cm of the soil layer, both mean soil moisture and SD increase with depth, the lowest mean value (8%) being observed at the top surface. This soil layer is influenced by rainfall infiltration and daily evaporation. For DSM observed at 70-420 cm, the moisture pattern can be further divided into 4 soil sublayers taking the mean soil moisture vertical distribution as reference: (i) a rainfall infiltration layer (70-160 cm) which appears mainly influenced by cumulative rainfall infiltration in addition to transpiration of grassland and crops (shallow root system); (ii) a rainfall-transpiration layer (170-250 cm) which is still an infiltration layer but more influenced by crops transpiration; (iii) a transpiration layer (260-350 cm) which can be recharged by rainfall infiltration during heavy rainfall and supply deep root system; and (iv) deep transpiration layer (360-400 cm) which has DSM that can be influenced by extremely deep root vegetation such as FA. The factors influencing the soil water content varied with the topography. The soil water content SWC (mean and median value of 27.2 and 29.6% respectively) in the lower slope was significantly higher than that at middle (mean and median value of 14.4 and 13.2 % respectively) and upper slope (mean and median value of 16.8 and 18.4 % respectively). At last, soil water content was positively correlated with the distance from the FA, regardless the slope. The higher water content for both SSM and DSM was observed outside the FA canopy. This result refutes the initial hypothesis of higher SWC under trees and support a more detailed analysis of the infiltration capacity in relationship with the FA position.</p><div> <div> <p>[1] Faidherbia-Flux : https://lped.info/wikiObsSN/?Faidherbia-Flux</p> </div> </div>

Does Topography Influence Millipede's Abundance and Biomass in an Oriental Beech Forest, Iran?

2020 ◽  
Author(s):  
Maryam Fazlollahi Mohammadi ◽  
Seyed Gholamali Jalali ◽  
Yahya Kooch
Keyword(s):  
Soil Moisture ◽  
Soil Depth ◽  
Beech Forest ◽  
Slope Position ◽  
Abundance And Diversity ◽  
Density And Biomass ◽  
Lower Slope ◽  
Return Process ◽  
Main Factor ◽  
Upper Slope

Abstract BackgroundMillipedes acting as one of the important soil organisms having an important influence on decomposition of vegetation and nutrient cycling and their return process to the soil ecosystem, and they usually can be found under the litter layer within the shallow depths. Topography with changing soil traits and plant’s composition will result in changes in soil biota, by the reaction of microsite condition to topography variables. It has been documented that millipedes are not considered as an exception to this trend, so we aimed at study the changes in millipede’s density and biomass with regard to the landforms and soil depth. We studied the effect of catena shape and slope position and different soil depths on millipede’s abundance and biomass. ResultsThe results of our study indicated that millipedes can affect by topography to high levels, in a way that they are more abundant with higher biomass in humid areas such as V-shaped catena and lower slope position than the C-shaped catena and upper slope positions. We also observed that the biomass and density of millipedes decrease with increasing the soil depth. ConclusionIt appears that the factors such as soil moisture, pH, plant composition, and N are the most important factors in millipede’s abundance and diversity with more emphasis on soil moisture as the main factor.

Stemflow infiltration areas into forest soils around American beech trees

2020 ◽  
Author(s):  
Pilar Llorens ◽  
Jérôme Latron ◽  
Darryl E. Carlyle-Moses ◽  
Kerstin Näthe ◽  
Jeff L. Chang ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Preferential Flow ◽  
Mean Value ◽  
Fagus Grandifolia ◽  
Soil Conditions ◽  
Nutrient Inputs ◽  
American Beech ◽  
Management Area ◽  
Loam Soil ◽  
Moisture Conditions

<p>Despite the fact that stemflow is often a small percentage of precipitation, it is a concentrated flux of water, solutes, and particulates to near-trunk soils. As a consequence, per unit area, near-trunk soils receive water and nutrient inputs that largely exceed those received by soils in the distal zone via throughfall. This funnelling effect of trees can contribute to preferential flow and groundwater recharge and can have important biogeochemical implications. However, to evaluate the importance of this flux for near-trunk soils is necessary to quantify the magnitude of the stemflow infiltration area.</p><p>This study presents a stemflow simulation experiment with the objective of determining the stemflow infiltration area in near-trunk soils.  The experiment was conducted at the Fair Hill Natural Resources Management area in northeastern Maryland (USA). We selected four American beech (Fagus grandifolia Ehrh.) trees with a DBH of ~29 cm, growing in a loam soil. Each tree was equipped with a collar, built with a tube with small holes, and installed around the tree. This tube was connected with a hose to a 36.5 L container positioned ~ 1 m above the collar. The hose had two stopcocks to regulate the water rate. Before starting the simulations, litterfall was removed.</p><p>A total of thirteen simulations were run with differing simulated stemflow rates (from 30 to 290 L/h) and differing initial soil moisture conditions (mean soil moisture from 25 to 43 m<sup>3</sup>m<sup>-3</sup>). Soil moisture was measured around the trees before each simulation with a TDR device. To further increase soil moisture between simulations, 40 L of water were carefully applied circumferentially around the trunk, at a maximum distance of 35 cm. Each simulation was performed with different colour dye tracer to enable accurate measurements of the stemflow infiltration area. After each simulation, the infiltration area was measured using a mesh grid of known area. At the end of the last simulations soil samples were taken around each tree.</p><p>The results show that in all cases the infiltration area is < 0.1 m<sup>2</sup>, with a mean value of about 0.03 m<sup>2</sup>. Likewise, there is a tendency to decrease the area of infiltration by increasing soil moisture. This trend seems to be modified for saturated conditions or when the stemflow rate is extreme. These small stemflow infiltration areas are explained by both the high infiltration rates of near-trunk soils in forests and the macroporosity produced by living or decaying roots. Moreover, these trees have slight buttressing that increase the perimeter of contact between the stem and the soil (with respect to the basal perimeter (calculated at breast height)), thus further promoting infiltration. Results suggest the importance of measuring the infiltration areas for different species and soil conditions to better evaluate the relevance of stemflow.</p>

scholarly journals Linking soil moisture balance and source-responsive models to estimate diffuse and preferential components of groundwater recharge

2013 ◽  
Vol 17 (3) ◽  
pp. 1003-1019 ◽  
Author(s):  
M. O. Cuthbert ◽  
R. Mackay ◽  
J. R. Nimmo
Keyword(s):  
Soil Moisture ◽  
Groundwater Recharge ◽  
Water Table ◽  
Preferential Flow ◽  
Numerical Models ◽  
Balance Model ◽  
Shallow Water Table ◽  
Soil Matrix ◽  
Moisture Balance ◽  
Soil Moisture Balance

Abstract. Results are presented of a detailed study into the vadose zone and shallow water table hydrodynamics of a field site in Shropshire, UK. A conceptual model is presented and tested using a range of numerical models, including a modified soil moisture balance model (SMBM) for estimating groundwater recharge in the presence of both diffuse and preferential flow components. Tensiometry reveals that the loamy sand topsoil wets up via preferential flow and subsequent redistribution of moisture into the soil matrix. Recharge does not occur until near-positive pressures are achieved at the top of the sandy glaciofluvial outwash material that underlies the topsoil, about 1 m above the water table. Once this occurs, very rapid water table rises follow. This threshold behaviour is attributed to the vertical discontinuity in preferential flow pathways due to seasonal ploughing of the topsoil and to a lower permeability plough/iron pan restricting matrix flow between the topsoil and the lower outwash deposits. Although the wetting process in the topsoil is complex, a SMBM is shown to be effective in predicting the initiation of preferential flow from the base of the topsoil into the lower outwash horizon. The rapidity of the response at the water table and a water table rise during the summer period while flow gradients in the unsaturated profile were upward suggest that preferential flow is also occurring within the outwash deposits below the topsoil. A variation of the source-responsive model proposed by Nimmo (2010) is shown to reproduce the observed water table dynamics well in the lower outwash horizon when linked to a SMBM that quantifies the potential recharge from the topsoil. The results reveal new insights into preferential flow processes in cultivated soils and provide a useful and practical approach to accounting for preferential flow in studies of groundwater recharge estimation.

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