Re-conceptualizing the Soil and Water Assessment Tool to Predict Subsurface Water Flow Through Macroporous Soils

More water and nutrients from artificially-drained agricultural land reach surface waters by leaching through macropores than by percolating through the soil matrix. However, the Soil and Water Assessment Tool (SWAT) describes water flows poorly in land with subsurface drainage because it does not partition water between macropore and matrix transport processes. We produced a new percolation algorithm to distinguish the macropore flow pathway, which was integrated in the SWAT-MAC model and used to predict water flows in a 30 km2 agricultural subwatershed in southern Quebec, Canada. Partitioning of subsurface flow between macropore and matrix components was reasonable, compared to a chemical-based hydrograph separation of streamflow in this subwatershed. The macropore flow algorithm also improved water allocation between the annual surface runoff and subsurface flow in the SWAT-MAC model. We predict more macropore flow into tile drains under fine-textured soils than coarse-textured soils, which is consistent with experimental observations. However, macropore flow was underestimated in the non-growing season and over-predicted during the growing season, which can be adjusted in the macropore flow algorithm by accounting for dynamic macropore connectivity or effective macroporosity. There are too few observations of regional-specific effects of soil moisture and management practices on macropore flow to correct the algorithm at this time. We conclude that the percolation algorithm of SWAT-MAC represents the macropore flow pathway and improves the description of water movement through agricultural soils with subsurface drainage systems, which are important for transferring water and nutrients to downstream aquatic systems in cold, humid temperate regions.

Organic matter-driven electrical resistivity of immature lacustrine oil-prone shales

Organic matter (OM) and minerals are major particle components in lacustrine organic-rich shales. Their association and distribution control the development of primary pore space. The resistivity response of OM-driven by modifying the pore-space volume and structure in organic-rich shales of the virgin zone is still unclear. Based on a detailed study of geochemical, mineralogical, and geophysical properties from immature lacustrine oil-prone shales of the Songliao Basin (NE China), we observe a novel continuous variation of electrical resistivity driven by large ranges of total organic carbon (TOC) content (0.64–24.51 wt.%). The reduced resistivity at low TOC content (<4.5 wt.%) and then enhanced resistivity at high TOC content (>4.5 wt.%) are present in our immature shales. These variations in electrical resistivity are confirmed by fluid (S1) and solid organic compounds (S2). Furthermore, clay and detrital minerals in shales contribute to the variation of electrical resistivity as well as OMs at both low and high TOC contents. The electrical resistivity of shales is closely related to pore-space volume and structure for the electrical flow pathway. Two resistivity trends are highlighted by pore parameters such as pore volume, throat/pore ratio, pore diameter, and bulk density. Although reduced amounts and the arrangement of large pores for low TOC content cannot decrease the conduction, enhanced additional clay conduction and low OM concentration reduce the resistivity of shales. Moreover, increased amounts of non-conductive fluid and solid organic compounds and the effect of OM filling on pore space during high TOC content enhance the resistivity of shales. Thus, modified minerals and pore space driven by various OMs affect the electrical resistivity of immature shales. These results improve the understanding of OM-driven conduction in shales and contribute to the evaluation of source rocks using well log method.

Quantifying groundwater fluxes from an aapa mire to riverside esker formation

Water flows in peatland margins is an under-researched topic. This study examines recharge from a peatland to an esker aquifer in an aapa mire complex of northern Finland. Our objective was to study how the aapa mire margin is hydrogeologically connected to the riverside aquifer and spatial and temporal variations in the recharge of peatland water to groundwater (GW). Following geophysical studies and monitoring of the saturated zone, a GW model (MODFLOW) was used in combination with stable isotopes to quantify GW flow volumes and directions. Peatland water recharge to the sandy aquifer indicated a strong connection at the peatland–aquifer boundary. Recharge volumes from peatland to esker were high and rather constant (873 m3 d−1) and dominated esker recharge at the study site. The peat water recharging the esker boundary was rich in dissolved organic carbon (DOC). Stable isotope studies on water (δ18O, δ2H, and d-excess) from GW wells verified the recharge of DOC-rich water from peatlands to mineral soil esker. Biogeochemical analysis revealed changes from DOC to dissolved inorganic carbon in the flow pathway from peatland margin to the river Kitinen. This study highlights the importance of careful investigation of aapa mire margin areas and their potential role in regional GW recharge patterns.

Material flow in construction sites – a case study

The efficient movement of materials at sites in fair quantity at fair time without any interruption is called material flow. Operation and flow of these materials is a challenge experienced in sites today due to material scarcity, delivery delays, inadequate transportation facilities, loss and wastage, insufficient storage space etc. Data on material flows and inventory levels is intended to promote circular economy and resource efficiency in the construction sector. This paper presents a case study in Kerala, India with the purpose to quantify the flow of materials and stocks in the construction site. A questionnaire survey was conducted to find out the main factors that can affect the flow of materials in the building industry. Out of 65 respondents labour, equipment, material, time and cost are identified as the main factors which can contribute towards material flow. Based on the identified parameters, a material flow pathway is developed for the case study. It demonstrates the management of logistics and factors influencing the movement of materials on work sites. It therefore helps in the analysis of factors concerning the efficient use of materials in infrastructure projects. Keywords-material flow, logistics management, material scarcity, infrastructure projects.

Reducing Nutrient Loads in Northern Irish Catchments: A Modelling Approach Based on Load Apportionment and Flow Pathway Identification

&lt;p&gt;Northern Ireland has been somewhat overlooked in terms of water quality modelling in the past. Many of its catchments have consistently failed to meet Water Framework Directive targets especially due to high levels of dissolved nutrients and poor ecological status. A catchment based modelling study to address this issue has not been undertaken here previously and the approach described here uses two water quality models to achieve this aim. The objectives of the modelling were firstly to identify the total load reductions (in terms of Phosphorus (P)) required to reduce in-stream loadings sufficiently for concentrations of soluble reactive P (SRP) to be reduced to achieve the WFD &amp;#8220;Good&amp;#8221; status levels, and secondly to split these loadings into diffuse and point components. The third objective was to identify the most likely flow pathways for the transport of the diffuse component of P to the watercourses particularly for the agricultural (mostly intensive grassland farming) land use which dominates in almost all NI catchments.&lt;/p&gt;&lt;p&gt;The first model applied is the Source Load Apportionment Model (SLAM) developed by the Irish EPA. This model provides a large-scale assessment of the point and diffuse load components across catchments where multiple pressures are occurring. The second model us the Catchment Runoff Flux Assessment Tool (CRAFT) which is able to back-calculate nutrient loads associated with three major flow pathways. SLAM is a static model which uses averaged loadings from diffuse agriculture and non-agricultural land uses, and point sources (where information can be obtained from various sources) to calculate N and P exports. For P, the agricultural diffuse load component uses an enhanced version of the export coefficient approach based on combining the sources of P from applied nutrients (slurry and fertiliser) and soil P. A modelling tool allows the user to evaluate load reduction scenarios where one or several components of P (both point and diffuse) are adjusted downwards to achieve the catchment&amp;#8217;s required load reduction. The CRAFT model works on a dynamic (daily) modelling scale and has simulated sub-catchments where the SLAM model has identified the need for significant load reductions. It identifies the different reductions (P export) that are required for each flow pathway, which will then inform on the type of additional measures (e.g. sediment traps, riparian buffer strips and wetlands) that may also be required.&lt;/p&gt;&lt;p&gt;The initial aim of this study is to complete a pilot application to the trans-border (UK and ROI) Blackwater catchment (1360 km&lt;sup&gt;2&lt;/sup&gt;). Through a review of alternative modelling options for the whole area of NI, an assessment of whether this approach is suitable for application to the entire territory can be made.&lt;/p&gt;

Highly Hydrophobic Polydimethylsiloxane-Coated Expanded Vermiculite Sorbents for Selective Oil Removal from Water

Naturally abundant vermiculite clay was expanded by using an aqueous solution of H2O2 and its surface was modified with ultra-thin polydimethylsiloxane (PDMS) using facile thermal vapor deposition to prepare an ecologically friendly, low-cost oil sorbent that plays an important role in oil spillage remediation. The resulting PDMS-coated expanded vermiculite (eVMT@PDMS) particles exhibited adequate hydrophobicity and oleophilicity for oil/water separation, with numerous conical slit pores (a size of 0.1–100 μm) providing a great sorption capacity and an efficient capillarity-driven flow pathway for oil collection. Simply with using a physically-packed eVMT@PDMS tube (or pouch), selective oil removals were demonstrated above and beneath the surface of the water. Furthermore, these sorbents were successfully integrated and then applied to the advanced oil-collecting devices such as a barrel-shaped oil skimmer and a self-primed oil pump.

Cervical spinal epidural arteriovenous fistulae presenting as compressive myelopathy

Epidural Arterio-venous fistulae (EDAVF) are rare. They occur as abnormal Arterio-Venous or Capillary communications arising from major arteries of the neck or viscera and anastomose with intracranial venous sinuses or intradural spinal venous plexi, thereby short-circuiting the blood flow pathway and causing sudden and sustained venous hypertension. The retrograde flow results in venous bleeds, which may range from small petechiae on the cortical surface to major venous bleeds resulting in severe disability and even death. The shift of blood flow also can result in a steal phenomenon, serious enough to cause infarcts. Mechanical compression of the spinal cord remains thankfully the commonest symptom and is caused by the high flow fistulae leading to medullary and radicular symptoms, especially in conjunction with neurofibromatosis 1. Proper Identification and management depend on understanding the pathology, location and flow dynamics of the fistula. We present our experience with a large cervical epidural fistula with a review of literature and analysis of management protocols.

Assessing surface flow pathway connectivity in semi-natural unimproved grasslands using structure from motion

&lt;p&gt;In addition to providing a valuable habitat, semi-natural unimproved grasslands may have significant value as part of natural flood management strategies. However, further understanding of the hydrological functioning of these landscapes is required and this study is developing new methods for using proximal remote sensing techniques to assess surface flow pathway connectivity.&lt;/p&gt;&lt;p&gt;Purple moor grass (&lt;em&gt;Molinia caerulea&lt;/em&gt;) dominated fields are seasonally saturated and have a dense tussock structure, hypothesised to result in long surface flow pathways with low hydrological connectivity and greater surface roughness than neighbouring intensively managed improved grassland. Quantifying these surface flow pathways required fine-scale understanding of topography not available from available datasets such as airborne LiDAR. After prescribed burning (a local management practice) at a study site in South West England, the underlying &lt;em&gt;M. caerulea&lt;/em&gt; tussock structure and flow pathways were exposed. A DJI Mavic Air quadcopter was flown over the &lt;em&gt;M. caerulea&lt;/em&gt; field shortly after to capture this structure. A neighbouring improved grassland field of similar size and slope was also surveyed.&lt;/p&gt;&lt;p&gt;Drone surveys were carried out using an automated flight path over an area of 1.7ha of &lt;em&gt;M. caerulea&lt;/em&gt; and 2.2 ha of improved grassland. Imagery was captured with an overlap/sidelap of 85% and with a ground sampling distance of 25m. Ground control points were geolocated, using a GNSS with an accuracy of ~0.03m to constrain subsequent structure from motion (SFM) photogrammetry processing.&lt;/p&gt;&lt;p&gt;SFM was used to create dense point clouds, from which digital surface models (DSM) of the two sites were derived at a resolution of 0.03m. The standard deviation of points within each DSM grid cell was also calculated to describe the uncertainty resulting from converting point cloud data to raster. An automated classification method was developed, in R using the LidR package, to identify individual &lt;em&gt;M. caerulea&lt;/em&gt; tussocks. The edges of tussocks were characterised by greater error due to the variability in topography and therefore could be used to identify tussock features.&lt;/p&gt;&lt;p&gt;The resulting DSMs were used to quantify surface flow pathway length in both sites using the Arc GIS flow routing algorithm. This included flow pathway length and drainage density (length of flow path per unit area). &lt;em&gt;M. caerulea&lt;/em&gt; had longer, more sinuous surface flow pathways through the dense tussocks, with an average drainage density of 2.54m m&amp;#175;&amp;#178;. This was significantly greater than drainage density in the improved field (1.82m m&amp;#175;&amp;#178;). Flow pathways in the improved grassland were straighter and more in-line with the slope in comparison. Longer, tenuous surface flow pathways in &lt;em&gt;M. caerulea&lt;/em&gt; sites theoretically result in a slower velocity of surface runoff, reduced soil erosion, greater evapotranspiration and root uptake than improved grassland sites. It is proposed that this understanding will be incorporated into hydrological modelling to improve understanding of the hydrological functioning and possible natural flood management potential of these landscapes.&lt;/p&gt;