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Showing 1 to 20 of 60 for “"preferential flow"”.
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Preferential flow in vertically oriented, unsaturated soil layers
Preferential flow paths develop where particular areas of a geologic profile become more conductive than the surrounding material. Research has been conducted in recent years on preferential flow and the flow of water through unsaturated soils. Unfortunately, the research has been completed by …
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Measurement and Simulation of Preferential Flow in Frozen Soils
… and hydrological functioning of cold regions. Preferential flow in macropores may enhance infiltration into frozen soil, but flow dynamics are complicated by coupled water and heat transfer processes. Field studies were conducted in the Canadian Prairies to evaluate the dominant mechanisms …
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Seasonal variations in preferential flow under corn and soybean cropping
… knowledge of spatial and temporal variations in preferential flow under different cropping systems and tillage practices during the growing season is lacking, which has complicated the making of sound and reasonable regulatory decisions on the use of agrichemicals. In order to investigate the …
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Patterns of water table dynamics and runoff generation in a watershed with preferential flow networks
Our understanding of subsurface flow depends on assumptions of how event characteristics and spatial scale affect the relationships between subsurface water velocity, discharge, water table dynamics, and runoff response. In this thesis, three chapters explore some of these patterns for a hillslope …
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Preferential flow mechanisms : their interaction and effect on dye movement in till and glaciolacustrine sediment
… to the population of the Northern Great Plains. Preferential flow (macropore, finger, and funnel) allows such chemicals to move relatively rapidly through materials considered to be aquitards. Preferential flow mechanisms at two sites in North Dakota, one in till, the other in glaciolacustrine …
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Modification of the Field Moisture Balance Water Quality model (FMBWQ) to simulate subsurface drainage and preferential flow
… capability of simulating subsurface drainage and preferential flow to FMBWQ. The modified FMBWQ was calibrated and validated for an agricultural plot in the Iowa State University North East Research Center near Nashua, Iowa (hereafter referred to as the Nashua site). The study has been undertaken …
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Analysis of flow patterns and flow mechanisms in soils
Matrix flow and preferential flow can occur concurrently in the same soil. Both flow regimes produce typical flow patterns that can be visualised in dye tracer experiments. To extract quantitative information from dye tracer studies a vast variability of approaches exists. One of them is to …
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MONITORING INFILTRATION FROM NATURAL STORMS USING TIME-LAPSE ELECTRICAL RESISTIVITY TOMOGRAPHY
… characterization of the heterogeneity of flow through the unsaturated zone especially when compared to point measurements taken within the same survey area. The most powerful tool for understanding the unsaturated zone is a combination of several techniques. Many models of unsaturated zone …
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Preferential movement of solutes through soils
… have inspired investigations of the role of preferential movement of chemicals through agricultural soils. This research focuses on preferential flow and solute transport processes and the effects of agricultural management practices on these processes. Experimental methods for monitoring …
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Illuminating controls on solute and water transport in the critical zone
… emerging contaminants due to issues such as flow heterogeneity. Thus, there is a need to better evaluate controls on pollutant partitioning in Earth's critical zone. Our first study investigated the transport and distribution of the neonicotinoid insecticide thiamethoxam (TMX) by growing …
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Flow and Distribution of Water in Fractional Wettability Unsaturated Porous Media
In recent years, interest in fluid flow and transport in the unsaturated zone has gained more attention, due to growing concerns that the quality of the subsurface environment is adversely affected by agricultural, industrial, and municipal activities. The wettability properties (e.g., water …
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A Mesocosm Study of Bioretention Functionality Under Frozen Conditions
… the ability of the media to support preferential flow under frozen conditions. Preferential flow also limited the effects of refreezing midwinter meltwater, as no significant difference in infiltration rate was seen following the midwinter melt event. Nutrient performance was …
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Infiltration Models for Engineered Media in Living Roofs and Bioretention
… or 100-cm depth) subjected to simulated large inflows was realized in the HYDRUS-1D software, which can numerically solve the Richards equation for uniform flow modeling as well as offers a mobile-immobile model for preferential flow modeling. The magnitudes of Ks values range 10-2 to 10-1 cm/s. …
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Comparison of non-reactive solute transport models for the evaluation of fluid flow in leaching beds
… challenges related to the contact efficiency is preferential flow, cited to result in low extraction rates and in extreme cases, heap failure. Preferential flow reveals itself on two scales in drip irrigated heaps, referred to as the bed and solution scale. The bed scale takes a macro view of the …
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Identification of Recharge Source Areas in a Fractured Crystalline-rock Aquifer in Ploemeur, France
… A contact zone, which acts as the main localized flow path through the aquifer, separates the two crystalline units, and a sub-vertical permeable fault zone cross-cuts the crystalline bedrock and contact zone. Using field observations, recharge estimates, and a calibrated three-dimensional …
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Abundance, Distribution, and Geometry of Naturally Occurring Macropores in Stream Banks
Preferential flow paths are areas of substantially higher permeability than surrounding media. Macropores and soil pipes are a type of preferential flow path where conduit-like voids in the subsurface are typically greater than three millimeters in diameter. They are known to occur in agricultural …
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Surface Water and Groundwater Hydraulics, Exchange, and Transport During Simulated Overbank Floods Along a Third-Order Stream in Southwest Virginia
… field evaluations of surface and groundwater flows during overbank floods are rare. We conducted five sets of experimental floods to mimic floodplain reconnection. Experimental floods entailed pumping stream water onto an existing floodplain swale, and were conducted throughout the year to …
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Ground-penetrating radar images of a dye tracer test within the unsaturated zone at the Susquehanna-Shale Hills CZO
… radar (GPR) were used to image preferential flow paths in the shallow, unsaturated zone on hillslopes in two adjacent watersheds within the Susquehanna-Shale Hills Critical Zone Observatory (CZO). At each site we injected about 50 L of water mixed with brilliant blue dye (4 g/L) …
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MOUNTAINHYDRO: INTEGRATING GEOLOGY, GEOPHYSICS AND HYDROGEOLOGY IN A MULTIDISCIPLINARY APPROACH
… framework for the interpretation of groundwater preferential flow paths. The geophysical pillar involves the use of high resolution DC resistivity surveys and densely spaced transient electromagnetic (EM) methods, both ground-based and airborne. Geophysical surveys play a key role in capturing …
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Water Flow and Chemical Transport in a Subsurface Drained Watershed
… Mississippi River. An improved understanding of flow and transport is essential to better manage these ecosystems. However, such systems are extremely difficult to characterize and model since the regulating processes are dominated by preferential flow mechanisms that exhibit great spatial and …
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