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Copyright of Wool Textile Journal is the property of National Wool Textile Science & Technology Information Center and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Hydrogeology Journal is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

With increasing urbanization, wastewater and industrial effluents are being discharged into watercourses. Due to high-density development, it is difficult to construct conventional flow measurement structures like weirs. Hence, to measure the flow, dye tracing studies are an appropriate method for urban drainage channels. Dye tracing studies along with water quality monitoring can be analyzed to understand the behavior of pollutants in specific sections of the study area. This paper presents a state-of-the-art review for employing dye tracing studies to ascertain the pathways of pollutants and a case study. A dye tracing study was carried out at the Kolshet drain, Thane, India, to conceptualize contaminant transport using rhodamine WT (water tracer) dye. The study was carried out jointly by the Indian Institute of Technology Bombay, India and the University of Warwick, UK. Rhodamine WT dye was injected at the injection point and the distribution of dye concentration with time was logged with four portable fluorometers installed at measurement points. The data were analyzed and the longitudinal dispersion coefficient ('DL') for solute transport in the drain was computed. [ABSTRACT FROM AUTHOR]

Determination of recharge sources for karst springs can be essential in protection against their quantity diminishment and quality deterioration but has been challenged with complexity of karst water systems. This paper discusses an innovative approach consisting of multiple lines of evidence to investigate the water and turbidity sources for a pristine karst spring (Spring #1) that is located adjacent to and downgradient of a marble quarry. The approach is based on data collected on different scales and included characterization of turbidity dynamics in the spring itself, statistical analysis on relationships between turbidity and precipitation as well as between turbidity and blasting, infiltration tests within the quarry pit, X-ray diffraction analysis of sediments samples, and dye tracing tests. Eleven dye tracing tests conducted in five phases confirmed that Spring #1 receives water from both allogenic and autogenic sources. The allogenic recharge is from four sinking streams (Sinking Streams #1 through #4) and sinkholes (Sinkhole #1 area) on the borderlands, whereas the autogenic recharge is from the karst land including the quarry pit. The groundwater flow rates estimated from the tracing tests vary from 9 to 841 m/day, indicative of presence of solution-enlarged conduits in the marble aquifer. The X-ray diffraction analysis of sediment samples collected at Spring #1, the marble quarry, and Sinking Stream #2 suggested multiple turbidity sources in Spring #1. Based on the statistical analysis of data collected over 10 years, precipitation is the most important factor impacting the turbidity in Spring #1. On average, rainfall events can raise the turbidity level by approximately 14 Nephelometric Turbidity Unit (NTU). Although the infiltration test did not identify turbidity changes in Spring #1 in response to pooling of muddy water on the quarry floor, the statistical analysis suggests that, on average, blasting in the quarry could elevate turbidity value by up to 2 NTU. The blasting impact appears to become more noticeable when blasting occurred on the lower two benches of the quarry. [ABSTRACT FROM AUTHOR]

Management of groundwater resources requires a large amount of data, coupled with an understanding of the aquifer system behavior. In developing countries, the scarcity in groundwater data has led to aquifers being managed according to rule-of-thumb standards or even abandoned as unmanageable at times. Groundwater quality protection thus has been through prescribed separation distances often without due regard for internal and boundary characteristics that affect response rates of groundwater movement, attenuation of pollutants, and recharge. In this study, we examine the boundary characteristics of the highly vulnerable karst aquifer system in the rapidly expanding city of Lusaka using a dye tracer technique. We investigate the flow dynamics (magnitude and direction) of groundwater using dye tracer dyes (fluorescein and rhodamine) spiked in pit latrines and observed at discharge springs. The results provide irrefutable evidence that pit latrines are a source and a pathway to contamination of groundwater. Dye tracer movement in groundwater was rapid, estimated at 340 and 430 m/day for fluorescein and rhodamine, respectively, through interconnected conduit density. The vadose zone (epikarst) tends to store diffuse recharge before release to the phreatic zone. These rapid groundwater movements render regulatory separation minimum distances of 30 m between abstraction wells and pit latrines/septic tanks in such environments to be an ineffective means of reducing contamination. The policy focus in the protection of groundwater quality should henceforth be on robust sanitation solutions especially for low-income communities that recognize the socio-economic diversity. [ABSTRACT FROM AUTHOR]

Abstract Soil preferential flow infiltrating rapidly through the rock–soil interface is an important hydrological process in karst rocky desertification area. However, how does the water leakage in the near-surface fissures, especially those filled with soil, proceed? The role of preferential flow at rock–soil interface of those fissures on water leakage process still puzzles us. The goal of this study was to reveal the role of soil preferential flow at the rock–soil interface in the process of water leaking of near-surface fissures. Five typical types of near-surface fissures were selected in an area experiencing severe rocky desertification in Guizhou Province, China. Dye tracer testing was applied, combined with digital image processing techniques. The results indicated that the rock–soil interface flow on both sides of the fissures is the most important preferential flow form in the fissures in karst area. The dyed area ratio of preferential flow varied from 0.12 to 0.48 in the rock + soil profiles, from 0.06 to 0.37 in the soil profiles, and between 0.02 and 0.16 in the rock–soil interface. The rock–soil interface is the smallest in terms of both their variation range of dyed area ratio and preferential flow patterns compared with soil and rock–soil profiles. The soil preferential flow in near-surface fissures mainly occurs in the soil depth range of 0–20 cm. The preferential flow path is mainly affected by the rock–soil interface on both sides and can pass through the clay layer with poor permeability. However, the soil depth of the dyed part was more than 50 cm. The soil preferential flow at the rock–soil interface is the main form of rapid downward leakage of water in near-surface fissures in the karst rocky desertification area, which can flow to the bottom of clay layer with poor permeability.

Rivers are important passages for land-based materials transported to the sea, such as fresh water, sediment, pollutants, and nutrients. River discharge with land-based materials will form a river plume with a buoyancy flow. The river plume is subject to the interaction between nearshore runoff with seawater. In this study, the movement characteristics of the river plume are investigated based on particle image velocimetry (PIV) and the dye tracing method. It is found that the change of flow rate and environmental water density will shape the river plume pattern in both the plan view and the side view. The combined effect of flow rate and environmental water density could be described by the Froude number. The river plume has a free surface in the x-z plane and the horizontal velocity of the plume can be fitted with a 1/2 Gaussian distribution curve. The change of flow rate has little effect on the type of plume thickness curve, while the increase of environmental water density will change the thickness curve type of the river plume. The stable thickness of the river plume increases with the increase of the Froude number. The maximum value of turbulent kinetic energy is located in the middle layer, and the increase of the flow rate or the density difference leads to the increase in the turbulent kinetic energy.

Groundwater is contaminated with chlorinated volatile organic compounds (CVOCs) including trichloroethene (TCE), tetrachloroethene (PCE), and their degradation products at a 230-acre formerly used defense site in Pennsylvania. Unconsolidated overburden materials ranging in thicknesses from 15 to 60 feet overlie two types of bedrock: quartzitic sandstone and phyllite on the eastern sloping hills and limestone and dolomite on the western flat-lying terrane. Karst is well developed in the carbonate rocks and is characterized by a pinnacle-and-cutter bedrock surface, solution-enlarged fractures/conduits at depths up to 450 feet below ground surface (bgs), caverns in tens of feet, and frequent occurrence of sinkholes. The PCE and TCE concentrations in groundwater samples suggest that dense non-aqueous phase liquid penetration extended to depths on the order of 400–450 feet bgs in the carbonate bedrock. A dye trace study was conducted to help refine the conceptual site model. The study consisted of five fluorescent dyes that were injected in five wells that encountered karst conduits/caverns at various depths from 32 to 216 feet bgs. The dyes were monitored at 40 monitoring wells and 16 points along a stream to the west of the site. The dye tracing results established positive dye detections at seven monitoring points in the stream. Field observations, infrared thermography imaging, and water quality survey confirmed that three of them, i.e., Spring-15, Spring-17, and Spring-26, are groundwater discharge points in the stream, i.e., submerged springs. Discovery of the submerged springs significantly contributed to the refinement of the conceptual site model and provided an opportunity to effectively remediate and manage the contaminated groundwater. These springs confirmed the exposure pathways that connect the site-impacted groundwater to surface water receptors, and the final remedy included measures to address potentially unacceptable risks to human beings and the environment in the stream and ensure that the state-regulated ambient water quality criteria are met for the site CVOCs at established compliance monitoring stations. These springs also helped optimize an existing pump and treat system that has been active since 1994. Shutdown and restart-up tests were conducted to evaluate the effectiveness of different extraction scenarios in the removal of the CVOCs at the springs under wet and dry seasons. The results led to a new configuration of the extraction wells by including a previously inactive extraction well CW-20. [ABSTRACT FROM AUTHOR]

Soil preferential flow infiltrating rapidly through the rock–soil interface is an important hydrological process in karst rocky desertification area. However, how does the water leakage in the near-surface fissures, especially those filled with soil, proceed? The role of preferential flow at rock–soil interface of those fissures on water leakage process still puzzles us. The goal of this study was to reveal the role of soil preferential flow at the rock–soil interface in the process of water leaking of near-surface fissures. Five typical types of near-surface fissures were selected in an area experiencing severe rocky desertification in Guizhou Province, China. Dye tracer testing was applied, combined with digital image processing techniques. The results indicated that the rock–soil interface flow on both sides of the fissures is the most important preferential flow form in the fissures in karst area. The dyed area ratio of preferential flow varied from 0.12 to 0.48 in the rock + soil profiles, from 0.06 to 0.37 in the soil profiles, and between 0.02 and 0.16 in the rock–soil interface. The rock–soil interface is the smallest in terms of both their variation range of dyed area ratio and preferential flow patterns compared with soil and rock–soil profiles. The soil preferential flow in near-surface fissures mainly occurs in the soil depth range of 0–20 cm. The preferential flow path is mainly affected by the rock–soil interface on both sides and can pass through the clay layer with poor permeability. However, the soil depth of the dyed part was more than 50 cm. The soil preferential flow at the rock–soil interface is the main form of rapid downward leakage of water in near-surface fissures in the karst rocky desertification area, which can flow to the bottom of clay layer with poor permeability. [ABSTRACT FROM AUTHOR]

Soil bunds are a common land reconstruction practice in the Three Gorges Reservoir area of China, and play a key role in runoff regulation and soil conservation on cultivated hillslopes. This study investigated water movement pathways and retaining effects of soil bunds using water transport trajectory observations inferred from field dye tracing experiments. It was found that water infiltration in the bund was characterised by spatial heterogeneity in three dimensions. The stained area ratio (SAR) of the bund was much lower than that of the adjacent field at all depths. Dye patterns resembled inclined strips in the bund, and lateral seepage occurred mainly on the top of hard pan. SAR, stained path width (SPW) <20 mm, and stained path number (SPN) all decreased with increasing horizontal distance. The SPW <20 mm proportion and SAR both decreased according to a logarithmic function, while the changing trend of SPN followed a first‐order exponential decay. Three pathways of water movement in the bund could be distinguished, namely, vertical infiltration, lateral seepage and flow along the bund–bedrock interface. The primary water seepage channel in the bund was likely to be the bund–bedrock interface (accounting for around 80% of the total flow). These results provide preliminary realisation of water movement mechanisms in the purple soil bunds on sloping farmland and inform management options for bund stability maintenance. [ABSTRACT FROM AUTHOR]

• Determining the geometric shape of cracks generated from the physical crust crack. • Investigating cracks on the preferential flow under the control of physical crusts. • Examining the hydrological processes of physical crusts. • Indexes for crack properties in structural crusts were larger than deposition crusts. • Preferential flow in structural crust was superior to those of deposition crust. Studies have shown that preferential flow induced by cracks establishes multiple features such as morphology in different soil profiles. However, there has been little experimental evidence of the contribution of physical crust towards crack features and preferential flow. Essentially, this investigation focused on physical crusts (structural and deposition crust) of Lou soil, a loam and silt loam-textured soil, to demarcate the formation of cracks and preferential flow under artificial rainfall. The crack initiation and propagation processes were defined as the formation of primary cracks in the initial phase and narrow cracks around primary cracks, respectively. The cylindrical soil containers and cubical stainless-steel boxes were employed to trace preferential flow in the horizontal and vertical profile, respectively. The cracks in structural and deposition crusts were dominated by initiation and propagation cracks, respectively. The area, length, and width of the cracks in the structural crusts (5.7 cm2, 815, and 1.44 mm) were notably larger than deposition crusts (1.7 cm2, 604, and 0.96 mm). The maximum dyed depths of the structural and deposition crusts reached 35, 45, and 65 mm, and 35, 55, and 75 mm under the infiltration amounts of 10, 30, and 50 mm, respectively. The uniform infiltration depth, length index and PF-fr of structural crusts were in the ranges of 6.7 ∼ 25.5 mm, 19 ∼ 46 %, and 83 ∼ 111 %, respectively. Corresponding values for deposition crusts were 7.2 ∼ 26.2 mm, 10 ∼ 46 %, and 87 ∼ 103 %, respectively. The preferential flow in the soil profiles with structural crusts was superior to deposition crust. An assessment of the potential function of the physical crust for preferential flow is a supplement to study the effect of soil surface morphology on hydrological process. [ABSTRACT FROM AUTHOR]

Virkisjökull is a rapidly retreating glacier in south-east Iceland. A proglacial lake has formed in the last ten years underlain by buried ice. In this study we estimate water velocities through the glacier, proglacial foreland and proglacial river using tracer tests and continuous meltwater flow measurements. Tracer testing from a glacial moulin to the glacier outlet in September 2013 demonstrated a rapid velocity of 0.58 m s−1. This was comparable to the velocity within the proglacial river, also estimated from tracer testing. A subsequent tracer test from the same glacial moulin under low flow conditions in May 2014 demonstrated a slower velocity of 0.07 m s−1. The glacier outlet river sinks back into the buried ice, and a tracer test from this sink point through the proglacial foreland to the meltwater river beyond the lake indicated a velocity of 0.03 m s−1, suggesting that an ice conduit system within the buried ice is transferring water rapidly beneath the lake. Ground penetrating radar profiles confirm the presence of this buried conduit system. This study provides an example of rapid deglaciation being associated with extensive conduit systems that enable rapid meltwater transfer from glaciers through the proglacial area to meltwater rivers.

The aim of this study was to quantify the effects of compaction on water flow patterns at the soil profile scale. Control and trafficked plots were established in field trials at two sites. The trafficked treatment was created by four passes track‐by‐track with a three‐axle dumper with a maximum wheel load of 5.8 Mg. One year later, dye‐tracing experiments were performed and several soil mechanical, physical and hydraulic properties were measured to help explain the dye patterns. Penetration resistance was measured to 50 cm depth, with saturated hydraulic conductivity (Ks), bulk density, and macroporosity and mesoporosity being measured on undisturbed soil cores sampled from three depths (10, 30 and 50 cm). Significant effects of the traffic treatment on the structural pore space were found at 30 cm depth for large mesopores (0.3–0.06 mm diameter), but not small mesopores (0.06–0.03 mm) or macroporosity (pores > 0.3 mm). At one of the sites, ponding was observed during the dye‐tracing experiments, especially in the trafficked plots, because of the presence of a compacted layer at plough depth characterized by a larger bulk density and smaller structural porosity and Ks values. Ponding did not induce any preferential transport of the dye solution into the subsoil at this site. In contrast, despite the presence of a compacted layer at 25–30 cm depth, a better developed structural porosity in the subsoil was noted at the other site which allowed preferential flow to reach to at least 1 m depth in both treatments. [ABSTRACT FROM AUTHOR]

Abstract While the supraglacial hydrology of debris-covered glaciers is relatively well studied, almost nothing is known about how water is transported beneath the glacier surface. Here, we report the results of sixteen fluorescent dye tracing experiments conducted in April–May 2018 over the lowermost 7 km of the high-elevation, debris-covered Khumbu Glacier, Nepal, to characterise the glacier's surface and subsurface drainage system. Dye breakthroughs indicated a likely highly sinuous and channelised subsurface hydrological system draining water from the upper part of the ablation area. This flowpath was distinct from the linked chain of supraglacial ponds present along much of the glacier's lower ablation area, through which water flow was extremely slow (∼0.003 m s−1), likely reflecting the study's timing during the pre-monsoon period. Subsurface drainage pathways emerged at the glacier surface close to the terminus, and flowed into small near-surface englacial reservoirs that typically delayed meltwater transit by several hours. We observed rapid pathway changes resulting from surface collapse, indicating a further distinctive aspect of the drainage of debris-covered glaciers. We conclude that the surface and subsurface drainage of Khumbu Glacier is both distinctive and dynamic, and argue that further investigation is needed to refine the characterisation and test its regional applicability to better understand future Himalayan debris-covered glacier meltwater delivery to downstream areas. Highlights • Dye tracing used to investigate hydrology of debris-covered Khumbu Glacier, Nepal. • A subsurface drainage system exists, and is likely highly sinuous and channelised. • The subsurface drainage system does not link to the chain of supraglacial ponds. • Flow through the pond chain is slow and comprises a small part of total discharge. • Rapid pathway changes are observed, resulting from variable surface lowering. [ABSTRACT FROM AUTHOR]

Highlights • Debris-covered glaciers have a distinct hydrological structure. • Debris cover reduces supraglacial catchment size and reduces melt rates. • Beneath continuous debris on the lower glacier the drainage network is inefficient. • An efficient conduit system drains the clean and dirty ice on the upper glacier. • A channelized and distributed system co-exist beneath the lower glacier. Abstract Supraglacial debris is known to strongly influence the distribution of glacier surface melt. Since melt inputs drive the formation and evolution of glacial drainage systems, it should follow that the drainage systems of debris-covered glaciers will differ from those of debris-free glaciers. This would have implications for the proglacial runoff regime, subglacial erosion and glacier dynamics. This paper presents analysis of return curves from 33 successful dye injections into the extensively debris-covered Miage Glacier, Italian Alps. It demonstrates that the spatial distribution of supraglacial debris influences the structure and seasonal evolution of the glacial drainage system. Where the debris cover is continuous, melt is lower and the surface topography is chaotic, with many small supraglacial catchments. These factors result in an inefficient englacial/subglacial drainage network beneath continuous debris, which drains to the conduit system emanating from the upper ablation zone. Melt rates are high in areas of clean and dirty ice above the continuous debris. Runoff from these areas is concentrated by inter-moraine troughs into large supraglacial streams, which encourages the early-season development of an efficient englacial/subglacial conduit system downstream of this area. Drainage efficiency from the debris-covered area increases over the melt season but dye-trace transit velocity remains lower than from moulins on the upper glacier. Future runoff models should account for the influence of supraglacial debris on the hydrological system. [ABSTRACT FROM AUTHOR]

• Secondary vegetation succession promotes preferential flow. • Secondary vegetation succession changes soil texture and structure. • Soil structure independently explains 26% variation of preferential flow pattern. • Reforestation intensifies preferential flow by improving soil structure. Preferential flow benefits water storage in deep soils that contribute to hydrological sustainability under different vegetations in the Karst regions, however, how vegetation specializes preferential flow pattern by changing soil architecture remains unclear. The study investigated the variations of soil architecture and preferential flow patterns in the agricultural field, abandoned field, and young and mature woodlands that representing four vegetation succession stages during the implementation of returning cultivated land into forest in the Karst region, to explored how soil texture and structure interact to specialize preferential flow patterns under the vegetation succession, using the dye-tracing technique, the principal component analysis (PCA), and the variation partitioning analysis (VPA). The dyed soil profiles illustrated heavy preferential flow under the four vegetations. The maximum infiltration depth (D max), actual infiltration depth (D actual), total dye coverage (C total), and length index (LI) significantly increased following the sequence of vegetation succession stages (P < 0.05), and the preferential pathway contribution (D pr) was the significantly lowest under the agricultural field and young woodland and the highest under the mature woodland (P < 0.05), which indicated of intensified preferential flow with ongoing vegetation succession. The preferential flow pattern index (PFP) was constructed by the D max , D actual , C total , D pr , and LI after the PCA, which gradually increased (from −0.82 ± 0.69 to 1.37±0.80) during the succession, suggesting that preferential flow percolated deeper, more preferential flow was received, and preferential flow contribution increased during the succession. Soil texture (sand content, silt content, and geometric mean soil particle size) and structure (bulk density, air-filled porosity, total porosity, air-filled porosity, and ratio of air-filled and capillary porosity to total porosity) significantly correlated to the PFP (P < 0.05). The VPA revealed that soil texture and structure independently explained 9 % and 26 % variation of the PFP. This situation means although reforestation intensified preferential flow by improving soil structure, adverse impacts of improper soil texture management of could offset the intensification efficiency by reforestation. Therefore, the results benefit to meet ecological and hydrological sustainability challenges rooted by preferential flow in the Karst regions. [ABSTRACT FROM AUTHOR]

We studied excitation spectra of uranine fluorescence in eluates from charcoal traps saturated in cave waters and in reference uranine solutions and found that the most appropriate excitation wavelength is 295±5 nm, because it excites fluorescence of uranine many times stronger than fluorescence of natural fluorescent compounds in groundwater. This allows us to lower the detection limit of uranine fluorescence with one order of magnitude, even below the level of natural fluorescence of karst waters at integral UV excitation. [ABSTRACT FROM AUTHOR]

Highlights • First attempt of coupling CFPv2 and OSTRICH for optimization of conduit parameters. • Calibration of CFPv2 based on considering both breakthrough and spring discharge. • A reliable scenario is selected that improves understanding of karst groundwater. • The results contributed to the decision of not constructing a dam at the site. Abstract In order to better define the characteristics of a karst conduit, an integrated hydrogeological study including numerical modeling using CFPv2 is conducted at a karst aquifer in the Zagros Mountain Region of Iran. The Sarvak limestone aquifer in the Nil Anticline is the main karst aquifer of the study area with major groundwater discharge taking place at Sarkur spring. An annual water balance and a dye tracing test confirmed that the karst system is mainly recharged through rainfall and the Maroon River. Several depressions are observed along the banks of the river with a major one classified as a sinkhole used for dye injection. A groundwater flow model was developed based on the available hydrogeological information. A probable direct conduit flow path with an estimated groundwater flow velocity of 96 m/h is estimated between the injection point and the Sarkur spring. Four scenarios are assumed to simulate the probable conduit flow path using the CFPv2 code. As one of the first attempts in regional groundwater flow modeling of a karst aquifer, CFPv2 is automatically calibrated with field measurements of spring discharge and a dye breakthrough curve through a parameter estimation code OSTRICH to optimize the characteristics of the conduit through the minimization of the weighted sum of square error. Simulated results reveal that a conduit with a diameter of 2.9 m is required to adequately simulate spring discharge and dye tracer migration between the injection and discharge points. Our new approach (linking of CFPv2 and OSTRICH) provides a deeper understanding of groundwater flow and solute transport in karst terrains even when available data are limited and the approach should be applicable to other areas. [ABSTRACT FROM AUTHOR]

The accurate measurement of velocities of shallow overland flows normally found in the field of hydrology is essential to understand the kinematics of these flows. In view of this, we have tested the capability of a new thermal particle tracer (cold oil droplets) under controlled laboratory conditions to measure the velocity of shallow overland flows (<2 mm depth) using the infrared-based particle tracking velocimetry (PTV) technique. Experimental apparatus comprised a soil flume 3 m long and 0.3 m wide with a feeder tank attached to the upstream end. Flow velocities acquired through infrared-based PTV were compared with corresponding values given by the volumetric discharge method, dye tracing, and conventional PTV (using polystyrene beads as tracer) for eleven flow conditions that combined different slopes (5, 7, 10 and 15%) and discharges (0.15 to 0.51 L s −1  m −1 ). The Reynolds number (569 to 1938) marked it as quasi-laminar flow. The results showed that acquired flow velocity given by through infrared-based PTV and conventional PTV techniques was closer to the mean velocity estimated by the volumetric discharge method than it was to dye tracing estimated velocity. The mean correction factor value (0.78) estimated by the infrared-based PTV technique was higher than the dye tracing estimated correction factor value (0.48). Furthermore, the detection of the leading edge of the dye tracer was difficult and the stagnation of polystyrene beads at lower discharges resulted in an underestimation of mean velocity. This research stresses the potential of using thermal imaging to estimate the velocity of shallow water bodies, because of the tracer's conspicuous visibility and independence from illuminating conditions. [ABSTRACT FROM AUTHOR]

Recharge processes of karst aquifers are difficult to assess given their strong heterogeneity and the poorly known effect of vadose zone on infiltration. However, recharge assessment is crucial for the evaluation of groundwater resources. Moreover, the vulnerability of karst aquifers depends on vadose zone behaviour because it is the place where most contamination takes place. In this work, an in situ experimental approach was performed to identify and quantify flow and storage processes occurring in karst vadose zone. Cave percolation monitoring and dye tracing were used to investigate unsaturated zone hydrological processes. Two flow components (diffuse and quick) were identified and, respectively, account for 66% and 34% of the recharge. Quickflow was found to be the result of bypass phenomenon in vadose zone related to water saturation. We identify the role of epikarst as a shunting area, most of the storage in the vadose zone occurring via the diffuse flow component in low permeability zones. Relationship between rainfall intensity and transit velocity was demonstrated, with 5 times higher velocities for the quick recharge mode than the diffuse mode. Modelling approach with KarstMod software allowed to simulate the hybrid recharge through vadose zone and shows promising chances to properly assess the recharge processes in karst aquifer based on simple physical models. [ABSTRACT FROM AUTHOR]

Virkisjökull is a rapidly retreating glacier in south-east Iceland. A proglacial lake has formed in the last ten years underlain by buried ice. In this study we estimate water velocities through the glacier, proglacial foreland and proglacial river using tracer tests and continuous meltwater flow measurements. Tracer testing from a glacial moulin to the glacier outlet in September 2013 demonstrated a rapid velocity of 0.58 m s-1. This was comparable to the velocity within the proglacial river, also estimated from tracer testing. A subsequent tracer test from the same glacial moulin under low flow conditions in May 2014 demonstrated a slower velocity of 0.07 m s-1. The glacier outlet river sinks back into the buried ice, and a tracer test from this sink point through the proglacial foreland to the meltwater river beyond the lake indicated a velocity of 0.03 m s-1, suggesting that an ice conduit system within the buried ice is transferring water rapidly beneath the lake. Ground penetrating radar profiles confirm the presence of this buried conduit system. This study provides an example of rapid deglaciation being associated with extensive conduit systems that enable rapid meltwater transfer from glaciers through the proglacial area to meltwater rivers. [ABSTRACT FROM AUTHOR]

Copyright of Chinese Journal of Applied Ecology / Yingyong Shengtai Xuebao is the property of Chinese Journal of Applied Ecology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Surface soil hydrology is a major control on the terrestrial water cycle in Earth's Critical Zone (CZ). Partitioning of vertical preferential flow and subsurface lateral flow is commonly attributed to the heterogeneity of slope, soil profile horizon, and soil structure, but the influences of land-use types are largely unknown. Agroforestry systems (AF) can intercept subsurface lateral flow for reducing nitrogen losses to drainage water and for alleviating secondary salinity in central China and southeast Australia. These effects have been attributed to enhanced evapotranspiration and canopy interception in the agroforestry systems compared to monocropping systems (MC). Here, we show the differences in lateral and vertical soil hydrological pathways between AF and MC with dye-tracing experiments before and during a simulated rainfall event. Before the rainfall, the vertical and horizontal dye-staining patterns demonstrated that preferential flow occurred through isolated macropores with fine tree roots in AF and through connected cracks in MC. The dye coverage area and depth indicated greater vertical preferential flow in AF than in MC. During the 2-h rainfall event, the dye-staining area at different depths indicated that the preferential flow contributed to greater near-surface lateral flow in MC than in AF. The changes in the hydrological pathways were attributed to deep roots and no physical barrier from plough pan in AF and the presence of the plough pan in MC. These results suggest that land use has strong water partitioning effects not only above ground but also in the subsurface, and that understanding the landscape hydrology in the Earth's Critical Zone required quantification of the considering coupled pedological and biological processes. [ABSTRACT FROM AUTHOR]

A myriad of downstream communities and industries rely on streams fed by both groundwater discharge and glacier meltwater draining the Cordillera Blanca, Northern Peruvian Andes, which contains the highest density of glaciers in the tropics. During the dry season, approximately half the discharge in the region's proglacial streams comes from groundwater. However, because of the remote and difficult access to the region, there are few field methods that are effective at the reach scale to identify the spatial distribution of groundwater discharge. An energy balance model, Rhodamine WT dye tracing, and high-definition kite-borne imagery were used to determine gross and net groundwater inputs to a 4-km reach of the Quilcay River in Huascaran National Park, Peru. The HFLUX computer programme () was used to simulate the Quilcay River's energy balance using stream temperature observations, meteorological measurements, and kite-borne areal photography. Inference from the model indicates 29% of stream discharge at the reach outlet was contributed by groundwater discharge over the study section. Rhodamine WT dye tracing results, coupled with the energy balance, show that approximately 49% of stream water is exchanged (no net gain) with the subsurface as gross gains and losses. The results suggest that gross gains from groundwater are largest in a moraine subreach but because of large gross losses, net gains are larger in the meadow subreaches. These insights into pathways of groundwater-surface water interaction can be applied to improve hydrological modelling in proglacial catchments throughout South America. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Quantitative dye-tracing methods were utilized in a portion of the greater Springfield, Missouri metropolitan area. These methods were used to evaluate factors influencing groundwater movement through the shallow karst system in the area. Fortuitous timing of these studies with a summer drought allowed for very low-flow conditions to be tested, and the results of these tests suggest that shallow groundwater in the study area occurs in fractures and along bedding planes, with a significant input component from flow along bedding planes or other sub-horizontal features. Based on one unique trace, it appears that recent dye traces may be affected by groundwater elevations, where crossover from one conduit system to another occurs under most water level conditions, but ceases under the lowest flow conditions. [ABSTRACT FROM AUTHOR]

Dye tracing field data were collected in small, steep streams in Ontario and used to calculate longitudinal dispersion coefficients for these headwater streams. A predictive equation for longitudinal dispersion coefficient is developed using combined data sets from five steeper head - water streams and 24 milder and larger rivers. The predictive equation relates the longitudinal dispersion coefficient to hydraulic and geometric parameters of the stream and has been developed using multiple regression analysis. The newly developed equation shows impressive accuracy of predictions for longitudinal dispersion coefficient ( R2 = 0.86, RMSE = 25, Nash-Sutcliffe coefficient Ens = 0.86 and Index of Agreement D = 0.96) for both small, steep headwater streams as well as large, mild rivers. The Froude number has been introduced as a third key parameter to capture the effect of slope of the reach - in addition to the aspect ratio and bed material surface roughness - on the longitudinal dispersion coefficient. The pronounced improvement in the accuracy of the prediction is due to the addition of the Froude number to capture the effect of the slope of the reach on longitudinal dispersion coefficient. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The sinuosity factor (SF) is a critical value in karst systems in terms of estimating their hydrodynamic parameters including groundwater velocity, coefficient of dispersion, etc., through dye tracer experiments. SF has been used in a number of different dye tracer experiments in karstic systems to estimate a representative flow path. While knowing SF is crucially important in the estimation of hydrodynamic parameters, its calculation is associated with significant uncertainty due to the complexity of subsurface karstic features. And yet, only a few studies have discussed its uncertainties, which might lead some errors in estimation of hydrodynamic parameters from dye tracer experiment. In this study, dye tracer experiments were conducted in two consecutive years (2003 and 2004) representing low and high flow conditions in the Beyyayla sinkhole (Eskişehir, Turkey) where the flow path is well known. Uranine was used in experiments as a tracer and QTRACER computer program was used to determine the hydrodynamic properties of the Beyyayla karst system as well as to gain insights into the effects of SF from dye tracer experiments on estimated parameters. The results showed that the breakthrough curve follows a unimodal and a bimodal distribution in low and high flow conditions, respectively. These different distributions stem from the water transport mechanisms, where velocities were calculated as 58.2 and 93.6 m h during low and high flow conditions observed in a spring emerging from the south side of the studied system. The results also show that the coefficient of dispersion, Reynolds number, and Peclet number increased and longitudinal dispersivity decreased with the higher flow rate. Furthermore, the estimated parameters did not vary with either the flow conditions or the tracer transit time, but they have shown some variations with SF. When SF was increased by 50 %, a change in these parameters was obtained in the range of 50-125 %. [ABSTRACT FROM AUTHOR]

Gravely calcareous soils cover approximately most of arid lands (in percent); however, the solute transport behavior in these soils remains a current issue. This research aimed at estimating and correlating the solute transport parameters in gravely calcareous soils as being affected by different land uses through the knowledge of the soil morphological, physical, and chemical properties. Four different land use sites were selected: irrigated trees and bare, range, and alluvial sediment lands. Solute transport parameters of soil pore water velocity ( V), dispersion coefficient ( D), and retardation factor ( R) were estimated using bromide breakthrough curve tests for surface soil columns. In addition, field Brilliant Blue FCF dye tracing experiment was conducted to determine the maximum dimensional movements. Soil morphological analysis was able to explain the heterogeneity in the solute transport parameters. Conductive solute transport mechanism with V of 17.99 m/day was favored in a high continuous pore system observed under tree lands. Presence of high gravel and CaCO contents under range lands increased pore system tortuosity and thus increased D magnitude up to 1,339.88 cm/day. Existence of thin surface crusts at both bare soils and alluvial sediments had considerably restricted V down to 1.46 m/day. Dye staining technique aided the explanation of the existing variations by providing visual evidence on the preferential flow paths and patterns governing the solute transport mechanism at each site. [ABSTRACT FROM AUTHOR]