Surface mining for coal in the Central Appalachians contributes total dissolved solids (TDS) to headwater streams, especially below larger mines and associated valley fills. My objective was to characterize the geochemical properties of a range of surface soils and associated geologic strata from the Central Appalachian coalfields and to relate those properties to simple field indicators, such as color or rock type. I hypothesized that these indicators can accurately predict certain geochemical properties. Thirty-three vertical weathering sequences were sampled from eight surface mines throughout the Central Appalachian coalfields, for a total of 204 individual samples. No differences were found among sites in overall saturated paste specific conductance (SC; used as a proxy for TDS) levels, but significant geochemical differences existed among samples. Sulfate release dominated SC levels, followed closely by Ca and Mg. Surficial soils and sandstones were yellowish-brown in color, high in citrate dithionite (CD) - extractable Al, Fe, and Mn, and low in SC, compared to underlying sandstones, shales, and mudstones, which were grayish to black, low in CD-extractable Al, Fe, and Mn, and significantly higher in SC. Saturated paste As and P were higher in A horizons, whereas Se was significantly higher in unweathered bedrock than in soil or weathered bedrock. Samples generating exothermic reactions with 30% H2O2 produced higher SC levels, sulfate, Mg, and Se. In conclusion, the mine spoils studied varied widely in geochemical properties. The simple field indicators presented here, such as color, weathering status, rock type, and H2O2 reaction can provide valuable guidance for identifying TDS risk which would greatly improve operator's ability to actively minimize TDS release. I recommend using soil and weathered, yellowish-brown sandstone layers as a source of low TDS spoil material whenever possible. The H2O2 field test is useful for identification of TDS and Se risk. Underlying unweathered bedrock layers should be treated as "potentially high TDS spoils". Particularly high risk spoils include gray to black mudstones and shales, coals, and coal associated shales, mudstones, and clays directly associated with coal seams. I recommend hydrologically isolating these spoils using techniques similar to those used historically for acid-forming materials. / Ph. D.

The Powell River is located in southwestern Virginia and northeastern Tennessee, USA and supports a diverse freshwater mussel assemblage of 29 extant species. Throughout the river major ion and trace element concentrations have increased over the last several decades due to extensive surface coal-mining in the headwaters in Virginia. As watershed area affected by mining has increased, mussel populations have declined, especially in Virginia where populations have been severely reduced or extirpated. The upper watershed now has been extensively mined for coal, causing widespread effects on water and sediment quality. To investigate how mining may be affecting mussel populations, I first conducted a laboratory bio-assay to assess the effects of elevated major ions and the trace element nickel (Ni) on growth and survival of juvenile mussels, including one common species (Villosa iris) and one endangered species (Epioblasma capsaeformis). No significant differences in overall survival between treatments and control were observed for either species over a 70 day test period. Total growth was not significantly different between treatments and control for either species. However, overall growth varied significantly (p=0.009) between species, with V. iris (2.49 mm) exhibiting greater growth compared to E. capsaeformis (1.97 mm). Results suggest that major ion chronic toxicity alone or in combination with Ni at or below my test concentration is not a likely source of toxicity to juvenile mussels in the Powell River. Secondly, I conducted a field study in the Powell River using two cohorts of juveniles of Villosa iris to assess the effects of trace elements and PAH contamination related to mining on mussel survival and growth. Specific conductance was elevated throughout the Powell River, where site means ranged from 450 to 900 µS/cm. While mortality was high at all eight sites it was not significantly different among these sites (p>0.28); however, growth of juvenile mussels was significantly higher (p<0.001) in the lower river in Tennessee. Regression analysis showed significant relationships (p<0.001) of river kilometer with temperature, specific conductance, and aqueous major ion concentrations. A principal component analysis (PC) was conducted on all trace element data. Growth of Cohort 1 on Day 106 was best explained by the PC dominated by aqueous major ion concentrations (p<0.0001, R2= 0.65) and growth of Cohort 2 on Day 106 was best explained by specific conductance (p<0.0001, R2= 0.68). Growth of Cohort 2 at Day 423 was best explained by tissue trace element concentration PC1 and PC2 (p<0.0001, R2= 0.73). This study suggests major ions and select trace elements (Ba, Ni, Fe, Se, and Sr) in the Powell River are negatively affecting the growth of freshwater mussels and that the source of these contaminants is primarily from mining in the headwaters. / Master of Science / The Powell River is located in southwestern Virginia and northeastern Tennessee, USA and supports a diverse freshwater mussel assemblage of 29 extant species. Throughout the river major ion and trace element concentrations have increased over the last several decades. As watershed area affected by coal mining has increased mussel populations have declined, especially in Virginia where populations have been severely reduced or extirpated. The upper Powell River watershed has been extensively mined for coal, causing widespread decline in the river’s water and sediment quality. My study consisted of a laboratory and field exposure to assess the toxicity of the mining related contaminants, such as major ions, trace elements, and polycyclic aromatic hydrocarbons (PAHs) to freshwater mussels. Further, the study investigated the concentrations of these contaminants in the river and their effects on the survival and growth of exposed juvenile mussels. In my laboratory study, mussels of a common species (Villosa iris) and an endangered species (Epioblasma capsaeformis) showed no effect when exposed to a suite of major ions and the trace element Ni similar to levels measured in the Powell River. When juvenile Villosa iris were exposed in the Powell River at eight sites in Virginia and Tennessee, high rates of mortality were observed at all eight sites and growth of juveniles showed a significant spatial trend, with higher growth observed downstream in Tennessee. Water quality analysis revealed increased concentrations of major ions at all sites but concentrations of trace elements were generally below EPA water quality criteria. Further, many of the major ions and trace elements trended spatially with higher concentrations measured in the headwaters in Virginia and lower concentrations observed downstream in Tennessee. Statistical analysis revealed that major ions and trace elements (Ba, Ni, Fe, Se, and Sr) may have negatively affected growth of exposed mussels. This study revealed that laboratory conditions may not adequately be representing river conditions and that in the river major ions and trace elements likely are negatively effecting growth and survival of freshwater mussels. This study revealed that conditions in the Powell River likely are not suitable for mussel reintroduction and that mining is the main source of the contaminants in the river.

Anthropogenic salinization of freshwater is a global concern. In freshwater environments, elevated levels of major ions, measured as total dissolved solids (TDS) or specific conductance (SC), can cause adverse effects on aquatic ecosystem structure and function. In central Appalachia, eastern USA, studies largely rely on Rapid Bioassessment Protocols with semi-quantitative sampling to characterize benthic macroinvertebrate community response to increased salinity caused by surface coal mining. These protocols require subsampling procedures and identification of fixed numbers of individuals regardless of organism density, limiting measures of community structure. Quantitative sampling involves enumeration of all individuals collected within a defined area and typically includes larger sample sizes relative to semi-quantitative sampling, allowing expanded characterization of the benthic community. Working in central Appalachia, I evaluated quantitative and semi-quantitative methods for bioassessments in headwater streams salinized by coal mining during two time periods. I compared the two sampling methods for capability to detect SC-induced changes in the macroinvertebrate community. Quantitative sampling consistently produced higher estimates of taxonomic richness than corresponding semi-quantitative samples, and differences between sampling methods were found for community composition, functional feeding group, dominance, tolerance, and habit metrics. Quantitative methods were generally stronger predictors of benthic community-metric responses to SC and were more sensitive for detecting SC-induced changes in the macroinvertebrate community. Quantitative methods are advantageous compared to semi-quantitative sampling methods when characterizing benthic macroinvertebrate community structure because they provide more complete estimates of taxonomic richness and diversity and produce metrics that are stronger predictors of community response to elevated SC. / Master of Science / Surface coal mining in central Appalachia, eastern USA, contributes to increased salinity of surface waters, causing adverse effects on water quality and aquatic life. Stream condition is often evaluated through sampling of benthic macroinvertebrates because they are ubiquitous in aquatic environments and differ in sensitivity to various types of pollution and environmental stressors. In central Appalachia, studies have largely relied on semi-quantitative sampling methods to characterize effects of elevated salinity on benthic macroinvertebrate communities in headwater streams. These methods are ‘semiquantitative’ because processing of samples requires subsampling procedures and identification of a fixed number of individuals, regardless of the number of organisms that were originally collected. In contrast, quantitative sampling involves identification and counting of all collected individuals, often resulting in organism counts that are much higher than those of semi-quantitative samples. Quantitative samples are typically more time-consuming and expensive to process but allow for expanded description of the benthic macroinvertebrate community and characterization of community-wide response to an environmental stressor such as elevated salinity. Working in central Appalachian streams, I compared 1) depictions of benthic macroinvertebrate community structure; 2) benthic community response to elevated salinity; and 3) the minimum levels of salinity associated with community change between quantitative and semi-quantitative methods. Quantitative sampling methods provide many advantages over semi-quantitative methods by providing more complete enumerations of the taxa present, thus enhancing the ability to evaluate aquatic-life condition and to characterize overall benthic macroinvertebrate community response to elevated salinity caused by surface coal mining.

Analytical baseflow separation techniques such as those used in the automated hydrograph separation program HYSEP rely on a single input parameter that defines the period of time after which surface runoff ceases and all streamflow is considered baseflow. In HYSEP, this input parameter is solely a function of drainage basin contributing area. This method cannot be applied universally since in most regions the time of surface runoff cessation is a function of a number of different hydrologic and hydrogeologic basin characteristics, not just contributing drainage area. This study demonstrates that streamflow conductivity can be used as a natural tracer that integrates the different hydrologic and hydrogeologic basin characteristics that influence baseflow response. Used as an indicator of baseflow as a component of total flow, streamflow conductivity allows for an empirical approach to hydrograph separation using a simple mass balance algorithm. Although conductivity values for surface-water runoff and ground-water baseflow must be identified to apply this mass balance algorithm, field studies show that assumptions based on streamflow at low flow and high flow conditions are valid for estimating these end member conductivities. The only data required to apply the mass balance algorithm are streamflow conductivity and discharge measurements. Using minimal data requirements, empirical hydrograph separation techniques can be applied that yield reasonable estimates of baseflow. This procedure was performed on data from 10 USGS gaging stations for which reliable, real-time conductivity data are available. Comparison of empirical hydrograph separations using streamflow conductivity data with analytical hydrograph separations demonstrates that uncalibrated, graphical estimation of baseflow can lead to substantial errors in baseflow estimates. Results from empirical separations can be used to calibrate the runoff cessation input parameter used in analytical separation for each gaging station. In general, collection of stream conductivity data at gaging stations is relatively recent, while discharge measurements may extend many decades into the past. Results demonstrate that conductivity data available for a relatively short period of record can be used to calibrate the runoff cessation input parameter used for analytical separation. The calibrated analytical method can then be applied over a much longer period record since discharge data are the only requirement.

Title from PDF of title page. / Document formatted into pages; contains 75 pages. / Thesis (M.S.C.E.)--University of South Florida, 2003. / Includes bibliographical references. / Text (Electronic thesis) in PDF format. / ABSTRACT: Analytical baseflow separation techniques such as those used in the automated hydrograph separation program HYSEP rely on a single input parameter that defines the period of time after which surface runoff ceases and all streamflow is considered baseflow. In HYSEP, this input parameter is solely a function of drainage basin contributing area. This method cannot be applied universally since in most regions the time of surface runoff cessation is a function of a number of different hydrologic and hydrogeologic basin characteristics, not just contributing drainage area. This study demonstrates that streamflow conductivity can be used as a natural tracer that integrates the different hydrologic and hydrogeologic basin characteristics that influence baseflow response. Used as an indicator of baseflow as a component of total flow, streamflow conductivity allows for an empirical approach to hydrograph separation using a simple mass balance algorithm. / ABSTRACT: Although conductivity values for surface-water runoff and ground-water baseflow must be identified to apply this mass balance algorithm, field studies show that assumptions based on streamflow at low flow and high flow conditions are valid for estimating these end member conductivities. The only data required to apply the mass balance algorithm are streamflow conductivity and discharge measurements. Using minimal data requirements, empirical hydrograph separation techniques can be applied that yield reasonable estimates of baseflow. This procedure was performed on data from 10 USGS gaging stations for which reliable, real-time conductivity data are available. Comparison of empirical hydrograph separations using streamflow conductivity data with analytical hydrograph separations demonstrates that uncalibrated, graphical estimation of baseflow can lead to substantial errors in baseflow estimates. / ABSTRACT: Results from empirical separations can be used to calibrate the runoff cessation input parameter used in analytical separation for each gaging station. In general, collection of stream conductivity data at gaging stations is relatively recent, while discharge measurements may extend many decades into the past. Results demonstrate that conductivity data available for a relatively short period of record can be used to calibrate the runoff cessation input parameter used for analytical separation. The calibrated analytical method can then be applied over a much longer period record since discharge data are the only requirement. / System requirements: World Wide Web browser and PDF reader. / Mode of access: World Wide Web.

Kentucky’s Upper Green River Basin has received significant attention due to the area’s high biodiversity and spectacular karst development. While carbonate bedrock is present throughout the watershed, it is more extensive and homogenous along the river between Greensburg and Munfordville than upstream from Greensburg where the geology is more heterogeneous. This research quantitatively evaluated how lithological differences between the two catchment areas impact hydrochemistry and inorganic carbon cycling. This first required correcting catchment boundaries on previous US Geological Survey Hydrologic Unit Maps to account for areas where the boundaries cross sinkhole plains. Basin boundaries using existing Kentucky Division of Water dye trace data differed from the earlier versions by as much as three kilometers. The river at the downstream site is more strongly influenced by carbonate mineral dissolution, reflected in higher specific conductance (SpC) and pH. The SpC at Munfordville ranges from 0.9 to 4.8 times that at Greensburg, averaging 2.0 times higher. Although rainfall is impacted by sulfuric acid from coal burning, river pH is buffered at both sites. The pH is higher at Munfordville 91% of the time, by an average of 0.28 units. Diurnal, photosynthetic pH variations are damped out downstream suggesting interactions between geologic and biological influences on river chemistry. River temperature differences between the two sites are at least 4oC higher at Greensburg under warm season conditions, but there is a clear trend of temperature differences diminishing as the river cools through the fall and winter. This results from a relatively stable temperature at Munfordville, impacted by large spring inputs of groundwater within the karst region downstream. Although weak statistical relationships between SpC and HCO3 - create uncertainties in high resolution carbon flux calculations, measurement of these fluxes is more highly impacted by discharge variations than concentration variations, which resulted in average daily atmospheric flux estimates within 34% between the two basins using weekly concentration data (3.3x108 vs. 2.2x108 gkm-2 d-1, where km2 is the outcrop area of carbonate rocks), and within only 12% using 15-minute concentration data from regressions (2.6x108 vs. 2.3x108 gkm-2 d-1) for Greensburg and Munfordville, respectively.

Increased loading of dissolved ions (salinization) and trace elements from surface coal mining is a common alteration to headwater streams in the central Appalachian region. However, temporal and spatial trends of water quality and associated influences on biota in these stream systems have not been well-studied. To address this research need, I analyzed temporal trends in specific conductance, ion matrix, and benthic macroinvertebrate communities in 24 headwater streams, including 19 influenced by surface mining, from 2011-2019. There was limited evidence of recovery of water chemistry or macroinvertebrate communities in these streams, indicating lasting impacts from surface coal mining. Among benthic macroinvertebrates, Ephemeroptera and the scraper functional feeding group were most-impacted by chronic salinization in study streams. In addition, I analyzed spatial patterns of water chemistry in a subset of these streams using synoptic sampling of multiple constituents under baseflow and highflow conditions. Study results indicate that water chemistry is spatially dynamic and can be influenced by both groundwater dilution and inputs from tributaries. Lastly, I investigated patterns in selenium bioaccumulation across and within streams, from particulate matter to top trophic levels (i.e. fish and salamanders). I found that benthic macroinvertebrates had the highest concentrations of selenium in these ecosystems, with lower concentrations in salamander and fish species. However, there was limited evidence of longitudinal trends in bioaccumulation dynamics downstream of mining impacts. Collectively, this work indicates long-term (ca. decades) coal-mining influences but also highlights future research needs to better understand downstream impacts to water quality and biotic communities. / Master of Science / Surface coal mining affects water quality in central Appalachian headwater streams. However, long-term and downstream patterns of impacted water quality and potential effects on aquatic life have not been well-studied. To address this research need, I analyzed trends in water quality parameters and aquatic insect communities in 24 headwater streams from 2011-2019. There was limited evidence of recovery of water chemistry or aquatic life in these streams, indicating lasting impacts from surface coal mining. Certain aquatic insects including Ephemeroptera (mayflies) appear to be more impacted than others by long-term altered water quality. In addition to trends over time, I also analyzed downstream variation in water chemistry in a subset of these streams under baseflow conditions and after a rain event. Results indicate that water chemistry can vary greatly within a stream network and is influenced by tributary inputs and dilution from groundwater. Concentrations of the trace element selenium can also be elevated as a result of surface mining. This is of environmental concern because selenium can biomagnify, where concentrations increase in organisms higher in the food chain and can cause toxic effects. Here, I investigated selenium bioaccumulation patterns across organisms in the food chain and with distance downstream across six headwater streams. I found that aquatic insects had the highest concentrations of selenium, with lower concentrations in salamanders and fish. This work indicates that surface coal mining has longterm (ca. decades) effects on headwater streams, but also points to future research to better understand downstream impacts to water quality and aquatic life.

Headwater catchments play a large role in the storage and release of water and chemical constituents, thereby influencing downstream flows and water quality. Recent advances in water quality monitoring technologies have created an opportunity to better assess water chemistry variation by using high temporal resolution, in situ sensors. However, despite these new technologies, there have been limited studies on installation approaches and their effects on sensor measurements. Accurate in situ monitoring is particularly important to capture catchment disturbance effects that may be highly dynamic over time (e.g., following storms) or limited in duration. For example, prescribed fire is a commonly applied forest management tool, but there remain questions regarding how this disturbance affects catchment soils and resultant stream water chemistry. Effective assessment of prescribed fire thus requires coupled monitoring of both soil properties and water chemistry. In this thesis, I addressed two linked objectives: i) assess the effects of commonly used protective housings on in situ sensor measurements (Chapter 2) and ii) evaluate prescribed burn effects in a southwestern Virginia, USA headwater catchment (Chapter 3). In Chapter 2, I compared four different housing types (mesh, screen, holes, and open) using in situ specific conductance measurements over time and from salt tracer injections for discharge estimates. This study demonstrated substantial effects from some of the housing types evaluated, where flow resistance reduced water exchange between stream water and water in contact with the sensor. From these findings, I suggest that in situ water quality sensors should be deployed in housing types with large openings perpendicular to flow. In Chapter 3, I assessed prescribed fire effects on soil properties (particle size, aggregate stability, and chemistry), stream discharge, and fine-scale water chemistry dynamics. Findings demonstrated some significant differences following fire in soil properties (e.g., overall decrease in aggregate stability, general decreases in total carbon and nitrogen of mineral soils), water quality (e.g., increased levels of DOC, turbidity, and nitrate) and discharge (increases in stage and flow). While these changes were statistically significant, differences in parameters before and after fire were generally small. Future work should examine if these effects persist through time, and whether the minor level of disturbance observed in this study results in any negative environmental impacts. / Master of Science / Headwater catchments (where precipitation first becomes streamflow) provide important aquatic habitat and regulate downstream water flows and chemistry. Recent advances in water quality monitoring technologies have created an opportunity to better assess water chemistry variability by using high frequency, submerged water quality sensors. However, these new technologies present new, unique challenges, such as measurement errors that may be induced by different installation methodologies. Accurate measurements are particularly important to evaluate how changes in catchment conditions (e.g., soils, vegetation) impact local and downstream water quality. For example, prescribed fire is a commonly used forest management tool, but questions remain about how it affects catchment soils and headwater stream chemistry. Consequently, understanding the effects of this and other catchment disturbances requires coupled monitoring of both soil properties and water quality. In this thesis, I addressed two objectives: i) assess the effects of commonly used protective housings on water quality sensor measurements (Chapter 2) and ii) evaluate prescribed burn effects in a southwestern Virginia, USA headwater catchment (Chapter 3). In Chapter 2, I demonstrated substantial effects from some of the housings evaluated and suggest that water quality sensors should be deployed in housing types with large openings perpendicular to flow. In Chapter 3, I demonstrated some significant effects of prescribed fire on soil properties (e.g. overall decrease in soil stability, general decreases in total carbon and nitrogen of mineral soils), water quality (e.g., increased levels of dissolved organic matter, turbidity, and nitrate) and flow (increases in stream water levels and flow). While these changes were statistically significant, differences in parameters before and after fire were generally small. Future work should examine if these effects persist through time, and whether this minor level of disturbance causes any negative environmental impacts.

Benthic macroinvertebrates are heavily relied on to indicate stream condition because of their ease of sampling, broad span of sensitivities to pollution among taxa, and diverse life histories that utilize various habitats and environmental conditions. Surface-coal mining in central Appalachia often results in salinization of headwater streams, with documented responses in macroinvertebrate communities across streams that vary in specific conductance (SC), an index of degree of salinization. Mining-influenced headwater streams can also exhibit within-stream spatial variation in SC, frequently via dilution with downstream distance from mining. However, the extent to which coal-mining alters downstream patterns in water chemistry and macroinvertebrate communities is largely unknown. This study aimed to determine macroinvertebrate community responses to physical and chemical gradients within six Appalachian headwater streams (four mining-impacted, two reference). Streams were sampled for benthic macroinvertebrates, habitat characteristics, and water chemistry in fall 2021 and spring 2022 at six-to-nine locations per stream over a range of 1.5 – 3 km. Mining-impacted streams exhibited greater spatial variation in macroinvertebrate community composition compared to reference streams, particularly in spring. Bray-Curtis Community similarity determined highly-impacted streams experienced the greatest within-stream shifts in community similarity. Metrics of macroinvertebrate communities and community similarity showed some correlation with SC at within-stream scales, particularly in highly impacted streams in spring; however, such trends were much fewer and weaker compared to relationships among streams when collectively examining communities. Redundancy Analysis (RDA) and Variation Partitioning (VP) indicated water quality, habitat, and location do overlap in explanation of community variation although they often additionally explain variance in unique ways. Significant variables identified by RDA within at least two of the six streams include channel slope, streamwater nutrients and hardness, stream channel embeddedness, and percent fines comprising the streambed. Redundancy Analysis also indicated 18 key macroinvertebrate taxa in study streams responding to location within stream, habitat, and water quality. Of those 18 taxa shredders, collectors, and clingers were most frequently impacted. Improved understanding of the spatial scale of coal-mining influences on headwater stream characteristics will help inform bioassessment protocols to most accurately assess stream condition, and inform remediation efforts within the central Appalachian region and in other salinized stream systems. / Master of Science / Small streams (or headwater streams) originating in the central Appalachian Mountains harbor a variety of unique organisms and are essential to the quantity and quality of downstream freshwater for fishing, recreation, and other uses. Coal mining processes, including disturbance of coal-bearing bedrock, often increases the streams salinity by adding pollutants that elevate dissolved minerals, or salts. Salinization of streams can come from a variety of sources in addition to coal mining such as de-icing road salts and crop irrigation and is of growing concern regarding its impacts to the quality of freshwater available for wildlife and human use. A common way to determine stream health is by identifying which aquatic insects (or macroinvertebrates) are present in a stream, because different groups are present based on the type and intensity of a variety of pollutants. Previous studies determined stream health by identifying insects from one location in a stream and comparing it to others. Stream's habitat and water quality naturally change as they join with larger rivers and flow to lower elevations causing different macroinvertebrates to be present at locations within streams. This study aimed to determine how changes along stream distances may be different in streams salinized from coal mining. The objectives of this study were to determine if one sample is adequate to represent the entire condition of a headwater stream. Six streams were sampled for macroinvertebrate, water quality, and habitat at six-to-nine locations within each stream over distances of ca. 2,000 m. Four streams were impacted by mining, of which two were highly impacted and two were impacted to a low-level; the last two streams were unimpacted to represent reference condition. The study found the type and number of macroinvertebrates within streams were changing least within reference streams and most in highly impacted streams. Macroinvertebrate communities in highly-impacted streams changed more within streams because they had high concentrations of dissolved salts upstream near the source of coal-mining pollution and these salts diluted with distance downstream, most likely due to fresh spring water contributions with minimal dissolved salts. Therefore, highly-impacted headwater streams experience greater environmental and macroinvertebrate variability indicating more than one sample location may be helpful in accurately assessing what macroinvertebrates inhabit the stream length of interest. Ensuring accurate sampling technique to determine stream condition is essential to our understanding of stream health and how to remediate and monitor impacts of salinization on our freshwater resources.

Surface coal mining has altered Appalachian landscapes, affecting water quality and aquatic ecology. Valley fills created from excess overburden are prominent features of many mined landscapes. Increased total dissolved solids (TDS), as measured by its surrogate specific conductance (SC), is a significant water quality concern related to the exposure of fresh mineral surfaces to weathering in valley fills. Specific conductance levels in waters draining Appalachian mined areas are highly variable, yet the causes for this variability are not well known. Here we sought to improve understanding of such variability by investigating the interior subsurface structure and hydrologic flowpaths within a series of valley fills and relating that to valley fill characteristics such as age and construction method. We used electrical resistivity imaging (ERI) to investigate the subsurface structure of four valley fills in two dimensions. We combined ERI with artificial rainfall to investigate the location and transit time of hydrologic preferential infiltration flowpaths through the fills. Finally, we used our ERI results in conjunction with SC data from effluent streams to improve understanding of SC relationship to fill flowpaths and characteristics. ERI results indicated considerable variability in substrate type and widespread presence of preferential infiltration flowpaths among the valley fills studied. We estimated an average preferential flowpath length of 6.6 meters, average transit time of 1.4 hours, and average velocity of 5.1 m/h or 0.14 cm/s through preferential infiltration flowpaths. ERI successfully distinguished fills constructed using methods of conventional loose-dump and experimental controlled-material compacted-lift construction. Conventional fills had greater ranges of subsurface resistivity, indicating a wider range of substrate types and/or more variable moisture content. Conventional fills also showed more accumulation of water within the fill during artificial rainfall, possibly indicating more quick/deep preferential infiltration flowpaths than in the experimental fill. Relationships between other fill characteristics as well as stream effluent SC were not related in a statistically significant way to fill structure or flowpaths. ERI appears to be a robust non-invasive technique that provides reliable information on valley fill structure and hydrology, and experimental compacted-lift valley fill construction produces significantly altered hydrologic response, which in turn affects downstream SC. / MS / Surface coal mining has altered Appalachian landscapes, affecting water quality and aquatic ecology. Valley fills created from excess mine spoil are prominent features of many mined landscapes. The streams draining valley fills often have very poor water quality, including high levels of increased total dissolved solids (TDS) related to weathering of mine spoils within valley fills. In this work, we investigated the subsurface structure of a series of valley fills and identified preferential hydrologic flowpaths, which are the “paths of least resistance” water follows for rapid infiltration. We related our results to various valley fill characteristics such as age and construction method. We found that the subsurface of a conventionally built fill tends to have more variation in material and/or moisture content than a fill built with an experimental construction method. Conventional fills also showed more accumulation of water within the fill during artificial rainfall experiments, possibly indicating more quick/deep preferential infiltration flowpaths than in the experimental fill.