Keith N. Eshleman

Mountaintop Mining Consequences

Damage to ecosystems and threats to human health and the lack of effective mitigation require new approaches to mining regulation. There has been a global, 30-year increase in surface mining (1), which is now the dominant driver of land-use change in the central Appalachian ecoregion of the United States (2). One major form of such mining, mountaintop mining with valley fills (MTM/VF) (3), is widespread throughout eastern Kentucky, West Virginia (WV), and southwestern Virginia. Upper elevation forests are cleared and stripped of topsoil, and explosives are used to break up rocks to access buried coal (fig. S1). Excess rock (mine “spoil”) is pushed into adjacent valleys, where it buries existing streams.

Temporal patterns of nitrogen leakage from mid‐Appalachian forested watersheds: Role of insect defoliation

Fluxes of dissolved nitrogen (N) as nitrate from forested watersheds in the mid-Appalachian region have important water quality ramifications for small acid-sensitive streams and for downstream receiving waters such as the Chesapeake Bay. Previous studies of N leakage have suggested that annual dissolved N fluxes from small watersheds can vary by several orders of magnitude and may be increasing as second-growth forests gradually become N saturated from the accrual of atmospheric N loadings. In this study, we examined the temporal (intra-annual and interannual) variability in dissolved nitrate fluxes from five small (area < 15 km2) forested watersheds in the mid-Appalachian region from 1988 to 1995. At all sites, nitrate concentrations were observed to increase dramatically during storm flow events, with nitric acid contributing significantly to depressions in pH and acid-neutralizing capacity; annual nitrate fluxes were dominated by high-discharge periods. Interannually, the fluxes at each site varied by 1–2 orders of magnitude, but the patterns of N leakage displayed considerable synchrony with outbreaks of gypsy moth caterpillar defoliation that began in the late 1980s and early 1990s in this region. N leakage from forested watersheds apparently lagged the initial defoliation by several months to perhaps a year or more. Defoliation outbreaks by the gypsy moth caterpillar (or other herbivorous pests) thus provide an alternative explanation of N leakage from forest ecosystems. Poorly documented insect defoliations, rather than premature N saturation of intact forest ecosystems, need to be considered as a possible explanation of N leakage from forested watersheds in the mid-Appalachian region and elsewhere.

Surface mining and reclamation effects on flood response of watersheds in the central Appalachian Plateau region

Surface mining of coal and subsequent reclamation represent the dominant land use change in the central Appalachian Plateau (CAP) region of the United States. Hydrologic impacts of surface mining have been studied at the plot scale, but effects at broader scales have not been explored adequately. Broad-scale classification of reclaimed sites is difficult because standing vegetation makes them nearly indistinguishable from alternate land uses. We used a land cover data set that accurately maps surface mines for a 187-km{sup 2} watershed within the CAP. These land cover data, as well as plot-level data from within the watershed, are used with HSPF (Hydrologic Simulation Program-Fortran) to estimate changes in flood response as a function of increased mining. Results show that the rate at which flood magnitude increases due to increased mining is linear, with greater rates observed for less frequent return intervals. These findings indicate that mine reclamation leaves the landscape in a condition more similar to urban areas rather than does simple deforestation, and call into question the effectiveness of reclamation in terms of returning mined areas to the hydrological state that existed before mining.

Altered Ecological Flows Blur Boundaries in Urbanizing Watersheds

The relevance of the boundary concept to ecological processes has been recently questioned. Humans in the post-industrial era have created novel lateral transport fluxes that have not been sufficiently considered in watershed studies. We describe patterns of land-use change within the Potomac River basin and demonstrate how these changes have blurred traditional ecosystem boundaries by increasing the movement of people, materials, and energy into and within the basin. We argue that this expansion of ecological commerce requires new science, monitoring, and management strategies focused on large rivers and suggest that traditional geopolitical and economic boundaries for environmental decision making be appropriately revised. Effective mitigation of the consequences of blurred boundaries will benefit from a broad-scale, interdisciplinary framework that can track and explicitly account for ecological fluxes of water, energy, materials, and organisms across human-dominated landscapes.

REMOTE SENSING OF GYPSY MOTH DEFOLIATION TO ASSESS VARIATIONS IN STREAM NITROGEN CONCENTRATIONS

Disturbance is an important mechanism controlling dissolved nitrogen (N) leakage to receiving streams, rivers, lakes, and estuaries from forested watersheds. In oak forests of the eastern United States, defoliation by the gypsy moth caterpillar represents a recurring disturbance regime that can impact water quality. Following an upsurge in gypsy moth activity in the mid-Appalachian region in 2000–2001, we examined the relationship between defoliation and N export within the Fifteenmile Creek watershed in Maryland and Pennsylvania using intensive stream surveys and remotely sensed imagery. Concentrations of dissolved N species were determined six times during seasonal baseflow and once during stormflow conditions at the outlet of 35 randomly selected sub-watersheds between April 2001 and June 2002. Summer Landsat images were used to characterize forest disturbance within each of the sub-watersheds in 1999, 2000, and 2001. Quantitative differences in imagery between the defoliation years of 2000 and 2001 (a...

Surface Water Quality Is Improving due to Declining Atmospheric N Deposition

We evaluated long-term surface water nitrate and atmospheric nitrogen (N) deposition trends for a group of nine predominantly forested Appalachian Mountain watersheds during a recent multidecadal period (1986-2009) in which regional NOx emissions have been progressively reduced. Statistical analysis showed unexpected linear declines in both annual surface water nitrate-N concentrations (mean =46.4%) and yields (mean =47.7%) among the watersheds corresponding to comparable declines in annual wet N deposition (mean =34.4%) resulting from U.S. NOx emission control programs during the same time period. Nitrate-N concentration trends were robust across a large geographical region and appeared insensitive to watershed size across several orders of magnitude-suggesting that the improvements in water quality are probably propagated to surface and estuarine waters downstream. Surface waters are thus responding to declining atmospheric N deposition in much the same way they responded to declining sulfur deposition-although only one watershed showed a 1:1 relationship. Application of a kinetic N saturation model indicated that all nine forested watersheds are exhibiting signs of N saturation as evidenced by a limited, but variable, efficiency of demand for N. Further reductions in N deposition would be expected to produce additional reductions in streamwater N loads.

Hydrological Consequences of Land Use Change: A Review of the State-of-Science

Rates of deforestation, agriculturalization, urbanization, wetland drainage, and several other types of land use change have accelerated as a function of the growth of human populations. Hydrologists have recognized for nearly a half century that such land use changes can substantially affect hydrological processes at the scale of the research plot, the hillslope, and the small experimental catchment. The hydrological consequences of land use change are of interest not only to the academic hydrologist and ecologist, but they are of critical importance to the practicing civil engineer. At the beginning of the 21st century, these studies are increasingly being incorporated into multi-scale analyses used to address both scientific and management questions at landscape, river basin, and regional scales. Such efforts are being supported by major technological developments in collecting, analyzing, and modeling hydrological data, as well as new capabilities for observing and quantifying land use and land cover changes using remote sensors. In this chapter, I(1) summarize various scientific methods that have been used to determine the hydrological effects of land use change; (2) review the state-of-science with respect to understanding the effects of several different types of land use change on hydrological processes; and (3) identify key research issues related to uses of specific methodologies and to improved understanding, detection, quantification, and prediction of the hydrological consequences of specific land use changes.

Variation in physicochemical responses to urbanization in streams between two Mid-Atlantic physiographic regions

Urban development substantially alters the physicochemistry of streams, resulting in biodiversity and ecosystem function loss. However, interregional comparisons of physicochemical impact in urban streams suggest that geoclimatic heterogeneity may influence the extent of degradation. In the Mid-Atlantic United States, the adjacent Coastal Plain and Piedmont physiographic provinces possess distinctly different hydrogeomorphic properties that may influence how stream ecosystems respond to urbanization. Recent bioassessments have demonstrated that biotic sensitivity to urbanization is relatively acute in the Piedmont, suggesting that physicochemical change as a consequence of urbanization may be greater in that province. We compared hydrologic, chemical, and thermal characteristics of Mid-Atlantic Coastal Plain and Piedmont first- through fifth-order streams along gradients of impervious surface cover (ISC) at multiple spatial scales. Linear models were applied to test if conditions in rural streams and the degree of impact from ISC varied between provinces. Mean and maximum summer temperatures in Piedmont streams increased more per unit of ISC than in the Coastal Plain. Contrary to expectations, however, variables that quantified high-flow event frequency, magnitude and duration, exhibited significantly greater impact along the ISC gradient in the Coastal Plain. Most chemical changes associated with increasing ISC were similar in the two provinces, although the interregional chemical composition of rural streams differed substantially for most parameters. Our findings demonstrate consistent interregional heterogeneity in stream ecosystem responses to urbanization. Landscape-scale management decisions with stream ecosystem conservation, mitigation, or restoration as a goal must therefore carefully consider the geoclimatic context in order to maximize effectiveness.

A linear model of the effects of disturbance on dissolved nitrogen leakage from forested watersheds

The leakage of dissolved nitrogen (N), primarily in the form of nitrate, from forested watersheds in the mid-Appalachian region has important water quality ramifications for small acid-sensitive streams and for downstream receiving waters such as Chesapeake Bay. Dissolved N leakage is a common, well-documented response of forested watersheds to forest management practices such as clear-cutting. Patterns of N leakage from mid-Appalachian watersheds during the late 1980s and early 1990s have also been shown to display considerable temporal and spatial synchrony with outbreaks of defoliation by the gypsy moth (Lymantria dispar) larva (a nonnative forest insect pest). This evidence suggests that forest disturbance may be an important contributor to N leakage in the mid-Appalachian region. A logical first step in testing this hypothesis is evaluating the ability of a simple, unit nitrogen export response function (UNERF) model to explain temporal changes in annual N export from gaged forested watersheds in the years following disturbance. Annual N export data from seven such watersheds were analyzed as part of the study: two small (<0.5 km2) watersheds subjected to deforestation and five larger (1.6–12.6 km2) watersheds subjected to repetitive defoliation by the gypsy moth larva. Several forms of linear UNERF models, parameterized by deconvolution of annual time series of N export using linear programming or by a least squares method, were generally found to be minimally biased and to explain high percentages (38–98%) of the total variation in annual N export. Despite their neglect of spatial and temporal ecosystem nonlinearities these linear models appear reasonably robust, making them at least as useful as their more complex nonlinear brethren for purposes of regionalization.

Assessing Hydrologic Change in Surface-Mined Watersheds Using the Curve Number Method

The U.S. Surface Mining Control and Reclamation Act of 1977 requires that mine operators minimize disturbances to the prevailing hydrologic balance of surface-mined sites and associated off-site areas through land reclamation. The hydrologic evaluation to support this requirement is often performed using the curve number (CN) rainfall-runoff method. Accurate application is limited by a scarcity of tabulated CN values for reclaimed mine lands, and assumptions regarding the hydrologic behavior of reclaimed mine lands may be inaccurate. Four watersheds (three reclaimed surface coal mines and one forested reference) in the Georges Creek basin of western Maryland were instrumented for rainfall and runoff. CNs calculated for the reclaimed mine land watersheds using rainfall and runoff data (range=68–92) were generally higher than CNs estimated by prevailing engineering methods (range=65–79). The general agreement of these results with other studies indicates that a more conservative hydrologic approach may be w...