Impacts of Multiple Environmental Changes on Long- Term Nitrogen Loading From the Chesapeake Bay Watershed

Excessive nitrogen can enter estuarine and coastal areas from land, disturbing coastal ecosystems and causing serious environmental problems. The Chesapeake Bay is one of the regions that have experienced hypoxia and harmful algal blooms in recent decades. This study estimated nitrogen export from the Chesapeake Bay watershed (CBW) to the estuary from 1900 to 2015 by applying a state-of-the-art numerical model. Nitrogen loading from the CBW continually increased from the 1900s to the 1990s and has declined since then. The key contributors to nitrogen export have shifted from atmospheric nitrogen deposition (before the 1960s) to synthetic nitrogen fertilizer (after the 1980s). Antipollution policies and implementation measures have played critical roles in the decrease of nitrogen export since the 1980s, and further reduction in riverine nitrogen export will likely require regulation on the application of nitrogen fertilizer

Impacts of Multiple Environmental Changes on Long‐Term Nitrogen Loading From the Chesapeake Bay Watershed

Excessive nutrient inputs from land, particularly nitrogen (N), have been found to increase the occurrence of hypoxia and harmful algal blooms in coastal ecosystems. To identify the main contributors of increased N loading and evaluate the efficacy of water pollution control policies, it is essential to quantify and attribute the long‐term changes in riverine N export. Here, we use a state‐of‐the‐art terrestrial–aquatic interface model to examine how multiple environmental factors may have affected N export from the Chesapeake Bay watershed since 1900. These factors include changes in climate, carbon dioxide, land use, and N inputs (i.e., atmospheric N deposition, animal manure, synthetic N fertilizer use, and wastewater discharge). Our results estimated that ammonium (NH4+) and nitrate (NO3−) export increased substantially (66% for NH4+ and 123% for NO3−) from the 1900s to the 1990s and then declined (32% for NH4+ and 14% for NO3−) since 2000. The temporal trend of dissolved organic nitrogen (DON) export paralleled that of dissolved inorganic N, while particulate organic nitrogen export was relatively constant during 1900–2015. Precipitation was the primary driver of interannual variability in N export to the Bay. Wastewater discharge explained most of the long‐term change in riverine NH4+ and DON fluxes from 1900 to 2015. The changes in atmospheric deposition, wastewater, and synthetic fertilizer were responsible for the trend of riverine NO3−. In light of our model‐based attribution analysis, terrestrial non‐point source nutrient management will play an important role in achieving water quality goals

Impacts of Multiple Environmental Changes on Long‐Term Nitrogen Loading From the Chesapeake Bay Watershed

Excessive nutrient inputs from land, particularly nitrogen (N), have been found to increase the occurrence of hypoxia and harmful algal blooms in coastal ecosystems. To identify the main contributors of increased N loading and evaluate the efficacy of water pollution control policies, it is essential to quantify and attribute the long‐term changes in riverine N export. Here, we use a state‐of‐the‐art terrestrial–aquatic interface model to examine how multiple environmental factors may have affected N export from the Chesapeake Bay watershed since 1900. These factors include changes in climate, carbon dioxide, land use, and N inputs (i.e., atmospheric N deposition, animal manure, synthetic N fertilizer use, and wastewater discharge). Our results estimated that ammonium (NH4+) and nitrate (NO3−) export increased substantially (66% for NH4+ and 123% for NO3−) from the 1900s to the 1990s and then declined (32% for NH4+ and 14% for NO3−) since 2000. The temporal trend of dissolved organic nitrogen (DON) export paralleled that of dissolved inorganic N, while particulate organic nitrogen export was relatively constant during 1900–2015. Precipitation was the primary driver of interannual variability in N export to the Bay. Wastewater discharge explained most of the long‐term change in riverine NH4+ and DON fluxes from 1900 to 2015. The changes in atmospheric deposition, wastewater, and synthetic fertilizer were responsible for the trend of riverine NO3−. In light of our model‐based attribution analysis, terrestrial non‐point source nutrient management will play an important role in achieving water quality goals

Riverine Carbon Cycling Over the Past Century in the Mid-Atlantic Region of the United States

Rivers are an important component of the terrestrial-aquatic ocean continuum as they serve as a conduit for transporting carbon from the land to the coastal ocean. It is essential to track the fate of this carbon, including how much carbon is buried in the riverbed, outgassed to the atmosphere, and exported to the ocean. However, it is often difficult to quantify these carbon transport processes on the watershed scale because observational data obtained by field surveys can only be used to estimate the magnitude of these processes at distinct points. In this study, we used a coupled terrestrial-aquatic ecosystem model to assess the century-long full carbon budget of the riverine ecosystem across the watersheds of Chesapeake Bay and Delaware Bay. In addition, we examined the individual and combined impacts of climate change and anthropogenic activities on these terrestrial ecosystems and the resultant CO2emissions of their associated rivers. We found that climate variability and land conversion (from cropland to impervious surfaces and forest) are the most important factors governing the long-term change in riverine carbon dynamics. We also highlighted the importance of riverine CO2 emissions in the overall regional carbon budget

Water Supply Planning in Virginia: The Future of Groundwater and Surface Water

This paper begins by exploring the current state of water resources planning and permitting. Then, considers current water demand in Virginia, as well as future challenges. Next is an examination of management structures from other states and a discussion of potential solutions to the water scarcity issue, including wastewater purification, the Hampton Roads Sanitation District’s (HRSD) Sustainable Water Initiative For Tomorrow (SWIFT) project, and desalination. The paper concludes with various next steps and policy recommendations that the Commonwealth should consider as dwindling water resources could hamper economic growth and threaten drought conditions, such as regional planning to achieve the optimal use of ground and surface water and increased funding to develop a full model that evaluates the costs and benefits of utilizing different water resources. This abstract has been taken from the authors\u27 overview

Riverine Carbon Cycling Over The Past Century in the Mid‐Atlantic Region of the United States

The lateral transport and degassing of carbon in riverine ecosystems is difficult to quantify on large spatial and long temporal scales due to the relatively poor representation of carbon processes in many models. Here, we coupled a scale‐adaptive hydrological model with the Dynamic Land Ecosystem Model to simulate key riverine carbon processes across the Chesapeake and Delaware Bay Watersheds from 1900 to 2015. Our results suggest that throughout this time period riverine CO2 degassing and lateral dissolved inorganic carbon fluxes to the coastal ocean contribute nearly equally to the total riverine carbon outputs (mean ± standard deviation: 886 ± 177 Gg C∙yr−1 and 883 ± 268 Gg C∙yr−1, respectively). Following in order of decreasing importance are the lateral dissolved organic carbon flux to the coastal ocean (293 ± 81 Gg C∙yr−1), carbon burial (118 ± 32 Gg C∙yr−1), and lateral particulate organic carbon flux (105 ± 35 Gg C∙yr−1). In the early 2000s, carbon export to the coastal ocean from both the Chesapeake and Delaware Bay watersheds was only 15%–20% higher than it was in the early 1900s (decade), but it showed a twofold increase in standard deviation. Climate variability (changes in temperature and precipitation) explains most (225 Gg C∙yr−1) of the increase since 1900, followed by changes in atmospheric CO2 (82 Gg C∙yr−1), atmospheric nitrogen deposition (44 Gg C∙yr−1), and applications of nitrogen fertilizer and manure (27 Gg C∙yr−1); in contrast, land conversion has resulted in a 188 Gg C∙yr−1 decrease in carbon export

A Case-Study Application of the Experimental Watershed Study Design to Advance Adaptive Management of Contemporary Watersheds

settings Open AccessFeature PaperArticle A Case-Study Application of the Experimental Watershed Study Design to Advance Adaptive Management of Contemporary Watersheds by Jason A. Hubbart 1,*,Elliott Kellner 2 andSean J. Zeiger 3 1 West Virginia University, Institute of Water Security and Science, Davis College of Agriculture, Natural Resources and Design, Schools of Agriculture and Food, and Natural Resources, 3109 Agricultural Sciences Building, Morgantown, WV 26506, USA 2 West Virginia University, Institute of Water Security and Science, Davis College of Agriculture Natural Resources and Design, Division of Plant and Soil Sciences, 3011 Agricultural Sciences Building, Morgantown, WV 26506, USA 3 School of Natural Resources, University of Missouri, 203-T ABNR Building, Columbia, MO 65211, USA * Author to whom correspondence should be addressed. Water 2019, 11(11), 2355; https://doi.org/10.3390/w11112355 Received: 14 September 2019 / Revised: 30 October 2019 / Accepted: 6 November 2019 / Published: 9 November 2019 (This article belongs to the Special Issue Integrated Water Resources Research: Advancements in Understanding to Improve Future Sustainability) Download PDF Browse Figure Review Reports Cite This Paper Abstract Land managers are often inadequately informed to make management decisions in contemporary watersheds, in which sources of impairment are simultaneously shifting due to the combined influences of land use change, rapid ongoing human population growth, and changing environmental conditions. There is, thus, a great need for effective collaborative adaptive management (CAM; or derivatives) efforts utilizing an accepted methodological approach that provides data needed to properly identify and address past, present, and future sources of impairment. The experimental watershed study design holds great promise for meeting such needs and facilitating an effective collaborative and adaptive management process. To advance understanding of natural and anthropogenic influences on sources of impairment, and to demonstrate the approach in a contemporary watershed, a nested-scale experimental watershed study design was implemented in a representative, contemporary, mixed-use watershed located in Midwestern USA. Results identify challenges associated with CAM, and how the experimental watershed approach can help to objectively elucidate causal factors, target critical source areas, and provide the science-based information needed to make informed management decisions. Results show urban/suburban development and agriculture are primary drivers of alterations to watershed hydrology, streamflow regimes, transport of multiple water quality constituents, and stream physical habitat. However, several natural processes and watershed characteristics, such as surficial geology and stream system evolution, are likely compounding observed water quality impairment and aquatic habitat degradation. Given the varied and complicated set of factors contributing to such issues in the study watershed and other contemporary watersheds, watershed restoration is likely subject to physical limitations and should be conceptualized in the context of achievable goals/objectives. Overall, results demonstrate the immense, globally transferrable value of the experimental watershed approach and coupled CAM process to address contemporary water resource management challenges

Corn Residual Nitrate and its Implications for Fall Nitrogen Management in Winter Wheat

Corn (Zea mays, L.) production typically requires supplemental nitrogen (N) to optimize yields. In dryland corn production systems, where N is applied during the early to mid-vegetative growth stages, inappropriate N applications or limited moisture during the growing season can result in large disparities between optimum and applied N rates. This leads to variable post-harvest residual nitrate (NO3-N) accumulation, which is susceptible to loss. However, this NO3-N could provide the starter N requirement of the subsequent winter wheat (Triticum aestivum, L.) crop. Accounting for residual NO3-N present at wheat planting is important to avoid compounding N loss potential due to corn residual NO3-N accumulation. The objectives of this study were to 1) examine plant based tools for assessing soil NO3-N; 2) to examine post-harvest residual NO3-N accumulation patterns following corn production; 3) to determine optimum fall starter N rates for winter wheat production; and 4) to identify a soil NO3-N level above which starter N could be forgone without negative agronomic effect. This study found that plant canopy measurements are useful tools for assessing corn N management and for identifying drought sites, which had the greatest NO3-N accumulations. The corn stalk nitrate test was significantly (p<0.001) and positively correlated with soil residual NO3-N (r2=0.41). Greatest soil residual NO3-N accumulation occurred where drought conditions reduced production. The agronomic optimum fall starter N rate for winter wheat in Maryland is 17 to 34 kg N ha-1 where soil NO3-N concentration to 15 cm depth is less than 15 mg kg-1. However, the fall starter N response was highly variable and declined significantly (p<0.01) as fall precipitation after planting increased. The results of this study indicate that residual NO3-N levels at planting should be considered before applying fall starter N to winter wheat

Impacts of Sea Level Rise on Tidal Wetland Extent and Distribution

Tidal marshes are a major ecological resource in Virginia and a driver of many estuarine functions. Therefore, the long term sustainability of tidal marsh ecosystems is a question of great interest in the research community. Sea level is rising at an unusually high rate in the Chesapeake Bay relative to most of the Atlantic coastline, putting Bay marshes at high risk from drowning and erosion. Sea level rise-driven salinity changes communities and alters ecosystem services. Understanding the patterns of change and the importance of different drivers of change is critical to tidal marsh sustainability. The overarching goal of this research is to examine how changes in natural and anthropogenic factors interact to affect tidal wetland distribution, extent and plant composition with the intent of promoting coastal resiliency to sea level rise impacts through informed coastal management. I quantified changes in marsh extent over the past 40 years and related changes in marsh extent to sea level rise and other drivers of change. Then I examined shifts in plant community composition throughout the Chesapeake Bay, VA, looking for signals of increased inundation and salinity. In small headwater systems, I explored the utility of these changes in plant composition for predicting soil sulfur content (an early signal of salinity intrusion). These changes in marshes from the past 40 years were used to elucidate results from an elevation-based model of future marsh persistence under accelerating sea level rise. Several lessons emerged from this dissertation: 1. Analyses of changes in tidal marsh extent and plant communities are complementary, clarifying vulnerabilities and prognosis under future conditions. 2. Human shoreline use (e.g., development, shoreline hardening, boating activity) can dominate physical processes to alter the marsh response to sea level rise. 3. Defining sediment availability for a given marsh may not be sufficient to determine its potential for expansion or persistence under sea level rise. 5. Marsh plant communities can be an early signal of change, showing shifts in inundation frequency before there is any change in marsh extent. 6. Tidal marshes will continue to decline over the next 100 years. However, most of the loss will be in low salinity, riverine marshes. Some high salinity, Bayfront marshes will expand if the land they need to migrate is preserved. 7. Tidal marsh response to sea level rise has, and will continue to, vary by marsh form, geologic setting, location in the estuary, and surrounding land use decisions. 9. Targeted land use decisions coupled with active restoration may help minimize future marsh loss