Estimating Potential Climate Change Effects on the Upper Neuse Watershed Water Balance Using the SWAT Model

Climate change poses water resource challenges for many already water stressed watersheds throughout the world. One such watershed is the Upper Neuse Watershed in North Carolina, which serves as a water source for the large and growing Research Triangle Park region. The aim of this study was to quantify possible changes in the watershed’s water balance due to climate change. To do this, we used the Soil and Water Assessment Tool (SWAT) model forced with different climate scenarios for baseline, mid‐century, and end‐century time periods using five different downscaled General Circulation Models. Before running these scenarios, the SWAT model was calibrated and validated using daily streamflow records within the watershed. The study results suggest that, even under a mitigation scenario, precipitation will increase by 7.7% from the baseline to mid‐century time period and by 9.8% between the baseline and end‐century time period. Over the same periods, evapotranspiration (ET) would decrease by 5.5 and 7.6%, water yield would increase by 25.1% and 33.2%, and soil water would increase by 1.4% and 1.9%. Perhaps most importantly, the model results show, under a high emission scenario, large seasonal differences with ET estimated to decrease by up to 42% and water yield to increase by up to 157% in late summer and fall. Planning for the wetter predicted future and corresponding seasonal changes will be critical for mitigating the impacts of climate change on water resources.     

Comparison and Evaluation of Gridded Precipitation Datasets in a Kansas Agricultural Watershed Using SWAT

Gridded precipitation datasets are becoming a convenient substitute for gauge measurements in hydrological modeling; however, these data have not been fully evaluated across a range of conditions. We compared four gridded datasets (Daily Surface Weather and Climatological Summaries [DAYMET], North American Land Data Assimilation System [NLDAS], Global Land Data Assimilation System [GLDAS], and Parameter‐elevation Regressions on Independent Slopes Model [PRISM]) as precipitation data sources and evaluated how they affected hydrologic model performance when compared with a gauged dataset, Global Historical Climatology Network‐Daily (GHCN‐D). Analyses were performed for the Delaware Watershed at Perry Lake in eastern Kansas. Precipitation indices for DAYMET and PRISM precipitation closely matched GHCN‐D, whereas NLDAS and GLDAS showed weaker correlations. We also used these precipitation data as input to the Soil and Water Assessment Tool (SWAT) model that confirmed similar trends in streamflow simulation. For stations with complete data, GHCN‐D based SWAT‐simulated streamflow variability better than gridded precipitation data. During low flow periods we found PRISM performed better, whereas both DAYMET and NLDAS performed better in high flow years. Our results demonstrate that combining gridded precipitation sources with gauge‐based measurements can improve hydrologic model performance, especially for extreme events.     

Backwater Confluences of the Ohio River: Organic and Inorganic Fingerprints Explain Sediment Dynamics in Wetlands and Marinas

In the Ohio River (OR), backwater confluence sedimentation dynamics are understudied, however, these river features are expected to be influential on the system’s ecological and economic function when integrated along the river’s length. In the following paper, we test the efficacy of organic and inorganic tracers for sediment fingerprinting in backwater confluences; we use fingerprinting results to evidence sediment dynamics controlling deposition patterns in confluences used for wetland and marina functions; and we quantify the spatial extent of tributary drainages with wetland and marina features in OR confluences. Both organic and inorganic tracers statistically differentiate sediment from stream and river end‐members. Carbon and nitrogen stable isotopes produce greater uncertainty in fingerprinting results than inorganic elemental tracers. Uncertainty analysis of the nonconservative tracer term in the organic matter fingerprinting application estimates an apparent enrichment of the carbon stable isotopes during instream residence, and the nonconservativeness is quantified with a statistical approach unique to the fingerprinting literature. Wetland and marina features in OR confluences impact 42% and 11% of tributary drainage areas, respectively. Sediment dynamics show wetland and marina confluences experience deposition from river backwaters with longitudinally linear and nonlinear patterns, respectively, from sediment sources.     

Pollution,place, and premature death: evidence from a mid-sized city

ABSTRACT

Neighborhood life expectancy varies by as much as 10 years across the City of Louisville. In 2013, the Greater Louisville Project funded by local government, businesses, and foundations, argued these differences had little to do with environmental factors. The Greater Louisville Project (2013) study argued that these neighborhood differences could be attributed 40% to socio-economic factors (with a major emphasis on education), 10% to physical environment, 30% to health behaviors, and 20% to access to medical care. To test these claims, we construct our own model of neighborhood variation in years of potential life lost (YPLL) by adding two variables testing environmental degradation. We operationalise two separate measures of environmental contamination: proximity to EPA designated brownfield sites and proximity to chemical factories in an industrial park in the neighborhood known as “Rubbertown”. We conduct several regression analyses, which show a relationship between proximity to environmental contaminants and an increase in neighborhood YPLL. Our beta weights challenge the claims made by the Greater Louisville Project, which minimize the impact nearness to environmental contaminants has on reductions in life expectancy in Louisville neighborhoods.     

Organic interference of solidified/stabilized hazardous wastes

Liquid hazardous waste disposal in landfills is usually allowed only after solidification/stabilization. Although various procedures are commonly practiced, little is known about the mechanism(s) of the processes. A particular problem is the interference of organics. Small amounts of organics can interfere with the reaction between inorganic sludges and cementitous matrices. The present communication reports studies of the interaction between selected organic hazardous wastes and Type I Portland cement. Microscopic studies of the structural differences between cements set with water and those set with water plus organic liquids are discussed. In these studies the scanning electron microscope is used to observe samples fractured at 78K. The results provide technical background data on the ultimate stability of critical waste constituents solidified by various binding agents.     

CADMIUM ACCUMULATION AND TOXICITY IN SUBMERGED PLANT HYDRILLA VERTICILLATA (l.f.) ROYLE

Cadmium accumulation and its toxicity in relation tochlorophyll, protein, cysteine contents and in vivo nitrate reductaseactivity were studied under controlled conditions in Hydrillaverticillata, a submerged commonly occurring macrophyte. Plants weresubjected to six different concentrations of Cd ranging from 1.0 to 25.0 µM for 24, 48, 72 and 168 h. Tissue Cd concentration was maximum (13.71 µmoles/g dw) at 25 µM background concentration. At this concentration, a decrease of approximately 79 and 72% was found in chlorophyll and protein content. In vivo nitrate reductase activity was stimulated at 1.0 µM; however, the activity gradually declined beyond this concentration. Exposure to various cadmium concentrations resulted in an increase in cysteine content of the plant.     

A Global Overview of Atmospheric Acid Deposition Fluxes

This paper presents a summary of globalacid deposition flux data taken from a globalassessment report on acid deposition prepared forUNEP/WMO (Whelpdale and Kaiser, 1996). There is a largevariation in the spacial coverage and reliability ofmonitoring around the world. Many more stationsmeasure wet deposition than collect appropriate datafor estimating dry deposition. The widespread regionswith highest precipitation concentrations anddeposition fluxes of sulphate and nitrate coincideclosely with the regions of highest density ofSO₂ and NO_x precursor emissions occurringprimarily in the mid-latitude, northern hemispherebelt where a large fraction of the worlds fossilfuels is consumed. Organic acids in precipitation makea minor contribution to acidity (<20%) inindustrial regions, but in the rest of the world theyare of same order, or even exceed, inorganic acids.Less is known about dry deposition, but it appears topredominate near strong emission sources with wetdeposition predominating farther downwind. The molarratio of the N/S contribution to acidic deposition isclose to 1.0 over large areas of Europe and NorthAmerica, but is highly variable elsewhere, beinghighest in equatorial regions due to biomass burningand lowest near smelters and other large sources of SO₂.     

Biological complexity confounds the separation of point- and non-point sources of human impact on the natural world

Identifying process from pattern is one of the most vexing tasks inenvironmental monitoring. Given information on the distribution of speciesin a pre-defined area, together with comprehensive data on how environmentalconditions in that area have altered through time, is it possible toidentify the factors controlling the species‘ layout? Here, the practicalsignificance of this quandary is demonstrated using a series ofenvironmentally-degraded coastal lagoons in New South Wales. The TuggerahLakes (33°17′S,151°30′E) have over the last 50 yearsexperienced significant changes in species‘ distributions. Seagrasses,macroalgae, phytoplankton, molluscs, prawns and the jellyfish Catostylus mosaicus have altered in spatial pattern. Two human activitieshave been blamed for these perturbations: (1) agricultural clearance ofnative vegetation from the catchment, with associated input of top-soil andnutrients; (2) the commissioning of a coal-fired power station in 1967, withmassive uptake and recirculation of lake water for cooling purposes. In thispaper, spatial changes in macrophyte distributions over the last 50 yearsare reviewed in an attempt to identify the true source(s) of perturbation.The model adopted assumes that the power station is a point source of impactwhile nutrient inputs from the catchment are a diffuse source of impact;changes in species distributions can hypothetically be related back to thesesources according to whether they are localised or widespread. However,after a comprehensive analysis of available macrophyte data derived frominterviews, aerial photography and line transect methodologyies theconclusion is reached that changes in biogeographical pattern around theTuggerah Lakes cannot be attributed to specific anthropogenic pressures atanything beyond the coarsest of levels. This is considered to be the normfor most coastal management situations where natural background variation(’noise‘) and the complexity of linkages between physical, chemical andbiological components confounds the identification of causal relationships.The practical implications of this conclusion are discussed in the contextof litigation and remedial management design. Emphasis is placed on theneed to adopt an adaptive approach to estuarine management, incorporatingexplicit recognition of the limitations of available data, and to developnew techniques for identifying cause-effect relationships.     

Methods for constructing and balancing ecosystem flux charts: new techniques and software

We describe a general computer program which employs novel techniques to analyze carbon (energy) and nutrient flows in complex food webs. The program uses estimates of metabolic/physiological parameters and ecosystem fluxes to simultaneously calculate the most likely balanced flux charts for carbon and a nutrient. We give an example of how the model can explore the theoretical issues involved with nutrient limitation and recycling.