![[Old] Chesapeake Research Consortium](https://chesapeake.org/wp-content/uploads/2017/01/LogoForDarkBack.png)
- were subjected to external peer-review and accessible through library services;
- were published after January 1, 2016;
- were authored or co-authored by individuals employed with one of the seven principal CRC member institutions or with other major Chesapeake Bay Program partners; and
- have direct relevance to the science and/or management of the Chesapeake Bay or its watershed.
Further details about the the submission process can be found here. Further details about the purpose and "value added" of the RCCP collection (relative to other on-line databases) can be found here.
Impervious Comparison of NLCD Versus a Detailed Dataset over Time
To address accuracy concerns of the National Land Cover Dataset (NLCD), this case study compares impervious surface from the NLCD to a Detailed Land Cover Dataset (DLCD) for the Town of Blacksburg, Virginia over two time periods (2005/2006 and 2011) at spatial aggregation scales (30 m and 90 m) and scopes (site-specific to area-extent). When comparing the total impervious surface area, the NLCD overestimated significant amounts (12 to 27 percent) for the entire town and across all specified land use zones (single family, multi-family, and non-residential) for both time periods examined. A binary pixel-wise accuracy assessment of impervious surface revealed that the NLCD performed well for the multi-family and non-residential land use zones. However, accuracy level was quite low (user's accuracy <40 percent) for the single family land use zone. Percent impervious surface of NLCD and DLCD was further compared at 30 m and 90 m spatial scales. The spatial aggregation of pixels to 90 m led to improved agreement between the two datasets, although NLCD still showed an underestimate of high values and an overestimate of low values. An empirical normalization equation was successfully applied to the NLCD to further reduce such data skewness.
Get PDFDevelopment of Effective Procedures for Illicit Discharge Risk Mapping
Authorities of municipal separate storm-sewer systems (MS4s) are required to address illicit discharges as part of the United States’ National Pollutant Discharge Elimination System’s (NPDES) stormwater program. Field reconnaissance is an effective measure to detect and identify illicit discharges, but requires substantial staff and financial resources to conduct. While risk-analysis techniques and guidelines have been developed to facilitate MS4 prioritization of field operations, neither a standard set of indicators nor a standard operating procedure has been adopted. This study investigates the relationships among indicators of illicit-discharge potential (IDP) and the locations of illicit discharges in two Virginia MS4s. Results of the study indicate that certain risk factors are statistically more effective at predicting IDP, suggesting that a core set of factors can be used to map illicit-discharge risk. The results also show that risk-mapping tools are significantly impacted by uncertainty in model inputs. Recommendations are provided for MS4s interested in pursuing IDP risk mapping as a tool to improve cost-effectiveness and guide illicit-discharge program implementation.
Get PDFIncreased sediment oxygen flux in lakes and reservoirs: the impact of hypolimnetic oxygenation
Hypolimnetic oxygenation is an increasingly common lake management strategy for mitigating hypoxia/anoxia and associated deleterious effects on water quality. A common effect of oxygenation is increased oxygen consumption in the hypolimnion and predicting the magnitude of this increase is the crux of effective oxygenation system design. Simultaneous measurements of sediment oxygen flux (JO2) and turbulence in the bottom boundary layer of two oxygenated lakes were used to investigate the impact of oxygenation on JO2. Oxygenation increased JO2 in both lakes by increasing the bulk oxygen concentration, which in turn steepens the diffusive gradient across the diffusive boundary layer. At high flow rates, the diffusive boundary layer thickness decreased as well. A transect along one of the lakes showed JO2 to be spatially quite variable, with near-field and far-field JO2 differing by a factor of 4. Using these in situ measurements, physical models of interfacial flux were compared to microprofile-derived JO2 to determine which models adequately predict JO2 in oxygenated lakes. Models based on friction velocity, turbulence dissipation rate, and the integral scale of turbulence agreed with microprofile-derived JO2 in both lakes. These models could potentially be used to predict oxygenation-induced oxygen flux and improve oxygenation system design methods for a broad range of reservoir systems.
Get PDFA coupled three-dimensional hydrodynamic model for predicting hypolimnetic oxygenation and epilimnetic mixing in a shallow eutrophic reservoir
Artificial mixing and hypolimnetic oxygenation are two common methods for improving water quality in reservoirs. To examine the effects of their operation on the thermal structure of the water column, we used a three-dimensional hydrodynamic model coupled with a newly developed water-jet model and an existing linear bubble-plume model in conjunction with whole-reservoir in situ mixing experiments in a drinking-water reservoir. This reservoir has a side-stream supersaturation (SSS) hypolimnetic oxygenation system and a bubble-plume epilimnetic mixing (EM) system installed to reduce hypolimnetic hypoxia and algal blooms. The results show that the SSS successfully adds dissolved oxygen to the hypolimnion without destratifying the reservoir, whereas the EM, located at the lower metalimnetic boundary, deepens this boundary and partially mixes the metalimnion and epilimnion. The newly developed water-jet model coupled with the hydrodynamic model can successfully predict the variation of the thermal structure in the reservoir. The extent to which the SSS and EM systems affect the thermal structure of the reservoir is also quantified by further application of the coupled hydrodynamic model.
Get PDFImpacts of Coastal Land Use and Shoreline Armoring on Estuarine Ecosystems: an Introduction to a Special Issue
The nearshore land-water interface is an important ecological zone that faces anthropogenic pressure from development in coastal regions throughout the world. Coastal waters and estuaries like Chesapeake Bay receive and process land discharges loaded with anthropogenic nutrients and other pollutants that cause eutrophication, hypoxia, and other damage to shallow-water ecosystems. In addition, shorelines are increasingly armored with bulkhead (seawall), riprap, and other structures to protect human infrastructure against the threats of sea-level rise, storm surge, and erosion. Armoring can further influence estuarine and nearshore marine ecosystem functions by degrading water quality, spreading invasive species, and destroying ecologically valuable habitat. These detrimental effects on ecosystem function have ramifications for ecologically and economically important flora and fauna. This special issue of Estuaries and Coasts explores the interacting effects of coastal land use and shoreline armoring on estuarine and coastal marine ecosystems. The majority of papers focus on the Chesapeake Bay region, USA, where 50 major tributaries and an extensive watershed (~ 167,000 km2), provide an ideal model to examine the impacts of human activities at scales ranging from the local shoreline to the entire watershed. The papers consider the influence of watershed land use and natural versus armored shorelines on ecosystem properties and processes as well as on key natural resources.
Get PDFEffects of Local Watershed Land Use on Water Quality in Mid-Atlantic Coastal Bays and Subestuaries of the Chesapeake Bay
Nutrient inputs have degraded estuaries worldwide. We investigated the sources and effects of nutrient inputs by comparing water quality at shallow (< 2m deep) nearshore (within 200 m) locations in a total of 49 Chesapeake subestuaries and Mid-Atlantic coastal bays with differing local watershed land use. During July–October, concentrations of total nitrogen (TN), dissolved ammonium, dissolved inorganic N (DIN), and chlorophyll a were positively correlated with the percentages of cropland and developed land in the local watersheds. TN, DIN, and nitrate were positively correlated with the ratio of watershed area to subestuary area. Total phosphorus (TP) and dissolved phosphate increased with cropland but were not affected by developed land. The relationships among N, P, chlorophyll a, and land use suggest N limitation of chlorophyll a production from July–October. We compared our measurements inside the subestuaries to measurements by the Chesapeake Bay Program in adjacent estuarine waters outside the subestuaries. TP and dissolved inorganic P concentrations inside the subestuaries correlated with concentrations outside the subestuaries. However, water quality inside the subestuaries generally differed from that in adjacent estuarine waters. The concentration of nitrate was lower inside the subestuaries, while the concentrations of other forms of N, TP, and chlorophyll a were higher. This suggests that shallow nearshore waters inside the subestuaries import nitrate while exporting other forms of N as well as TP and chlorophyll a. The importance of local land use and the distinct biogeochemistry of shallow waters should be considered in managing coastal systems.
Get PDFIntegrating Regional Management Needs into a Mid-Atlantic Shorelines Research Project
We provide an example of how one estuarine research project engaged regional managers to help guide the research towards the needs of managers and policymakers dealing with shoreline management in the Mid-Atlantic region of the USA. Elements of the approach that contributed to success included a well-targeted initial request for proposals, a review process that included management input both as a review criterion and on the review panel, a careful process in choosing advisory members at the appropriate level in the agencies, regular opportunities for interactions between the management advisory group and the science team, and active involvement of a program manager as liaison throughout the life of the project. Engagement of a management advisory group changed some of the scientific approaches, helped to communicate results, and formed a foundation for incorporation into regional management and initiatives.
Get PDFPhosphorus Sequestration in Sediments Along the Salinity Gradients of Chesapeake Bay Subestuaries
We used a sequential extraction technique to compare the forms and amounts of particulate phosphorus (PP) deposited in the top meter of sediment spanning salinities from 0 to 10 in three Chesapeake Bay subestuaries: the Potomac, Choptank, and Bush Rivers. Fe-bound P (i.e., citrate-bicarbonate-dithionite (CDB)-extractable P) was the most dynamic fraction of PP, dominating oligohaline (salinity <3) sediments, but declining to near zero with depth in the most saline sediments of all three subestuaries. In contrast, we previously found Fe-P dominating the sediment PP at salinities ranging 0–11 in the Patuxent subestuary. Particulate organic P was relatively constant with depth and salinity and became the dominant form of PP in the most saline sediments. Fe-P was not replaced with diagenetic authigenic carbonate fluorapatite. In all the subestuaries, Fe-P generally persisted in the oligohaline sediments to 1 m depth, where sediment ages ranged from 60 to 200 years, based on 210Pb dating. At one site, PP burial reflected changing P loads from a nearby wastewater treatment plant. About 67% of the PP discharged from the Potomac watershed at the head of tide was buried in the sediments in the upper reaches of that subestuary. The form and amount of PP buried depended on the amount of CDB-extractable Fe in the sediments and on the distribution of sediment deposition along the salinity gradient. Even though CDB targets iron oxides, the predominant form of Fe in the sediments was ferrous iron suggesting that the predominant form of PP in oligohaline sediments may be ferrous phosphate.
Get PDFEffect of Biochar on Nitrate Removal in a Pilot-Scale Denitrifying Bioreactor
Bock, E. M., B. Coleman, and Z. M. Easton. 2016. Effect of Biochar on Nitrate Removal in a Pilot-Scale Denitrifying Bioreactor. J. Environ. Qual. 45:762-771. doi:10.2134/jeq2015.04.017
Get PDFImproved simulation of edaphic and manure phosphorus loss in SWAT
Collick, A.S., T.L. Veith, D.R. Fuka, P.J.A. Kleinman, A.R. Buda, J.L. Weld, R.B. Bryant, P.A. Vadas, M.J. White, D. Harmel, and Z.M. Easton. 2016. Improved simulation of edaphic and manure phosphorus loss in SWAT. J. Environ. Qual.
Get PDF