Analyzing the impact of agricultural BMPs on stream nutrient load and biotic health in the Susquehanna-Chemung basin of New York.

Despite the widespread use of agricultural best management practices (BMPs) to reduce watershed scale nutrient loads, there remain few studies that use directly observed data - instead of models - to evaluate BMP effectiveness at the watershed scale. In this study, we make use of extensive ambient water quality data, stream biotic health data, and BMP implementation data within the New York State portion of the Chesapeake Bay watershed to assess the role of BMPs on reducing nutrient loads and modifying biotic health in major rivers. The specific BMPs considered were riparian buffers and nutrient management planning. A simple mass balance approach was used to evaluate the role of wastewater treatment plant nutrient reductions, agricultural land use changes, and these two agricultural BMPs in matching observed downward trends in nutrient load. In the Eastern nontidal network (NTN) catchment - where BMPs have been more widely reported - the mass balance model suggested a small but discernible contribution of BMPs in matching the observed downward trend in total phosphorus. Contrastingly, BMP implementations did not show clear contributions towards total nitrogen reductions in the Eastern NTN catchment nor for the total nitrogen and phosphorus in the Western NTN catchment, where BMP implementation data are more limited. Assessment of the relationship between stream biotic health and BMP implementation using regression models found limited connection between extent of BMP implementation and biotic health. In this case, however, spatiotemporal mismatches between the datasets and the relatively stable biotic health, typically of moderate to good quality even before BMP implementation, may reflect the need for better monitoring design to assess BMP effects at the subwatershed scale. Additional studies, perhaps using citizen scientists, may be able to provide more suitable data within the existing frameworks of the long-term surveys. Given the preponderance of studies that rely only on modeling to understand nutrient loading reductions achieved by implementation of BMPs, it is essential to continue to collect empirical data to meaningfully evaluate whether there are actual measurable changes due to BMPs.

Improving risk estimates of runoff producing areas: formulating variable source areas as a bivariate process.

Predicting runoff producing areas and their corresponding risks of generating storm runoff is important for developing watershed management strategies to mitigate non-point source pollution. However, few methods for making these predictions have been proposed, especially operational approaches that would be useful in areas where variable source area (VSA) hydrology dominates storm runoff. The objective of this study is to develop a simple approach to estimate spatially-distributed risks of runoff production. By considering the development of overland flow as a bivariate process, we incorporated both rainfall and antecedent soil moisture conditions into a method for predicting VSAs based on the Natural Resource Conservation Service-Curve Number equation. We used base-flow immediately preceding storm events as an index of antecedent soil wetness status. Using nine sub-basins of the Upper Susquehanna River Basin, we demonstrated that our estimated runoff volumes and extent of VSAs agreed with observations. We further demonstrated a method for mapping these areas in a Geographic Information System using a Soil Topographic Index. The proposed methodology provides a new tool for watershed planners for quantifying runoff risks across watersheds, which can be used to target water quality protection strategies.

Testing of a custom, portable drill press to minimize probe misalignment in sap flow sensors.

The accurate estimation of plant transpiration is critical to the fields of hydrology, plant physiology and ecology. Among the various methods of measuring transpiration in the field, the sap flow methods based on head pulses offers a cost-effective and energy-efficient option to directly measure the plant-level movement of water through the hydraulically active tissue. While authors have identified several possible sources of error in these measurements, one of the most common sources is misalignment of the sap flow probes due to user error. Though the effects of probe misalignment are well documented, no device or technique has been universally adopted to ensure the proper installation of sap flow probes. In this paper we compare the magnitude of misalignment errors among a 5 mm thick drilling template (DT), a 10 mm thick DT, and a custom designed, field-portable drill press. The different techniques were evaluated in the laboratory using a 7.5 cm wood block and in the field, comparing differences in measured sap flow. Based on analysis of holes drilled in the wood block, we found that the portable drill press was most effective in assuring that drill holes remained parallel, even at 7.5 cm depth. In field installations, nearly 50% of holes drilled with a 5 mm template needed to be redrilled while none needed to be when drilled with the drill press. Widespread use of a portable drill press when implementing the heat pulse method would minimize alignment uncertainty and allow a clearer understanding of other sources of uncertainty due to variability in tree species, age, or external drivers or transpiration.

A low cost, low power sap flux device for distributed and intensive monitoring of tree transpiration.

Accurate estimation of transpiration in individual trees is important for understanding plant responses to environmental drivers, closing the water balance in forest stands and catchments, and calibrating earth system models, among other applications. However, the cost and power consumption of commercial systems based on sap flow methods still limit their usage. We developed and tested a cost-effective (<$150), simple to construct, and energy efficient sap flux device based on the heat pulse method. Energy savings were achieved by reducing the voltage of heat pulses and using an internal clock to completely shut down the device between pulses. Device accuracy was confirmed by laboratory estimates of sap flow made on excised branches of Acer saccharum and Tsuga canadensis (adjusted R2 = 0.96). In a 174-d field installation of 12 devices, batteries (eight rechargeable Ni-MH AA) needed to be replaced every 14 days. Sap flux measurements in the field tracked expected variations in vapor pressure deficit and tree phenology. The low cost, compact design, reliability, and power consumption of this device enable sap flux studies to operate with more replication and in more diverse ecological settings than has been practical in the past.

Landscape Features Associated With Blacklegged Tick (Acari: Ixodidae) Density and Tick-Borne Pathogen Prevalence at Multiple Spatial Scales in Central New York State.

Blacklegged ticks (Ixodes scapularis Say, Acari: Ixodidae) are the most commonly encountered and medically relevant tick species in New York State (NY) and have exhibited recent geographic range expansion. Forests and adjacent habitat are important determinants of I. scapularis density and may influence tick-borne pathogen prevalence. We examined how percent forest cover, dominant land cover type, and habitat type influenced I. scapularis nymph and adult density, and associated tick-borne pathogen prevalence, in an inland Lyme-emergent region of NY. I. scapularis nymphs and adults were collected from edge and wooded habitats using tick drags at 16 sites in Onondaga County, NY in 2015 and 2016. A subsample of ticks from each site was tested for the presence of Borrelia burgdorferi, Borrelia miyamotoi, Anaplasma phagocytophilum, and Babesia microti using a novel multiplex real-time polymerase chain reaction (PCR) assay, and deer tick virus using reverse transcription-PCR. Habitat type (wooded versus edge) was an important determinant of tick density; however, percent forest cover had little effect. B. burgdorferi was the most commonly detected pathogen and was present in ticks from all sites. Ba. microti and deer tick virus were not detected. Habitat type and dominant land cover type were not significantly related to B. burgdorferi presence or prevalence; however, ticks infected with A. phagocytophilum and B. miyamotoi were collected more often in urban environments. Similarity between B. burgdorferi prevalence in Onondaga County and hyperendemic areas of southeastern NY indicates a more rapid emergence than expected in a relatively naive region. Possible mechanistic processes underlying these observations are discussed.

Chloride sources in urban and rural headwater catchments, central New York.

Road salt used as a deicing agent in winter months has become an emerging contaminant to streams and groundwater. In central New York, road salts are applied heavily during winter months. Recognizing potential sources of salinity to a river may reveal processes controlling the salinization of freshwater systems, with implications for future management practices. The Tioughnioga River, located in central New York, is a headwater of the Susquehanna River, which flows into the Chesapeake Bay. Salinity of the Tioughnioga River water has been increasing since the late 1930s. In this study, water samples were collected weekly at the East and West Branches of the Tioughnioga River from 2012 to 2014. We characterize natural and anthropogenic sources of salinity in the Tioughnioga River, using two independent approaches: (1) chloride to bromide ratios (Cl/Br) and (2) linear discriminant analysis. Ratios of Cl/Br suggest that road salt runoff influence is notable in both branches, but is more significant in the West Branch, consistent with a greater area of urban land. Linear discriminant analysis confirms the results of Cl/Br in the West Branch and further indicates presence of Appalachian Basin Brines in the East Branch, although their contribution may be volumetrically small. Longitudinal stream Cl concentration profiles indicate that sources of pollution are particularly concentrated around urban areas. Residence time of Cl in the watershed is estimated to be approximately 20 to 30years using a mixing model, suggesting that stream Cl concentrations likely will continue to rise for several decades.

An assessment of radon in groundwater in New York state.

A set of 317 samples collected from wells throughout New York State (excluding Long Island) from 2003 through 2008 was used to assess the distribution of radon gas in drinking water. Previous studies have documented high concentrations of radon in groundwater from granitic and metamorphic bedrock, but there have been only limited characterizations of radon in water from sedimentary rock and unconsolidated sand-and-gravel deposits in New York. Approximately 8% of the samples from bedrock wells exceed 89 Bq L (eight times the proposed regulatory limit), but only 2% of samples from sand-and-gravel wells exceed 44 Bq L. Specific metamorphic and sedimentary rock formations in New York are associated with the high radon concentrations, indicating that specific areas of New York could be targeted with efforts to reduce the risk of exposure to radon in groundwater. Additionally, radon in groundwater from the sand-and-gravel aquifers was found to be directly correlated to radon in indoor air when assessed by county.