Road Salt Delivery Mechanisms and Water Quality Impacts in the Hudson River Watershed

Road Salt Delivery Mechanisms and Water Quality Impacts in

the Hudson River Watershed Kate Meierdiercks, Department of Environmental Studies & Sciences, Siena College [email protected]

Abstract. Road salt entering surface stream channels can negatively impact water quality and ecosystem and human health. While it is generally understood that salt runs off into surface water with melting snow, much less is known about how and when salt enters surface streams through groundwater baseflow. This project examines how land use and watershed structure control delivery of road salt to the Hudson River. This question is addressed in the Hudson River Watershed using publicly available Hudson River Environmental Conditions Observing System (HRECOS) and US Geological Survey (USGS) data and data from independent researchers participating in The Hudson River Tributary and Subwatershed (THuRST) research network. For the watersheds in this study, results suggest that salt is entering surface streams through groundwater baseflow, but there is less evidence that salt is also delivered by the road network as snowmelt. The one exception is the Patroon Creek, the most urban study watershed, where large fluxes of salt in the winter and spring months are likely the result of road salt runoff.

Three Summary Points of Interest  Salt concentrations and fluxes (quantified as specific conductance, SpC) are increasing in 86% of the watersheds examined in this study. At most sites, maximum daily discharge is increasing while 7-day minimum discharge is decreasing.  All sites exhibit bi-model seasonal SpC response with concentrations peaking around March and again September. However, there is no evidence that the March peak is tied to snow melt. Instead SpC concentrations and fluxes are closely associated with streamflow with high SpC concentrations resulting from low flow rates. Furthermore, SpC concentration is not significantly correlated with road density. Rather, the watershed characteristics that are most strongly and significantly correlated with SpC concentration are imperviousness, soil type, basin slope and outfall density, all characteristics that are known to impact stormwater runoff rate and volume. Results suggest that salt is entering the stream channel through groundwater baseflow and that this may be the more important delivery mechanism.  The exception and outlier compared to the other 23 watersheds in this study, is the Patroon Creek Watershed, the most urban of the study watersheds, and one of the watersheds with the highest road density. SpC concentrations in Patroon Creek are an order of magnitude greater than the other study watersheds and SpC fluxes peak in the winter. Results suggest that in the Patroon, salt is delivered to the stream channel both through groundwater baseflow and winter snow melt.

Keywords: Road salt, watershed, water quality, Hudson River

New York State Water Resources Institute | wri.cals.cornell.edu Road Salt Delivery Mechanisms and Water Quality Impacts in the Hudson River Watershed

Introduction  Analyze salt concentration (quantified as Road salt is applied to roads during winter specific conductance, SpC) data to identify months to improve driving conditions, but when it runs hotspots and examine spatiotemporal variability. off into surface and drinking water it can lead to  Correlate land use and watershed structure negative environmental, ecosystem, and health impacts geospatial characteristics with average annual (Kausal et al., 2018). Increased chloride concentrations and seasonal SpC concentrations. in surface waters can be linked to corrosivity and elevated lead levels in drinking water (Stets et al., 2018), as in the Flint, MI water crisis. There has been an increase in road salt use over the last 50 years in the northeast (Kausal et al., 2005). Kelting et al. (2012) note that New York State is one of the biggest users of road salt. Many studies attribute the rise in salt concentrations in surface water to increased urbanization and road salt applications (see for example, Goodwin et al., 2003). However, some studies have shown that salt concentrations can increase in surface waters without increases in urbanization or salt applications; these studies suggest that road salt is persisting in the environment and entering surface water streams through groundwater baseflow during non- winter months (Kelly et al., 2007; Corsi et al., 2015). However, how and when salt enters surface water bodies through groundwater baseflow is still not well understood (Kelly et al., 2007). Given the spatial variability of salt in groundwater (Kelly et al., 2018) and hydrologic response in urban watersheds (Meierdiercks et al., 2009), it’s unclear how or whether the results from these few watersheds translate to others in the region. This project examined the question, how do land use and watershed structure control delivery of road salt to the Hudson River? Land use and watershed structure characteristics of several Hudson watersheds were Figure 1. Locations of monitoring stations for the watersheds used in this study. computed using GIS data and geoprocessing models. Road salt contamination in these watersheds was Results examined using specific conductance (SpC) water Across 86% (12 out of 14) of this sites with quality data available through the Hudson River long-term data records, regardless of the location within Environmental Conditions Observing System the Hudson River Watershed and decade, SpC (HRECOS), US Geological Survey (USGS), and concentrations and fluxes increase for the period of independent researchers participating in The Hudson record. In many of the sites examined, max daily River Tributary and Subwatershed (THuRST) research discharge is increasing and 7-day minimum discharge is network (Figure 1). Both long-term trend and multi- decreasing. Long-term trends in SpC concentration, SpC watershed comparative analyses were performed on the flux, and discharge are consistent with trends reported water quality data. Relationships between land elsewhere in the literature (Kaushal et al., 2018, for use/watershed structure characteristics and average example). Most sites exhibit a bi-modal seasonal annual and seasonal SpC concentrations were explored response with SpC concentrations peaking around March through correlation analyses. The objectives of this and again around September. The exception is the project are summarized as follows: Patroon Creek Watershed where SpC concentrations and  Characterize Hudson subwatershed land use and fluxes peak in the winter months. SpC concentrations in watershed structure through geospatial analyses.

This report was prepared for the New York State Water Resources Institute (NYSWRI) and the Hudson River Estuary Program of the New York State Department of Environmental Conservation with support from the NYS Environmental Protection Fund. Road Salt Delivery Mechanisms and Water Quality Impacts in the Hudson River Watershed the Patroon are also an order of magnitude greater than in the environment and entering stream channels through the other study watersheds (Appendix A). groundwater baseflow. There is no significant increase GIS analyses of land surface and drainage in SpC fluxes in the winter and spring in all study network characteristics highlight the diversity of watersheds but one. The exception is the Patroon Creek watershed characteristics and development types Watershed where SpC fluxes increase in the winter and throughout the Hudson River Watershed. The largest spring without a corresponding increase in discharge watershed in this study is 11,900 square miles, while the (Figure 4). These fluxes are likely the result of smallest is less than 1 square mile. The study snowmelt (Erickson, 2004). Further examining watersheds range in percent urban from 96.6% to 0% hydrograph-pollutographs for this station will provide a urban, in road density from 89,000 ft/sq.mi to 0 ft/sq.mi, better understanding of the dynamics of road salt and in slope from 2000 to 151 ft/mi (Appendix A). The delivery mechanisms (Calvi et al., 2018). watershed characteristics with the strongest and most significant correlations with SpC concentrations are percent impervious, percent soil type B, mean basin slope, and outfall density (Figure 2). There is not a strong or significant correlation between SpC concentration and road density (Appendix A) .

Figure 3. Relationship between sampled specific conductance values and discharge (left) and specific conductance flux and discharge (right) for USGS 01357500 Mohawk River at Cohoes NY. Discussion Though seasonal SpC concentrations for all sites exhibit a bimodal response with SpC concentrations peaking around March and again around September, these peaks do not appear to be associated with an Figure 2. Specific conductance values (mS/cm) versus GIS increase in salt flux from snowmelt. Furthermore, characteristics for the HRECOS and THuRST stations. although salt concentrations tend to increase with For all study watersheds, SpC concentration is increasing imperviousness, they are not correlated with inversely proportional to discharge: as discharge road density. Instead, the peaks in SpC concentration increases, SpC concentration decreases. Subsequently, are closely tied to seasonal changes in discharge with SpC flux is highly correlated with discharge with SpC peaks in SpC concentration resulting from low discharge flux increasing as discharge increases (Figure 3, for values rather than increases in salt fluxes. Results example; see Appendix A for all sites). High SpC suggest that salt is indeed entering the stream channel concentration at low flows suggests that salt is persisting through groundwater baseflow and that, in fact, there is

This report was prepared for the New York State Water Resources Institute (NYSWRI) and the Hudson River Estuary Program of the New York State Department of Environmental Conservation with support from the NYS Environmental Protection Fund. Road Salt Delivery Mechanisms and Water Quality Impacts in the Hudson River Watershed less evidence of salt running off into surface water with the THuRST research network, can also help to fill gaps melting snow. The exception is in the Patroon Creek where they exist, but these researchers also need funding Watershed, the most urban of the study watersheds. In and support. the Patroon, SpC concentrations are an order of While evidence from this study suggests that salt magnitude greater than the other watersheds in this study is persisting in the environment and entering stream and SpC fluxes in the winter and spring are likely the channels through the Hudson River Watershed as result of snowmelt entering the stream channel through groundwater baseflow, it does not provide any insights roads and other impervious surfaces (Erickson, 2004). into how long salt may be stored in groundwater before However, more work is needed to better understand the it enters a stream channel. It is possible that dynamics between runoff and salt concentrations across communities that have implemented salt reduction different time scales and watershed development types management strategies may not see water quality (Calvi et al., 2018, Murphy and Sprague, 2019). benefits right away and long-term monitoring may be necessary. Furthermore, any community wishing to assess the impacts of road salt reductions on water quality needs to consider the impacts of discharge on salt concentration. Declining salt concentrations could be due to decreases in salt fluxes or increases in discharge.

Methods 24 watersheds were used in this study (Figure 1) and include stations operated by independent researchers participating in this project through the THuRST research network, stations run by the Hudson River Environmental Conditions Observing System (HRECOS), and the US Geological Survey (USGS). As of writing this paper, there are 72 USGS stream gages operating in the Hudson River Watershed that have historically (as early as the 1950s) or are currently measuring specific conductance. Most of these sites collect SpC data as grab samples. Patroon Creek (USGS 01359133) and the Hudson River at Poughkeepsie (USGS 01372058) stations also have continuous SpC data measured using a logger. Of the 72 USGS stream Figure 4. Relationship between measured specific conductance gaging stations in the Hudson River Watershed that are values and discharge (left) and specific conductance flux and collecting SpC, the 21 with the longest SpC data records discharge (right) for USGS 01359133 Patroon Cr at Northern Blvd at Albany NY. were used in this study. The stations are located as far north as Newcomb and as far south as Poughkeepsie and Policy Implications range in development from 0% to 36% impervious. The processes that control flooding and water HRECOS stations that were used in this study include quality in urban watersheds are complex and not well those with the highest quality data (smallest percentage understood. This study underscores the importance of of flagged data points). THuRST watersheds with a long-term stream monitoring datasets for understanding substantially long data record were included, however the connections between urban development, flooding, more THuRST watersheds can be added to these and water quality. If more urban watersheds were analyses as their data records increase in length. monitored and could be included in this study, it would The Hudson is a complicated river for likely reveal that rather than being an outlier, the Patroon conducting hydrological and water quality studies. First, is simply on one end of a continuous spectrum of road the Hudson River is tidal as far north as the Troy dam salt delivery mechanisms in the Hudson River and gaging stations along the river can record negative Watershed. The existing stations maintained by the flow. Second, the river also experiences a salt front. USGS and HRECOS should be funded and supported. Saline water can be detected north of Poughkeepsie Independent researchers, such as those that are part of depending on freshwater flow, tide stage, channel

This report was prepared for the New York State Water Resources Institute (NYSWRI) and the Hudson River Estuary Program of the New York State Department of Environmental Conservation with support from the NYS Environmental Protection Fund. Road Salt Delivery Mechanisms and Water Quality Impacts in the Hudson River Watershed geometry, and wind (de Vries & Weiss, 2001). For this Publications/Presentations reason, negative flow values and SpC concentrations Hudson River Watershed Alliance, Upper Hudson greater than 500 microsiemens/cm (the specific Speaker Series, “Road Salt: Impacts on Water Quality, conductance concentration corresponding to the salt Watersheds, and Communities,” Troy NY, March 13, front) were removed from discharge and SpC datasets. 2020 [Cancelled due to COVID-19] Analysis of discharge and SpC was conducted using Meierdiercks, K.L., Donahoo, B., Hill, C., Fitzgerald, Excel, R and R packages, Exploration and Graphics for E.T., Gallagher, L., Kuhne, A., and Smith, N., Road Salt RivEr Trends (EGRET) and dataRetrieval. These Delivery Mechanisms and Water Quality Impacts in the packages use “Weighted Regressions on Time, Hudson River Watershed. Poster presented at: Discharge and Season (WRTDS) to describe long-term Association for Environmental Studies and Sciences trends in both concentration and flux,” of water quality Annual Conference, virtual, July 15-17, 2020 parameters (Hirsch & De Cicco, 2015; Smith et al.,

2018). To compute flux, SpC was first multiplied by 0.64 to convert microsiemens/cm to mg/L. Acknowledgements Land use and watershed drainage network structure characteristics were computed for the study Funding for water quality data collection and preliminary watersheds using readily available data from federal, analyses was provided by the New York State Environmental Protection Fund through the Hudson River Estuary Program of state, and local GIS data repositories (ex. NYSGIS the New York State Department of Environmental Clearinghouse, NationalMap.gov). GIS characteristics Conservation. Thank you to the THuRST research partners were computed using ESRI ArcGIS Model Builder and and students who have contributed to this project: Brian USGS Streamstats. R was used to perform correlation Donahoo, Catherine Hill, Eileen Fitzgerald, Lauren Gallagher, analyses between GIS characteristics and average annual Anna Kuhne, and Nicole Smith. and seasonal SpC concentrations for the Mohawk Lock 8, Port of Albany, Schodack Island, Norrie Pt, and References Wappinger Watersheds. These watersheds were included Calvi, C., Dapeña, C., Martinez, D. E., & Londoño, O. M. Q. because they have a common period of record. (2018). Relationship between electrical conductivity, 18 O of Pearson’s r and p were calculated to identify strong and water and NO 3 content in different streamflow stages. Environmental earth sciences, 77(6), 1-12. significant relationships. Corsi, S. R., De Cicco, L. A., Lutz, M. A., & Hirsch, R. M. Outreach Comments (2015). River chloride trends in snow-affected urban A presentation of this project was planned in watersheds: increasing concentrations outpace urban growth coordination with the Hudson River Watershed Alliance rate and are common among all seasons. Science of the Total Environment, 508, 488-497. as part of their Upper Hudson Speaker Series. However, the presentation (planned for March 13, 2020) was De Vries, M. P., & Weiss, L. A. (2001). Salt-front Movement cancelled due to concerns related to COVID-19. Rather in the Hudson River Estuary, New York: Simulations by One- than doing a virtual meeting, we decided to present this dimensional Flow and Solute-transport Models (Vol. 99, No. 4024). US Department of the Interior, US Geological Survey. work as a StoryMap (https://www.esri.com/en- us/arcgis/products/arcgis-storymaps/overview). Emily Erickson, E. K. (2004). Road salt application and its effects on Vail, Executive Director the Watershed Alliance sodium and chloride ion concentrations in an urban stream provided feedback on an outline of this StoryMap. An Patroon Creek, Albany, NY. Geology Theses and undergraduate student will complete the StoryMap this Dissertations. 22.nhttp://scholarsarchive.library.albany.edu/cas_daes_geolog spring as in independent study project. Once completed, y_etd/22 the StoryMap can be shared with the watershed community through the Watershed Alliance digest and Godwin, K. S., Hafner, S. D., & Buff, M. F. (2003). Long- Siena College website. term trends in sodium and chloride in the Mohawk River, New York: the effect of fifty years of road-salt application. Environmental pollution, 124(2), 273-281. Student Training Three (3) undergraduate students worked on this Kaushal, S. S., Groffman, P. M., Likens, G. E., Belt, K. T., Stack, W. P., Kelly, V. R., ... & Fisher, G. T. (2005). Increased project and gained training in data analysis using Excel salinization of fresh water in the northeastern United States. and R, and GIS modeling and spatial analysis.

Proceedings of the National Academy of Sciences, 102(38), Stets, E. G., Lee, C. J., Lytle, D. A., & Schock, M. R. (2018). 13517-13520. Increasing chloride in rivers of the conterminous US and

Kaushal, S. S., Likens, G. E., Pace, M. L., Utz, R. M., Haq, S., linkages to potential corrosivity and lead action level Gorman, J., & Grese, M. (2018). Freshwater salinization exceedances in drinking water. Science of the Total syndrome on a continental scale. Proceedings of the National Environment, 613, 1498-1509. Academy of Sciences, 201711234. Appendices Kelly, V. R., Lovett, G. M., Weathers, K. C., Findlay, S. E., Strayer, D. L., Burns, D. J., & Likens, G. E. (2007). Long- term sodium chloride retention in a rural watershed: legacy Appendix A. All figures and tables effects of road salt on streamwater concentration. Appendix B. Hudson River Watershed Alliance, Upper Environmental science & technology, 42(2), 410-415. Hudson Speaker Series, presentation slides

Kelly, V. R., Cunningham, M. A., Curri, N., Findlay, S. E., & Appendix C. AESS conference poster Carroll, S. M. (2018). The Distribution of Road Salt in Private Drinking Water Wells in a Southeastern New York Suburban Appendix C. StoryMap outline Township. Journal of environmental quality.

Meierdiercks, K. L., Smith, J. A., Baeck, M. L., & Miller, A. J. (2010). Heterogeneity of hydrologic response in urban watersheds. Journal of the American Water Resources Association, 46(6), 1221-1237.

Murphy, J., & Sprague, L. (2019). Water-quality trends in US rivers: Exploring effects from streamflow trends and changes in watershed management. Science of the Total Environment, 656, 645-658.