Concentration, flux, and the analysis of trends of total and dissolved phosphorus, total nitrogen, and chloride in 18 tributaries to Lake Champlain, Vermont and New York, 1990–2011

Medalie, Laura

doi:10.3133/sir20135021

Cited by 5 publications

(17 citation statements)

References 11 publications

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“…Details of data collection, data analysis, and the application of WRTDS specifically to Lake Champlain tributary data are documented in Medalie (2013). Water-quality data were retrieved from the Vermont Department of Environmental Conservation (2013) Web site.…”

Section: Methodsmentioning

confidence: 99%

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Concentration and flux of total and dissolved phosphorus, total nitrogen, chloride, and total suspended solids for monitored tributaries of Lake Champlain, 1990-2012

Medalie¹

2014

Open-File Report

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Annual and daily concentrations and fluxes of total and dissolved phosphorus, total nitrogen, chloride, and total suspended solids were estimated for 18 monitored tributaries to Lake Champlain by using the Weighted Regressions on Time, Discharge, and Seasons regression model. Estimates were made for 21 or 23 years, depending on data availability, for the purpose of providing timely and accessible summary reports as stipulated in the 2010 update to the Lake Champlain "Opportunities for Action" management plan. Estimates of concentration and flux were provided for each tributary based on (1) observed daily discharges and (2) a flow-normalizing procedure, which removed the random fluctuations of climate-related variability. The flux bias statistic, an indicator of the ability of the Weighted Regressions on Time, Discharge, and Season regression models to provide accurate representations of flux, showed acceptable bias (less than ±10 percent) for 68 out of 72 models for total and dissolved phosphorus, total nitrogen, and chloride. Six out of 18 models for total suspended solids had moderate bias (between 10 and 30 percent), an expected result given the frequently nonlinear relation between total suspended solids and discharge. One model for total suspended solids with a very high bias was influenced by a single extreme value; however, removal of that value, although reducing the bias substantially, had little effect on annual fluxes.

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Section: Methodsmentioning

confidence: 99%

“…The first report evaluated TP and total nitrogen (TN) from 1990 through 2009 (Medalie and others, 2012). The second report evaluated TP, TN, dissolved phosphorus (DP), and chloride from 2009 through 2011 (Medalie, 2013). The current report evaluates TP, TN, DP, chloride, and is expanded to include TSS concentrations.…”

Section: Introductionmentioning

confidence: 99%

Concentration and flux of total and dissolved phosphorus, total nitrogen, chloride, and total suspended solids for monitored tributaries of Lake Champlain, 1990-2012

Medalie¹

2014

Open-File Report

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“…However, average TN river and TP river concentrations were strongly affected by changing land management over this period (Ghebremichael et al 2010). As a result, although TN river loads from rivers draining forested catchments increased over time as a result of increasing precipitation, average TN river concentrations declined as a result of decreased atmospheric N deposition (Canham et al 2012) and changes in nutrient management (Medalie 2013). The declines in TN river concentrations matched the observed declines in TN lake .…”

Section: Resultsmentioning

confidence: 77%

“…Because annual loads of nutrient inputs failed to explain trends in lake nutrients, particularly the decline in TN lake , we also calculated average annual concentrations of total and dissolved nutrient inputs and compared them to in-lake total nutrient concentrations. Trends in nutrient loads to the lake over the monitoring period were primarily controlled by changes in precipitation and tributary discharge (Medalie 2013). However, average TN river and TP river concentrations were strongly affected by changing land management over this period (Ghebremichael et al 2010).…”

Section: Resultsmentioning

confidence: 99%

“…Phytoplankton cell count data from 63-lm plankton net vertical plankton samples were obtained from the Vermont Department of Environmental Conservation by request. Tributary nutrient loads (daily and annual) for TN, TP, and DP from each of the 18 monitored tributaries to the lake for 1992-2012 were estimated by Medalie (2013). TN:TP in the lake and tributaries are expressed as TN:TP lake and TN:TP river to avoid ambiguity.…”

Section: Data Sourcesmentioning

confidence: 99%

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Climate-driven changes in energy and mass inputs systematically alter nutrient concentration and stoichiometry in deep and shallow regions of Lake Champlain

Isles

Stockwell

et al. 2017

Biogeochemistry

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Concentrations of nitrogen (N) and phosphorus (P) in lakes may be differentially impacted by climate-driven changes in nutrient loading and by direct impacts of temperature and wind speed on internal nutrient cycling. Such changes may result in systematic shifts in lake N:P under future climate warming. We used 21 years of monitoring data to compare long-term and intra-annual trends in total N (TN), total P (TP) and TN:TP at 15 sites in Lake Champlain to concurrent measurements of watershed nutrient inputs and meteorological drivers. TN:TP declined sharply lake-wide, particularly in the past decade, yet the drivers of this trend varied based on site depth. In deep sites, declines were driven by changes in watershed loading of dissolved P and N and (in some cases) by decreases in hypolimnetic dissolved oxygen. In shallow sites, declines in TN:TP were primarily driven by long-term increases in temperature and decreases in wind speed, and exhibited systematic seasonal variability in TN:TP due to the timing of sediment P loading, N removal processes, and external nutrient inputs. We developed a conceptual model to explain the observed trends, and suggest that while climate drivers have affected nutrient dynamics in shallow and deep sites differently, both deep and shallow sites are likely to experience further declines in N:P and increases in cyanobacteria dominance if recent climate trends continue.

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Evaluating Spatial Variability in Sediment and Phosphorus Concentration‐Discharge Relationships Using Bayesian Inference and Self‐Organizing Maps

Underwood

Rizzo

Schroth

et al. 2017

Water Resources Research

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Given the variable biogeochemical, physical, and hydrological processes driving fluvial sediment and nutrient export, the water science and management communities need data‐driven methods to identify regions prone to production and transport under variable hydrometeorological conditions. We use Bayesian analysis to segment concentration‐discharge linear regression models for total suspended solids (TSS) and particulate and dissolved phosphorus (PP, DP) using 22 years of monitoring data from 18 Lake Champlain watersheds. Bayesian inference was leveraged to estimate segmented regression model parameters and identify threshold position. The identified threshold positions demonstrated a considerable range below and above the median discharge—which has been used previously as the default breakpoint in segmented regression models to discern differences between pre and post‐threshold export regimes. We then applied a Self‐Organizing Map (SOM), which partitioned the watersheds into clusters of TSS, PP, and DP export regimes using watershed characteristics, as well as Bayesian regression intercepts and slopes. A SOM defined two clusters of high‐flux basins, one where PP flux was predominantly episodic and hydrologically driven; and another in which the sediment and nutrient sourcing and mobilization were more bimodal, resulting from both hydrologic processes at post‐threshold discharges and reactive processes (e.g., nutrient cycling or lateral/vertical exchanges of fine sediment) at prethreshold discharges. A separate DP SOM defined two high‐flux clusters exhibiting a bimodal concentration‐discharge response, but driven by differing land use. Our novel framework shows promise as a tool with broad management application that provides insights into landscape drivers of riverine solute and sediment export.

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Concentration, flux, and the analysis of trends of total and dissolved phosphorus, total nitrogen, and chloride in 18 tributaries to Lake Champlain, Vermont and New York, 1990–2011

Abstract: Map showing Lake Champlain Basin, physiographic provinces, water-quality monitoring stations, tributary boundaries, and parts of tributaries that include only the 12-digit hydrologic unit closest to the monitoring station ..

Cited by 5 publications

References 11 publications

Concentration and flux of total and dissolved phosphorus, total nitrogen, chloride, and total suspended solids for monitored tributaries of Lake Champlain, 1990-2012

Concentration and flux of total and dissolved phosphorus, total nitrogen, chloride, and total suspended solids for monitored tributaries of Lake Champlain, 1990-2012

Climate-driven changes in energy and mass inputs systematically alter nutrient concentration and stoichiometry in deep and shallow regions of Lake Champlain

Evaluating Spatial Variability in Sediment and Phosphorus Concentration‐Discharge Relationships Using Bayesian Inference and Self‐Organizing Maps

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