Tracking changes in nutrient delivery to western Lake Erie: Approaches to compensate for variability and trends in streamflow

Choquette, Anne F.; Hirsch, Robert M.; Murphy, Jennifer C.; Johnson, Laura T.; Confesor, Remegio

doi:10.1016/j.jglr.2018.11.012

Cited by 67 publications

(53 citation statements)

References 50 publications

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“…Flow normalization is an approach for identifying the "signal" of long-term systematic water-quality changes due to human actions on the landscape from the "noise" of high year-toyear variability. This process provides estimates of concentration that exclude effects of year-to-year fluctuations in streamflow, due largely to variability in weather, but it retains the effects from both seasonal streamflow variability and long-term, systematic streamflow trends, both of which may influence long-term systematic changes in water quality (Choquette et al, 2019). Trends are reported as the time series of FN annual values and as the change (in both milligrams per liter, mg L −1 , and percent change relative to initial concentrations) between the 1992 and 2012 FN sediment concentration.…”

Section: Description Of Water-quality Data and Trend Resultsmentioning

confidence: 99%

“…Thus, the 1992-2012 trend was calculated as (FN2012 − FN1992) / FN1992 ×100. See Hirsch et al (2010) and Choquette et al (2019) for a complete description of the trend methods, including the weighted regression approach and the flow-normalization process. These analyses were completed using the EGRET version 3.0 R pack-age (Hirsch et al, 2018a).…”

Section: Description Of Water-quality Data and Trend Resultsmentioning

confidence: 99%

“…Since the potential drivers of systematic, multi-decadal changes in sediment in US rivers and streams are varied, one useful approach is to conceptualize changes in sediment as a function of changes in the streamflow regime and changes on the landscape (Choquette et al, 2019;Murphy and Sprague, 2019). Thus, each sediment trend was parsed into two components of change: the amount of change due to changes in the streamflow regime, i.e., the streamflow trend component (QTC), and the amount of change in sediment due to changes in land management, i.e., the management trend component (MTC).…”

Section: Methods For Exploring Potential Drivers Of Changementioning

confidence: 99%

“…There are multiple approaches for linking changes in sediment at stream sites with changes in land use/cover, hydrol-ogy and climate. These approaches include using qualitative statements with or without data (e.g., Gao et al, 2013;Kreiling and Houser, 2016;Li et al, 2016), using processbased watershed and landscape models (e.g., Ficklin et a., 2013;Lacher et al, 2019), and teasing apart water-quality and streamflow records to identify and estimate the amount of change due to human actions, climate or hydrology (e.g., Gao et al, 2013;Li et al, 2016;Murphy and Sprague, 2019;Choquette et al, 2019;Rossi et al, 2009). Many of these approaches are hindered by the lack of available data that characterize potential drivers of change.…”

Section: Introductionmentioning

confidence: 99%

“…Thus, for a given year, annual mean concentrations of sediment are a function of the streamflow conditions for that year, changes that occurred in the watershed (i.e., land management activities, surface or channel disturbance, etc.) and, at some locations, a systematic change in some portion of the streamflow regime (Murphy and Sprague, 2019;Choquette et al, 2019). When trying to understand potential drivers of long-term changes in sediment, it is the influence of land management changes and systematic changes in streamflow that are of most interest.…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

Changing suspended sediment in United States rivers and streams: linking sediment trends to changes in land use/cover, hydrology and climate

Murphy

2020

Hydrol. Earth Syst. Sci.

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Abstract. Sediment is one of the leading pollutants in rivers and streams across the United States (US) and the world. Between 1992 and 2012, concentrations of annual mean suspended sediment decreased at over half of the 137 stream sites assessed across the contiguous US. Increases occurred at less than 25 % of the sites, and the direction of change was uncertain at the remaining 25 %. Sediment trends were characterized using the Weighted Regressions on Time, Discharge, and Season (WRTDS) model, and decreases in sediment ranged from −95 % to −8.5 % of the 1992 concentration. To explore potential drivers of these changes, the sediment trends were (1) parsed into two broad contributors of change, changes in land management versus changes in the streamflow regime, and (2) grouped by land use of the watershed and correlated to concurrent changes in land use or land cover (land use/cover), hydrology and climate variables and static/long-term watershed characteristics. At 83 % of the sites, changes in land management (captured by changes in the concentration–streamflow relationship over time; C–Q relationship) contributed more to the change in the sediment trend than changes in the streamflow regime alone (i.e., any systematic change in the magnitude, frequency or timing of flows). However, at >50 % of the sites, changes in the streamflow regime contributed at least a 5 % change in sediment, and at 11 sites changes in the streamflow regime contributed over half the change in sediment, indicating that at many sites changes in streamflow were not the main driver of changes in sediment but were often an important supporting factor. Correlations between sediment trends and concurrent changes in land use/cover, hydrology and climate were often stronger at sites draining watersheds with more homogenous, human-related land uses (i.e., agricultural and urban lands) compared to mixed-use or undeveloped lands. At many sites, decreases in sediment occurred despite small-to-moderate increases in the amount of urban or agricultural land in the watershed, suggesting conservation efforts and best-management practices (BMPs) used to reduce sediment runoff to streams may be successful, up to a point, as lands are converted to urban and agricultural uses.

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Section: Description Of Water-quality Data and Trend Resultsmentioning

confidence: 99%

Section: Description Of Water-quality Data and Trend Resultsmentioning

confidence: 99%

Section: Methods For Exploring Potential Drivers Of Changementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Changing suspended sediment in United States rivers and streams: linking sediment trends to changes in land use/cover, hydrology and climate

Murphy

2020

Hydrol. Earth Syst. Sci.

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Hydrologic flushing rates drive nitrogen cycling and plant invasion in a freshwater coastal wetland model

Sharp

Elgersma

Martina

et al. 2021

Ecological Applications

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Coastal wetlands intercept significant amounts of nitrogen (N) from watersheds, especially when surrounding land cover is dominated by agriculture and urban development. Through plant uptake, soil immobilization, and denitrification, wetlands can remove excess N from flow‐through water sources and mitigate eutrophication of connected aquatic ecosystems. Excess N can also change plant community composition in wetlands, including communities threatened by invasive species. Understanding how variable hydrology and N loading impact wetland N removal and community composition can help attain desired management outcomes, including optimizing N removal and/or preventing invasion by nonnatives. By using a dynamic, process‐based ecosystem simulation model, we are able to simulate various levels of hydrology and N loading that would otherwise be difficult to manipulate. We investigate in silico the effects of hydroperiod, hydrologic residence time, N loading, and the NH4+:NO3‐ ratio on both N removal and the invasion success of two nonnative species (Typha × glauca or Phragmites australis) in temperate freshwater coastal wetlands. We found that, when residence time increased, annual N removal increased up to 10‐fold while longer hydroperiods also increased N removal, but only when residence time was >10 d and N loading was >30 g N·m−2·yr−1. N removal efficiency also increased with increasing residence time and hydroperiod, but was less affected by N loading. However, longer hydrologic residence time increased vulnerability of wetlands to invasion by both invasive plants at low to medium N loading rates where native communities are typically more resistant to invasion. This suggests a potential trade‐off between ecosystem services related to nitrogen removal and wetland invasibility. These results help elucidate complex interactions of community composition, N loading and hydrology on N removal, helping managers to prioritize N removal when N loading is high or controlling plant invasion in more vulnerable wetlands.

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Long‐term effect of poultry litter application on phosphorus balances and runoff losses

et al. 2021

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Assessment of annual and cumulative impacts of phosphorus (P) management strategies at field and watershed scales is needed to improve crop use efficiency and minimize environmental impacts. The objectives of this study were (a) to assess relationships among P balance, soil test P (STP) concentration, and runoff dissolved reactive P (DRP) concentration from fields receiving different poultry litter application rates (0.0-13.4 Mg ha -1 ) and (b) to determine the effect of long-term poultry litter application to fields on watershed DRP loss. Nutrient management practices, crop yield, STP, and runoff losses were assessed from nine fields and two watersheds located near Riesel, TX, from 2000 to 2015. Field-scale P balances were largely controlled by P application rate and exhibited a positive relationship with STP and runoff DRP flow-weighted mean concentration. Using a before-after control-impact experimental design that included monitoring at both field and watershed scales showed the influence of field P management on watershed DRP loss varied according to both source (i.e., P application rate, impacted area) and transport (i.e., hydrological connectivity) factors. Increased risk of watershed DRP loss was observed during wet years and years with two poultry litter applications to fields within the watershed.The percentage of the total watershed area receiving high rates of poultry litter also played a critical role in determining the risk of DRP loss. Findings highlight the impact of long-term P management strategies on DRP loss at both field and watershed scales and show the importance of incorporating hydrologic connectivity when assessing conservation effects on water quality.

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Tracking changes in nutrient delivery to western Lake Erie: Approaches to compensate for variability and trends in streamflow

Cited by 67 publications

References 50 publications

Changing suspended sediment in United States rivers and streams: linking sediment trends to changes in land use/cover, hydrology and climate

Changing suspended sediment in United States rivers and streams: linking sediment trends to changes in land use/cover, hydrology and climate

Hydrologic flushing rates drive nitrogen cycling and plant invasion in a freshwater coastal wetland model

Long‐term effect of poultry litter application on phosphorus balances and runoff losses

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