Is the River a Chemostat?: Scale Versus Land Use Controls on Nitrate Concentration‐Discharge Dynamics in the Upper Mississippi River Basin

Marinos, Richard E.; Meter, K. J. Van; Basu, Nandita B.

doi:10.1029/2020gl087051

Cited by 35 publications

(48 citation statements)

References 51 publications

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“…Seasonal and annual c-Q slopes across all hydrologic regimes show only weak correlations with watershed area suggesting that drainage infrastructure and the distribution and intensity of agriculture are the dominant drivers 350 of NO3export regime in these watersheds. This is consistent with a recent study of 33 agricultural watersheds in the Midwest (Marinos et al, 2020). Our results show that both conditions that lead to high NO3loads, whether hydrologic (i.e.…”

Section: Nutrient Export Is Driven By the Spatial Distribution Of Lansupporting

confidence: 94%

“…The observation that low flow periods were more chemodynamic than high flow periods is consistent with other 255 studies that have partitioned the hydrograph seasonally (Ehrhardt et al, 2019), by breakpoint analysis (Marinos et al, 2020), or by median discharge (Moatar et al, 2017), suggesting that this is a general feature of watershed hydrologic routing. Bulk stormflow c-Q slope exhibited subtle seasonality with a slight dilution trend in winter c-Q slopes in several watersheds, and a slight enrichment trend in spring and summer ( Figure 4B).…”

Section: Stormflow C-q Patterns Show Stationarity In Seasonal No3sourcessupporting

confidence: 85%

“…The ability of a single anomalous period to influence the overall characterization of a hydrologic system 295 highlights the difficulty of representing nutrient export behavior based on a single parameter fit across several seasons and flow regimes (Diamond & Cohen, 2018;Dupas et al, 2017;Marinos et al, 2020). This also highlights the need for high-frequency data collection activities that allow researchers and water quality practitioners to observe anomalous events during periods of the year that are not traditionally targeted by discrete or synoptic sampling campaigns.…”

Section: Periods Of Anomalous Flow and No3concentrations Can Alter Ovmentioning

confidence: 99%

“…The short circuiting of subsurface flow paths and increased cropped area drives watershed nutrient export 335 patterns towards chemostatic behavior by homogenizing the source regions and limiting nutrient cycling during transport (Marinos et al, 2020;Musolff et al, 2015;Thompson et al, 2011). These patterns are most clear during both baseflow and stormflow periods in the spring months, when tile drains likely have their greatest influence on hydrologic routing.…”

Section: Nutrient Export Is Driven By the Spatial Distribution Of Lanmentioning

confidence: 99%

“…For example, antecedent moisture conditions, and precipitation timing and intensity reflect changes that occur over hours or days (Rozemeijer et al, 2010), while vegetation dynamics, and on-farm practices such as crop planting and fertilization reflect seasonal changes (Minaudo et al, 2019;Royer et al, 2006). Additionally, the influence of these factors are impacted by differences in watershed-specific characteristics, such as topography, soil type, land use practices, and geologic history 80 (Marinos et al, 2020;Moatar et al, 2017). Understanding how these processes and watershed characteristics interact across the relevant spatial and temporal scales in heavily managed watersheds is a crucial step in developing strategies to mitigate downstream impact (Hansen et al, 2018).…”

Section: Introductionmentioning

confidence: 99%

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Hydrologic regimes drive nutrient export behavior in human impacted watersheds

Gorski

Zimmer

2020

Preprint

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Abstract. Agricultural watersheds are significant contributors to downstream nutrient excess issues. The timing and magnitude of nutrient mobilization in these watersheds are driven by a combination of anthropogenic, hydrologic, and biogeochemical factors that operate across a range of spatial and temporal scales. However, how, when, and where these complex factors drive nutrient mobilization has previously been difficult to capture with low-frequency or spatially limited datasets. To address this knowledge gap, we analyzed daily nitrate concentration (c) and discharge (Q) data for a four-year period (2016–2019) from five nested, agricultural watersheds in the midwestern United States that contribute nutrient loads to the Gulf of Mexico. The watersheds span two distinct landforms shaped by differences in glacial history resulting in natural soil properties that necessitated different drainage infrastructure across the study area. To investigate nutrient export patterns under different hydrologic conditions, we partitioned the hydrograph into stormflow and baseflow periods and examined those periods separately through the analysis of their concentration-discharge (c-Q) relationships on annual, seasonal, and event time scales. Stormflow showed consistent chemostatic patterns across all seasons, while baseflow showed seasonally dynamic c-Q patterns. Baseflow exhibited chemodyanmic conditions in the summer and fall and more chemostatic conditions in the winter and spring, suggesting that water source contributions during baseflow were nonstationary. Baseflow chemodynamic behavior was driven by low-flow, low-NO3− conditions during which in-stream and near-stream biological processing likely moderated in-stream NO3− concentrations. Additionally, inputs from deeper groundwater with longer residence times and lower NO3− concentration likely contributed to low-NO3− conditions in-stream, particularly in the larger watersheds. Stormflow c-Q behavior was consistent across watersheds, but baseflow c-Q behavior was linked to intensity of agriculture and density of built drainage infrastructure, with more drainage infrastructure associated with higher loads and more chemostatic export patterns across the watersheds. This suggests that how humans replumb the subsurface in response to geologic conditions has implications for hydrologic connectivity, homogenization of source areas, and subsequently nutrient export during both baseflow and stormflow. Our analysis also showed that anomalous flow periods greatly influenced overall c-Q patterns, suggesting that the analysis of high-resolution records at multiple scales is critical when interpreting seasonal or annual patterns.

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Section: Nutrient Export Is Driven By the Spatial Distribution Of Lansupporting

confidence: 94%

Section: Stormflow C-q Patterns Show Stationarity In Seasonal No3sourcessupporting

confidence: 85%

Section: Periods Of Anomalous Flow and No3concentrations Can Alter Ovmentioning

confidence: 99%

Section: Nutrient Export Is Driven By the Spatial Distribution Of Lanmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Hydrologic regimes drive nutrient export behavior in human impacted watersheds

Gorski

Zimmer

2020

Preprint

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Controls on spatial variability in mean concentrations and export patterns of river chemistry across the Australian continent

Liu

Dupas

Guo

et al. 2022

Preprint

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Pulses within pulses: Concentration‐discharge relationships across temporal scales in a snowmelt‐dominated Rocky Mountain catchment

Hensley

Singley

Gooseff

2022

Hydrological Processes

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Concentration-discharge (C-Q) relationships can provide insight into how catchments store and transport solutes, but analysis is often limited to long-term behaviour assessed from infrequent grab samples. Increasing availability of high-frequency sensor data has shown that C-Q relationships can vary substantially across temporal scales, and in response to different hydrologic drivers. Here, we present 4 years of dissolved organic carbon (DOC) and nitrate-nitrogen (NO 3 -N) sensor data from a snowmelt-dominated catchment in the Rocky Mountains of Colorado. We assessed both the direction (enrichment vs. dilution) and hysteresis in C-Q relationships across a range of time scales, from interannual to sub-daily. Both solutes exhibited a seasonal flushing response, with concentrations initially increasing as solute stores are mobilized by the melt pulse, but then declining as these stores are depleted. The high-frequency data revealed that the seasonal melt pulse was composed of numerous individual daily melt pulses. The solute response to daily melt pulses was relatively chemostatic, suggesting mobilization and depletion to be progressive rather than episodic processes. In contrast, rainfall-induced pulses produced short-lived but substantial enrichment responses, suggesting they may activate alternative solute sources or transport pathways. Finally, we observed low-level diel variation during summer baseflow following the melt pulse, likely driven by effects of daily evapotranspiration cycles. Additional contributions from in-stream metabolic cycles, independent from but covarying with diel streamflow cycles, could not be ruled out. The results clearly demonstrate that solute responses to daily cycles and individual events may differ significantly from the longer-term seasonal behaviour they combine to generate.

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Is the River a Chemostat?: Scale Versus Land Use Controls on Nitrate Concentration‐Discharge Dynamics in the Upper Mississippi River Basin

Cited by 35 publications

References 51 publications

Hydrologic regimes drive nutrient export behavior in human impacted watersheds

Hydrologic regimes drive nutrient export behavior in human impacted watersheds

Controls on spatial variability in mean concentrations and export patterns of river chemistry across the Australian continent

Pulses within pulses: Concentration‐discharge relationships across temporal scales in a snowmelt‐dominated Rocky Mountain catchment

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