Interaction between Urbanization and Climate Variability Amplifies Watershed Nitrate Export in Maryland

Kaushal, Sujay S.; Groffman, Peter M.; Band, Lawrence E.; Shields, Catherine A.; Morgan, Raymond P.; Palmer, Margaret A.; Belt, Kenneth T.; Swan, Christopher M.; Findlay, Stuart E. G.; Fisher, Gary T.

doi:10.1021/es800264f

Cited by 235 publications

(241 citation statements)

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“…2,4,6,7 Much of the variation in DIN retention was due to variation in runoff, as has been observed at annual scales. 4,7 The proportion of DIN retained by each watershed was significantly related to the event runoff coefficient (runoff/precipitation; analysis of covariance (ANCOVA), F (1, 25) = 28.72, p < 0.0001), and there was a significant interaction with the number of noflow days preceding the storm (ANCOVA: F (1,25) = 5.231, p = 0.03, Figure 2), although no-flow days alone was not a significant predictor (ANCOVA: F (1,25) = 2.199, p = 0.15). The interaction with antecedent conditions, the number of days with no flow preceding the event, was such that retention was decreased by increasing no flow days.…”

Section: ■ Results and Discussionmentioning

confidence: 91%

Sources and Transport of Nitrogen in Arid Urban Watersheds

Hale

Turnbull

Earl

et al. 2014

Environ. Sci. Technol.

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Urban watersheds are often sources of nitrogen (N) to downstream systems, contributing to poor water quality. However, it is unknown which components (e.g., land cover and stormwater infrastructure type) of urban watersheds contribute to N export and which may be sites of retention. In this study we investigated which watershed characteristics control N sourcing, biogeochemical processing of nitrate (NO 3 − ) during storms, and the amount of rainfall N that is retained within urban watersheds. We used triple isotopes of NO 3 − (δ 15 N, δ 18 O, and Δ 17 O) to identify sources and transformations of NO 3 − during storms from 10 nested arid urban watersheds that varied in stormwater infrastructure type and drainage area. Stormwater infrastructure and land coverretention basins, pipes, and grass cover dictated the sourcing of NO 3 − in runoff. Urban watersheds were strong sinks or sources of N to stormwater depending on runoff, which in turn was inversely related to retention basin density and positively related to imperviousness and precipitation. Our results suggest that watershed characteristics control the sources and transport of inorganic N in urban stormwater but that retention of inorganic N at the time scale of individual runoff events is controlled by hydrologic, rather than biogeochemical, mechanisms.

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Section: ■ Results and Discussionmentioning

confidence: 91%

Sources and Transport of Nitrogen in Arid Urban Watersheds

Hale

Turnbull

Earl

et al. 2014

Environ. Sci. Technol.

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“…We have however, included a bit more discussion about how this model might differ in other regions (now lines [611][612][613][614][615][616][617][618].…”

Section: General Commentsmentioning

confidence: 99%

“…We've updated the text (now lines [611][612][613][614][615][616][617][618] to emphasize that these phases are context-specific and that stormwater infrastructure that looks similar (e.g., basins) may have very different functional consequences depending on the intended purpose (e.g., flow vs pollutant control). In your work, you quantify impervious area and the location/length of stormwater pipes.…”

Section: General Commentsmentioning

confidence: 99%

Stormwater Infrastructure Controls Runoff and Dissolved Material Export from Arid Urban Watersheds

et al. 2014

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. (2015) 'Stormwater infrastructure controls runo and dissolved material export from arid urban watersheds.', Ecosystems., 18 (1). pp. 62-75. Further information on publisher's website:http://dx.doi.org/10.1007/s10021-014-9812-2Publisher's copyright statement:The nal publication is available at Springer via http://dx.doi.org/10.1007/s10021-014-9812-2.Additional information: Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-pro t purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. General commentsOverall I was quite happy with the quality and scope of this paper. It is very well written and contains some important findings. Some general and more specific comments are provided below. I think the authors should have the opportunity to think about a few of my comments below; this calls for minor revision.While the paper concerns both hydrology and water quality, I think more attention is given to the latter. I would have liked to seen more results on hydrology. Maybe you could provide a graph (with associated discussion in the text) showing mean event runoff coefficients for each catchment? Given that the paper is already fairly long, this might not be possible. In any case, I recon you could expand your hydrological findings in a separate journal paper.• Response: We are planning a separate paper that details the hydrologic results of this work. However, since both reviewers requested more hydrologic data, we have added a table in the appendix that provides more details on runoff and storm characteristics (Table A1) In the discussion, you present a conceptual model of urban watershed ecosystem function and describe four periods of change. You suggest that the model is for arid urban catchments. I think it would be worth fleshing this section out a bit more. In doing this, maybe you could firstly describe in a general way, what is natural arid catchment hydrology.• Response: We have limited space to add more discussion here, and we already have some information on arid hydrology in the introduction (lines 191-194), and we reference key literature (Osterkamp and Freidman, 2000. We have however, included a bit more discussion about how this model might differ in other regions (now lines 611-618).Where I'm from, the "third" phase in your diagram is very different. We have been installing distributed stormwater infrastructure for the last 15 years. But, our systems are generally designed for pollutant-load reduction-aimed to protect our largest receiving water (a bay). These systems are not designed to restore/protect natural hydrology. Because of this, runoff/ratios tend to still be c...

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“…They may also partially result from the rapid changes of land use and land cover in the watershed since late 1990s [17]. According to a study in Maryland, USA, urban streams have lower NO 3 -N concentrations (0-280 mol L 1 ) than streams draining agricultural watersheds (70-1000 mol L 1 ), but higher than streams draining forest watersheds (~70 mol L 1 ) [12]. In the upper reach of the JRE, NO 3 -N concentrations in the 1990s were very similar to streams draining forest watersheds in Maryland (Figure 4(a)).…”

Section: Characteristics and Decadal Changes Of Jre Nutrientsmentioning

confidence: 99%

“…Therefore, variation in riverine fluxes of nutrients has been highlighted over the past 30 years, and is a major theme in the Land-Ocean Interactions in the Coastal Zone (LOICZ) program [8]. The synergistic effect between climate and land-use/land-cover change has been recently emphasized, since it may increase nutrient export fluxes from rivers into adjacent coastal zones [12,13].…”

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confidence: 99%

Distribution, fluxes and decadal changes of nutrients in the Jiulong River Estuary, Southwest Taiwan Strait

et al. 2012

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The Jiulong River Estuary (JRE) is a typical subtropical macro-tide estuary on the southwest coast of the Taiwan Strait (TWS), which has been greatly impacted by human activities over the past 30 years. To understand nutrient dynamics and fluxes under such a heavy background of anthropogenic perturbation, eight cruises were conducted from April 2008 to April 2011, covering both wet (May to September) and dry (October to April next year) seasons. Nutrient concentrations were very high for the freshwater end-member in the upper reach of the JRE (nitrate (NO 3 In dry seasons, concentrations of these nutrients were higher than in wet seasons. Nitrate was the dominant chemical species of dissolved inorganic nitrogen (DIN), with percentages of 67%-96% in wet seasons and 55%-72% in dry seasons. Distributions of NO 3 -N and DSi against salinity were nearly constant during all cruises, and showed generally conservative mixing behaviors in the estuary (1

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Interaction between Urbanization and Climate Variability Amplifies Watershed Nitrate Export in Maryland

Cited by 235 publications

References 40 publications

Sources and Transport of Nitrogen in Arid Urban Watersheds

Sources and Transport of Nitrogen in Arid Urban Watersheds

Stormwater Infrastructure Controls Runoff and Dissolved Material Export from Arid Urban Watersheds

Distribution, fluxes and decadal changes of nutrients in the Jiulong River Estuary, Southwest Taiwan Strait

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