Relating nitrogen export patterns from a mixed land use catchment in NW Spain with rainfall and streamflow

Rodríguez‐Blanco, M. L.; Taboada-Castro, M.T.; Oropeza-Mota, José Luis

doi:10.1002/hyp.10388

Cited by 19 publications

(27 citation statements)

References 31 publications

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“…The evaluation of interventions showed that policy-makers still struggle to set appropriate goals for water quality improvement, particularly in heavily human-impacted watersheds. Studies in Europe and the United States showed that interventions like reduced N inputs mainly in agricultural land use do not immediately result in declining riverine NO 3 -N concentrations (Bouraoui and Grizzetti, 2011;Sprague et al, 2011;Howden et al, 2011) and fluxes (Worrall et al, 2009), although fast responding headwaters have been reported as well (Rozemeijer et al, 2014).…”

mentioning

confidence: 99%

Trajectories of nitrate input and output in three nested catchments along a land use gradient

Ehrhardt

Kumar

Fleckenstein

et al. 2019

Hydrol. Earth Syst. Sci.

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Increased anthropogenic inputs of nitrogen (N) to the biosphere during the last few decades have resulted in increased groundwater and surface water concentrations of N (primarily as nitrate), posing a global problem. Although measures have been implemented to reduce N inputs, they have not always led to decreasing riverine nitrate concentrations and loads. This limited response to the measures can either be caused by the accumulation of organic N in the soils (biogeochemical legacy) -or by long travel times (TTs) of inorganic N to the streams (hydrological legacy). Here, we compare atmospheric and agricultural N inputs with longterm observations of riverine nitrate concentrations and loads in a central German mesoscale catchment with three nested subcatchments of increasing agricultural land use. Based on a data-driven approach, we assess jointly the N budget and the effective TTs of N through the soil and groundwater compartments. In combination with long-term trajectories of the C-Q relationships, we evaluate the potential for and the characteristics of an N legacy.We show that in the 40-year-long observation period, the catchment (270 km 2 ) with 60 % agricultural area received an N input of 53 437 t, while it exported 6592 t, indicating an overall retention of 88 %. Removal of N by denitrification could not sufficiently explain this imbalance. Log-normal travel time distributions (TTDs) that link the N input history to the riverine export differed seasonally, with modes spanning 7-22 years and the mean TTs being systematically shorter during the high-flow season as compared to low-flow conditions. Systematic shifts in the C-Q relationships were noticed over time that could be attributed to strong changes in N inputs resulting from agricultural intensification before 1989, the break-down of East German agriculture after 1989 and the seasonal differences in TTs. A chemostatic export regime of nitrate was only found after several years of stabilized N inputs. The changes in C-Q relationships suggest a dominance of the hydrological N legacy over the biogeochemical N fixation in the soils, as we expected to observe a stronger and even increasing dampening of the riverine N concentrations after sustained high N inputs. Our analyses reveal an imbalance between N input and output, long timelags and a lack of significant denitrification in the catchment. All these suggest that catchment management needs to address both a longer-term reduction of N inputs and shorterterm mitigation of today's high N loads. The latter may be covered by interventions triggering denitrification, such as hedgerows around agricultural fields, riparian buffers zones or constructed wetlands. Further joint analyses of N budgets and TTs covering a higher variety of catchments will provide a deeper insight into N trajectories and their controlling parameters.

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mentioning

confidence: 99%

Trajectories of nitrate input and output in three nested catchments along a land use gradient

Ehrhardt

Kumar

Fleckenstein

et al. 2019

Hydrol. Earth Syst. Sci.

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“…In general, model simulations can be considered satisfactory (R 2 > 0.5; NSE > 0.5) according to the criteria given by Moriasi et al [20], indicating that it is a valid tool to identify crucial pollution areas within the catchment. Although simulated NO 3 -N yield replicated the measured data trend quite well (Figure 2), the model underestimated the measured values during the autumn-winter 2005/2006 when high nitrate levels in stream were observed [16]. This fact may be due to underestimation of some discharge peaks in this period [21], which led to underestimating corresponding NO 3 -N yield because NO 3 -N, like other water quality parameters, depends on hydrological processes, and therefore errors in discharge simulations are magnified in their simulation.…”

Section: Swat Model Performance For Nitrate Yield Estimation At Catchmentioning

confidence: 63%

“…However, forest areas are not fertilized. The annual N input to the catchment is approximately 37.8 kg N ha −1 , 49% comes from organic fertilizers, 16% from inorganic fertilizers, 2% from population centres and the remaining 33% of atmospheric deposition [15,16].…”

Section: Study Area and Datamentioning

confidence: 99%

Modelling the Contribution of Land Use to Nitrate Yield from a Rural Catchment

Rodríguez-Blanco¹,

Arias²,

Maria-MercedesTaboada-Castro³

et al. 2016

Landscape Ecology - The Influences of Land Use and Anthropogenic Impacts of Landscape Creation

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The nutrient flow dynamics in rural landscapes are among the basic characteristics of landscape functioning. In this study, the ecohydrological model SW"T Soil and Water "ssessment Tool was applied in a small rural catchment in northwest NW Spain to evaluate the contribution of land use on nitrate losses and to assess the relative importance of different pathways by which nitrate is delivered to the drainage network. The model was first calibrated and validated at a monthly time step. The SW"T model performance was satisfactory R > . Nash-Sutcliffe efficiency NSE > . and percent bias P"I"S < % during both the calibration and validation periods, indicating that SW"T predicted the nitrate discharge accurately. Using the calibrated SW"T model, this study showed that agricultural lands, even though they represent only % of the catchment, were main contributor to the nitrate losses accounting for about % of the total nitrate yield. The model results also indicated that, irrespective of the land use, groundwater flow is the main pathway for nitrate losses % therefore, appropriate management practices aimed at decreasing nitrate leaching will be key factors in reducing nitrate yield in the study catchment.

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“…For examples, in the 2008/2009 hydrological year, TN, N-NO 3 and TKN concentrations were significantly lower in spring than summer, when it reached the highest daily flow-weighted mean TKN concentration, which was notably influenced by two large rainfall-runoff events in July of 2009. The summer of the 2008/2009 water year was characterized by elevated rainfall in July (170% higher than mean rainfall for July in the period 1983-2009) concentrated in two intense rainfall events, which caused high surface runoff and particulate material delivery to the stream [11] and consequently high TKN concentrations were observed. However, the very dry autumn 2007/2008 led to very low TKN concentrations, very similar to those observed in summer.…”

Section: Intra-annual Variation Of N Concentrationsmentioning

confidence: 99%

“…In addition, the N concentrations display wide variability within the same catchment. For example, for a given rainfall event, the N concentrations may differ greatly at different times of the year [11,12]. Climate and land use change is expected to alter the transfer of nutrients from land to water, although the results are controversial [13][14][15][16].…”

Section: Introductionmentioning

confidence: 99%

Inter‐ and Intra‐Annual Variability of Nitrogen Concentrations in the Headwaters of the Mero River

Rodríguez‐Blanco¹,

RicardoArias²,

Taboada-Castro³

2018

Nitrogen in Agriculture - Updates

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This study examines the inter-and intra-annual variability of different forms of N [total nitrogen (TN), nitrate-nitrogen (N-NO 3 ) and total Kjeldahl nitrogen (TKN)] in stream waters of a rural headwater catchment in Galicia (NW Spain) during a 5-year period, covering 2004-2009 water years (October-September). Daily time series were used to verify the temporal variability and to characterize the nitrogen pollution. The TN concentrations were low, although the values constantly exceeded the critical range (0.5-1.0 mg L −1 ) over which potential risk of eutrophication of water systems exists. Nitrate was the predominant form of nitrogen in the river throughout the study period, accounting for 82-85% of the TN. Significant differences were found for different forms of N between water years and seasons, indicative of wide inter-and intra-annual variability of nitrogen concentrations, mainly related to rainfall and flow oscillations. The seasonal pattern in the concentrations of TN, N-NO 3 and TKN in stream water was similar to many humid and temperate catchments, with higher concentrations in winter, when variability was also the highest in the period, and lower values in summer.

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Relating nitrogen export patterns from a mixed land use catchment in NW Spain with rainfall and streamflow

Cited by 19 publications

References 31 publications

Trajectories of nitrate input and output in three nested catchments along a land use gradient

Trajectories of nitrate input and output in three nested catchments along a land use gradient

Modelling the Contribution of Land Use to Nitrate Yield from a Rural Catchment

Inter‐ and Intra‐Annual Variability of Nitrogen Concentrations in the Headwaters of the Mero River

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