30 Nov 2021
30 Nov 2021
Status: a revised version of this preprint is currently under review for the journal HESS.

Improving the understanding of N transport in rural catchments under Atlantic climate conditions from analysis of the concentration-discharge relationship derived from a high frequency data set

María Luz Rodríguez-Blanco1, María Mercedes Taboada-Castro2, and María Teresa Taboada-Castro3 María Luz Rodríguez-Blanco et al.
  • 1History, Art and Geography Department, GEAAT Group, University of Vigo, Campus As Lagoas, 36310 Ourense, Spain
  • 2ETSIIAA, Area of Soil Science and Soil Chemistry, University of Valladolid, 34004 Palencia, Spain
  • 3Faculty of Sciences, Centre for Advanced Scientific Research (CICA), University of A Coruna 15071 A Coruña, Spain

Abstract. Understanding processes controlling stream nutrient dynamics over time is crucial for implementing effective management strategies to prevent water quality degradation. In this respect, the study of the nutrient concentration-discharge (C-Q) relationship during individual runoff events can be a valuable tool for extrapolating the hydrochemical processes controlling nutrient fluxes from streams. This study investigated nitrogen concentration dynamics during events by analyzing and interpreting the nitrogen C-Q relationship in a small Atlantic (NW Iberian Peninsula) rural catchment. To this end, nitrate (NO3) and total Kjeldahl nitrogen (TKN) concentrations were monitored at high temporal resolution during 102 runoff events over a 6-year period. For each of the selected runoff events, C-Q response was examined visually for the presence and direction of hysteresis loops and classified into three types of responses: clockwise and anticlockwise and no hysteresis. Some metrics, such as the change in concentration (ΔC) and the overall dynamics of hysteresis loops (ΔR), were used to quantify nitrogen behavior during the runoff events. The results showed how transport mechanisms varied between parameters. The most frequent hysteretic response for NO3 was enrichment with anticlockwise rotation, indicating that subsurface flow is the main pathway to the stream. On the contrary, the TKN dynamic was dominated by clockwise hysteresis, suggesting that surface runoff is mainly responsible for the transport of TKN to the river. Hysteresis direction (ΔR) and magnitude (ΔC) were better explained by event characteristics, such as rainfall, runoff, and discharge increase than by antecedent conditions (antecedent precipitation and baseflow).

María Luz Rodríguez-Blanco et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on hess-2021-536', Anonymous Referee #1, 13 Jan 2022
    • AC1: 'Reply on RC1', María Luz Rodríguez-Blanco, 27 Feb 2022
  • RC2: 'Comment on hess-2021-536', Anonymous Referee #2, 13 Jan 2022
    • AC2: 'Reply on RC2', María Luz Rodríguez-Blanco, 27 Feb 2022

María Luz Rodríguez-Blanco et al.

María Luz Rodríguez-Blanco et al.


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Short summary
The study examines the N dynamics on a small Atlantic headwater catchment localized in NW Iberian Peninsula, using high-frequency measurements of NO3 and TKN during runoff events. The divergence dynamics observed between N components exemplifies the complexity and variability of NO3 and TKN processes, highlighting the need to understand dominant hydrological pathways for the development of N-specific management plans to ensure that control measures are most effective at the catchment scale.