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Poster communications

The Influence of Landscape Spatial Distribution on Nitrogen and Phosphorus Concentrations in Headwater Streams

Abstract : Nitrogen (N) and Phosphorus (P) losses from rural landscapes are of major concern as they can cause eutrophication of inland and coastal waters. Spatial management of landscape features distribution is sometimes proposed as a viable solution to limit nutrient transfer to streams and rivers. However, the effectiveness of such measures is rarely quantified at the catchment scale. We propose a spatially explicit data analysis to assess whether the spatial distribution of nutrient sources in agricultural landscapes influences nitrate and total phosphorus (TP) exports. We sampled water in 19 independent headwater catchments (1 to 14 km²) every two weeks for 18 months and analyzed nitrate and TP. The headwaters studied were located within the same 375 km² catchment and they had similar soil type, climate and farming systems but their landscapes differ in their composition (i.e. percentage of agricultural land) and distribution (i.e. agricultural land distance to ditches/streams & degree of overlay with flow accumulation zones). The method consisted in comparing a model only accounting for the land use composition (lumped) with a spatially explicit index that weights agricultural land according to its spatial distribution. We derived a hydrological distance to the stream (HDS) map, and a flow accumulation map (FAcc) from a 10m resolution digital elevation model. We aggregated land-use, HDS and FAcc maps within a catchment-level metric defined as Σ(LU*FAcc^a / HDS^b), where LU takes the value of 1 for agricultural land use and 0 for other land-uses. The parameters a and b were calibrated against median concentration of TP and nitrate, with the objective of maximizing the correlation on ranks. Results showed that median nitrate concentrations depended largely on landscape composition whereas the landscape distribution had a great influence on TP exports. From the optimal values of a and b we showed that both distance to the stream and overlay with flow accumulation influence TP exports. Our research provides useful insights to design new landscape management strategies.
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Poster communications
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Contributor : Isabelle Dubigeon Connect in order to contact the contributor
Submitted on : Monday, May 10, 2021 - 2:37:16 PM
Last modification on : Thursday, June 2, 2022 - 2:48:12 PM


  • HAL Id : insu-03222753, version 1


Antoine Casquin, Rémi Dupas, Sen Gu, Patrice Petitjean, Gérard Gruau, et al.. The Influence of Landscape Spatial Distribution on Nitrogen and Phosphorus Concentrations in Headwater Streams. American Geophysical Union Fall Meeting 2020 (AGU 2020), Dec 2020, Online, United States. pp.H057-0015, 2020. ⟨insu-03222753⟩



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