Nitrogen Dynamics and Patterns of Catchment Response as a Result of Legacies and Transit Times under changing Land Use and Management
Abstract
The worldwide nitrate (N) pollution is a thread for the water quality of surface and ground water bodies. Despite many regulations and measures to reduce N input (mainly fertilizers, manure), international stakeholders experience limited response in the improvement of water quality in catchments worldwide. These measures often fail due to the lack of understanding the catchment's heterogeneity. As a result, increasing N loads cause eutrophication and ecological degradation in freshwater and marine ecosystems. As watersheds are complex heterogeneous systems, we have to understand the impact of their natural and anthropogenic controls as well as the long-term catchment responses (hysteresis) under spatial and temporal changes in nutrient inputs. In the present work, we focus on the long-term N dynamics in subcatchments of German rivers (1-38000 km2) and the interpretation of the relation between N input at catchment scale and measured riverine nitrate concentration as an N output. Therefore, we conceptualize each catchment as a biogeochemical reactor, driven by N inputs and characterized by biogeochemical (degradation) and hydrological (travel times) processes with a specific riverine nitrate output as the result. Based on large data sources for German wide diffusive and point N sources as well as measured riverine nitrate concentrations, we derive long-term trajectories of N input and N output that are classified and interpreted according to their hysteresis characteristics and geophysical catchment properties. In Weser river basin, Germany's largest national river basin, we identified the majority of 60 subcatchments according to their hysteresis loop and classified them into four archetype response patterns. Here, we extend our analysis on several hundreds of water quality stations in whole Germany. We present different patterns in watershed N dynamics, focusing on hydrological and biogeochemical processes. Our results show how we can understand the catchment's N dynamics on basis of long-term N input and N output trajectories and catchment properties.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2020
- Bibcode:
- 2020AGUFMH092...06W
- Keywords:
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- 1803 Anthropogenic effects;
- HYDROLOGY;
- 1831 Groundwater quality;
- HYDROLOGY;
- 1834 Human impacts;
- HYDROLOGY;
- 1871 Surface water quality;
- HYDROLOGY