Changes in diffuse phosphorus and nitrogen inputs into surface waters in the Rhine watershed in Switzerland

Prasuhn, Volker; Sieber, Ulrich

doi:10.1007/s00027-005-0774-5

Cited by 29 publications

(11 citation statements)

References 1 publication

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“…in the Harz Mountains and extends to the northeast to the central German lowlands with an outlet at 85 m a.s.l. The longterm annual mean precipitation shows a remarkable decrease from a colder and humid climate in the Harz Mountains (1262 mm) down to the warmer and dryer climate of the central German lowlands on the leeward side of the mountains (614 mm; Rauthe et al, 2013;Frick et al, 2014). Discharge time series, provided by the State Office of Flood Protection and Water Management (LHW) of Saxony-Anhalt show a mean annual discharge at the outlet in Nienhagen of 1.5 m 3 s −1 , corresponding to 172 mm a −1 .…”

Section: Study Areamentioning

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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Section: Study Areamentioning

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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“…This degradation is caused by the ability of nitrogen species to increase primary production and to change food web structures (Howarth et al, 1996;Turner & Rabalais, 1991). Especially the coastal marine environments, where nitrate (NO 3 ) is typically the limiting nutrient, are affected by these eutrophication problems (Decrem 20 et al, 2007;Prasuhn and Sieber, 2005).…”

Section: Introductionmentioning

confidence: 99%

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

Ehrhardt¹,

Kumar²,

Fleckenstein³

et al. 2018

Preprint

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Increased anthropogenic inputs of nitrogen (N) to the biosphere during the last decades have resulted in increased groundwater and surface water concentrations of N (primarily as nitrate) posing a global problem. Although measures have 10 been implemented to reduce N-inputs especially from agricultural sources, they have not always led to decreasing riverine nitrate concentrations and loads. The limited response to the measures can either be caused by the accumulation of slowly mineralized organic N in the soils acting as a biogeochemical legacy or by long travel times (TTs) of inorganic N to the streams forming a hydrological legacy. Both types of legacy are hard to distinguish from the TTs and N budgets alone. Here we jointly analyze atmospheric and agricultural N inputs with long-term observations of nitrate concentrations and discharge 15 in a mesoscale catchment in Central Germany. For three nested sub-catchments with increasing agricultural land use, we assess the catchment scale N budget, the effective TT of N. In combination with long-term trajectories of C-Q relationships we finally evaluate the potential for and the characteristics of an N-legacy. We show that in the 42-year-long observation period, the catchment received an N-input of 42 758 t, of which 97 % derived from agricultural sources. The riverine Nexport sums up to 6 592 t indicating that the catchment retained 85 % of the N-input. Removal of N by denitrification could 20 not fully explain this imbalance. Log-normal travel time distributions (TTD) for N that link the input history to the riverine export differed seasonally, with modes spanning 8-17 years. Under low-flow conditions, TTs were found to be systematically longer than during high discharges. Systematic shifts in the C-Q relationships could be attributed to significant changes in N-inputs resulting from agricultural intensification and the break-down of the East German agriculture after 1989 and to the longer travel times of nitrate during low flows compared to high flows. A chemostatic export regime of 25 nitrate was only found after several years of stabilized N-inputs. We explain these observations by the vertical migration of the N-input and the seasonally changing contribution of subsurface flow paths with differing ages and thus differing N-loads.The changes in C-Q relationships suggest a dominance of hydrological N-legacy rather than a biogeochemical N-fixation in the soils, which should result in a stronger and even increasing dampening of riverine N-concentrations after sustained high N-inputs. Despite the strong N-legacy, a chemostatic nitrate export regime is not necessarily a persistent endpoint of intense 30 agricultural land use, but rather depends on a steady replenishment of the mass of N propagating through the catchments subsurface. The input-output imbalance, the long time-lags and the lack of significant denitrification in the catchment let us Hydrol. Earth Syst. Sci. Discuss., https://doi.

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“…In W European countries, although fertilizer-P use has decreased in recent years, the average input is higher than the average off-take and thus the risk of P loss via leaching and erosion is increasing (Tunney et al, 2003;Andersen et al, 2005). Switzerland, where concerns related to P loss early appeared (1950s), has developed an effective policy decreasing P load of lake waters: Switzerland fulfilled the international objective of halving P inputs into the Rhine and North Sea, achieving a calculated reduction of 51% between 1985 and 2001 (Prasuhn and Sieber, 2005). On the other side, the contribution of agricultural P to eutrophication in S European countries remains largely unassessed and thus warrants pertinent research at the soil, field, and catchment levels.…”

Section: P Losses From Soilsmentioning

confidence: 99%

Aspects of phosphorus transfer from soils in Europe

Delgado

Scalenghe

2008

Z. Pflanzenernähr. Bodenk.

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Imbalanced nutrient management has caused soil phosphorus (P) to become an environmental rather an agronomic problem in more economically developed countries. This subject has been the topic of numerous journal special issues, conferences, and reviews but we consider yet another review of this subject is necessary with the main target of providing a point of view on nonpoint transfer from soils and control strategies for an improved environmental management of P. This review considers the causes of the excessive P transfer from soil to surface water in Europe and the scientific knowledge necessary to develop control strategies. There has been an increasing trend towards the P-research integration across Europe. The identification of critical source areas (CSA) for P loss at catchment level and the selection of best management practices (BMP) adapted at individual CSA are recognized by the scientific community as a main goal to reduce P losses. However, the adaptation of the CSA conceptual framework at European scale is not undemanding, not only due to the administrative differences between countries, but also to the heterogeneity of the landscape (area, as perceived by people, whose character is the result of the action and interaction of natural and/or human factors; CoE [2000]) in Europe (larger than in N America), the wide range of land use and management, and also to differences in the basic scientific information available in each country necessary to perform it. In the EU, policy context and environmental concerns about the effect of nutrient excesses in water were reflected in EU directives (early 1990s) mainly focussed on the reduction of nitrogen loads. Nevertheless, a large number of scientific outcomes have revealed that reduction of P loss to surface water bodies is one of the main factors for obtaining higher quality of fresh-and seawaters, which must result in new EU directives also focussed in nonpoint pollution related to P load.

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Changes in diffuse phosphorus and nitrogen inputs into surface waters in the Rhine watershed in Switzerland

Cited by 29 publications

References 1 publication

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

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

Aspects of phosphorus transfer from soils in Europe

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