Role of water table dynamics on stream nitrate export and concentration in agricultural headwater catchment (France)

Molénat, Jérôme; Gascuel‐Odoux, Chantal; Ruiz, Laurent; Gruau, Gérard

doi:10.1016/j.jhydrol.2007.10.005

Cited by 134 publications

(143 citation statements)

References 45 publications

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“…These results are consistent with previous studies: the distinction between riparian groundwater and hillslope groundwater components has also been identified in similar catchments (by Molénat et al (2008) based on nitrate concentration analysis and by Aubert et al (2013a) based on a range of solutes) and at other site (by Haught and van Meerveld (2011)) using such Q-S relationships and lag time analysis.…”

Section: Discussionsupporting

confidence: 93%

“…Agriculture dominates the land use, with 86 % of the total area covered by grassland, maize and wheat, none of them irrigated. The base flow index is about 80 to 90 %; thus, the hillslope aquifer is the main contributor to stream flow (Molénat et al, 2008;Ruiz et al, 2002). Both stream flow and shallow groundwater tables exhibit a strong annual seasonality in this catchment (Figs.…”

Section: Study Sitesmentioning

confidence: 92%

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Hydrological hysteresis and its value for assessing process consistency in catchment conceptual models

Fovet

Ruiz

Hrachowitz

et al. 2015

Hydrol. Earth Syst. Sci.

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Abstract. While most hydrological models reproduce the general flow dynamics, they frequently fail to adequately mimic system-internal processes. In particular, the relationship between storage and discharge, which often follows annual hysteretic patterns in shallow hard-rock aquifers, is rarely considered in modelling studies. One main reason is that catchment storage is difficult to measure, and another one is that objective functions are usually based on individual variables time series (e.g. the discharge). This reduces the ability of classical procedures to assess the relevance of the conceptual hypotheses associated with models.We analysed the annual hysteric patterns observed between stream flow and water storage both in the saturated and unsaturated zones of the hillslope and the riparian zone of a headwater catchment in French Brittany (Environmental Research Observatory ERO AgrHys (ORE AgrHys)). The saturated-zone storage was estimated using distributed shallow groundwater levels and the unsaturated-zone storage using several moisture profiles. All hysteretic loops were characterized by a hysteresis index. Four conceptual models, previously calibrated and evaluated for the same catchment, were assessed with respect to their ability to reproduce the hysteretic patterns.The observed relationship between stream flow and saturated, and unsaturated storages led us to identify four hydrological periods and emphasized a clearly distinct behaviour between riparian and hillslope groundwaters. Although all the tested models were able to produce an annual hysteresis loop between discharge and both saturated and unsaturated storage, the integration of a riparian component led to overall improved hysteretic signatures, even if some misrepresentation remained. Such a system-like approach is likely to improve model selection.

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Section: Discussionsupporting

confidence: 93%

Section: Study Sitesmentioning

confidence: 92%

Hydrological hysteresis and its value for assessing process consistency in catchment conceptual models

Fovet

Ruiz

Hrachowitz

et al. 2015

Hydrol. Earth Syst. Sci.

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“…This included a landscape-scale component that aimed to provide new knowledge on N losses from agricultural landscapes, closing parts of the information gap between plot/field-scale experiments, and regional/national scale N statistics (Dalgaard et al, 2009;Bende-Michl et al, 2011). The authors of the present paper and the related research institutions all contributed to this landscape component of NitroEurope, including the inventory of six study landscapes with significant farm-related N-emission hotspots, and experiences from previous national research projects (Bouraoui et al, 1999;Dalgaard et al, 2002a, b;Dragosits et al, 2002Dragosits et al, , 2006Hansen, 2004;Molenat et al, 2008).…”

Section: Introductionmentioning

confidence: 83%

Farm nitrogen balances in six European landscapes as an indicator for nitrogen losses and basis for improved management

Dalgaard

Bieńkowski²,

Bleeker

et al. 2012

Biogeosciences

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Abstract. Improved management of nitrogen (N) in agriculture is necessary to achieve a sustainable balance between the production of food and other biomass, and the unwanted effects of N on water pollution, greenhouse gas emissions, biodiversity deterioration and human health. To analyse farm N-losses and the complex interactions within farming systems, efficient methods for identifying emissions hotspots and evaluating mitigation measures are therefore needed. The present paper aims to fill this gap at the farm and landscape scales. Six agricultural landscapes in Poland (PL), the Netherlands (NL), France (FR), Italy (IT), Scotland (UK) and Denmark (DK) were studied, and a common method was developed for undertaking farm inventories and the derivation of farm N balances, N surpluses and for evaluating uncertainty for the 222 farms and 11 440 ha of farmland included in the study.In all landscapes, a large variation in the farm N surplus was found, and thereby a large potential for reductions. The highest average N surpluses were found in the most livestock-intensive landscapes of IT, FR, and NL; on average 202 ± 28, 179 ± 63 and 178 ± 20 kg N ha −1 yr −1 , respectively. All landscapes showed hotspots, especially from livestock farms, including a special UK case with large-scale landless poultry farming. Overall, the average N surplus from the land-based UK farms dominated by extensive sheep and cattle grazing was only 31 ± 10 kg N ha −1 yr −1 , but was similar to the N surplus of PL and DK (122 ± 20 and 146 ± 55 kg N ha −1 yr −1 , respectively) when landless poultry farming was included.We found farm N balances to be a useful indicator for N losses and the potential for improving N management. Significant correlations to N surplus were found, both with ammonia air concentrations and nitrate concentrations in soils and groundwater, measured during the period of N management data collection in the landscapes from [2007][2008][2009]. This indicates that farm N surpluses may be used as an independent dataset for validation of measured and modelled N emissions in agricultural landscapes. No significant correlation was found with N measured in surface waters, probably because of spatial and temporal variations in groundwater buffering and biogeochemical reactions affecting N flows from farm to surface waters.A case study of the development in N surplus from the landscape in DK from 1998-2008 showed a 22 % reduction related to measures targeted at N emissions from livestock farms. Based on the large differences in N surplus between average N management farms and the most modern and Nefficient farms, it was concluded that additional N-surplus reductions of 25-50 %, as compared to the present level, were realistic in all landscapes. The implemented N-surplus Published by Copernicus Publications on behalf of the European Geosciences Union. T. Dalgaard et al.: Farm nitrogen balances as indicator for nitrogen lossesmethod was thus effective for comparing and synthesizing results on farm N emissions and the potentials of miti...

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“…Previous studies conducted on this site provide evidence for the structuration of the hydrological year into three different periods: period A, where the water table reaches the surface in down-slope wetlands but stays below the surface in the slope; period B, where rainfall intensification is responsible for the rise of water table in the slope which creates a hydrological connection between the slope soils, riparian soils and stream (Fig. 2); and period C, which is characterized by the return of the water table to deep soil horizons, resulting in the progressive drying of wetland soils (Aubert et al, 2013;Humbert et al, 2015;Lambert et al, 2013;Molenat et al, 2008). With the water table rise during period B, the water flow path geometry in riparian wetlands changes from a vertical to horizontal circulation.…”

Section: Study Sitementioning

confidence: 99%

New molecular evidence for surface and sub-surface soil erosion controls on the composition of stream DOM during storm events

et al. 2017

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Abstract. Storm events are responsible for more than 60 % of the export of dissolved organic matter (DOM) from headwater catchments due to an increase in both the discharge and concentration. The latter was attributed to changing water pathways inducing the mobilization of DOM from the surface soil horizons. Recent molecular investigations have challenged this view and hypothesized (i) a contribution of an in-stream partition of organic matter (OM) between eroded particles and the dissolved fraction and (ii) the modification of the composition of soil DOM during storm events. To investigate these assumptions, soil solutions in the macropores, surface runoff and stream outlet were sampled at high frequency during three storm events in the KervidyNaizin catchment, part of the French critical zone observatory AgrHyS. The molecular composition of the DOM was analysed by thermally assisted hydrolysis and methylation (THM) with tetramethylammonium hydroxide (TMAH) coupled to a gas chromatograph and a quadrupole mass spectrometer. These analyses highlighted a modification of the DOM composition in soil solution controlled by the watertable dynamic and pre-event hydrological conditions. These findings fit with the mechanism of colloidal and particulate destabilization in the soil macroporosity. The different behaviour observed for lignins, carbohydrates and fatty acids highlights a potential chemical segregation based on their hydrophobicity. The composition of surface runoff DOM is similar to the DOM composition in soil solution and could be generated by the same mechanism. The DOM composition in both soil solution and surface runoff corresponds to the stream DOM composition observed during storm events. On the basis of these results, modifications of the stream DOM composition during storm events seem to be due to surface and sub-surface soil erosion rather than in-stream production.

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Role of water table dynamics on stream nitrate export and concentration in agricultural headwater catchment (France)

Cited by 134 publications

References 45 publications

Hydrological hysteresis and its value for assessing process consistency in catchment conceptual models

Hydrological hysteresis and its value for assessing process consistency in catchment conceptual models

Farm nitrogen balances in six European landscapes as an indicator for nitrogen losses and basis for improved management

New molecular evidence for surface and sub-surface soil erosion controls on the composition of stream DOM during storm events

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