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The changing trend in nitrate concentrations in major aquifers due to historical nitrate loading from agricultural land across England and Wales from 1925 to 2150

The changing trend in nitrate concentrations in major aquifers due to historical nitrate loading from agricultural land across England and Wales from 1925 to 2150
The changing trend in nitrate concentrations in major aquifers due to historical nitrate loading from agricultural land across England and Wales from 1925 to 2150
Nitrate is necessary for agricultural productivity, but can cause considerable problems if released into aquatic systems. Agricultural land is the major source of nitrates in UK groundwater. Due to the long time-lag in the groundwater system, it could take decades for leached nitrate from the soil to discharge into freshwaters. However, this nitrate time-lag has rarely been considered in environmental water management. Against this background, this paper presents an approach to modelling groundwater nitrate at the national scale, to simulate the impacts of historical nitrate loading from agricultural land on the evolution of groundwater nitrate concentrations. An additional process-based component was constructed for the saturated zone of significant aquifers in England and Wales. This uses a simple flow model which requires modelled recharge values, together with published aquifer properties and thickness data. A spatially distributed and temporally variable nitrate input function was also introduced. The sensitivity of parameters was analysed using Monte Carlo simulations. The model was calibrated using national nitrate monitoring data. Time series of annual average nitrate concentrations along with annual spatially distributed nitrate concentration maps from 1925 to 2150 were generated for 28 selected aquifer zones. The results show that 16 aquifer zones have an increasing trend in nitrate concentration, while average nitrate concentrations in the remaining 12 are declining. The results are also indicative of the trend in the flux of groundwater nitrate entering rivers through baseflow. The model thus enables the magnitude and timescale of groundwater nitrate response to be factored into source apportionment tools and to be taken into account alongside current planning of land-management options for reducing nitrate losses.
0048-9697
694-705
Wang, L.
ff28fc9d-dbeb-460f-943c-f49997f58bf7
Stuart, M.E.
a25b6756-b906-4f11-ac22-82903498316c
Lewis, M.A.
6f575eff-7f2e-4bdd-91aa-c81e23fff5df
Ward, R.S.
f65b520a-c9fc-46af-b033-ce6dbc95a8a5
Skirvin, D.
f819d227-c07f-4927-bf93-8d3c17707181
Naden, P.S.
94009f2b-9d27-4341-9fdd-daffc281d76d
Collins, A.L.
eb72a479-2336-4268-a837-79d926239de3
Ascott, M.J.
244c7868-303d-46de-9b45-2fa005034bdb
Wang, L.
ff28fc9d-dbeb-460f-943c-f49997f58bf7
Stuart, M.E.
a25b6756-b906-4f11-ac22-82903498316c
Lewis, M.A.
6f575eff-7f2e-4bdd-91aa-c81e23fff5df
Ward, R.S.
f65b520a-c9fc-46af-b033-ce6dbc95a8a5
Skirvin, D.
f819d227-c07f-4927-bf93-8d3c17707181
Naden, P.S.
94009f2b-9d27-4341-9fdd-daffc281d76d
Collins, A.L.
eb72a479-2336-4268-a837-79d926239de3
Ascott, M.J.
244c7868-303d-46de-9b45-2fa005034bdb

Wang, L., Stuart, M.E., Lewis, M.A., Ward, R.S., Skirvin, D., Naden, P.S., Collins, A.L. and Ascott, M.J. (2016) The changing trend in nitrate concentrations in major aquifers due to historical nitrate loading from agricultural land across England and Wales from 1925 to 2150. Science of the Total Environment, 542 (A), 694-705. (doi:10.1016/j.scitotenv.2015.10.127).

Record type: Article

Abstract

Nitrate is necessary for agricultural productivity, but can cause considerable problems if released into aquatic systems. Agricultural land is the major source of nitrates in UK groundwater. Due to the long time-lag in the groundwater system, it could take decades for leached nitrate from the soil to discharge into freshwaters. However, this nitrate time-lag has rarely been considered in environmental water management. Against this background, this paper presents an approach to modelling groundwater nitrate at the national scale, to simulate the impacts of historical nitrate loading from agricultural land on the evolution of groundwater nitrate concentrations. An additional process-based component was constructed for the saturated zone of significant aquifers in England and Wales. This uses a simple flow model which requires modelled recharge values, together with published aquifer properties and thickness data. A spatially distributed and temporally variable nitrate input function was also introduced. The sensitivity of parameters was analysed using Monte Carlo simulations. The model was calibrated using national nitrate monitoring data. Time series of annual average nitrate concentrations along with annual spatially distributed nitrate concentration maps from 1925 to 2150 were generated for 28 selected aquifer zones. The results show that 16 aquifer zones have an increasing trend in nitrate concentration, while average nitrate concentrations in the remaining 12 are declining. The results are also indicative of the trend in the flux of groundwater nitrate entering rivers through baseflow. The model thus enables the magnitude and timescale of groundwater nitrate response to be factored into source apportionment tools and to be taken into account alongside current planning of land-management options for reducing nitrate losses.

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Published date: 15 January 2016
Organisations: Geography & Environment

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Local EPrints ID: 389594
URI: https://eprints.soton.ac.uk/id/eprint/389594
ISSN: 0048-9697
PURE UUID: 94aa334f-d8f7-46f2-aa26-039abbbecfb3

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Date deposited: 09 Mar 2016 13:12
Last modified: 09 Dec 2019 19:43

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