『Abstract
As the second largest aquifer in the United Kingdom, the Sherwood
Sandstone is threatened by high nitrate concentrations and water
shortages. Land-use change from arable agriculture to woodland
could help mitigate agricultural diffuse pollution and this study
provides an evaluation of the effects of woodland cover on groundwater
quality. Six land-use change scenarios focusing on two public-supply
borehole capture zones on the unconfined Sherwood Sandstone aquifer
in Nottinghamshire were examined in predictive simulations of
nitrate concentrations until 2025. Groundwater flow modelling
(MODFLOW) and mass transport modelling (MT3DMS), incorporating
outputs from a groundwater recharge model and an export coefficient
model enabled a quantitative comparison between different scenarios
on groundwater quality. Results revealed that the greatest decrease
by 2025 in nitrate concentration (35%) was associated with the
entire target zone covered with forest, whereas a decrease dependent
on the application of best agricultural practice achieved a 20%
reduction. Conversion of 80 ha and 240 ha of agricultural land
to woodland in two borehole capture zones (with areas of 210 ha
and 484 ha, respectively) could potentially restrict nitrogen
losses such that the EU groundwater nitrate limit (50 mg L-1
could be achieved in abstracted groundwater. It is concluded that
the combination of forest creation and application of best agricultural
practice in a borehole capture zone is a recommended approach
to control nitrate pollution in the long term and provides scientific
support for pollution control strategies that rely on land-use
change to woodland to achieve water quality objectives.
Keywords: Nitrate pollution; Groundwater modelling; Sandstone
aquifer; Land-use change; Forestry』
1. Introduction
2. Study area
3. Methods
3.1. Groundwater flow model
3.2. Export coefficient model
3.3. Mass transport model
3.4. Land-use change scenarios
3.5. Scenario nitrogen loadings
4. Results
5. Discussion
6. Conclusions
Acknowledgements
References