Future Flows and Groundwater Levels: Regional groundwater model projections

Projections of changes in groundwater level have been generated using the BGS ZOOMQ3D regional groundwater model of the Marlborough and Berkshire Downs and south-west Chilterns. These projections have been based on:

the 11-member ensemble of climate projections from the Met Office Hadley Centre's Regional Climate Model (RCM), and
a subset of 1000 of the 10 000 probabilistic climate change factors for the 2050s under a medium (A1B) greenhouse gas emissions scenario.

ZOOMQ3D groundwater model

The modelled region is located 70 km west of London and covers an area of approximately 2600 square km. It encloses the Marlborough and Berkshire Downs and the south-western part of the Chilterns, which are areas of gently undulating Chalk downland. The River Thames flows onto the area, and the Chalk, near Wallingford and off the study area near Windsor.

The model is described in the following Journal of Hydrology article, which details its use in a previous climate change impact assessment study:

Jackson C R, Meister R & Prudhomme C. 2011. Modelling the effects of climate change and its uncertainty on UK Chalk groundwater resources from an ensemble of global climate model projections. Journal of Hydrology, 399, 12–28.

The model has been calibrated through comparison with measured groundwater levels at 207 observation boreholes and river baseflow at 20 gauging stations over the period 1971 to 2003. The calibrated model includes anthropogenic abstractions and discharges to and from rivers and the aquifer. Prior to the use of the model to make the projections, these abstractions and discharges are switched off. Consequently, all projections are based on a 'naturalised' system.

Summary of groundwater model projections

Projections of change in groundwater level are provided for the following observation boreholes:

Name	Location	Easting	Northing
Ashridge Wood	SU47/140	449410	177910
Axford	SU27/44	424530	171550
Blind Man's Gate	SU46/139	443820	161780
Bottom Farm	SU68/66	464780	183810
Churn Estates	SU58/68	451640	185390
Compton	SU57/154	452630	179390
Gallowstree Common	SU68/22	469120	180210
Gibbet Cottages	SU47/141	445480	178870
Hodcott	SU48/69	448750	181750
Letcombe Bowers	SU38/33	438490	182600
Levetts Farm	SU16/2	417340	165670
Membury House	SU37/17	430030	174700
Old Hat	SU36/108	439900	165520
Prebendal Farm	SU28/66	425900	181810
Three Barrows	SU06/40	405790	167430
Whitehouse	SU47/47	448870	171410

Projections of change in groundwater level can are provided for the following observation boreholes

Downloads

11–member ensembles of transient 1951–2099 RCM projections under the medium (A1B) greenhouse gas emissions scenario

Groundwater levels (m aOD)

Ensembles of 1000 change factors for the 2050s under the medium (A1B) greenhouse gas emissions scenario

Groundwater level change factors (m)

Spatial grids (.asc files) of change factors for the 11–member RCM ensemble for six 30-year time-slices (2030s to 2080s) under the medium (A1B) greenhouse gas emissions scenario at the end of March, June, September and December.