A modelling approach to determine the origin of urban ground water

Sam A. Trowsdale and David N. Lerner

Journal of Contaminant Hydrology, Volume 91, Issues 1-2, 1 April 2007, Pages 171-183

Abstract

This paper sets out the development of a simple modelling approach to link patterns of urban land-use with ground water flow and chemistry in three dimensions. This method is applied to characterize the origin of recharge in the aquifer beneath the old industrial city of Nottingham, UK. The approach involves dividing land uses into types, and times into periods, and assigning the recharge from each an individual tracer-solute with a unit concentration. The computer code MT3DMS is used to track the multiple tracer-solutes in transient, three-dimensional simulations of the important urban aquifer. A depth-specific hydrochemical dataset collected in parallel supports the model predictions. At depth under the industrial area studied, a large component of ground water originated of older agricultural origin with relatively low nitrate concentrations. Shallower ground water originated mainly from residential and industrial areas, with higher nitrate concentrations probably arising from leaking sewers and contaminated land. The results highlight the spectrum of ground water from different origins that amalgamate even at short well screens in a non-pumped borehole and remind us that the non-point source pollution of ground water from anthropogenic activities will involve more years of slow degradation of quality.

a)

Modelled percentages of recharge diagram a


b)

Modelled percentages of recharge diagram b