Borehole Optimisation System (BOS)—A GIS based risk analysis tool for optimising the use of urban groundwater

Urban groundwater is generally an underused resource, partially due to the perceived risk of pollution and the strategic difficulties in placing boreholes in built-up areas. The development of a probabilistic risk based management tool that predicts groundwater quality at potential new urban boreholes is beneficial in determining the best sites for future resource development. The Borehole Optimisation System (BOS) is a custom Geographic Information System (GIS) application that has been developed in the ArcView 3.1 environment with the objective of locating the optimum locations for new boreholes in urban areas. It couples three component models, the Catchment Zone Probability Model (CZPM), the Land-use Model (LM) and the Pollution Risk Model (PRM). The CZPM produces probabilistic catchment zones for a user-defined abstraction borehole location under uncertain and variable hydrogeological parameters. The LM identifies current and historical industries located within the selected probabilistic catchment zone. The PRM uses these industrial and the associated hydrogeological and contaminant data to predict probabilistic contaminant concentrations in a particular analysis year. This paper outlines the methodologies employed in the development of BOS and attempts to validate the approach by presenting a simulation that forecasts PCE concentrations at an actual borehole location in the Nottingham urban aquifer. The results predict contaminant levels in the abstracted water that are in agreement withobserved values, bothbeing above the UK Drinking Water Standard of 10 lg/l. These demonstrate the applicability of BOS as a tool for informing decision-makers on the development of urban groundwater resources.