Saline intrusion groundwater model: water company

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Courtesy of ESI Ltd - Environment Specialists

Client: Water Industry

Location: Sussex

Services: Groundwater Modelling, Water Quality and Groundwater Protection

Issues: Impact on deployable groundwater resources from saline intrusion within a Chalk aquifer

Summary: ESI was commissioned to produce a scoping model to simulate the effect of intrusion of seawater caused by abstractions from a Chalk aquifer. The modelling showed that observed levels of salinity were more strongly controlled by antecedent rainfall than by local abstraction from the aquifer thereby informing the local water resource plan.

ESI has recently carried out a thorough review of the hydrogeology of a block of Chalk aquifer that is at risk from saline intrusion.  The aquifer is an important source of public water supply for the local water company.  However, due to the highly transmissive nature of the Chalk aquifer, many of the local abstractions are at risk of drawing in brackish groundwater from the coastal zone.  This places a constraint on the deployable output of these sources.

The local water company required this constraint to be investigated and quantified as far as possible in order to have a reliable estimate of the deployable output of these sources.  Careful review of hydrograph and water quality data allowed convincing correlations to be developed between different data sets. 

A scoping model was constructed in FEFLOW to simulate the development of the saline wedge with time.  This provided numerical support for the conclusion that levels of salinity observed in boreholes were more strongly controlled by antecedent rainfall than by actual abstraction rates.  This has important conclusions for the way in which the aquifer should be managed. 

The project was carried out in 3 months from start to finish and delivered its conclusions on time to support the development of the local water resource plan

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