Stochastic modeling for seawater intrusion risk assessment in exploited coastal aquifers: the Oristano (Sardinia, Italy) case study

Groundwater contamination by seawater intrusion is a problem of growing concern to water resources managers worldwide. We present here a stochastic modeling technique, based on a 3D coupled flow and transport groundwater model, to assess the risk of salinization in a multilayered coastal aquifer, under model parameter uncertainty. The 127 km2 aquifer system of the Oristano plain (Sardinia, Italy) consists of two main productive units interbedded by a thin, possibly vanishing, clayey aquitard. Hydrogeological data and previous modeling studies revealed hydraulic interconnection between aquifers. Available data does not enable, however, an adequate characterization of spatial discontinuities in the confining layer, leading us to identify aquitard conductivity as the target parameter to be varied during stochastic simulations. Using a Monte Carlo technique, a range of aquifer system configurations has been explicitly simulated for three different schemes of pumping (phreatic aquifer only, deep aquifer only, and both aquifers simultaneously). The modeling approach, designed to perform probabilistic threshold analysis on the simulated groundwater concentrations, relies entirely on a suite of in-house developed and/or integrated computational modules. Results show that predicting the effect of aquitard spatial discontinuities was essential to evaluate the potential risk of groundwater contamination due to different exploitation schemes and to identify aquifer protection zones showing some level of vulnerability to seawater intrusion. The same quantitative methodology can be further developed to ensure the most cost effective decisions, e.g. about proposed mitigation plans and future field investigations, are made consistent with environmental protection.

@InProceedings{LC04,
  author       = {Lecca, G. and Cau, P.},
  title        = {Stochastic modeling for seawater intrusion risk assessment in exploited coastal aquifers: the Oristano (Sardinia, Italy) case study},
  booktitle    = {Developments in Water Science},
  volume       = {55},
  pages        = {1619--1628},
  year         = {2004},
  publisher    = {Elsevier},
  organization = {Proceedings of the XV International Conference On Computational Methods In Water Resources (CMWR XV),  Chapel Hill, NC, USA, June 13-17},
  note         = {isbn: 0444517693, idxproject: ISR8-C11/B MURST-GW, INCO ICA3-2001-20004 SWIMED},
  keywords     = {Monte Carlo analysis, groundwater models, water resources management},
  url          = {https://publications.crs4.it/pubdocs/2004/LC04},
}