Hydrogeological investigation of soil salinity adjacent to a flood protection infrastructure

Groundwater modelling is a commonly used technique to determine the influence of surficial processes on subsurface aquifers. In this study, a groundwater monitoring study was conducted on an agricultural field adjacent to a large drainage canal to determine the effects of the canal's operation as it relates to soil salinity during periods around flood events. The groundwater monitoring program consisted of twenty standpipes instrumented with groundwater pressure transducers that took four daily measurements. A finite element model was generated using data collected from the 2017 flood year to determine the effect of the flood on the local groundwater regime within one area consisting of four standpipes. The analysis of the model calibration yielded good to excellent results using the Nash–Sutcliffe Model Efficiency technique, with three of the four standpipes. The salt content within the model area was primarily gypsum initially derived from the underlying till and bedrock units. Model analysis indicated that various processes might impact soil salinity, including canal seepage, evapotranspiration and excessive snowmelt/recharge. The largest flood event on record for the canal was used in the calibrated model to determine the maximum extent of influence the canal has on the adjacent lands. The maximum extent of impact was found to be 112 m in the alluvial sediments and 240 m in the surficial sand structure.