Salt wedge intrusion modeling along the lower reaches of a Mediterranean river

Abstract

A three-dimensional numerical model was used to simulate the dynamics of a salt-wedge intruding along the lower Strymon River mouth (northern Greece). The area is microtidal and under the summer increased freshwater demand for irrigation, Strymon outflux at the mouth reduces to near zero. Forcing at boundaries was provided a) from the e-HYPE hydrological model, at the upstream river boundary; b) from the TPXO tidal model, imposed at the open sea boundary, c) from CMEMS for water temperature and salinity open sea profiles, and d) from NOAA-GDAS for meteorological forcing. The model was calibrated with field measurements during summer 2003 and produced fairly reliable results of salt wedge intrusion during summer 2004. The coefficient of determination for salinity reached 0.95; higher correlation was exhibited at the river upstream. Model results underestimated slightly the velocity and salinity along-channel observations. Salt wedge enters the lower river channel in late May 2004, under limited river discharge (< 10 m3/s) and intrudes up to 4.6 km upstream. The wedge length is controlled by the low river flow, the microtidal domain and complex bottom topography. Logarithmic and power law expressions were derived relating saline water intrusion length (L30) and Strymon River discharge from validated model results. Retention time (RT) calculated based on model outputs varies in Strymon salt wedge between 10 and 20 days. Future work includes the operationalization of Strymon salt wedge model to produce reliable salinity and velocity forecasts along the lower channel.