Modeling renewal times in Amvrakikos Gulf, Greece

The Amvrakikos Gulf, located in the northwest Greece, is one of the largest semi-enclosed
embayments being about 40 km long and 15 km wide. Water renewal is made via a narrow channel
which connects the Gulf with the Ionian Sea having a 3.0 km length, width ranging from 0.8 to 2.0
km and depth from 2.0 to 13.0 m. The most common terms being used to indicate how fast the water
of semi-enclosed coastal embayments is renewed are hydraulic retention time (HRT) and residence
time (RT).
A preliminary estimation of HRT and RT is performed via a 3-D integrated model consisting of the
hydrodynamic sub-model FLOW-3DL and the water quality sub-model QUAL-3DL. The models
involve the 3-D non-steady state continuity, momentum and convection-diffusion equations
expressed in layer formulation. A space-staggered computational grid was used and the following
conclusions were drawn: (1) The HRT ranges from 1.86 to 2.42 years. (2) The flow rates of Louros
and Arachthos rivers, which gush into the Gulf, reduce the HRT by 0.56 years. (3) The effect of the
wind on HRT is minor due to the small size of the entrance to the Gulf. (4) The theoretical RT is
equal to 3.85 years.