Salt-wedge dynamics in microtidal Neretva River estuary

Abstract

The Neretva River estuary, located in Croatia, on the eastern coast of the Adriatic Sea, is a typical example of a micro-tidal salt-wedge estuary. Here, the salt-wedge dynamics was investigated based on continuous field measurements and numerical modeling for the period 2015-2018. A two-layer shallow-water numerical model proved to be an accurate and reliable tool for computing the salt-wedge dynamics in the Neretva River estuary. The simulations showed that the river inflow has the strongest impact on the salt-wedge dynamics, whereas sea levels and tides have a much smaller effect, mainly related to daily variations of the salt-wedge length and volume. A set of simple equations were derived, which link the salt-wedge intrusion length, salt-wedge volume, and salt-wedge spread to the river flow rate. It was shown that, during summer, the salt-wedge intrudes more than 20 km upstream from the mouth, exacerbating the salinization of aquifers and soils. The assessment of salt-wedge dynamics in the Neretva River estuary is thus a crucial element for planning, designing, and managing the irrigation system in this coastal region, for sustainable development of agriculture and protection of water resources.