Multi component analysis of processes controlling seawater intrusion dynamics in Neretva delta area

Abstract:

River Neretva delta is an area of app. 4200 ha in its downstream part, located in the south-eastern part of Croatia, confronting the Adriatic sea. In its origin, mostly marsh area has been meliorated starting from mid of 20^th century when significant melioration infrastructure work has begun thus creating the area in its present form. Up to date, plenty of human impact has been present through embankment construction, drain channels network development and pumping stations for water delineation to create favourable agricultural pre-conditions.

To capture for transient nature of piezometric states and saltwater concentration, in-situ monitoring system has been established with capability to give temporally continuous insight to processes found within this coastal system.

Observed signals of piezometric heads, electrical conductivity and temperature are analysed via tidal methods, spectral components and regression analysis. Ground and surface water samples are faced to hydrogeochemical analysis, enabling further understanding of internal mechanisms affecting quality of the water bodies found within this coastal system. Besides abovementioned parameters we use meteorological and climatological data as well as irrigation system operative regime to point out the relevance and the intensity of its role in salt water dynamics.

By incorporating available results of in situ geological and hydrogeological work, we emphasize following findings: i) main corridor for saltwater intrusion in aquifer is defined from the sea towards inland, ii) while lowest confined aquifer is shown to be dominantly influenced by the sea dynamics, upper unconfined aquifer is shown to be significantly influenced by both meteo-climatic conditions and irrigation system operative regime, iii) during both wet and dry season, Neretva coastal system does not show locally expected features of groundwater salinity dynamics thus emphasizing its complexity.