Characterization of seawater intrusion dynamics under the influence of hydro-meteorological conditions, tidal oscillations and melioration system operative regimes to groundwater in Neretva valley coastal aquifer system

Abstract

Study regionRiver Neretva coastal aquifer system located in the south eastern part of Croatia. Study focusThe study is focused to determination of the seasonal and non-seasonal variations of the groundwater features, when influenced by external loadings found at the study area. Based on time series observed from the monitoring systems, in-situ profiling and observed external loadings, a spectrogram and coherence analysis is performed to detect the peculiarities of the groundwater regimes at three different subareas along the study area. New hydrological insights for the regionBy using several methodological approaches, this paper emphasizes the combined effects of precipitation, river Neretva hydrological regime, melioration system operational regimes and tidal effects to the groundwater regime during the dry and rain seasons. During the dry period groundwater regime is mainly influenced by the seawater intrusion directly from the sea and from the river Neretva bed. Rain periods are characterized by the increase of the Neretva discharge thus eliminating the seawater from the river bed. This scenario results in improved quality of the groundwater. While Diga subarea faces active seawater intrusion, Jasenska's unconfined aquifer is fed by seawater from the river Neretva during the dry season. Vidrice is the only area where groundwater quality decreases during rain season due to the presence of salinized springs and the fact the area is found below the mean sea level.