Review article

Numerical analysis of dam action preventing saltwater intrusion along the Neretva riverbed

Goran Lončar orcid.org/0000-0002-6466-3677 ; Sveučilište u Zagrebu, Građevinski fakultet, Zagreb, Hrvatska
Nino Krvavica orcid.org/0000-0001-5014-5476 ; Sveučilište u Rijeci, Građevinski fakultet, Rijeka, Hrvatska
Hrvoje Gotovac ; Sveučilište u Splitu, Fakultet građevinarstva arhitekture i geodezije, Split, Hrvatska
Dijana Oskoruš ; Državni hidrometeorološki zavod, Zagreb, Hrvatska
Tin Kulić orcid.org/0000-0001-6817-4603 ; Sveučilište u Zagrebu, Građevinski fakultet, Zagreb, Hrvatska

Abstract

A numerical analysis of saltwater transfer in the Neretva river bed in the section 0+000.0 m - 25+000.0 m was conducted using a 3D numerical model. In addition to the existing state of the riverbed, hypothetical situations including a construction of one dam in the profile 2+000.0 m (large depth and small width) or 4+000.0 m (small depth and large width) as well as the construction of 4 dams in the profiles 2/4/6/8+000.0 were also analyzed. The regulation of dam lifting and lowering is related to the mean measured discharge at the monitoring station Metković in the previous 24-hour period (QSR-24) or 6-hour period (QSR-6). In the situations where QSR-24 > 300 and 350 m3/s and QSR-6 > 300 m3/s, the dam was fully lowered whereas at smaller mean discharge values the dam is lifted up to a certain level (from -2 m to -5 m) during one hour. The 3D numerical model Mike 3fm, based on the finite volume method, was implemented. The discharges, levels and salinity measured at monitoring stations in 2018 were used for the model calibration and the 2017 data for the model results validation. Data on the sea temperature and salinity in the waters of the Neretva river mouth were taken from the national marine environment monitoring programmes. The model dynamics of the upstream-downstream translation of the salt “wedge” in non-stationary circulation conditions is in line with the measurements. The model thickness of the dividing zone between the freshwater and saltwater is larger than the one measured as a result of the numerical diffusion and adopted discretization of the calculation in the vertical direction of 1 m. The measured values and modeling results point to the conclusion that a complete extrusion of the salt “wedge” from the riverbed occurs at non-stationary discharges larger than 700 m3/s whereas the salt “wedge” advances upstream to 20+909.0 m (Metković) and further at discharges lower than 150 m3/s.
If the intrusion of the salt “wedge” upstream of the dam (2+000.0 m or 4+000.0 m) is to be prevented, a dam with a lifting to the depth of -2 m, under the condition of dam lifting at QSR-24 < 300 m3/s, must be executed.

Keywords

Neretva River; river mouth; numerical model; saltwater intrusion; dam

Hrčak ID:

241064

URI

https://hrcak.srce.hr/241064

Publication date:

24.6.2020.

Article data in other languages: croatian german

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