HighlightsThe results of the model and observation showed the similarity of the amplitude and phase formedAt the highest tide was in the position above the Sea Mean level and the current velocity was lower than when heading to the tideThere was a difference in the direction of the current when heading towards high tideStratification of the water column in both seasons tended to be classified in well-mixed watersAbstractBalikpapan Bay is significant as a link between the cities within and outside of East Kalimantan by becoming the primary path used for local transportation and distribution of produced goods. The various anthropogenic activities increased liquid wastes and debris, which flowed through channels and rivers along the bay. This study aimed to determine tidal current patterns in Balikpapan Bay and its influence on salinity and temperature distributions. This study applied a baroclinic three-dimensional (3D) hydrodynamic model, employing wind, tides, and density variations, resulting from the differences of temperature and salinity, as the model input. To simulate the tidal current flow, we applied MOHID Water Modeling System, which the tidal current patterns depicted current directions and speeds at the different tidal conditions. During the displacement toward the high tidal condition, the water mass moves northwestward entering the river body, while at the displacement toward the low tidal condition, the water mass moves southeastward, which flows toward the coast and without the bay. The current speed varies at certain tidal conditions. At the highest tidal condition, the surface elevation ranged 1.3 - 1.5 m above mean sea level; the current rate is lower compared to the displacement toward high tidal condition, which ranged from 0.01 - 0.15 m/s. At the lowest tidal condition, the surface elevation reached 1 - 1.2 m below mean sea level, and the weaker flow velocity took place (less than 0.15 m/s). The results also showed that the water mass temperature tends to be higher in the inner part of Balikpapan Bay, the Balikpapan Bay waters profile that is increasingly shallow towards the bay head also causes this area to tend to have a higher temperature. Also, areas located on the inside of the bay tend to get more freshwater input from rivers, so this area has lower salinity while the area located at the mouth of the bay tends to be of higher salinity because it gets a lot of mass input of seawater from the Makassar Strait.

An estimate of energetic barotropic and baroclinic tides over Sangihe-Talaud ridge (STR) - Sulawesi Sea is carried out by using a three-dimensional ROMS (Regional Ocean Modeling System) ocean model. The model is validated with satellite data. The estimate of tidal energy consists of generation, radiation, and dissipation. The model identified the generating internal tide area with strong barotropic-to-baroclinic conversion (above 10 kW/m) over S-T ridge. Away from this generating internal tides area that is in deep Sulawesi Sea basin, energy conversion is very weak (below 10⁻³Wm⁻²). Baroclinic energy is mostly dissipated in area near the coast. From the total of 9.45 GW (100%) of barotropic-to-baroclinic energy conversion, about 7.19 GW (76%) is converted into baroclinic energy through the generation of internal tide and about 4.13 GW (57%) of this baroclinic energy radiate to deep open sea. Distribution of tidal energy is highly dependent on topographic features. Estimate of strong vertical eddy diffusivity (K_V) over the steep S-T ridge varies between 10⁻³ and 10⁻² m²/s, in contrast to the weak KV in deep flat Sulawesi basin of about 10⁻⁴ m²/s.

Laut Sulawesi merupakan salah satu jalur penting perlintasan Arus Lintas Indonesia (Arlindo) yang memiliki energi pasang surut internal yang kuat. Arus pasang surut tinggi yang berinteraksi dengan topografi yang kasar akan menciptakan gelombang internal yang kuat. Disipasi dari pasang surut internal akan menyebabkan terjadinya percampuran yang akan memberikan efek penting untuk sistem perubahan iklim dan sumber daya laut. Tujuan dari penelitian ini adalah untuk mengkuantifikasi dinamika dan energetik gelombang internal di Laut Sulawesi dengan pendekatan pemodelan laut tiga dimensi NEMO. Hasil penelitian menunjukkan bahwa gelombang internal dibangkitkan pada daerah Kepulauan Sulu dan Sangihe-Talaud dengan nilai konversi energi lebih dari 10-3Wm-2 dan berpropagasi masuk ke area basin Laut Sulawesi. Disipasi energi yang terjadi pada pusat pembangkitan berkisar 10,8 GW dan berpopagasi pada area dekat pusat pembangkitan dan area basin Laut Sulawesi. Sekitar 25% (5 GW) didisipasi terjadi dekat pusat pembangkitan, peningkatan disipasi energi baroklinik terjadi pada saat gelombang internal berpopagasi menjauhi daerah pusat pembangkitan dengan nilai yang bervariasi antara 1,4 sampai 4,8 GW. Daerah dengan jarak 36 km sampai 54 km terjadi penurunan disipasi energi baroklinik, signal yang kuat dari Kepulaun Sangihe-Talaud berangsur menurun pada saat propagasi dari 10-2sampai 10-3W/m2.

The shrimp nursery infrastructure consists of nursery tanks, mechanical filters, biological filters, and ultraviolet (UV) filters. This study aimed to simulate the water level elevation (head) of shrimp nursery infrastructure, especially nursery tanks. The placement of the nursery greatly affects the elevation of the water table owing to the loss of energy (headloss) that occurs in the flow. The nursery tub used in this study was round and consisted of four tubs made of fiber resin measuring 250 cm in diameter and 120 cm in height. The bottom of the tub was placed at an elevation of +40 cm above the ground. The simulation was conducted for 24 hours. The results of the EPANET 2.2 simulation showed head fluctuations in each nursery with the highest elevation (1.38 m and the lowest (1.20 m, from the data. The head fluctuated constantly after 6 h of the flow. The optimal pipe diameters were 3" (80 mm) PVC and 4" (110 mm) PVC.