Seawater intrusion (SWI) is a significant threat to freshwater resources in coastal aquifers around the world. Previous studies have focused on SWI impacts involving salinization of the lower domain of coastal aquifers. However, under certain conditions, SWI may cause salinization of the entire saturated zone of the aquifer, leading to water table salinization (WTS) in unconfined aquifers by replacing freshwater within the upper region of the saturated zone with seawater, thereby posing a salinity threat to the overlying soil zone. There is presently limited guidance on the extent to which WTS may occur as a secondary impact of SWI. In this study, physical experiments and numerical modeling were used to explore WTS associated with SWI in various nontidal, unconfined coastal aquifer settings. Laboratory experiments and corresponding numerical simulations show that significant WTS can occur under active SWI (i.e., the freshwater hydraulic gradient slopes toward the land) because the cessation of freshwater discharge to the sea and the subsequent landward flow across the entire sea boundary eventually lead to water table salinities approaching seawater concentration. WTS during active SWI is larger under conditions of high hydraulic conductivity, rapid SWI, high dispersivity and for deeper aquifers. Numerical modeling of four published field cases demonstrates that rates of WTS of up to 60 m/yr are plausible. Under passive SWI (i.e., the hydraulic gradient slopes toward the sea), minor WTS may arise as a result of dispersive processes under certain conditions (i.e., high dispersivity and hydraulic conductivity, and low freshwater discharge). Our results show that WTS is probably widespread in coastal aquifers experiencing considerable groundwater decline sustained over several years, although further evidence is needed to identify WTS under field settings.

The inland migration of seawater in coastal aquifers, known as seawater intrusion (SWI), can be categorised as passive or active, depending on whether the hydraulic gradient slopes downwards towards the sea or the land, respectively. Despite active SWI occurring in many locations, it has received considerably less attention than passive SWI. In this study, active SWI caused by an inland freshwater head decline (FHD) is characterised using numerical modelling of various idealised unconfined coastal aquifer settings. Relationships between key features of active SWI (e.g., interface characteristics and SWI response timescales) and the parameters of the problem (e.g., inland FHD, freshwater-seawater density contrast, dispersivity, hydraulic conductivity, porosity and aquifer thickness) are explored for the first time. Sensitivity analyses show that the SWI response timescales under active SWI situations are influenced by both the initial and final boundary head differences. The interface is found to be steeper under stronger advection (i.e., caused by the inland FHD), higher dispersivity and hydraulic conductivity, and lower aquifer thickness, seawater density and porosity. The interface movement is faster and the mixing zone is wider with larger hydraulic conductivity, seawater-freshwater density difference, and aquifer thickness, and with lower porosity. Dimensionless parameters (Peclet number and mixed convection ratio) from previous steadystate analyses offer only limited application to the controlling factors of passive SWI, and are not applicable to active SWI. The current study of active SWI highlights important functional relationships that improve the general understanding of SWI, which has otherwise been founded primarily on steady-state and passive SWI.

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Excessive groundwater exploitation may lead to groundwater depletion, causing groundwater level at the inland lower than sea level and result in seawater intrusion (SWI) in a coastal aquifer. To control the occurrence of SWI, an alternative solution is to increase the replenishment of groundwater using a recharge reservoir. If a recharge reservoir is built in a region with soil hydraulic conductivity below 10-5 cm/s (semi impermeable), then a sand column is usually proposed, put on the bottom of the recharge basin and directly connected to the aquifer layer. The purpose of this study is to analyze the effectiveness of the sand column’s application in the recharge reservoir to control SWI. This research is an experimental study that combines physical and numerical modeling of the recharge basin with sand columns under a laboratory scale. The results of this research are beneficial for field applications because the process that occurs in the recharge reservoir can be determined prior to the real construction in the field. The results of the research are also useful to investigate whether the recharge reservoir is effective or not as a buffer of SWI in coastal aquifers. The expected result is that by using sand columns in the recharge basin, seawater intrusion can be controlled. It is hypothesized that the higher the number of sand column density and water level on the reservoir, the farther the freshwater saltwater interface is pushed toward the sea.

Drainase Sinrijala merupakan salah satu jaringan sistem drainase perkotaan kota Makassar yang memiliki banyak permasalahaan. Permasalahan-permasalahan tersebut diantaranya sedimentasi yang menumpuk pada dasar saluran, tumpukan sampah rumah tangga dan limbah industri, permasalahan interkoneksi saluran sekunder dan tersier ke saluran primer, serta kondisi eksisting struktur bangunan yang mengalami kerusakan.Dari permasalahan tersebut mengakibatkan terjadinya genangan di beberapa titik pada daerah sekitar drainase.Permasalahan sistem drainase sangat erat kaitannya dengan operasi dan pemeliharaan.Sehingga tujuan dari penelitian ini yaitu untuk menganalisis kapasitas Drainase Sinrijala dan mencari solusi alternative dalam melakukan operasi dan pemeliharaan untuk peningkatan kapasitas Drainase Sinrijala.Dalam penelitian ini dilakukan dua analisis yaitu analisis kondisi saluran dan analisis kinerja operasi dan pemeliharaan saluran. Analisis terkait kondisi saluran dengan melakukan inventarisasi kondisi eksisting saluran dan menghitung debit penampang saluran (Qs) dan debit rencana (Qt) untuk mendapatkan nilai kapasitas saluran. Analisis kapasitas penampang dilakukan dengan menggunakan aplikasi HEC-RAS versi 4.1.0. Selain itu, melakukan penilaian terhadap kinerja operasi dan pemeliharaan dengan penyebaran kuesioner pada instansi terkait yang berwenang dalam pengelolaan drainase perkotaan kota Makassar. Penilaian responden menggunakan metode skala likert dan menganalisisnya dengan menggunakan aplikasi IBM SPSS versi 26. Berdasarkan hasil penelitian yang dilakukan diperoleh debit rencana yang dihasilkan pada drainase Sinrijala adalah Q2 = 8,798 m3/detik dan Q5 = 10,304 m3/detik. Dari hasil simulasi eksisting dengan Q 2 tahun diperoleh P.16, P.17, P.18, P.19, P.20, P.21, P.22, P.23, P.24, P.25, P.26, P.27, P.28, P.29, P.30, P.32, P.33, dan P.34 tidak memenuhi syarat kapasitas saluran, sementara untuk Q 5 tahun tidak memenuhi syarat kapasitas saluran pada P.16, P.17, P.18, P.19, P.20, P.21, P.22, P.23, P.24, P.25, P.26, P.27, P.28, P.28, P.29, P.30 P.32, P.33, dan P.34. Sementara untuk penilaian kinerja, variabel Fisik Bangunan (X4) merupakan faktor yang berpengaruh dominan dalam kinerja peningkatan kapasitas Drainase Sinrijala, upaya dalam mengatasi permasalahan banjir dan genangan adalah melakukan normalisasi berupa pengerukan, penambahan tanggul dan perbaikan dinding saluran yang mengalami kerusakan berat menjadi prioritas utama untuk meningkatkan fisik bangunan drainase Sinrijala.

Cabenge River is part of the WalanaeCenranae River area in Soppeng Regency. Annually, the area around the Cabenge River gets the most losses from floods, both in terms of facilities and infrastructures. This study aims to map the areas prone to flood and flood risk, based on the field that gets the most significant impact. This study uses a Geographic Information System (GIS) as a tool and ArcGis Software in determining the level of vulnerability and risk of flooding at the study site. This type of research is a combination of mapping (topographic results) and map analysis. The variables used are DEM (Digital Elevation Model) data and flood volume. The data processing technique used is the GIS-based inundation model approach using inundation height (H) based on a comparison between the volume of water (V) in inundated areas and the volume of water (Q) of flood sources. The results showed that Lilirilau District was in the high hazard class with an area of 100 km2 and had the biggest impact, while in Liliriaja District, the area that was in a high hazard class was 34 km2 and Ganra District was 21 km2.

Penelitian ini menggunakan metode critical path untuk mencari item pekerjaan yangtergolong dalam pekerjaan kritis atau mengalami keterlambatan dengan menggunakanaplikasi Microsoft project 2013 yang berpengaruh terhadap jalannya pekerjaan,kemudian menganalisa data berupa analisa alat berat pada masing-masing alat berat dantipenya sehingga memunculkan data kebutuhan produksi yang harus dicapai dalamwaktu tertentu. Hasil yang diperoleh dari penelitian ini adalah jumlah total alat beratyang dibutuhkan agar pekerjaan timbunan bendungan utama dapat selesai sesuai denganwaktu yang direncanakan dengan kesimpulan, 8 unit Excavator PC200, 12 unitDumptruck Fuso 220 PS, 9 unit Bulldozer D65, 6 unit Vibrator Roller 10 ton, 8 unitWatertank Truck 5000 ltr, 8 unit Crawler Drilling. Dimana total biaya sebelumpemilihan dan penambahan alat berat sebesar Rp39,521,513,700.84 dan setelahpemilihan dan penambahan alat berat sebesar Rp44,266,770,960.07, maka selisih yangterjadi antara sebelum dan setelah pemilihan dan penambahan alat berat adalah sebesarRp4,745,257,259.22.