Since 1900, Semarang City has been meeting its industrial water needs by pumping groundwater through its underlying aquifers. The trend toward exploiting groundwater resources has driven the number of deep wells and their production capacity to increase, and therefore leads to the water table to drop from time to time, which has been marked as one of the primary causes of land subsidence there. The main aim of the current study was to numerically model the temporal and spatial evolution of groundwater table under excess abstraction so that a groundwater management strategy can be accordingly drawn up for ensuing the sustainability of groundwater resources in the future. A series of numerical simulations were carried out to take into account hydrogeological data, artificial and natural discharges of deep wells, and boundary effects in Semarang City. The groundwater modeling is calibrated under two flow conditions of the steady state from 1970 to 1990 and the transient state from 1990 to 2005 for six observation wells distributed in Semarang City. Four scenarios that reflect potential management strategies were developed, and then their effectiveness was systematically investigated. The results of our study indicate that the implementation of proper groundwater control management and measure is able to restore the groundwater level to rise back in Semarang City, and in turn achieve the sustainability of groundwater resources.

In regional groundwater management, it is necessary to find out the water balance between the supply and demand of groundwater. One of the most important in analyzing the water balance of groundwater is groundwater recharge. Semarang city that has a groundwater management problem needs to know the groundwater recharge to analyze the groundwater balance. On the other hand, it is difficult to measure groundwater recharge accurately, consequently, the groundwater recharge should be estimated. There are several methods to estimate groundwater recharge. To verify the groundwater recharge estimation, more than one method of groundwater recharge estimation should be used. In this paper, the determination of groundwater recharge is using the Chaturvedi formula and Krishna Rao formula based on the amount of rainfall, and well level data method that based on the difference in water level. Based on the final results, the well level data method seems the best fit in estimating the groundwater recharge.

On January 27, 2017, the Indonesian Government started building a new international airport in Yogyakarta Province, named Yogyakarta International Airport (YIA) to replace Adisucipto International Airport. YIA is located near the beach, which means that an awareness of natural disasters, such as coastal flooding, is essential. One of the causes of sea water flooding is land subsidence phenomenon. This land subsidence phenomenon can be monitored by using Sentinel-1 Interferometric Synthetic Aperture Radar (InSAR) data. To monitor the crustal deformation, the data used in this research are from years 2016-2019. The data were processed through LiCSBAS software which is published by the COMET in the UK. In the processing scheme, interferograms with many unwrapping errors are detected and removed via loop closure. Reliable time series and velocities are extracted using several noise indices, with the help of masking. The results show the subsidence phenomenon in the YIA area (up to 25 mm).

Abutmen jembatan merupakan bagian struktur jembatan yang cukup rawan terhadapproses gerusan lokal. Proses gerusan lokal pada abutmen jembatan dapat menyebabkan kegagalanstruktur pada jembatan, dan mengakibatkan jembatan tidak dapat berfungsi kembali. Untukmengetahui efektivitas bentuk abutmen jembatan terhadap gerusan lokal, dilakukan simulasiterhadap 2 buah model abutmen jembatan, vertical wall abutment dan semi – end – circularabutment, yang diletakkan di hamparan sedimen untuk 3 variasi debit sebesar 0,45 lt/det, 0,51lt/det, dan 0,79 lt/det diflume, kemudian diukur perubahan elevasi di sekitar jembatanmenggunakan alat ukur digital. Hasil simulasi menunjukkan bahwa model vertical wall abutmentmemberikan kedalaman gerusan yang lebih dalam pada debit simulasi terbesar jika dibandingkandengan model semi – end – circular abutment, dengan kedalaman gerusan berturut-turut sebesar -2,35 cm dan -2,12 cm. Untuk pola gerusan lokal, gerusan yang terjadi pada model vertical wallabutment hanya terjadi pada arah C, sedangkan pada model semi – end – circular abutment terjadipada arah A dan C. Untuk itu, model semi – end – circular lebih efektif mengurangi kedalamangerusan, namun menghasilkan pola gerusan yang lebih banyak.

Penelitian ini bertujuan untuk mengetahui titik konsumsi air terbesar dan efisiensi penggunaan air serta upaya yang dilakukan Holcim Indonesia Pabrik Cilacap dalam konservasi air. Analisis awal dilakukan dengan mengetahui tingkat penggunaan air perusahaan, baik untuk penggunaan air hujan maupun air PDAM serta jumlah flow meter yang terpasang sebagai alat ukur konsumsi air.Data yang digunakan diperoleh dari data konsumsi air Holcim Indonesia Pabrik Cilacap tahun 2010 – Juli 2014. Untuk mengetahui titik konsumsi terbesar digunakan analisis pareto terhadap data konsumsi air. Dari hasil analisis dapat diambil kesimpulan bahwa penggunaan air PT Holcim Indonesia Pabrik Cilacap 2013 menurun 9% dari penggunaan air di tahun 2010, dengan komposisi air hujan lebih banyak dibandingankan dengan air PDAM. Jumlah flow meter yang terpasang mempengaruhi tingkat keakurasian pencatatan internal.Persentase selisih yang terjadi antara pencatatan internal dengan PDAM menurun seiring dengan peningkatan jumlah flow meter yang terpasang.Oleh karena itu,identifikasi kehilangan air belum dapat dilakukan karena masih ada titik – titik konsumsi yang belum terukur dengan flow meter.Hasil dari analisis pareto menunjukan bahwa departemen terkait dengan titik konsumsi torn dist dan supply RM mengkonsumsi air terbesar. Untuk mengetahui dan memantau keberhasilan pengelolaan penggunaan air, pada penelitian ini juga akan dilakukan studi perbandingan “Benchmarking” dengan beberapa Pabrik Semen di dunia dalam bidang penggunaan air. Dari hasil studi perbandingan diperoleh rata – rata pemanfaatan air terhadap produksi semen Holcim Indonesia Pabrik Cilacap lebih rendah dibandingkan dengan grup semen dunia lainnya, yaitu sebesar 103 l/t cli.