Floating net cage activities can cause  water quality to decrease. The feed remains and the metabolism of the fish  from these activities produces nitrogen and phosphorus .  The objective of this study  is to obtain the calculation model and the amount of phosphorus released into the waters of Laut Tawar Lake  as a result of floating  cage activities. The resulting  formula  was Pw = (F x [P]p) – ((It – Io) x [P]i), where their variables were given feed (F), phosphorus concentration of feed ([P]p), the final weight of fish (It), the initial weight of fish (Io), and phosphorus concentration in fishes ([P]i). It can be used to predict the increase in phosphorus waste based on the increase in floating net cage area. The weight of tilapia increases exponentially with the  day of cultivation in the equation Y = 12.70e0.02x and the goldfish followed the formula  Y = 2.28e0.03x. Phosphorus in tilapia varies  from 1.58% to 2.23% with an average of 1.97%. Goldfish contain  1.19 - 2.02% phosphorus, with an average of 1.52%. Goldfish  growth  was not optimal due to inadequate feeding,   so  without excessive feeding and did not generate  phosphorus waste. The cultivation of  tilapia releases  0.09 Kg P/m2 of phosphorus waste from floating cages .

The trophic status of Laut Tawar Lake was increasingly leading to an alarming level of degradation. Efforts to anticipate an increase in trophic status require scientific knowledge of the trophic phenomena of the waters empirically. This research examines the trophic status parameters to produce a model of the trophic status of Laut Tawar Lake. The proposed model was a modification of Carlson's Trophic State Index Method. Analysis of the relationship examined the interaction of water clarity (SD) with chlorophyll-a (Chl), Total Suspended Solid, and Total Dissolved Solids, and the interaction of chlorophyll-a with nutrient concentration (TP, TN). Data were analyzed descriptively quantitatively, correlation, and regression. The results showed that the waters of Laut Tawar Lake contain phosphate (TP) 34 µg/L, Total Nitrogen 687 µg/L, chlorophyll-a 10 µg/L, Total Suspended Solid 47 mg/L, Total Dissolved Solid 84 mg/L, and water clarity 4.0 m. The regression test showed that the abundance of phytoplankton (Chl) was affected by nutrient phosphate with the empirical model equation Chl = 0.565 TP – 9.161. Nitrogen nutrients did not partially affect the concentration of chlorophyll-a in the waters of Laut Tawar Lake. Water clarity is influenced by chlorophyll-a and TSS, where TDS has no effect partially. The empirical model obtained is Ln SD = 1.757 – 0.013 Chl – 0.008 TSS. Modification of Carlson's TSI by substituting the two equations obtained the equation TSIdlt = 13.46 + 8.08 ln TP + 0.04 TP + 0.04 TSS. This model simulation gives an estimation rate of 91.06%.

Abstrak : Perkembangan teknologi digital yang sangat cepat berdampak besar dalam percepatan pembangunan infrastruktur sehingga diperlukan suatu teknologi yang sudah terintegrasi yang di dalamnya harus berisi semua informasi yang dibutuhkan dalam proses desain, konstruksi, dan maintenance. Maka penerapan Building Information Modelling (BIM) adalah solusi dari permasalahan tersebut. Penerapan BIM sendiri perlu didukung oleh alat bantu berupa software, salah satunya OpenBuilding Designer. OpenBuilding Designer merupakan perangkat lunak yang sudah terintegrasi sehingga pekerjaan akan lebih efektif dan efisien. Penelitian ini bertujuan untuk dapat mengimplementasikan konsep BIM menggunakan Software  OpenBuildings Designer, untuk mengetahui bentuk permodelan 3D dari gedung Kantor Cabang BRI Batusangkar yang berupa permodelan arsitektur, struktur, dan mekanikal. Memodelkan suatu bangunan terdapat langkah-langkah yang harus dilakukan. Dengan adanya langkah-langkah tersebut memudahkan dalam memodelkan suatu bangunan. Hasil dari penerapan BIM yang dilakukan berupa permodelan 3D arsitektur, struktur dan mekanikal. Kelebihan dari penerapan BIM  yang dilakukan menggunakan Software Openbuilding Designer yaitu dapat membantu pekerjaan arsitek, insinyur, dan ahli sipil. Kekurangan BIM dalam implementasi Building Information Modeling menggunakan Software Openbuilding Designer adalah tidak dapat menggantikan profesi arsitek, insinyur, dan ahli sipil.Kata Kunci      : BIM, Permodelan 3D, Openbuilding Designer