Laboratory Study on Comparison of the Scour Depth and Scour Length of Groundsill with the Opening and Groundsill without the Opening

River bed control structure what so called groundsill or bottom sill is built for controlling a river bed to remain stable against degradation. Unlike other river obstacles, the presence of groundsill might cause sediment retention upstream of the structure; hence it reduces the supply of sediment to the downstream part of the river. At some extent, the above situation might create unexpected negative impact, not only cease the sediment migration but also disable fish migration, as well as the utilization of river for navigation. This paper presents the hydraulic investigation on various models of groundsill, i.e. groundsill without the opening and groundsill with a certain type of the opening. Series of laboratory experiments were conducted on an open channel flow of 0.75m width and longitudinal slope of 0.05%. There were two types of groundsill, i.e. groundsill without the opening with 0.75m width and 0.05m height, and groundsill with the opening of 0.39m width and 0.005m height of crest at the opening and 0.05m at the wings. Various flow rates were then introduced, necessary data were taken, and the hydraulic phenomena were studied. The results showed that groundsill without the opening produced non-dimensional (relative to the channel width) scour depth of 0.036, and scour length of 0.253. Groundsill with the opening produced scour depth of 0.013 and 0.024 near the downstream end of the wing section and the opening respectively. The scour length of the groundsill with the opening is 0.080 and 0.293 near the downstream end of the wing section and the opening section respectively. Moreover, it can be noted that the presence of the scour depth and scour length of the groundsill with the opening was generally much smaller rather than that of groundsill without the opening. The above results give the evidence that groundsill with the opening is much friendlier and also more suitable for the environment needs.Keywords: control structure, environmentally sound, groundsill, hydraulic phenomeno

ANALISIS PENETAPAN HARGA JUAL AIR BERSIH PADA SPAMDES TIRTO SARI, KULON PROGO

Abstrak Pengelolan SPAMDes Tirtosari masih memperhitungkan biaya operasional dan harga pokok produksi berdasarkan perkiraan dan kesepakatan bersama, belum mempertimbangan biaya produksi. Metode full costing untuk memperhitungkan harga pokok produksi, kemudian digunakan metode cost plus pricing dan rumus berdasarkan Permendagri Nomor 71 Tahun 2016 untuk menentukan harga jual air. Dari hasil analisis, biaya operasional terbesar terjadi pada tahun 2018 yaitu sebesar Rp. 64.273.209. Selain itu diperoleh nilai harga jual air per m3 yang lebih tinggi dibandingkan harga pokok produksinya. Seperti pada tahun 2022, harga pokok produksi yang dihasilkan sebesar Rp. 1.899 dan harga jual yang dihasilkan sebesar Rp. 2.713. Hasil perhitungan harga jual air per m3 yang mengacu pada metode cost plus pricing dan Permendagri Nomor 71 Tahun 2016 dengan menambahkan nilai laba pada perhitungannya juga menunjukkan nilai yang lebih besar dibanding harga pokok produksi air yang telah dihitung sebelumnya yaitu berkisar antara Rp. 3.940 – Rp. 9.158. Jika perusahaan menetapkan harga jual air sesuai hasil perhitungan, maka perusahaan sudah mampu untuk menutupi biaya operasional air serta mendapatkan laba. Kata kunci: Biaya operasional, harga pokok produksi, full costing, harga jual, cost plus pricing  Abstract Management of SPAMDes Tirtosari still takes into account operational costs and cost of production based on estimates and mutual agreement, not considering production costs. The full costing method is used to calculate the cost of production, then the cost plus pricing method and the formula based on Permendagri Number 71 of 2016 are used to determine the selling price of water. From the results of the analysis, the largest operational costs occurred in 2018 which amounted to Rp. 64,273,209. In addition, the selling price of water per m3 is obtained which is higher than the cost of production. As in 2022, the cost of production produced is Rp. 1,899 and the resulting selling price is Rp. 2,713. The results of the calculation of the selling price of water per m3 which refers to the cost plus pricing method and Permendagri Number 71 of 2016 by adding the profit value to the calculation also shows a value that is greater than the cost of water production that has been calculated previously, which ranges from Rp. 3.940 – Rp. 9,158. If the company determines the selling price of water according to the calculation results, then the company is able to cover the operational costs of water and earn a profit Keywords: Operational cost, cost of production, full costing, selling price, cost plus pricing

Rainfall Monitoring to Support Temporal and Spatial Information of Debris Flow Initiation in Merapi Volcano

Debris flow frequently attacks rivers on slopes of Merapi Volcano and causes fatalities and damage of infrastructures. To reduce the risk of debris flow, a warning system has been developed by Sabo Office Center. Critical line and snake line graph are applied in Merapi Volcano to monitor characteristics of rainfall in the upland river basin. However, this warning system cannot predict the arrival time and location of the debris flow occurrence. Numerical simulation seems to be a good tool to improve its performance. This research proposed an idea to combine rainfall-based warning system with the numerical simulation model. This model used slope stability theory to identify debris flow initiation. Results of this research showed that fluctuation of rainfall intensity reflects changes of debris flow initiation area. The more severe rainfall intensity, the larger volume of surface flow, and thus the greater debris flow initiation takes place. When the rainfall monitoring is combined with the debris flow simulation results, there is a tendency of the enlargement of the debris flow area to follow the growth of the hourly rainfall

Snake Line Performance Applying Single Pixel X-Band MP Radar Data (Case of Mt. Merapi Area, Indonesia)

The short-duration-rainfall monitoring techniques have become important recently due to the high demand for disaster risk miti­gation. Such techniques produce important information on the rainfall intensity during heavy rainfall in the form of snake line. At the same time, use of X-Band Multi-Parameter Radar (XMP Radar) in rainfall monitoring has increased significantly be­cause of its capacity to cover wide area. An assessment on the snake line performance that was developed based on XMP Radar and ground rainfall monitoring instrument (i.e. Automatic Rainfall Recorder or ARR) has been applied to Mt. Merapi area, Java, Indonesia. Selected rainfall data of November-December 2018 were examined. The assessment used a single pixel of radar data at the location of the ARR. The result shows that rainfall data obtained from XMP Radar are lower than those from ARR. The computed snake line obtained from XMP Radar differs from that from ARR data. The XMP Radar underestimates the warning level by about two level out of four

The Effect of Slope on the Infiltration Capacity and Erosion of Mount Merapi Slope Materials

The infiltration on slopes has a specific behavior capable of being parameterized and one of the reasons is due to the ability of the slope to generate less ponding on the sloping soil surface. This, therefore, affects infiltration rate and surface runoff proportion of water from any kind of rainfall distribution and the tendency of the surface runoff to be higher usually leads to a higher erosion rate on the slope. Moreover, slope steepness is the most important parameter of a slope, and its effect at 36%, 47%, and 58% was tested on the infiltration capacity and erosion rate of Mt. Merapi bare slope material in a laboratory using a rainfall simulator. The rainfall intensity was set constant at a rate of 116.31 mm/hour while the infiltration rate was measured by the volumetric balance principle and the erosion rates by collecting the eroded grains at the downstream end flume. Furthermore, the infiltration capacity was evaluated using the Horton method by fitting the equation to the recorded infiltration rate data while the average erosion was through the eroded grain data for each test. The results obtained represent the relationship between slope steepness, the affected infiltration capacity, and erosion for each test, and the infiltration capacity was found to be decreasing in lower slope < 47% and increasing in a higher slope while the erosion rate was increasing between 7% and 15% for each 1% increase in the slope steepness. In addition, polynomial and linear equations were developed to express the relationship between these three indicates at the Mt. Merapi bare slope material

POTENSI PENGGUNAAN INTENSITAS HUJAN HASIL PENGAMATAN SATELIT UNTUK AMBANG HUJAN PEMICU TANAH LONGSOR

Kejadian longsor yang dipicu oleh hujan sangat berkaitan erat dengan intensitas dan durasi hujan. Informasi waktu terjadinya longsor memerlukan rekaman curah hujan yang akurat melalui pengukuran di lokasi longsor. Namun, seringkali rekaman curah hujan tidak diperoleh di area longsor. Naskah ini menyajikan hasil kajian curah hujan hasil pengukuran di stasiun hujan permukaan (ground station) dan pengukuran satelit. Penelitian bertujuan mengkaji hubungan data curah hujan hasil pengukuran dengan rain gauge (RG) dengan data hujan satelit Tropical Rainfall Masuring Mission (TRMM) dan Global Precipitation Measurement (GPM). Lokasi kajian berada di Kalibawang yang berada pada koordinat 7o40’33”LS/110o15’49”BT. Hasil kajian menyimpulkan bahwa hubungan antara rain gauge dengan data satelit termasuk dalam kategori sedang dengan nilai korelasi dari 0,50 hingga 0,55. Data satelit memiliki performa yang lebih baik dalam pengukuran curah hujan dibandingkan pengukuran curah hujan langsung di lapangan karena intensitas TRMM &gt; intensitas GPM &gt; intensitas rain gauge

The effect of sediment density parameter values on the debris flow velocity parameters

Debris flow is a phenomenon where the material from the eruption is carried away by the flow of water due to rain in the upstream area of the river and usually crashes into watersheds around the volcano. The potential for large debris flows can be caused by high rainfall and sediment deposits that occur during debris flows. Rainfall and sediment carried by water flow can affect the volume and velocity of debris flows. A debris flow simulation was carried out to anticipate casualties and damage using SIMLAR V2.1 by modifying rain intensity and the density of sediment carried by the debris flow. Based on the result, we can obtain the results of the velocity, volume, and area affected by the debris flow. The flow velocity values obtained for testing with rainfall intensity of 162 mm with a density of sediment 1370 kg/m3, 2340 kg/m3, 2635 kg/m3, and 2820 kg/m3, respectively, were 2.72 m/s, 2.16 m/s, 2.50 m/s, and 2.57 m/s. The volume values with the same intensity and density of sediment are 186,381 m3, 311,116 m3, 274,030 m3, and 294,987 m3. Based on the test results, it can be concluded that sediment density significantly affects the velocity and volume of the debris flow. Where sediment density is inversely proportional to the flow velocity, the higher the sediment density, the slower the flow velocity, while the volume is directly proportional to the sediment density. The higher the density of the sediment, the higher the volume

Changes of Soil Chemical Properties during Rice Straw Decomposition in Different Types of Acid Sulphate Soils

Organic residues often exhibit different physico-chemical properties and affect the soil ecosystem in different ways. Hence, the study of their impact on soil is essential to benefit from their potential as amendments and to avoid adverse environmental effects. It is required to study the role of rice straw in the changes of soil properties during decomposition processes in the rice field. The research was conducted on potential acid sulphate soil (PASS) and actual acid sulphate soil (AASS) in the glass house. Soil pH, Fe2+, organic-Fe, total N and available P were observed at 2, 4, 6 and 8 weeks after planting (WAP). The results showed that rice straw application : (1) decreased soil pH of PASS and increase soil pH of AASS; (2) tended to increase Fe2+ both in PASS and AASS; (3) stimulated the organic-Fe concentration that was higher than in PASS; (4) had no different effect in total N and decreased P concentration in the both of soil during observation. P concentration on PASS was lower than on AASS

Correlation Analysis Between Measured Rain Data with Satellite at Rainfall Station in Merapi

Manual and automatic rain gauges often need to be revised in measuring rainfall due to various constraints. Therefore, using rain data from satellites will be a promising alternative. The rain data used is measured hourly rainfall data 20mm in 2012, 2017, and 2022. In addition, rain data from the PERSIANN and GPM satellites were also used. The analysis was carried out using the correlation coefficient (r) method, which aims to find the correlation between measured rain data and satellite rain data. The results show that the PERSIANN satellite has the highest correlation value in rain duration in two years, while the GPM satellite has the highest total depth and intensity correlation value in two years. Therefore, it can be concluded that the GPM satellite has better accuracy than the PERSIANN satellite in monitoring rain

Pendampingan Perhitungan Tarif Air Bersih Spamdes Tirta Lestari Kulon Progo

ABSTRAK Pengeloaan air bersih di pedesaan yang terjadi selama ini belum memberikan keuntungan yang memadai. Harga tarif air belum menutup biaya produksi dan operasional yang layak. Harga tarif masih berdasar kesepakatan dengan masyarakat yang cenderung mengusulkan harga termurah. Penentuan harga tarif yang layak perlu dianalisis ulang agar semua biaya produksi, operasinal tercukupi dan tersedia anggaran cadangan untuk pengembangan. Kegiatan pengabdian berupa pendampingan perhitungan harga air bersih bersama pengelola Organisasi Kelola Air Mandiri Sistem Penyediaan Air Bersih Pedesaan (OKAM SPAMDes) Tirta Lestari yang berada di Dusun Kaliapak, Kelurahan Banjarsari, Kecamatan Samigaluh, Kabupaten Kulon Progo. Pendampingan dimulai dengan pengumpulan data keuangan, berupa anggaran pemasukan dan pengeluaran. Perhitungan penetapan tarif air dari data-data tersebut mengacu Permendagri Nomor 21 Tahun 2020. Data yang digunakan untuk analisis adalah laporan keuangan dan pemakaian air pelanggan SPAMDES Tirta Lestari mulai dari tahun 2018 – 2020. Hasil perhitungan yang dijelaskan dalam pendampingan berikutnya dengan penjelasan secara sederhana.  Harga tarif dasar air bersih yang layak minimal Rp. 8.362/m³ dari yang sebelumnya Rp. 5.000/m3. OKAM Tirta Lestari dapat memahami perhitungan harga air agar dapat menutupi biaya operasional dan mendapatkan laba dari SPAMDes tersebut.   Kata Kunci: Pendampingan, Harga Air, SPAMDes  ABSTRACT The management of clean water in rural areas that has occurred so far has not provided adequate benefits. The price of water tariffs has not adequately covered production and operational costs. Tariff prices are still based on an agreement with the public who tend to propose the cheapest price. The determination of proper tariff prices needs to be re-analyzed so that all production and operational costs are met, and a reserve budget is available for development. Community service activities in the form of assisting in calculating the price of clean water with the manager of Tirta Lestari's Independent Water Management Organization for Rural Clean Water Supply Systems (OKAM SPAMDes) in Kaliapak Hamlet, Banjarsari Village, Samigaluh District, Kulon Progo Regency. Assistance begins with the collection of financial data, in the form of income and expenditure budgets. The calculation of setting water rates from these data refers to Permendagri Number 21 of 2020. The data used for analysis is the financial reports and water usage of SPAMDES Tirta Lestari customers starting from 2018 – 2020. Calculation results explained in the next mentoring with detailed explanations simple. The basic tariff price for clean water is a minimum of Rp. 8,362/m³ from the previous Rp. 5,000/m3. OKAM Tirta Lestari can understand the calculation of water prices to cover operational costs and get profit from the SPAMDes. Keywords: Assistance, Water Price, SPAMDe